JP2023024200A - Hierarchical transmission system transmission device and receiving device - Google Patents

Abstract

A transmitting device and a receiving device capable of correcting non-linear distortion caused by a broadcasting transmission line of satellite broadcasting while increasing resistance to rain attenuation and the like when hierarchically transmitting modulated signals of two systems with a single carrier. . Kind Code: A1 A transmitting apparatus 1 of the present invention synchronizes each data of an upper layer and a lower layer transmitted by a hierarchical power transmission system (LDM), and adds a pilot signal for correction of transmission line distortion of LDM only to the upper layer. functions (11, 12, 13) for forming modulation signals for upper and lower layers, and functions (14, 15) for generating a complex baseband signal by synthesizing each modulation signal through level adjustment and performing quadrature modulation (14, 15). And prepare. The receiving device 2 of the present invention includes functional units (22, 23, 24, 25) for detecting and correcting nonlinear distortion caused by a satellite broadcasting transmission path in the complex baseband signal obtained from the transmitting device 1, and an LDM. a function unit (21, 26, 27, 28) for synchronizing and restoring each data of the upper hierarchy and the lower hierarchy based on the data. [Selection drawing] Fig. 1

Description

The present invention relates to a transmitting device and a receiving device that hierarchically transmit two systems of modulated signals with a single carrier.

Modulation schemes in 12 GHz band satellite digital broadcasting include BPSK including π/2 shift BPSK, QPSK including π/4 shift QPSK, 8PSK, 16APSK, etc., and are transmitted by a single carrier. The transmission system of this 12 GHz band satellite broadcasting is called ISDB-S3. The strength of the transmission system is determined by the modulation system and the coding rate of the error correction code (see Non-Patent Document 1, for example). In this satellite broadcasting, a strong hierarchy (a hierarchy that uses a low-order modulation method and a low coding rate to increase transmission resistance) and a weak hierarchy (a hierarchy that uses a high-order (multilevel) modulation method and a high coding rate, Hierarchical transmission is possible in combination with a hierarchy capable of capacity transmission. For example, QPSK and coding rate 1/2 are used for strong layers, and 16APSK and coding rate 7/9 are used for weak layers. Hierarchical transmission of 12 GHz band satellite broadcasting is a time-division hierarchical transmission system in which one frame is divided into a strong hierarchy and a weak hierarchy and transmitted in a time division manner. Although the number of transmission bits per symbol differs between the strong layer and the weak layer, the symbol rate is constant. In recent years, 21 GHz band satellite broadcasting has also been considered.

Further, in terrestrial digital broadcasting, a multi-carrier modulation system called OFDM is adopted, and the carrier modulation system includes QPSK, 16QAM, 64QAM, and the like. This digital terrestrial broadcasting transmission system is called ISDB-T (see, for example, Non-Patent Document 2). In recent years, in terrestrial broadcasting for the next generation, power hierarchical transmission (hereinafter referred to as "LDM"), which multiplexes an existing ISDB-T modulated signal by adding another modulated signal in terms of power, has been studied. It is In this LDM system, the existing ISDB-T data carrier (hereinafter referred to as the 2K layer) is OFDM-modulated and multiplexed with the next-generation broadcast data carrier (hereinafter referred to as the 4K layer), and the same one as before It is a hierarchical transmission scheme that broadcasts both 2K and 4K on a channel (see, for example, Non-Patent Document 3). In this method, the 4K layer is multiplexed with a small power for the 2K layer, and transmission is performed with two power differences between the strong layer (upper layer: 2K) and the weak layer (lower layer: 4K). On the receiving side, a 2K data signal is obtained by demodulating and error-correction decoding from the upper layer, and the decoded signal is again error-correction-encoded and re-modulated, and only the 2K signal, which is the transmission signal of the upper layer, is obtained. By subtracting the reproduced 2K signal from the received signal (combined signal including both the upper layer (2K) and the lower layer (4K)), a signal of only the lower layer (4K) is obtained, demodulated, and error corrected. A 4K data signal is obtained by decoding (see, for example, Non-Patent Document 4). In this LDM system, generally, the FFT clocks of OFDM in the upper layer and the lower layer are the same for simplification of demodulation.

"Transmission system for advanced wideband digital satellite broadcasting (ISDB-S3) standard ARIB STD-B44 Version 2.1", [online], revised on March 25, 2016, ARIB, [July 5, 2021 Search], Internet <URL: https://www.arib.or.jp/kikaku/kikaku_hoso/std-b44.html> "Transmission method standard for terrestrial digital television broadcasting ARIB STD-B31 Version 2.2", [online], revised on March 18, 2014, ARIB, [searched on July 5, 2021], Internet < URL: https://www.arib.or.jp/kikaku/kikaku_hoso/std-b31.html> Sato, Kanbara, Okano, Tsuchida, "Evaluation of transmission characteristics during integrated demodulation of a method for multiplexing next-generation broadcasting to ISDB-T with LDM", ITE Winter Annual Convention 2019 14C-5 , Institute of Image Information and Television Engineers, December 12, 2019 Okada, "Carrier superimposition method in satellite communication - Toward the realization of LDM -", ITE Technical Report Vol.41, No.11, BCT2017-47, The Institute of Image Information and Television Engineers, Announced on March 10, 2017

In transmission of satellite broadcasting, reception power is attenuated by rainfall attenuation, and reception C/N is lowered. In time-division hierarchical transmission, the strength of hierarchical transmission can be differentiated only by the difference in transmission strength due to the modulation method and the coding rate of the error correction code. The difference in C/N is about 9.5 dB. For example, the required C/N is about 1.2 dB when the strong hierarchy is QPSK and the coding rate is 1/2, and the required C/N is about 10.8 dB when the weak hierarchy is 16APSK and the coding rate is 7/9. is. When receiving with a 45 cm parabolic antenna in Tokyo, the reception C/N in fine weather is about 20 dB, but the attenuation due to rain exceeds 10 dB, and may be 20 dB or more. In addition, attenuation due to rainfall is extremely large in 21 GHz band satellite broadcasting. In order to further increase the required C/N difference between the strong hierarchy and the weak hierarchy, there is a limit to the difference in coding rate between the modulation scheme and the error correcting code.

When rain attenuation exceeds 20 dB in satellite broadcasting, the reception C/N becomes 0 dB or less. I couldn't do it.

Therefore, there is a demand for an LDM transmitter and receiver that can transmit the minimum amount of information in a strong hierarchy even when transmission signals are attenuated by rainfall attenuation of 20 dB or more.

Furthermore, in satellite broadcasting, since the distance between the satellite transponder and the receiving device is extremely long (the artificial satellite is stationary at an altitude of 36000 km), as a broadcasting transmission path, from the satellite transponder It is desirable to send satellite signals at high power (maximum power). Near the maximum output of the satellite broadcasting signal, nonlinear distortion occurs due to the input/output characteristics of the repeater amplifier (traveling wave tube amplifier (TWTA)) in the satellite repeater. In other words, the input/output characteristics of the repeater amplifier are the characteristics of the normalized output power with respect to the normalized input power (AM-AM characteristics), and the characteristics of the relative phase shift of the normalized output with respect to the normalized input power (AM-PM characteristics). ) is not linear (straight line). However, in general, if the output is several dB lower than the maximum output of the satellite broadcast signal, the input/output characteristics are almost linear, so any transmission method including LDM is affected by nonlinear distortion. can be ignored.

However, depending on the input signal level of the repeater amplifier, it is assumed that the maximum output of the normalized output power is close to 0 dB. Unless it is provided, any transmission method including LDM will be affected by nonlinear distortion and the transmission performance will be degraded.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a transmission apparatus capable of correcting non-linear distortion caused by a satellite broadcasting transmission path while increasing resistance to rain attenuation and the like when hierarchically transmitting two systems of modulated signals with a single carrier. and to provide a receiver.

