JP2008005259A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver for achieving satisfactory receiving characteristics when such a disturbance wave as adjacent channel disturbance is present and in the case of HSDPA reception, and for reducing current consumption when any disturbance wave as adjacent channel disturbance is absent. <P>SOLUTION: This receiver is provided with filters 11 and 12 for performing the band restriction of an analog base band signal and equalizers 40 and 41 for compensating the band characteristics of the filters 11 and 12. When disturbance adjacent to the reception channel is received, the characteristics of the filters 11 and 12 and the characteristics of equalizers 40 and 41 are varied. Concretely, only when the cutoff frequency of the filters 11 and 12 for removing a disturbance signal is set low or in the case of HSDPA reception, the equalizers 40 and 41 are operated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal, and more particularly to a filter control circuit used in a receiving device that receives a digitally modulated high-frequency signal, such as a portable terminal. It is related to effective technology.

  For example, the GSM system is used mainly in Europe and the like for mobile phones, and the WCDMA system (2 GHz band with transmission and reception bands of 1920-1980 MHz and 2110-2170 MHz, hereinafter referred to as WCDMA2000) has been started as the third generation system in Japan. It was. In the WCDMA system, 3GPP (3rd generation partnership project) formulates transmission / reception standards. As shown in Non-Patent Document 1 and Patent Document 1, a direct conversion system that directly converts a received RF signal into an IQ signal in a baseband is used for a receiving circuit of a GSM or WCDMA mobile phone. Since the direct conversion method does not use an intermediate frequency signal, there is an advantage that an intermediate frequency filter is not necessary. However, the direct conversion method is used for suppressing interference waves such as adjacent channel interference (ACS) and narrow band blocking described in Non-Patent Document 2. Therefore, it is necessary to configure a low-frequency filter (hereinafter referred to as an analog filter) in the baseband.

When an analog filter is used, an equalizer is used to compensate for a phase change caused by the filter. There exists patent document 2 as an example using an equalizer. This compensates for HPF distortion with an equalizer. Non-Patent Document 3 also describes an example of performing phase compensation near the cutoff of an analog filter using an equalizer.
“A Single-Chip Quad-Band Direct-Conversion GSM / GPRS RF Transceiver with Integrated VCOs and Fractional-N Synthesizer”, ISSCC 2002, 14.2. 3GPP standard (Release 7) M.M. E. VAN. VALKENBURG, “Analog Filter Design”, P576 US Pat. No. 5,483,691 Japanese Patent Laid-Open No. 10-70482

  By the way, according to the latest 3GPP receiver standard (Release 7) described above, the bandwidth of one channel of the WCDMA system is 5 MHz and the transmission chip rate is 3.84 MHz. In addition, the reception band is band 1 (2110-2170 MHz), band 2 (1930-1990 MHz), band 3 (1805-1880 MHz), band 4 (2011-2155 MHz), band 5 (869-894 MHz), band 6 ( 875-885 MHz), band 7 (2620-2690 MHz), band 8 (925-960 MHz), and band 9 (1844.9-1879.9 MHz) are allocated. In the 3GPP standard, adjacent channel interference is defined for all these bands. This is an interference wave received in the adjacent channel 5 +/− 3.84 MHz, and needs to be suppressed by the receiver.

  In addition, since band 2, band 3, band 4, band 5, and band 8 overlap with the GSM band, the 3GPP receiver standard includes a narrow band blocking item in which a GSM signal is an interference wave. This assumes an interference wave very close to the desired signal such as an offset frequency of 2.7 MHz from the center of the WCDMA signal. On the other hand, band 1, band 6, band 7, and band 9 are specified for adjacent channel interference with an offset frequency of 5 MHz, but there is no specification for adjacent interference waves such as narrow band blocking.

  Further, the high-speed data communication system HSDPA (High Speed Data Packet Access) is defined in the 3GPP receiver standard. This is a multi-level modulation method using 16QAM or a method for obtaining a data transmission rate up to 14.4 Mbps by reducing the error correction coding rate.