The transmitting apparatus of the present invention defines two systems of modulated signals of transmission line coding schemes as an upper layer and a lower layer, respectively, and adds the modulated signals of the two systems at different levels in terms of power to perform satellite broadcasting with a single carrier. A power hierarchical transmission system transmission apparatus for transmission via a broadcast transmission path, wherein m is a symbol rate for transmitting the upper layer data, n is a symbol rate for transmitting the lower layer data, and the symbol rate is m. where M is the symbol clock frequency corresponding to and N is the symbol clock frequency corresponding to the symbol rate n, a quadruple M×N reference clock common to the upper layer and the lower layer is generated. A reference clock generation unit, a clock generation unit having a frequency divider for generating sampling clocks obtained by dividing the reference clock for upper layers and lower layers, respectively, and upper layer data transmitted at a symbol rate m. to configure a modulation frame for the upper layer in which a predetermined pilot signal for correcting transmission line distortion of the power hierarchical transmission system can be stored in the preceding stage of the data for the upper layer; For the modulation frame, based on the sampling clock for the upper layer with reference to the reference clock, at least the error correction coding rate, the modulation method, and the roll-off rate of waveform shaping are specified for the upper layer. an upper layer transmission line coding unit that generates an upper layer complex baseband signal based on the transmission line coding method and forms the upper layer modulated signal sampled with the reference clock, and transmits at a symbol rate n Inputting data for the lower layer, forming a modulation frame for the lower layer having the same structure as the modulation frame for the upper layer without storing the pilot signal, and for the modulation frame for the lower layer, A predetermined transmission line coding scheme designating at least an error correction coding rate, a modulation scheme, and a waveform shaping roll-off rate for the lower layer based on the sampling clock for the lower layer based on the reference clock. a lower layer channel coding unit for generating a lower layer complex baseband signal based on the reference clock and forming it as the lower layer modulated signal sampled with the reference clock; After adjusting the level of one or both of the modulated signal of the upper layer and the modulated signal of the lower layer so as to have a predetermined level difference with respect to the average amplitude level of the modulated signal of the lower layer, The modulated signal of and the modulated signal of the lower hierarchy a power addition unit that generates a complex baseband signal synthesized by power addition; and a modulated wave signal for transmission by orthogonally modulating the synthesized complex baseband signal using the reference clock as a sampling clock. and a quadrature modulation unit that generates the signal.

Further, in the transmitting apparatus of the present invention, the ratio of the symbol rate m for transmitting the upper layer data to the symbol rate n for transmitting the lower layer data is m:n=1:1, 1:2, 1: 4, 2:3, or 3:4.

Further, in the transmitting apparatus of the present invention, as a ratio of the symbol rate m for transmitting the upper layer data to the symbol rate n for transmitting the lower layer data, n is an integral multiple of m, and the reference clock generation unit is configured to generate four times N reference clocks with M=1.

The receiving device of the present invention is a receiving device that receives the modulated wave signal generated by the transmitting device of the present invention via a satellite broadcasting transmission line and restores the upper layer data and the lower layer data. a reception-side reference clock generating unit for generating a reference clock of four times M×N common to the upper layer and the lower layer; a reception-side clock generator having a reception-side frequency divider for generating a frequency-divided sampling clock; and quadrature demodulation of a received signal in a predetermined frequency band in the received modulated wave signal using the reference clock as a sampling clock, A quadrature demodulation/analog/digital converter that acquires a complex baseband signal in a digital signal format, and for the complex baseband signal, detects an operating point on a nonlinear distortion curve of input/output characteristics that occurs in the broadcasting transmission path of the satellite broadcasting. a nonlinear distortion correction unit that corrects distortion of the complex baseband signal based on the operating point; and a complex baseband signal after the distortion correction is treated as an upper-layer complex baseband signal and input. an upper layer demodulation/decoding unit that restores the data of the upper layer by performing demodulation and decoding processing at a symbol rate m based on the channel coding scheme for the upper layer corresponding to the transmission device side, and Input the upper layer data restored by the demodulation and decoding unit for the upper layer, and specify at least the error correction coding rate, modulation method, and waveform shaping roll-off rate for the upper layer. an upper-layer retransmission line coding unit that regenerates an upper-layer complex baseband signal and forms a replica signal of the upper-layer complex baseband signal; Average amplitude of a replica signal of the upper layer complex baseband signal formed by the upper layer retransmission line coding section, forming a lower layer complex baseband signal subjected to waveform shaping for the lower layer roll-off rate either one of the replica signal of the upper-layer complex baseband signal and the lower-layer complex baseband signal so that the level becomes the predetermined level difference with respect to the average amplitude level of the lower-layer complex baseband signal; Alternatively, the levels of both are adjusted, and after the level adjustment, power is subtracted so as to subtract the replica signal of the complex baseband signal for the upper layer from the complex baseband signal for the lower layer, thereby providing only the complex baseband signal for the lower layer. for a new lower hierarchy consisting of generating a complex baseband signal, performing demodulation/decoding processing at a symbol rate n based on the channel coding scheme for the lower layer corresponding to the transmission device side on the new complex baseband signal for the lower layer, and a lower layer demodulation/decoding unit for restoring lower layer data.

Further, in the receiving apparatus of the present invention, the nonlinear distortion detector holds an input/output characteristic having nonlinear distortion of the broadcasting transmission path of the satellite broadcast, and on the input/output characteristic, the quadrature-demodulated complex signal is detected. It is characterized by having means for detecting the average power and peak power of the baseband signal, and analogizing and detecting each operating point on the input/output characteristics of the broadcasting transmission line of the satellite broadcasting from these two points.

Further, in the receiving apparatus of the present invention, a pilot signal predetermined for transmission path distortion correction of the power hierarchical transmission system is stored in the modulation frame for the upper layer in the transmitting apparatus, and The modulation frame for the lower layer, which is hierarchically transmitted in synchronization with the modulation frame for the upper layer, does not store the pilot signal during the signal period for storing the pilot signal in the modulation frame for the upper layer. is a signal,
The nonlinear distortion detector holds input/output characteristics having nonlinear distortion of the broadcasting transmission path of the satellite broadcast, and on the input/output characteristics, the amplitude differs from the pilot signal period of the quadrature-demodulated received signal. characterized by having means for detecting pilot signals of at least three types of signal levels, and detecting by analogy each operating point on the input/output characteristics of the broadcasting transmission line of the satellite broadcasting from the at least three types of signal levels. do.

Further, in the receiving apparatus of the present invention, the nonlinear distortion correcting section is configured to correct nonlinearity in the input/output characteristics based on each operating point on the input/output characteristics in the broadcasting transmission path of the satellite broadcast obtained from the nonlinear distortion detecting section. Correction operating points on the linear characteristics corresponding to each operating point on the input/output characteristics are obtained using the linear characteristics assumed to be distortion-free, and the complex baseband signal, which is the quadrature-demodulated received signal, is obtained. Means for correcting distortion by correcting the amplitude and phase of the complex baseband signal so that the characteristic becomes linear with respect to each corrected operating point when positioned between the operating points on the input/output characteristics. It is characterized by

Further, in the receiving apparatus of the present invention, the ratio of the symbol rate m for transmitting the data of the upper layer to the symbol rate n for transmitting the data of the lower layer is m:n=1:1 according to the transmitting apparatus, It is characterized by being one of 1:2, 1:4, 2:3 and 3:4.

Further, in the receiving apparatus of the present invention, as a ratio between the symbol rate m for transmitting the upper layer data and the symbol rate n for transmitting the lower layer data, n is an integral multiple of m, and the receiving side reference clock The generator is characterized in that it is configured to generate four times N reference clocks with M=1.

According to the present invention, the difference in transmission strength (difference in required C/N) between the strong layer and the weak layer in the power division layered transmission (LDM) method is made larger than in the conventional time division layered transmission method. In particular, even under the influence of non-linear distortion of the satellite transponder, the receiving side corrects the distortion, and receives transmission data of strong hierarchy even if attenuation of 20 dB or more occurs due to rainfall. The operation can be stabilized, and it is possible to obtain information on transmission data of both the strong hierarchy and the weak hierarchy in a more robust manner.

1 is a block diagram showing a schematic configuration of a transmission system including a power division hierarchical transmission (LDM) transmission device and a reception device according to an embodiment of the present invention; FIG. FIG. 4 is a diagram illustrating input/output characteristics (AM-AM characteristics, AM-PM characteristics) indicating nonlinear distortion characteristics of a repeater amplifier in a satellite repeater; FIG. 2 is a schematic diagram of a transmission spectrum in a power division hierarchical transmission (LDM) transmission apparatus according to the present invention; FIG. 4 is a diagram schematically showing a transmission spectrum including interference wave components caused by nonlinear distortion output from a satellite repeater in the transmission system according to the present invention; 1 is a block diagram showing a schematic configuration of a power division hierarchical transmission (LDM) transmission apparatus according to an embodiment of the present invention; FIG. FIG. 4 is a diagram showing insertion positions of pilot signals for transmission path distortion correction of LDM transmitted by a power division hierarchical transmission (LDM) transmission apparatus according to an embodiment of the present invention; FIG. 4 is an IQ plan view showing an example of a pilot signal for LDM transmission channel distortion correction transmitted by a power division hierarchical transmission (LDM) transmission apparatus according to an embodiment of the present invention; FIG. 10 is an IQ plan view showing another example of a pilot signal for LDM transmission channel distortion correction transmitted by a power division hierarchical transmission (LDM) transmission apparatus according to an embodiment of the present invention; 1 is a block diagram showing a schematic configuration of a power division hierarchical transmission (LDM) receiver according to an embodiment of the present invention; FIG. FIG. 10 is a diagram illustrating how a reception signal that has undergone quadrature demodulation is used as distortion correction in Example 1 in a receiving apparatus according to an embodiment of the present invention, and a correction characteristic thereof is obtained; FIG. 11 is a diagram illustrating how correction characteristics for a quadrature-demodulated received signal are obtained by using a pilot signal obtained from the quadrature-demodulated received signal as distortion correction in Example 2 in the receiver of one embodiment according to the present invention; is.

A transmission device 1 and a reception device 2 of a power division hierarchical transmission (LDM) system according to one embodiment of the present invention will be described below with reference to the drawings. Further, as an embodiment according to the present invention, an example will be described assuming that the upper layer data is a 2K data signal and the lower layer data is a 4K data signal.

(transmission system)
FIG. 1 is a block diagram showing a schematic configuration of a transmission system 100 including a power division hierarchical transmission (LDM) transmission device 1 and a reception device 2 according to one embodiment of the present invention. The transmission system 100 of one embodiment shown in FIG. 101, a transmitting antenna 102, a receiving antenna 103, a satellite repeater 104 and a transmitting antenna 105 at the satellite repeater station, and a receiving antenna 106 and the receiving device 2 at the receiving facility.

The transmission device 1 receives as a main signal transmission data composed of TS packets (or IP packets) such as video, audio, and data broadcasting in TS (or IP (Internet Protocol)) of each broadcaster, and generates a modulated wave. A signal is generated and output to power amplifier 101 . The power amplifier 101 amplifies the modulated wave signal output from the transmission device 1 and transmits it to the satellite relay station via the transmission antenna 102 as an uplink signal.

The satellite repeater 104 in the satellite repeater station receives the uplink signal via the receiving antenna 103, and extracts a band for each channel from the modulated wave signal that constitutes the uplink signal. A repeater amplifier 1042 for power-amplifying the extracted signal, a transmission filter 1043 for generating a broadcast wave signal with suppressed out-of-band unwanted frequency components (spectrum regrowth) after the power amplification, and a combiner following the transmission filter 1043. (not shown) generates a satellite broadcast signal by synthesizing broadcast wave signals for all channels, and transmits the signal as a downlink signal to a reception facility on the ground.

The receiving device 2 receives the downlink signal from the satellite relay station via the receiving antenna 106, demodulates it, performs decoding processing corresponding to the inverse processing of each processing in the transmitting device 1, and transmits it by the transmitting device 1. It is configured as a device for restoring transmitted data as received data.

In such satellite broadcasting, as described above, the distance between the satellite transponder 104 and the receiving device 2 is extremely long (the artificial satellite is stationary at an altitude of 36000 km). It is desirable that the satellite repeater 104 should transmit the satellite broadcasting signal with the highest possible power (maximum power). Near the maximum output of the satellite broadcast signal, nonlinear distortion occurs due to the input/output characteristics of the repeater amplifier 1042 in the satellite repeater 104 . FIG. 2 illustrates input/output characteristics (AM-AM characteristics, AM-PM characteristics) indicating nonlinear distortion characteristics of the repeater amplifier 1042 in the satellite repeater 104 .

In other words, as the input/output characteristics of the relay amplifier 1042, the AM-AM characteristics and the AM-PM characteristics are not linear (straight line), and depending on the input signal level of the relay amplifier 1042, the maximum output of the normalized output power is close to 0 dB. In this case, unless a device is provided to compensate or correct nonlinear distortion caused by the broadcasting transmission path of satellite broadcasting, any transmission method including LDM will be affected by nonlinear distortion, and transmission Performance will degrade. In particular, in the transmission system 100 shown in FIG. 1, when the transmitting device 1 and the receiving device 2 are configured as a power division hierarchical transmission system (LDM), the interference wave component caused by the nonlinear distortion output from the satellite repeater 104 A transmission spectrum including is formed.

More specifically, the transmission device 1 and the reception device 2 of the power division hierarchical transmission (LDM) system according to one embodiment of the present invention are assumed to be applied to satellite digital broadcasting systems such as 12 GHz band and 21 GHz band satellite broadcasting. , the outline of the transmission spectrum in this transmitter 1 is as shown in FIG. FIG. 3 shows an outline of a transmission spectrum in the power division hierarchical transmission (LDM) transmission apparatus 1 according to the present invention. As shown in FIG. 3, the Nyquist frequency bandwidth of the lower layer is BWb (symbol rate is n, roll-off rate is b), and the Nyquist frequency bandwidth of the upper layer is BWa (symbol rate is m, roll-off rate is a). Then, a new modulated signal is generated by adding the modulated signal of the upper layer (strong layer) to the modulated signal of the lower layer (weak layer) at a level α times the average amplitude level of the modulated signal of the lower layer (weak layer). , is hierarchically transmitted to the receiving device 2 . Here, m≦n (same bandwidth when m=n) and α≧1. Also, the modulation scheme for each layer may be BPSK, QPSK, 8PSK, 16QAM, 16APSK, 32APSK, or the like, which may be different or the same among layers. In addition, in this example, concatenated codes of LDPC and BCH, etc. are assumed as an error correction method for each layer, although this is not a limitation.

On the other hand, FIG. 4 schematically shows a transmission spectrum containing interference wave components caused by nonlinear distortion output from the satellite repeater 104 in the transmission system 100 according to the present invention. As shown in FIG. 4, when the satellite transponder 104 has an input/output characteristic with nonlinear distortion, mainly the third-order distortion component of the upper layer with a high signal level becomes an interference wave component, and the frequency of the upper layer becomes It occurs over a bandwidth three times the bandwidth BWa. However, since the band is limited by the transmission filter 1043 of the satellite transponder 104, the actually radiated satellite broadcast signal has a lower layer bandwidth that is almost the same as the channel bandwidth, but the interference wave component causes a unique nonlinearity. Distortion begins to occur.

Therefore, conventionally, a form in which a modulated wave signal compensated in advance by a transmitting apparatus using the inverse characteristic of nonlinear distortion caused by a broadcasting transmission path of satellite broadcasting is generated and transmitted, or a pilot signal transmitted from the transmitting apparatus is used. However, in the transmission system 100 shown in FIG. 1, when the transmitting device 1 and the receiving device 2 are configured as a power division hierarchical transmission system (LDM), the LDM It is necessary to provide a device for compensating or correcting the unique nonlinear distortion, that is, before demodulating the upper and lower layers, it is necessary to correct the distortion of the complex baseband signal for the upper layer.

Therefore, the detailed configurations of the transmitting device 1 and the receiving device 2 according to the present embodiment will be described later. 2 side constructs a modulation frame including a pilot signal for an upper layer that can be corrected, and transmits a modulated wave signal. Then, the receiving device 2 uses the quadrature-demodulated received signal (higher-layer complex baseband signal) or the pilot signal to determine the correction characteristics for the quadrature-demodulated received signal (upper-layer complex baseband signal). Then, distortion correction is performed during LDM demodulation.

There are two embodiments for the distortion correction on the receiving device 2 side. The distortion correction of the first embodiment is a method of obtaining the correction characteristics by using a quadrature-demodulated received signal (LDM complex baseband signal). In the distortion correction of the second embodiment, correction characteristics for a received signal (LDM complex baseband signal) that has been quadrature demodulated using a pilot signal obtained from a received signal that has been quadrature demodulated (complex baseband signal for upper layer) is a method for obtaining

In the transmitting apparatus 1 of the present embodiment, in particular, in the modulation frame for the upper layer of the power division hierarchical transmission system (LDM), LDM transmission A pilot signal for road distortion correction is included.

Hereinafter, the configurations and operations of the transmitting device 1 and the receiving device 2 of this embodiment will be described more specifically.

(Transmitter)
FIG. 5 is a block diagram showing a schematic configuration of a power division hierarchical transmission (LDM) transmission apparatus according to an embodiment of the present invention.

The transmitting apparatus 1 shown in FIG. 5 applies an error correction code to each of two systems of data, ie, upper layer (strong layer) data transmitted at symbol rate m and lower layer (weak layer) data transmitted at symbol rate n. It has a function unit that performs modulation, modulation mapping, and roll-off filtering, and adds the two systems of modulation signals (combination of symbol rate, error correction coding rate, modulation method, roll-off rate) in terms of power. It is configured as a single-carrier power division hierarchical transmission (LDM) transmitter. More specifically, the transmitting apparatus 1 shown in FIG. 5 has, as a basic configuration, a clock generation unit 11, an upper layer transmission line coding unit 12, a lower layer transmission line coding unit 13, a power addition unit 14, and an orthogonal A modulation unit 15 is provided.

The clock generator 11 includes a reference clock generator 111 and a frequency divider 112 .

The reference clock generator 111 generates four times M×N (M is the symbol clock frequency of the upper layer and corresponds to the symbol rate m. N is the symbol clock frequency of the lower layer and corresponds to the symbol rate n. ) is a functional unit that generates a reference clock with a frequency of . And m≦n and M≦N.