  When configuring a receiving unit corresponding to the 3GPP receiving unit standard, it is necessary to suppress adjacent channel blocking and narrow band blocking with a baseband analog filter in the direct conversion receiving method. In the conventional general receiver, the characteristics of the analog filter are designed so that the maximum jamming signal can be sufficiently suppressed regardless of whether or not the jamming signal is received. For this reason, the phase characteristics near the cutoff frequency of the analog filter are distorted and the EVM (Error Vector Magnetode) is deteriorated. Therefore, it is necessary to compensate the phase with an equalizer. In this case, it is conceivable that the current consumption of the receiving unit increases due to the equalizer.

  Therefore, the present invention solves these problems, and reduces current consumption when there is an interference wave such as adjacent channel interference and when there is no interference wave such as adjacent channel interference while realizing good reception characteristics during HSDPA reception. It is an object of the present invention to provide a receiving device intended to reduce.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  In order to achieve the above object, the present invention comprises a filter that limits the band of an analog baseband signal and an equalizer that compensates for the band characteristics of the filter, and when interference close to the reception channel is received, The characteristic of the filter and the characteristic of the equalizer are variable.

  For example, when no interference wave is received in an adjacent channel or the like, if the cutoff frequency of the analog filter is sufficiently higher than the modulation band, good values of BER and EVM can be obtained without phase compensation by an equalizer. On the other hand, when adjacent channel interference or narrow band blocking is received, if the cutoff of the analog filter is high, the BER or EVM characteristics deteriorate due to the interference wave. For this reason, when there is interference in the adjacent channel, it is desirable to set the cutoff frequency of the analog filter low. However, when the cutoff frequency of the analog filter becomes about the same as the modulation band, the EVM characteristics deteriorate.

  Therefore, in the present invention, when adjacent channel interference or narrow band blocking is received, the equalizer is operated to improve the EVM characteristics. However, it is in the case of HSDPA reception that the degradation of the EVM characteristics leads to a significant degradation of the reception characteristics. Therefore, the equalizer may be operated when adjacent channel interference or narrow band blocking is received during HSDPA reception and the cutoff frequency of the analog filter is set low.

  In this way, when the cutoff frequency of the filter is set low for removing the interference signal, or when the equalizer is operated only when receiving HSDPA, the normal audio signal is received when the interference signal is not received. In this case, the power consumption can be reduced.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, when there is interference close to the reception channel, the cut-off frequency of the filter is set low and the equalizer is operated. According to this configuration, only when a channel with interference close to the reception channel is received, the cutoff frequency of the filter is set low and the equalizer is operated, so that a good channel with interference near the reception channel can be obtained. It is possible to reduce the power consumption at the time of channel reception without reception characteristics and interference close to the reception channel.

  Also, by operating the equalizer only when receiving HSDPA, it is possible to reduce power consumption when HSDPA is not received. In addition, it is possible to reduce power consumption by operating the equalizer only when there is an interference close to the reception channel and when HSDPA is received.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

(First embodiment)
FIG. 1 shows a block diagram of a receiving apparatus according to the first embodiment of the present invention. FIG. 1 shows a receiving apparatus that receives a digitally modulated signal. The receiving apparatus includes an antenna 1, a duplexer (DPX) 2, a low noise amplifier (LNA) 3, mixers 4, 5, and a 90 degree phase. Shifter (π / 2) 6, VCO 7, AGC amplifiers 8 and 9, filters (LPF) 11 and 12, AD converters 13 and 14, FIR filters 15 and 16, equalizers (EQ) 40 and 41, demodulator 27, control The unit 17 is configured to input / output various signals between the constituent circuits.

  The various signals include the control signal 19 of the AGC amplifiers 8 and 9, the control signal 10 of the filters 11 and 12, the control signal 42 of the equalizers 40 and 41, the control signal 25 of the FIR filters 15 and 16, and the control signal 20 of the demodulator 27. And a transmission signal 22 from the transmission system.