The frequency divider 112 is a functional unit that divides the frequency of the reference clock generated by the reference clock generation unit 111 and generates sampling clocks necessary for each unit of the transmission device 1 shown in FIG. It has a portion 112a and a dividing portion 112b.

The frequency divider 112a divides the frequency of the reference clock generated by the reference clock generator 111 by 1/(N×4) to generate a sampling clock of frequency M. FIG.

The frequency divider 112b divides the frequency of the reference clock generated by the reference clock generator 111 by 1/(M×4) to generate a sampling clock of frequency N. FIG.

As described above, in the transmission device 1 shown in FIG. 5, the clock generation unit 11 uses four times M×N as a common reference clock for the upper and lower layers. M and N sampling clocks are generated. However, the clock generator 11 may generate other sampling clocks (for example, 2M and 2N sampling clocks). It can be used for upsampling accompanying the level adjustment unit 141 or the like.

The upper layer transmission line coding unit 12 includes a frame construction unit 120 , an error correction coding unit 121 , a modulation mapping unit 122 and a roll-off filter unit 123 .

Frame construction section 120 inputs data of an upper layer (for example, a strong layer of 2K) for transmission as encoded data of symbol rate m, and applies LDM transmission path distortion to the data of the upper layer used as a main signal. A modulation frame is formed by adding a correction pilot signal to the LDM pilot signal period preceding the data (described later with reference to FIGS. 6 to 8), and output to error correction coding section 121 .

Error correction coding section 121 receives, from frame configuration section 120, a modulated frame of an upper layer (for example, a strong layer of 2K) for transmission as encoded data of symbol rate m, and converts the modulated frame of the upper layer to On the other hand, error correction coding that forms coded data by adding an error correction parity by a block code (for example, a concatenated code of LDPC and BCH) with a predetermined coding rate (for example, coding rate 1/2) for the upper layer It is processed and output to modulation mapping section 122 .

The modulation mapping unit 122 synchronizes with a sampling clock of frequency M corresponding to the symbol rate m, and applies a predetermined digital modulation method (for example, QPSK) to the encoded data of the upper layer obtained from the error correction encoding unit 121. , and mapped onto the complex (IQ) plane, the upper-layer complex baseband signal (a quadrature signal of an in-phase component I and a quadrature-phase component Q, which can be expressed as a signal point on the IQ plane. possible signal point series) and outputs to roll-off filter section 123 .

The roll-off filter unit 123 is configured with a root roll-off filter that is a kind of band-limiting filter having a predetermined roll-off rate (the roll-off rate of the upper layer is a), and the upper-layer filter obtained from the modulation mapping unit 122 is Appropriate upsampling is applied to the complex baseband signal, waveform shaping is performed to remove unnecessary high-frequency components, and the complex baseband for the upper layer is upsampled so that the sampling clocks match between the upper layer and the lower layer. A signal is formed and output to the level adjustment section 141 .

The lower layer transmission line coding unit 13 includes a frame construction unit 130 , an error correction coding unit 131 , a modulation mapping unit 132 and a roll-off filter unit 133 .

Frame configuration section 130 receives data of a lower layer (for example, a weak layer of 4K) for transmission as encoded data of symbol rate n, and generates a modulated frame having the same structure as the modulated frame in frame configuration section 120 described above. However, in the LDM pilot signal period in the preceding stage of the lower layer data used as the main signal, there is no signal without adding the pilot signal for LDM transmission channel distortion correction (that is, Null is inserted) ) to form a modulation frame (described later with reference to FIG. 6) and output to error correction coding section 131 .

The error correction coding unit 131 inputs a modulated frame of a lower layer (for example, a weak layer of 4K) for transmission as encoded data at a symbol rate of n, and converts the modulated frame of the lower layer in advance for the lower layer. A modulation mapping unit that performs error correction coding processing to form coded data by adding an error correction parity by a block code (for example, a concatenated code of LDPC and BCH) with a predetermined coding rate (for example, a coding rate of 7/9). 132.

The modulation mapping unit 132 applies a predetermined digital modulation method (for example, 16APSK) to the encoded data of the lower layer obtained from the error correction encoding unit 131 in synchronization with the sampling clock of frequency N corresponding to the symbol rate n. is mapped onto the constellation of the complex (IQ) plane to generate a lower-layer complex baseband signal that is mapped onto the complex (IQ) plane and output to roll-off filter section 133 .

The roll-off filter unit 133 is configured with a root roll-off filter that is a kind of band-limiting filter having a predetermined roll-off rate (the roll-off rate of the lower layer is set to b). Appropriate upsampling is applied to the complex baseband signal, waveform shaping is performed to remove unnecessary high-frequency components, and the complex baseband for the lower layer is upsampled so that the sampling clocks match between the upper layer and the lower layer. A signal is formed and output to the adder 142 .

Note that in upsampling so as to match the sampling clocks between the upper and lower layers in the roll-off filter section 123 and the roll-off filter section 133, a clock with a frequency of 4 MN, which is the same as the reference clock, is used here as an example. Alternatively, by using a clock twice the lowest common multiple of M and N for upsampling, it is possible to handle the lowest possible frequency.

The power adder 14 includes a level adjuster 141 and an adder 142 .

The level adjustment unit 141 adjusts the average amplitude level of the upper-layer complex baseband signal obtained from the roll-off filter unit 123 by α times the average amplitude level of the lower-layer complex baseband signal. (See FIG. 3 or FIG. 4), and outputs the level-adjusted upper-layer complex baseband signal to the adder 142 .

The adder 142 combines the level-adjusted upper-layer complex baseband signal obtained from the level adjuster 141 (in this example, QPSK and coding rate 1/2) with the lower-layer complex baseband signal obtained from the up-sampling unit 135. A band signal (in this example, 16APSK, coding rate 7/9) is added on the complex plane (synthesizing by adding power of symbols sampled at the same timing) to obtain a modulated wave signal of a single frequency band , a single-symbol-rate hierarchical transmission complex baseband signal is generated and output to the quadrature modulation/D/A conversion unit 151 .

The quadrature modulation unit 15 includes a quadrature modulation/digital/analog (D/A) conversion unit 151 and a bandpass filter (BPF) unit 152 .

The quadrature modulation/D/A conversion unit 151 uses a reference clock with a frequency of 4 MN as a sampling clock, and converts the I-axis signal and the Q-axis signal at 90-degree positions with respect to the hierarchically transmitted complex baseband signal obtained from the addition unit 142 . After addition (quadrature modulation) with a phase difference (time difference), digital/analog (D/A) conversion is performed to generate a hierarchically transmitted modulated wave signal of a single frequency band, which is output to the BPF unit 152 .

The BPF unit 152 applies band-pass filter processing for band limitation to the modulated wave signal obtained from the quadrature modulation/D/A conversion unit 151 in order to extract only the signal near the reference clock with a frequency of 4 MN, and converts the intermediate frequency A modulated wave signal in the (IF) band is generated, set to a level corresponding to the transmission power standardized in the state of the IF band signal, and transmitted. For the modulated wave signal of the IF band, the total transmission power of the upper layer and the lower layer is predetermined in order to transmit to the receiving device 2 via a transmission path including a satellite repeater for 12 GHz band, 21 GHz band satellite broadcasting, etc. Transmit at (normalized) transmit power.

(modulation frame)
FIG. 6 is a diagram showing insertion positions of pilot signals for transmission path distortion correction of LDM transmitted by the power division hierarchical transmission (LDM) transmission apparatus 1 according to one embodiment of the present invention. As described above, frame construction section 120 in upper layer transmission line coding section 12 generates a pilot signal for LDM transmission line distortion correction for upper layer data to be transmitted as encoded data at symbol rate m. A modulation frame added within the LDM pilot signal period in the preceding stage of the data is configured. On the other hand, frame configuration section 130 in lower layer transmission line coding section 13 configures a modulation frame having the same structure as the modulation frame in frame configuration section 120, but the lower layer for transmission as encoded data at symbol rate n. A modulated frame is constructed by inserting Null (no signal) without adding a pilot signal for transmission channel distortion correction of LDM to hierarchical data. In this example, the modulation frame is configured with the "repetition period" shown in FIG. 6 (the "data" area shown in FIG. 6 includes the data area of the main signal and the parity area of the concatenated code). The modulation frame according to this embodiment can also be configured with the same structure as the modulation slot conforming to ISDB-S3, for example. In this case, the frame header (176 bits) provided before the data of the main signal A pilot signal for correcting transmission line distortion of LDM is added in.

In the transmitting apparatus 1 of the present embodiment, power A modulated frame for an upper layer of the division hierarchical transmission system (LDM) contains a pilot signal for correcting transmission line distortion of the LDM.

FIG. 7 is an IQ plan view showing an example of an LDM transmission path distortion correction pilot signal transmitted by the transmitting apparatus 1 of the present embodiment, and FIG. 8 is an IQ plan view showing another example thereof.

FIG. 7 or FIG. 8 shows three types of pilot signals that differ only in amplitude, that is, a reference pilot signal with an amplitude of "1", a double amplitude of "2", and a half amplitude of "2". A pilot signal of "0.5" is shown. A pilot signal for LDM transmission channel distortion correction as illustrated in FIG. 7 or FIG. 8 is periodically inserted only in the modulation frame of the upper layer (strong layer). The signal point arrangement of the pilot signal for LDM transmission channel distortion correction is determined in advance by the transmitter 1 regardless of the modulation scheme (BPSK, QPSK, 8PSK, 16QAM, 16APSK, 32APSK, etc.) used in the upper layer. , the receiver 2 performs reception processing for distortion correction based on the predetermined amplitude and phase of the pilot signal. As described with reference to FIG. 6, it is assumed that there is no signal (no signal) in the lower layer (weak layer) during the period in which the pilot signal is inserted in the upper layer.

(receiving device)
FIG. 9 is a block diagram showing a schematic configuration of a power division hierarchical transmission (LDM) receiving apparatus 2 according to one embodiment of the present invention.

The receiver 2 shown in FIG. 9 receives the satellite broadcast signal through a receiving antenna 106 for receiving the satellite broadcast frequency transmission signal, and inputs the received signal converted to the intermediate frequency (IF) band. Then, the receiving device 2 extracts only the IF signal transmitted by the transmitting device 1 shown in FIG. layer) data and data of a lower layer (weak layer) transmitted at a symbol rate n can be individually received. More specifically, the receiving apparatus 2 shown in FIG. 9 has, as a basic configuration, a clock generation unit 21, a BPF unit 22, a quadrature demodulation/analog/digital (A/D) conversion unit 23, a nonlinear distortion detection unit 24, a nonlinear distortion It comprises a correction unit 25 , an upper layer demodulation/decoding unit 26 , an upper layer retransmission line encoding unit 27 , and a lower layer demodulation/decoding unit 28 .

The clock generator 21 includes a reference clock generator 211 and a frequency divider 212 .

The reference clock generator 211, like the reference clock generator 111 on the side of the transmitting device 1 shown in FIG. , N is the symbol clock frequency of the lower layer and corresponds to the symbol rate n).

The frequency divider 212 divides the frequency of the reference clock generated by the reference clock generation unit 211 in the same manner as the frequency divider 112 on the side of the transmission device 1 shown in FIG. It is a functional unit that generates a sampling clock, and in this example, includes a frequency dividing unit 212a and a frequency dividing unit 212b.

The frequency divider 212a divides the frequency of the reference clock generated by the reference clock generator 211 by 1/(N×4) to generate a sampling clock of frequency M. FIG.

The frequency divider 212b divides the frequency of the reference clock generated by the reference clock generator 211 by 1/(M×4) to generate a sampling clock of frequency N. FIG.

As described above, in the receiving device 2 shown in FIG. 9, the clock generation unit 21 uses four times M×N as a common reference clock for the upper and lower layers. M and N sampling clocks are generated. Furthermore, the frequencies of the reference clocks of the transmitting device 1 shown in FIG. 5 and the receiving device 2 shown in FIG. 9 are made the same. However, the clock generator 21 may generate other sampling clocks (for example, 2M and 2N sampling clocks). , and for upsampling and downsampling associated with the level adjustment unit 272 and the like.

BPF section 22 performs bandpass filtering on the IF signal received via receiving antenna 106, and extracts only the received signal in the desired frequency band from the IF signal transmitted by transmitting apparatus 1 shown in FIG. and outputs to the quadrature demodulation/A/D conversion unit 23 .

The quadrature demodulation/A/D conversion unit 23 quadrature demodulates the received signal obtained from the BPF unit 22 using a reference clock with a frequency of 4MN as a sampling clock, divides it into I-axis data and Q-axis data, and converts it into analog/ By performing digital (A/D) conversion processing, the received signal of the complex baseband signal is obtained and output to the nonlinear distortion detector 24 and the nonlinear distortion corrector 25 .

The nonlinear distortion detector 24 detects the operating point on the nonlinear distortion curve of the input/output characteristics generated in the satellite repeater 104 for the complex baseband signal obtained from the quadrature demodulation/A/D converter 23, and the nonlinear distortion corrector 25. More specifically, although the details will be described later, the nonlinear distortion detector 24 detects in advance the input/output characteristics of the satellite repeater 104 having nonlinear distortion (in this example, the AM-AM characteristics and AM-PM characteristics of the repeater amplifier 1042). However, the input/output characteristics of the reception filter 1041 and the transmission filter 1043 may be included.), and on the input/output characteristics, the orthogonally demodulated reception The average power and peak power of the signal (complex baseband signal) are detected, and each operating point on the input/output characteristics of the satellite repeater 104 is analogized from these two points. At least three types of pilot signals with different amplitudes are detected from the pilot signal period of the received signal, and each operating point on the input/output characteristics of the satellite repeater 104 is detected by analogy from the at least three types of signal levels. and output to the nonlinear distortion corrector 25 .

The nonlinear distortion corrector 25 corrects the distortion of the complex baseband signal obtained from the quadrature demodulator/A/D converter 23 based on each operating point on the input/output characteristics of the satellite repeater 104 obtained from the nonlinear distortion detector 24 . Correction is performed, and the received signal after distortion correction is output to the upper layer demodulation/decoding section 26 and the lower layer demodulation/decoding section 28 . More specifically, the nonlinear distortion correction unit 25 corrects nonlinearity in the input/output characteristics based on each operating point on the input/output characteristics of the satellite repeater 104 obtained from the nonlinear distortion detection unit 24, although the details will be described later. Correction operating points on the linear characteristics corresponding to each operating point on the input/output characteristics are obtained using the linear characteristics assumed to have no distortion, and the quadrature-demodulated received signal (complex baseband signal) is applied to the input. By correcting the amplitude and phase of the quadrature-demodulated received signal (complex baseband signal) so as to have linear characteristics based on each correction operating point when positioned between operating points on the output characteristics, The orthogonally demodulated received signal obtained from the orthogonal demodulation/A/D conversion unit 23 is subjected to distortion correction, and the distortion-corrected received signal is output to the upper layer demodulation/decoding unit 26 and the lower layer demodulation/decoding unit 28 .

The upper layer demodulation/decoding unit 26 is a functional unit that demodulates and decodes the upper layer complex baseband signal from the distortion-corrected received signal, and includes a roll-off filter unit 261 , a demodulation demapping unit 262 , and an error correction decoding unit 263 . Prepare.

The roll-off filter unit 261 is configured with a root roll-off filter that is a kind of band-limiting filter having the same roll-off rate (roll-off rate a in the upper layer) as that on the transmission device 1 side, and is obtained from the nonlinear distortion correction unit 25. Symbols of the received signal after distortion correction are appropriately down-sampled, and waveform shaping is performed to remove unnecessary high-frequency components to generate a waveform-shaped upper-layer complex baseband signal, which is output to demodulation demapping section 262 . do.

The demodulation demapping unit 262 samples the upper layer complex baseband signal obtained from the roll-off filter unit 261 at the symbol rate m using a sampling clock of frequency M, and corresponds to the transmitting apparatus 1 side for the upper layer. Demapping onto the complex plane of a digital modulation method (eg QPSK), comparing with a constellation of ideal signal points, acquiring soft decision data (likelihood value) of bits constituting each symbol, and error correction decoding section 263 output to

Error correction decoding section 263 applies block code (for example, LDPC and BCH concatenated code) is subjected to error correction decoding processing to restore upper layer (strong layer) data, which is output to the outside and to the error correction coding unit 271 .

The upper layer re-transmission line coding unit 27 performs the same processing as the transmission line coding processing in the upper layer transmission line coding unit 12 on the transmitting device 1 side, and performs the upper layer (strong layer) obtained from the error correction decoding unit 263. ) data is channel-encoded again to generate a replica of the complex baseband signal for the upper layer. An adjuster 274 is provided.

The error correction coding unit 271 receives the data of the upper layer (strong layer) obtained from the error correction decoding unit 263, and applies a predetermined coding rate for the upper layer to the data of the upper layer used as the main signal. (For example, coding rate 1/2) block code (for example, LDPC and BCH concatenated code) error correction parity is added to form encoded data, and error correction encoding processing is performed, and the data is output to remodulation mapping section 272 . .

The remodulation mapping unit 272 applies a predetermined digital modulation method (this example QPSK) constellation, mapping is performed on the complex (IQ) plane to generate an upper-layer complex baseband signal, which is output to the roll-off filter unit 273 .