  Hereinafter, the operation of the receiving apparatus according to the present embodiment will be described. A radio high frequency signal (hereinafter referred to as RF signal) input from the antenna 1 is demultiplexed from the transmission signal 22 by the duplexer 2 and input to the reception system circuit 56. In the reception system circuit 56, the signal is amplified by the low noise amplifier 3, and is orthogonally detected by the mixers 4 and 5 using the oscillation signals from the VCO 7 and the 90-degree phase shifter 6, thereby providing an I (In-phase) / Q (Quadrature-phase) signal. Is converted to The gain of the I / Q signal is controlled by the AGC amplifiers 8 and 9, respectively, the unnecessary waves are removed by the filters 11 and 12, and then the phase equalization is performed by the equalizers 40 and 41. The output signals of the equalizers 40 and 41 are converted into digital signals by the AD converters 13 and 14. The I / Q digital signal is subjected to unnecessary wave removal and waveform shaping by the FIR filters 15 and 16 and demodulated by the demodulator 27.

  The demodulator 27 calculates a bit error rate (BER) corresponding to the quality of the received signal, EVM, and the like, and detects quality information (CQI) of the received channel reported to the base station. If this calculation and detection result is equal to or less than the reference value compared with the reference value, the control signal 20 is updated and transmitted to the control unit 17, and the characteristics of the filters 11, 12 and the equalizers 40, 41 are controlled from the control unit 17. The control signals 10 and 42 for changing are updated. If the quality of the received signal exceeds the reference value by these updates, the update of the control signals 20, 10, and 42 is stopped, and the values finally obtained by the control signals 20, 10, and 42 are changed to the filters 11, 12, The set values of the equalizers 40 and 41 are used. If the reference value is not reached, the control signals 20, 10, and 42 for obtaining the best received signal quality (BER, EVM, CQI) and the filters 11, 12, and equalizers 40, 41 given by the control signal are set. Set value.

  As another method, the control signals 20, 10, and 42 that can obtain the best received signal quality by changing the control signals 20, 10, and 42 within a predetermined range without setting a reference value and the control thereof. The settings of the filters 11 and 12 and the equalizers 40 and 41 given by signals may be set values.

  In the present embodiment, low-pass filters (LPF) such as Butterworth filters and Chebyshev filters can be used as the filters 11 and 12. The equalizers 40 and 41 can use primary and secondary all-pass filters.

  In the present embodiment, the power consumption can be reduced by turning on the equalizer only when necessary according to the detected quality (BER, EVM, CQI).

  It is also possible to control as follows. When the reception signal is WCDMA band 1, band 6, band 7, or band 9, there is no interference close to the reception channel, so the filter cutoff frequency of the filters 11 and 12 is set high (for example, 2.2 MHz or more). ), The equalizers 40 and 41 are turned off to pass the signal. On the other hand, when receiving band 2, band 3, band 4, band 5, and band 8, there is a possibility that interference close to the reception channel may exist, so the cutoff frequency of the filters 11 and 12 is set low. Then, the equalizers 40 and 41 are operated (for example, about 2.0 MHz). According to this configuration, only when a channel with interference close to the reception channel is received, the cutoff frequencies of the filters 11 and 12 are set low, and the equalizers 40 and 41 are operated, thereby causing interference close to the reception channel. It is possible to reduce the power consumption at the time of channel reception with good reception characteristics of a certain channel and no interference close to the reception channel.

  It is also possible to control as follows. By operating the equalizers 40 and 41 only when receiving HSDPA, it is possible to reduce power consumption when HSDPA is not received. Also, when receiving band 2, band 3, band 4, band 5, band 8, etc., there may be interference close to the receiving channel, so band 2, band 3, band 4, band 5, The power consumption can be reduced by operating the equalizers 40 and 41 only when receiving the band 8 or the like and when receiving the HSDPA.

  According to this configuration, since the characteristics of the filters 11 and 12 are optimized based on the quality of the received signal such as BER and EVM, the signal can always be received with the optimum received signal quality, and only when necessary. By using the equalizers 40 and 41, power consumption can be reduced.

  In the present embodiment, as an example of changing the cutoff frequency of a Butterworth filter or the like as the characteristics of the filters 11 and 12, an effect in the case where there is an interference wave in the received signal and there is no interference wave will be described.