The roll-off filter unit 273 is configured with a root roll-off filter, which is a type of band-limiting filter having a roll-off rate (roll-off rate a of the upper layer), and the upper-layer complex baseband signal obtained from the remodulation mapping unit 272. is appropriately up-sampled to remove unnecessary high-frequency components, and the replica signal of the complex baseband signal for the upper layer is up-sampled so as to match the sampling clocks between the upper layer and the lower layer. is formed and output to the level adjustment section 274 .

The level adjuster 274 cooperates with the level adjuster 282 (to be described later) to adjust the average amplitude level of the replica signal of the upper-layer complex baseband signal obtained from the roll-off filter 273 to the lower-layer complex baseband signal. (see FIG. 3 or FIG. 4), and outputs a replica signal of the upper layer complex baseband signal after the level adjustment to the subtraction unit 283 .

On the other hand, the lower layer demodulation/decoding unit 28 is a functional unit that demodulates and decodes the received signal of the lower layer (weak layer). and an error correction decoding unit 285 .

The roll-off filter unit 281 is configured with a root roll-off filter, which is a type of band-limiting filter having the same roll-off rate (lower layer roll-off rate b) as that on the transmission device 1 side, and is obtained from the nonlinear distortion correction unit 25. Symbols of the received signal after distortion correction are appropriately down-sampled, waveform shaping is performed to remove unnecessary high-frequency components, and a complex baseband signal for the lower layer after waveform shaping is generated and output to level adjustment section 282 . do.

The level adjuster 282 cooperates with the level adjuster 274 described above to reduce the average amplitude level of the upper-layer complex baseband signal for the lower-layer complex baseband signal obtained from the roll-off filter 281 to the lower-layer complex baseband signal. The level is adjusted so that the average amplitude level of the complex baseband signal is multiplied by α (see FIG. 3 or FIG. 4), and the lower-layer complex baseband signal after the level adjustment is output to the subtracting section 283 .

The subtraction unit 283 subtracts the replica signal of the level-adjusted upper-layer complex baseband signal obtained from the level adjustment unit 274 from the level-adjusted lower-layer complex baseband signal obtained from the level adjustment unit 282 . Subtraction on the complex plane (power subtraction for symbols sampled at the same timing) generates a complex baseband signal for the lower layer consisting of only the original lower layer (weak layer) complex baseband signal, and demodulation demapping section H.284 output.

The demodulation demapping unit 284 samples the lower layer complex baseband signal obtained from the subtraction unit 283 at a symbol rate n using a sampling clock of frequency N, and performs digital modulation corresponding to the transmitting apparatus 1 side for the lower layer. Demap on the complex plane of the system (for example, 16ASK), compare with a constellation of ideal signal points, obtain soft decision data (likelihood value) of bits constituting each symbol, and output to error correction decoding section 285 do.

Error correction decoding section 285 applies block code (for example, LDPC and BCH concatenated code) is subjected to error correction decoding processing to restore lower layer (weak layer) data and output to the outside.

In the above-described embodiment, an example in which the upper layer and lower layer symbol rates are m:n has been described, but as the simplest example, m:n=1:1 or 1:2 is preferable. . When m:n=1:1, that is, when the symbol rate of the upper layer is the same as the symbol rate of the lower layer, the basic configuration of the transmitting device 1 and the receiving device 2 is 4MN=4N and M=N. do it. By setting m:n=1:1, it is advantageous that the operating clock is as low as 4N at maximum and that the clock generator 11 can be a simple 1/2 frequency dividing circuit. Similarly, when m:n=1:2, that is, when the symbol rate of the upper layer is half the symbol rate of the lower layer, the basic configuration of the transmitting device 1 and the receiving device 2 is 4MN=4N, It suffices to set M=N/2. By setting m:n=1:2, it is advantageous that the operating clock is as low as 4N at maximum and that the clock generator 11 can be a simple 1/2 frequency dividing circuit. Here, since N is the symbol clock of the lower layer, when a multi-level (5-bit) modulation method such as 32APSK is used as a digital modulation method, the bit rate of the lower layer is 5N, which is higher than 4N. A large clock is required.

However, as a preferred example, m:n=1:4, 3:4, 2:3, etc. can be used instead of m:n=1:1 or 1:2. In the case of these ratios, the least common multiple of 2M and 2N becomes relatively smaller than, for example, m:n=3:5, and the frequency of the 4MN reference clock becomes lower, so that the operation can be stabilized. can. Therefore, the m:n ratio shall be set as a simple integer ratio, in particular m:n = 1:1, 1:2, 1:4, 2:3, 3:4. and preferably m:n=1:1 or 1:2. Then, the reference clock generation unit 111 sets M= The clock generator 11 is configured to generate N reference clocks four times as high as 1, so that the clock generation unit 11 can be configured with a simple frequency dividing circuit, and a highly stable operation can be realized.

Next, the distortion correction of the first and second embodiments in the nonlinear distortion detector 24 and the nonlinear distortion corrector 25 in the receiver 2 will be described more specifically.

(Distortion correction in Example 1)
In the distortion correction of the first embodiment in the receiving device 2, the nonlinear distortion detector 24 detects in advance the input/output characteristics of the satellite repeater 104 having nonlinear distortion (in this example, the AM-AM characteristics and AM-PM characteristics of the repeater amplifier 1042). However, the input/output characteristics of the receive filter 1041 and the transmit filter 1043 may be included.) are held, and on the input/output characteristics, the quadrature-demodulated received signal (complex baseband signal) The average power and peak power are detected, and the most probable input value (normalized input power) is obtained so that the least square error with respect to the input/output characteristics is minimized, two operating points on the input/output characteristics are estimated by analogy, and output to the nonlinear distortion correction unit 25 . The nonlinear distortion correction unit 25 uses linear characteristics assumed to have no nonlinear distortion in the input/output characteristics to obtain two corrected operating points on the linear characteristics corresponding to the two operating points on the input/output characteristics. and when the received signal (complex baseband signal) after quadrature demodulation is located between two operating points on the input/output characteristics, quadrature demodulation is performed so that the characteristics are linear with respect to each correction operating point. By correcting the amplitude and phase of the obtained received signal (complex baseband signal), distortion correction of the quadrature-demodulated received signal obtained from the quadrature demodulator/A/D converter 23 is performed.

FIG. 10 illustrates how the nonlinear distortion detector 24 obtains the correction characteristics using the quadrature-demodulated received signal as the distortion correction of the first embodiment in the receiving device 2 of one embodiment according to the present invention. It is a diagram. In FIG. 10, the solid line is the previously measured nonlinear distortion characteristic curve of the repeater amplifier 1042, and the dotted line is the linear characteristic without nonlinear distortion. As the distortion correction of Example 1 in the receiving device 2 of this embodiment, the nonlinear distortion detector 24 detects the average power and peak power of the received signal that has undergone quadrature demodulation, and holds the respective values from these two points in advance. The input/output characteristics (AM-AM characteristics, AM-PM characteristics) of the repeater amplifier 1042 are fitted to the curves of the nonlinear distortion characteristics so that the minimum error is reduced. The most probable input value (normalized input power) that It is obtained by analogy of the two operating points on the output characteristics. It is preferable to select the average power centering around a few dB lower than 0 dB of the normalized power of the distortion curve, and the peak power centering around 0 dB. Then, since the difference between the average power and the peak power when there is no nonlinear distortion is known, using that constraint condition, two operating points with the smallest least square error as shown in FIG. (“●” and “▲” in the figure). The non-linear distortion correction unit 25 obtains correction values (“◯” and “△” in the drawing) on the linear characteristics for the normalized input power corresponding to the operating points (“●” and “▲” in the drawing). Based on the two operating points (“●” and “▲” shown in the figure) on the input/output characteristics, perform distortion correction that associates the level relationship between the amplitude and phase of the complex baseband signal and the linear characteristics. can be done. Since the level of the received signal is not limited to the two operating points ("●" and "▴" in the drawing), the nonlinear distortion corrector 25 uses these two points as references for the operating points to obtain the complex baseband signal. Distortion correction is performed according to the amplitude level.

(Distortion correction in Example 2)
In the distortion correction of the second embodiment in the receiving device 2, the nonlinear distortion detector 24 detects in advance the input/output characteristics of the satellite repeater 104 having nonlinear distortion (in this example, the AM-AM characteristics and AM-PM characteristics of the repeater amplifier 1042). but may include the input/output characteristics of the receive filter 1041 and the transmit filter 1043.), and on the input/output characteristics, the amplitude from the pilot signal period of the quadrature-demodulated received signal is Pilot signals with at least three different signal levels are detected, and the output values (normalized output power and relative phase shift) of the input/output characteristics of the satellite transponder 104 are most likely to correspond to the at least three signal levels. The input value (normalized input power) is obtained so that the least square error for the input/output characteristics is minimized, and the operating points of at least three types of signal levels on the input/output characteristics are estimated by analogy. Output. The non-linear distortion correction unit 25 corrects at least three points on the linear characteristic corresponding to at least three types of signal levels on the input/output characteristic using the linear characteristic assumed to have no non-linear distortion in the input/output characteristic. Determine the operating point, and when the quadrature-demodulated received signal (complex baseband signal) is located between at least three operating points on the input/output characteristics, make linear characteristics based on each correction operating point. , corrects the amplitude and phase of the quadrature-demodulated received signal (complex baseband signal), thereby correcting the distortion of the quadrature-demodulated received signal obtained from the quadrature demodulator/A/D converter 23 .