  FIG. 2 is a characteristic diagram of the relationship of the amplitude to the filter frequency, and FIG. 3 is a characteristic diagram of the relationship of the group delay (phase) to the filter frequency. A signal bandwidth 67 indicates a modulation bandwidth of a desired reception signal, and is 1.92 MHz in the baseband band (3.84 MHz in the RF band) in the WCDMA system. The characteristics of the broken lines 68 and 69 are the frequency characteristics of the filters 11 and 12, the broken line 68 is the setting with the highest cutoff frequency, and the broken line 69 is the setting with the lowest cutoff frequency. A solid line 70 represents the interference wave of the adjacent channel. In the WCDMA system, adjacent channel interference exists at 5 MHz +/− 1.92 MHz.

  Considering the case where there is no (or very small) adjacent channel interference in the solid line 70, in order to pass the desired signal band 67 without signal loss, the characteristics of the filters 11 and 12 are represented by the broken line 68 having no loss in the signal band. It may be a characteristic. The characteristics of the filters 11 and 12 can be set to the characteristics indicated by the broken line 68 based on the algorithm shown in FIG. When the desired signal band 67 is passed without loss as shown by the broken line 68 in FIG. 2, the amplitude characteristic of the desired signal is flat as shown by the broken line 68 in FIG. 2, and the phase characteristic is obtained as shown by the broken line 68P in FIG. Since no distortion occurs (group delay characteristics are flat), the demodulator 27 can obtain good EVM and BER characteristics. Accordingly, it is possible to improve the reception sensitivity particularly in the HSDPA method using the 16QAM modulation method or the like and to receive at a high data rate up to 14.4 Mbps.

  Next, consider the case where a strong level of jamming signal 70 is in the adjacent channel. In this case, in order to sufficiently suppress the adjacent channel interference signal (solid line 70), the cut-off frequency of the filters 11 and 12 is lowered and set to a characteristic as shown by a broken line 69. If the filter characteristic indicated by the broken line 69 is used, the interference signal can be sufficiently suppressed, and saturation of the AD converters 13 and 14 shown in FIG. 1 can be prevented. However, since the group delay characteristic (phase characteristic) is not flat in the required band 67 as shown by the broken line 69P in FIG. 3, the group delay characteristic (broken line 71) of the equalizer is added to the band delay 67 as shown in the broken line 72. Thus, a flat group delay characteristic can be realized. As described above, by using the equalizers 40 and 41, the EVM and BER characteristics in the demodulator 27 can be improved, and the minimum reception sensitivity can be improved during normal call or HSDPA reception.

  FIG. 4 shows the result of simulating the effect when the equalizer is used. In the simulation, a signal is inputted from the input of the AGC amplifier 8 in the block diagram shown in FIG. 1, and the phase characteristic with respect to the frequency (freq) of the signal obtained from the output of the equalizer 40 is simulated. FIG. 4A shows the phase characteristic LPF phase response when the equalizer is not used and FIG. 4B shows the phase characteristic LPF phase response when the equalizer is used. It can be seen that by using the equalizer, a value close to a reference phase (Reference phase response) without phase distortion can be obtained.

(Second Embodiment)
FIG. 5 shows a block diagram of a receiving apparatus according to the second embodiment of the present invention. FIG. 5 is obtained by adding equalizers 43 and 44 operating in the digital signal domain in place of the equalizers 40 and 41 operating in the analog signal domain of the first embodiment. The operation of the receiving apparatus of this embodiment is the same as that of the first embodiment, and the equalizers 43 and 44 are operated instead of the equalizers 40 and 41. The characteristics of the equalizers 43 and 44 are changed by a control signal 45.

  According to the present embodiment, as in the first embodiment, the characteristics of the filters 11 and 12 are optimized based on the quality of the received signal such as BER and EVM. Therefore, the signal always has the optimum received signal quality. Can be received, and power consumption can be reduced by using the equalizers 43 and 44 only when necessary.

(Third embodiment)
FIG. 6 is a block diagram of a transmission / reception apparatus according to the third embodiment of the present invention. FIG. 6 shows a transmission / reception apparatus when used in a WCDMA mobile phone system defined by 3GPP. This transmission / reception apparatus includes an antenna 1, a duplexer 2, a reception system circuit 56, a control unit 17, and baseband signal processing. Section 58, transmission system circuit 59, PA 61, and the like. The configuration of the first and second embodiments is used for the reception system circuit 56.

  In the operation of the transmission / reception apparatus according to the present embodiment, the reception signal received by the antenna 1 is demultiplexed from the transmission signal 22 by the duplexer 2, and the reception system circuit 56 shown in the first and second embodiments. Is input. The output of the reception system circuit 56 is input to the baseband signal processing unit 58. On the other hand, transmission data output from the baseband signal processing unit 58 is input to the transmission system circuit 59. The output of the transmission system circuit 59 is transmitted via the PA 61, the duplexer 2, and the antenna 1. In the present embodiment, it is obvious that the same effects as those described in the first and second embodiments can be obtained.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention relates to a receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal, and more particularly to a filter control circuit used in a receiving device that receives a digitally modulated high-frequency signal, such as a portable terminal. Is available.

It is a block diagram which shows the receiver of 1st Embodiment in this invention. In the first embodiment of the present invention, it is a characteristic diagram showing the relationship of the amplitude with respect to the frequency of the filter. In the first embodiment of the present invention, it is a characteristic diagram showing the relationship of the group delay (phase) with respect to the frequency of the filter. In 1st Embodiment in this invention, it is a characteristic view which shows the result of having simulated the effect of the case of using an equalizer (b) with respect to the case of not using an equalizer (a). It is a block diagram which shows the receiver of 2nd Embodiment in this invention. It is a block diagram which shows the transmission / reception apparatus of 3rd Embodiment in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Splitter, 3 ... Low noise amplifier, 4, 5 ... Mixer, 6 ... 90 degree phase shifter, 7 ... VCO, 8, 9 ... AGC amplifier 10, 19, 20, 25, 42, 45 ... Control signal 11,12 ... Filter, 13,14 ... AD converter, 15,16 ... FIR filter, 17 ... Control unit, 22 ... Transmission signal, 27 ... Demodulation unit, 40,41,43,44 ... Equalizer , 56... Reception system circuit, 58... Baseband signal processing unit, 59... Transmission system circuit, 61.

Claims (6)

A receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal,
A filter that limits the band of the analog baseband signal and an equalizer that compensates for the band characteristics of the filter. When interference close to the reception channel is received, the characteristics of the filter and the characteristics of the equalizer are variable. And a receiving device. A receiving device that receives a high-frequency signal used in a communication or broadcasting system and converts the frequency into a baseband signal,
A filter that limits a band of the analog baseband signal; and an equalizer that compensates for a band characteristic of the filter. When interference close to a reception channel is received, the characteristic of the filter is varied, and the equalizer is A receiving device that is turned on. The receiving apparatus according to claim 1 or 2,
A receiving apparatus using a low-pass filter as the filter and lowering a cutoff frequency of the low-pass filter when interference close to a reception channel is received. A receiving device that receives a high-frequency signal of a WCDMA mobile phone system defined by 3GPP and converts the frequency into a baseband signal,
A filter that limits the band of the analog baseband signal and an equalizer that compensates for the band characteristic of the filter are provided. Band 2 (1930 to 1990 MHz), Band 3 (1805 to 1880 MHz), Band 4 (2011 to 2155 MHz), Band 5 (869-894 MHz) and band 8 (925-960 MHz), when receiving a band in which interference close to the reception channel is specified, the bandwidth of the filter is set narrow, and the equalizer is used for the filter. A receiving apparatus that compensates for passband characteristics. A receiving device that receives a high-frequency signal of a WCDMA mobile phone system defined by 3GPP and converts the frequency into a baseband signal,
A receiving apparatus characterized in that the equalizer is turned on only when receiving HSDPA. The receiving apparatus according to any one of claims 1 to 5,
A receiving apparatus using a CDMA system as a communication system.

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