FIG. 11 shows, as distortion correction of Example 2 in the receiving device 2 of one embodiment according to the present invention, using a pilot signal obtained from a received signal that has undergone quadrature demodulation (complex baseband signal for upper layer), quadrature demodulation FIG. 10 is a diagram illustrating how correction characteristics are obtained for a received signal (complex baseband signal for upper layer) obtained by applying the received signal; In FIG. 11, the solid line is the previously measured nonlinear distortion characteristic curve of the repeater amplifier 1042, and the dotted line is the linear characteristic when there is no nonlinear distortion. As the distortion correction of Example 2 in the receiving device 2 of the present embodiment, the nonlinear distortion detector 24 detects pilot signals of at least three signal levels with different amplitudes from the pilot signal period of the received signal that has undergone quadrature demodulation, Each operating point on the input/output characteristics of the satellite transponder 104 is inferred from these at least three types of signal levels.

FIG. 11 shows an example of a reference pilot signal of amplitude "1" and three pilot signals of amplitudes "0.5" and "2" corresponding to FIG. 7 or FIG. 8 described above. In other words, these pilot signals have a power difference of 3 dB. As described with reference to FIG. 6, the pilot signal is transmitted only in the upper layer, while the lower layer is in a period of no signal. The curve of the nonlinear distortion characteristic on the input/output characteristics (AM-AM characteristic, AM-PM characteristic) of the repeater amplifier 1042 holding each value in advance from these three points and the fitting so as to reduce the minimum error, that is, the satellite relay The most probable input value (normalized input power) corresponding to the at least three types of signal levels from the output values (normalized output power and relative phase shift) of the input/output characteristics in the device 104 is the least square for the input/output characteristics The minimum error is obtained, and the operating points of at least three types of signal levels on the input/output characteristics are obtained by analogy. The reference pilot signal of amplitude "1" is several dB lower than the normalized power of 0 dB of the distortion curve, and the other two types of pilots are +3 dB (normalized power near 0 dB) and -3 dB. A central choice is preferred. In the illustrated example, the pilot signals are set to three points with a difference of 3 dB. Therefore, while maintaining the intervals, the point where the distortion characteristic curve and the least square error are minimized is searched to obtain the minimum error as shown in FIG. The operating point with the smallest squared error is determined (“●”, “▲” and “■” in the figure). The nonlinear distortion correction unit 25 calculates correction values ("○", "△" in the drawing) on the linear characteristics for the normalized input power corresponding to the operating points ("●", "▲" and "■" in the drawing), respectively. and "□"), the amplitude and phase of the complex baseband signal and the linear Distortion correction can be performed that relates level relationships to characteristics. Since the level of the received signal is not limited to the three operating points ("●", "▴" and "▪" in the figure), the nonlinear distortion corrector 25 uses these three points as references for operating points, Distortion correction is performed according to the amplitude level of the baseband signal.

Then, the transmitting device 1 and the receiving device 2 according to the present invention use a power division hierarchical transmission (LDM) system, and can not only use the same symbol rate in the upper layer and the lower layer, but also use different symbol rates. As a result, it is possible to realize a difference of 10 dB or more in required C/N between the upper layer and the lower layer, and obtain the information of the transmission data of the strong layer even when the signal attenuation of 20 dB or more occurs. By making it possible to stabilize the operation, it becomes possible for the receiving device 2 to obtain the information of the transmission data of both the strong hierarchy and the weak hierarchy in a more robust manner.

In particular, in the transmission device 1, the symbol rate is different (m≠n), that is, the bandwidth is different, and the error correction coding rate, digital modulation method, roll-off rate, and transmission level can all be set independently. For the modulated signal of each layer, based on a single reference clock that is the same between each layer (also the same between the transmitting device 1 side and the receiving device 2 side) regardless of the difference in the symbol rate of each layer. It can be transmitted by one multiplexed single frequency band and one layered transmission modulated wave signal with a single symbol rate.

Moreover, even if there is non-linear distortion due to the satellite transponder 104, the receiver 2 can demodulate the upper and lower layers after correcting the non-linear distortion. When the receiving device 2 demodulates and decodes the received signals of the upper layer (strong layer) and the lower layer (weak layer), the upper layer (symbol rate (m≤n, in the case of the same (lower symbol rate, including low symbol rate), error correction coding rate, digital modulation method, roll-off rate, and difference in transmission level) are demodulated and decoded first, and then based on the highly reliable upper layer demodulation and decoding results Using the retransmission path-encoded replica signal, subtracting the replica signal from the received signal containing the modulated signals of the upper and lower layers and demodulating and decoding the received signal, the data of the lower layer with high reliability can be obtained. become.

Therefore, according to the transmission device 1 and the reception device 2 of the power division hierarchical transmission (LDM) system of the present embodiment, compared with the conventional time division hierarchical transmission system in satellite broadcasting, the power division hierarchical transmission (LDM) system Then, by making the symbol rates between the layers the same or different, the difference in transmission strength between the upper layer (strong layer) and the lower layer (weak layer) (difference in required C/N) can be increased, and even if rainfall or the like causes attenuation of 20 dB or more, it is possible to obtain information on transmission data of a strong hierarchy, thereby stabilizing the operation and increasing the resistance on the receiving device 2 side. It becomes possible to receive data of each layer in a high mode.

As described above, according to the transmission device 1 and the reception device 2 of the power division hierarchical transmission (LDM) system of the present embodiment, the transmission path distortion peculiar to LDM that affects not only the signal transmission of the upper layer but also the signal transmission of the lower layer can be efficiently corrected to improve the transmission performance of both the upper layer and lower layer signals.

Although the above-described one embodiment has been described as a representative example, it will be apparent to those skilled in the art that many modifications and substitutions may be made within the spirit and scope of the invention. For example, in each of the above-described embodiments, the distortion correction of the first embodiment and the distortion correction of the second embodiment are described separately. can be configured to perform both distortion corrections selectively or in combination. Further, the receiving device 2 holds in advance information on the input/output characteristics of the satellite repeater 104 (the input/output characteristics of the repeater amplifier 1042 in the above-described embodiment). Information on the input/output characteristics of the satellite transponder 104 may be transmitted to the receiving device 2 each time or periodically, and may be stored in the receiving device 2 . In the above-described embodiment, the average amplitude level of the modulated signal in the upper layer is α times the average amplitude level of the modulated signal in the lower layer. A configuration may be employed in which a level adjustment section is provided to set the average amplitude level to 1/α times the average amplitude level of the modulated signal of the upper layer. That is, a level adjusting section is provided for adjusting the level so that the average amplitude level of the modulated signal in the upper layer has a predetermined level difference (average amplitude level difference multiplied by α) with respect to the average amplitude level of the modulated signal in the lower layer. Any configuration is acceptable. In the above example, the upper layer is a 2K data signal and the lower layer is a 4K data signal. Anything that is defined as an upper layer and a lower layer may be used. Further, according to the transmitting device 1 and the receiving device 2 according to the present invention, it is possible to select and set various modulation schemes and error correction codes for upper and lower layers. Accordingly, the present invention should not be construed as limited by the above-described embodiments, but only by the appended claims.

According to the present invention, it is possible to improve resistance to attenuation while performing distortion correction for a transmission signal in a hierarchical transmission scheme in which modulated signals of two transmission line coding schemes are combined and transmitted by a single carrier. It is useful for transmission system applications that transmit.

1 transmitting device 2 receiving device 11 clock generation unit 12 upper layer transmission line coding unit 13 lower layer transmission line coding unit 14 power addition unit 15 quadrature modulation unit 21 clock generation unit 22 bandpass filter (BPF) unit 23 orthogonal Demodulator/Analog/Digital (A/D) converter 24 Nonlinear distortion detector 25 Nonlinear distortion corrector 26 Higher layer demodulator/decoder 27 Higher layer retransmission line encoder 28 Lower layer demodulator/decoder 100 Transmission system 101 Power amplifier 102 Transmission antenna of earth station 103 Reception antenna of satellite relay station 104 Satellite repeater 105 Transmission antenna of satellite relay station 106 Reception antenna of reception facility 111 Reference clock generator 112 Frequency divider 112a, 112b Frequency divider 120 upper hierarchy 121 error correction coding unit 122 modulation mapping unit 123 roll-off filter unit 130 lower layer frame construction unit 131 error correction coding unit 132 modulation mapping unit 133 roll-off filter unit 141 level adjustment unit 142 addition unit 151 quadrature modulation/digital/analog (D/A) conversion unit 152 bandpass filter (BPF) unit 211 reference clock generation unit 212 frequency divider 212a, 212b frequency division unit 261 roll-off filter unit 262 demodulation demapping unit 263 error correction decoding Section 271 Error Correction Coding Section 272 Remodulation Mapping Section 273 Roll-off Filter Section 274 Level Adjustment Section 281 Roll-off Filter Section 282 Level Adjustment Section 283 Subtraction Section 284 Demodulation Demapping Section 285 Error Correction Decoding Section 1041 Satellite Transponder Reception Filter 1042 Satellite repeater relay amplifier 1043 Satellite repeater transmission filter

Claims (9)

The modulated signals of the two systems of transmission line coding are defined as the upper layer and the lower layer, respectively, and the modulated signals of the two systems are added at different levels in terms of power and transmitted through the broadcasting transmission line of satellite broadcasting with a single carrier. A transmission device of a power hierarchical transmission system,
Let m be a symbol rate for transmitting the upper layer data, n be a symbol rate for transmitting the lower layer data, M be a symbol clock frequency corresponding to the symbol rate m, and a symbol clock corresponding to the symbol rate n. When the frequency is N, a reference clock generation unit for generating a reference clock of M×N, which is four times common for the upper layer and the lower layer, and for the upper layer and the lower layer using the reference clock as a reference a clock generator having frequency dividers for generating sampling clocks divided by
Upper layer data transmitted at symbol rate m is input, and a predetermined pilot signal for transmission line distortion correction of the power hierarchical transmission system can be stored in a stage preceding the upper layer data. A modulation frame is configured, and for the modulation frame for the upper layer, based on the sampling clock for the upper layer based on the reference clock, at least the error correction coding rate, the modulation method, and the An upper-layer transmission line for generating an upper-layer complex baseband signal based on a predetermined transmission-line coding method designating a waveform shaping roll-off rate, and forming the upper-layer modulated signal sampled with the reference clock. an encoding unit;
inputting lower layer data transmitted at a symbol rate n, constructing a lower layer modulation frame having the same structure as the upper layer modulation frame without storing the pilot signal; For the modulation frame, based on the sampling clock for the lower layer with reference to the reference clock, at least the error correction coding rate, the modulation method, and the roll-off rate of waveform shaping are specified for the lower layer. a lower layer transmission line coding unit that generates a lower layer complex baseband signal based on the transmission line coding method and forms it as the lower layer modulation signal sampled with the reference clock;
either one of the upper layer modulation signal and the lower layer modulation signal so that the average amplitude level of the upper layer modulation signal has a predetermined level difference from the average amplitude level of the lower layer modulation signal, or a power addition unit that adjusts the levels of both, and then adds the power of the modulated signal of the upper layer and the modulated signal of the lower layer to generate a combined complex baseband signal;
a quadrature modulation unit that quadrature modulates the combined complex baseband signal using the reference clock as a sampling clock to generate a modulated wave signal for transmission;
A transmitting device comprising: m:n=1:1, 1:2, 1:4, 2:3, 3:4 as a ratio of the symbol rate m for transmitting the upper layer data and the symbol rate n for transmitting the lower layer data 2. The transmitting device according to claim 1, characterized in that it is one of: As a ratio between the symbol rate m for transmitting the upper layer data and the symbol rate n for transmitting the lower layer data, n is an integer multiple of m,
2. The transmitting apparatus according to claim 1, wherein said reference clock generation unit is configured to generate four times N reference clocks with M=1. A modulated wave signal generated by the transmitting device according to any one of claims 1 to 3 is received via a broadcasting transmission line of satellite broadcasting, and the data of the upper layer and the data of the lower layer are restored. a receiving device,
A reception-side reference clock generating unit for generating a reference clock of four times M×N common to the upper layer and the lower layer, and dividing the reference clock into the upper layer and the lower layer, respectively. a receiver clock generator having a receiver divider for generating a sampling clock;
a quadrature demodulation/analog/digital conversion unit that quadrature demodulates a received signal in a predetermined frequency band in the received modulated wave signal using the reference clock as a sampling clock to obtain a complex baseband signal in digital signal format;
a nonlinear distortion detector for detecting an operating point on a nonlinear distortion curve of input/output characteristics of the complex baseband signal that occurs in the satellite broadcasting transmission path;
a nonlinear distortion correction unit that corrects distortion of the complex baseband signal based on the operating point;
The complex baseband signal after the distortion correction is treated as an upper layer complex baseband signal and input, and subjected to demodulation and decoding processing at a symbol rate m based on the transmission line coding scheme for the upper layer corresponding to the transmitting apparatus side. an upper layer demodulation/decoding unit that restores the upper layer data;
Inputting upper layer data restored by the upper layer demodulation/decoding unit, predetermined transmission path coding designating at least an error correction coding rate, a modulation scheme, and a waveform shaping roll-off rate for the upper layer an upper-layer retransmission line coding unit that regenerates an upper-layer complex baseband signal based on the scheme and forms a replica signal of the upper-layer complex baseband signal;
Inputting the complex baseband signal after the distortion correction, forming a complex baseband signal for the lower layer by performing waveform shaping with the roll-off factor for the lower layer, and forming the complex baseband signal for the upper layer by the retransmission line coding unit for the upper layer. replica of the complex baseband signal for the upper layer so that the average amplitude level of the replica signal of the complex baseband signal for the upper layer becomes the predetermined level difference from the average amplitude level of the complex baseband signal for the lower layer. Either or both of the signal and the complex baseband signal for the lower layer are adjusted in level, and after the level adjustment, the replica signal of the complex baseband signal for the upper layer is subtracted from the complex baseband signal for the lower layer. by subtracting the power from the lower layer to generate a new lower layer complex baseband signal consisting of only the lower layer complex baseband signal, and for the new lower layer complex baseband signal, the lower layer corresponding to the transmitting device side a demodulation/decoding unit for a lower layer that restores the lower layer data by performing demodulation and decoding processing at a symbol rate n based on the channel coding scheme for the lower layer;
A receiving device comprising: The non-linear distortion detector holds input/output characteristics having non-linear distortion of the broadcast transmission path of the satellite broadcast, and on the input/output characteristics, average power and peak power of the quadrature-demodulated complex baseband signal 5. The receiving apparatus according to claim 4, further comprising means for detecting by analogy each operating point on the input/output characteristics of the broadcasting transmission line of said satellite broadcasting from said two points. A pilot signal predetermined for transmission path distortion correction of the power hierarchical transmission system is stored in the modulation frame for the upper layer in the transmitting apparatus, and the modulation frame for the upper layer is synchronized with the modulation frame for the upper layer. the lower layer modulation frame to be transmitted does not store the pilot signal during a signal period for storing the pilot signal in the upper layer modulation frame, and is empty;
The nonlinear distortion detector holds input/output characteristics having nonlinear distortion of the broadcasting transmission path of the satellite broadcast, and on the input/output characteristics, the amplitude differs from the pilot signal period of the quadrature-demodulated received signal. characterized by having means for detecting pilot signals of at least three types of signal levels, and detecting by analogy each operating point on the input/output characteristics of the broadcasting transmission line of the satellite broadcasting from the at least three types of signal levels. 6. The receiving device according to claim 4 or 5, wherein The nonlinear distortion correcting unit corrects linear characteristics assumed to be free of nonlinear distortion in the input/output characteristics based on each operating point on the input/output characteristics of the broadcasting transmission path of the satellite broadcast obtained from the nonlinear distortion detecting unit. to obtain a correction operating point on the linear characteristic corresponding to each operating point on the input/output characteristic, and the complex baseband signal, which is the quadrature-demodulated received signal, is between the operating points on the input/output characteristic. 4, further comprising means for performing distortion correction by correcting the amplitude and phase of the complex baseband signal so as to have linear characteristics with reference to each correction operating point when positioned at 7. The receiver according to any one of 6. m:n=1:1, 1:2, 1:4, 2 as a ratio of the symbol rate m for transmitting the upper layer data and the symbol rate n for transmitting the lower layer data according to the transmitting apparatus 8. The receiver according to any one of claims 4 to 7, characterized in that it is one of: :3 and 3:4. As a ratio between the symbol rate m for transmitting the upper layer data and the symbol rate n for transmitting the lower layer data, n is an integer multiple of m,
8. The receiving apparatus according to any one of claims 4 to 7, wherein the reception-side reference clock generator is configured to generate four times N reference clocks with M=1. .

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