JP2000165339A - Both polarized wave transmission system using transmission lo synchronization system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a both polarized wave transmission system by using a digital demodulator and an XPIC of a quasi-synchronization detection system employing a transmission LO synchronization system. SOLUTION: Two orthogonal polarized wave signals are transmitted with the same frequency by synchronizing local oscillators, and a mixer 10 and a local oscillator 11 receiving the signals apply quasi-synchronization detection to the signals. Each signal that is quasi-synchronization-detected is given to an A/D converter 12, where the signal is converted into a digital signal, and the signal is demodulated by a demodulation circuit 14 that outputs a demodulated signal at a double modulation speed. The demodulated signal is given to an XPIC 19, where interference between different polarized waves is compensated on the basis of the correlation between the error signal obtained from the demodulated signal of its own polarized wave and the demodulation signal of a different polarized wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dual polarization transmission system, and more particularly to a dual polarization transmission system using a transmission LO (local oscillator) synchronization system.

[0002]

2. Description of the Related Art In a digital microwave communication apparatus, signals are transmitted using two orthogonal polarization planes of a radio wave, a vertical polarization (V) and a horizontal polarization (H), in order to increase the frequency use efficiency. A polarization transmission system is used. In this system, when the same frequency is used for V and H (the carrier frequency is the same), if there is a deviation in the orthogonality of the plane of polarization, the signal on the orthogonal side (different polarization) at the RF stage also becomes self-polarized. It becomes an interference component and causes deterioration of signal transmission quality.
In particular, in the case of the multi-level modulation method, this effect cannot be ignored, so that it is necessary to prepare an automatic equalizer on the receiving side to remove interference components.

The equalizer is used as a cross polarization interference compensator (XPI).
C: Cross Polarization Inte
Rancence Canceller).

FIG. 8 is a block diagram showing a configuration example of the XPIC. 7, the basic configuration of the XPIC is a five-stage delay circuit 61 for delaying an input signal, a multiplier 62 for multiplying the output of each delay circuit 61 by each of tap coefficients C1 to C5, and an output of each multiplier 62. , And a tap coefficient control circuit (TAP CONT) 64. In the case of the quadrature modulation method, a P-channel and a Q-channel actually have a two-dimensional configuration of a quadrature component and an in-phase component, respectively.
In order to simplify the explanation, FIG. 6 shows a single channel XPIC.
Is shown in a one-dimensional configuration with only in-phase components with 5 taps.

[0005] The tap coefficient control circuit 64 includes an error signal obtained from a self-polarized wave demodulator input from a terminal 102,
Each tap coefficient (C1 to C5) is generated by correlating with the demodulated signal of the different polarization input from the terminal 101. The tap coefficient corresponds to the impulse response of the inverse characteristic of the cross-polarization interference component, and the addition result of the output of each tap output from the terminal 103 corresponds to the interference component from the different polarization. By adding the self-polarized demodulated signal to the adder 63, cross-polarization interference is compensated. Note that the XPIC has a plurality of taps in order to cope with a case where the interference wave component has a frequency characteristic.

By the way, in order to be able to compensate for interference between different polarizations on the receiving side, a self-polarization demodulation device and a self-polarization signal of BB (baseband) and a different signal input to XPIC are used. The phase relationship with the signal on the polarization side needs to match the phase relationship between the self-polarization and the other polarization at the stage of interference RF. In order to satisfy this condition, two methods are used for setting the LO (Local Oscillator, Local Oscillator) frequency of the self-polarized wave and the cross-polarized wave.

One is a transmission LO synchronization method shown in FIG. 9, and the other is a reception LO synchronization method shown in FIG.

FIG. 9 is a block diagram showing a configuration of a transmission / reception system of the dual polarization transmission system using the transmission LO synchronization system. In the figure, V / H signals are input from terminals 1 and 2 to modulation devices 41 and 41 ', respectively. Modulation devices 41, 4
The IF output 1 ′ becomes an RF signal at the transmitters 42 and 42 ′ and is radiated from the transmission antennas 43 and 43 ′. At this time, the LOs of the modulators 41, 41 'and the transmitters 42, 42' are synchronized between V / H by using the common local oscillators 40, 44.

Next, the receiving side will be described. When the orthogonality of the polarization plane is maintained, each receiving antenna 4
At 5, 45 ', only the signal of the own polarization is received, but when the orthogonality is shifted, the signal of the other polarization is also received and becomes an interference component. The signals received by the receiving antennas 45 and 45 'are converted into IF signals by the receivers 47 and 47', respectively, and input to the demodulators 48 and 48 '. The LOs 46 and 46 'of the receivers 47 and 47' are independent between V / H and are asynchronous.

When the LO 51 synchronizes with the carrier frequency, the eye of the self-polarization side demodulator 48 opens at the output of the demodulator 50 and is converted into a digital signal by the A / D converter 52.
In the demodulation device 48 'on the different polarization side, the output of the demodulator 50' is also input to the self-polarization demodulation device 48 and converted into a digital signal by the same clock as the self-polarization A / D converter 52.

The output of the A / D converter 52 is an XPI
The signal is input to C55, and the inverse characteristic of the interference component in space is output. The adder 54 adds the XPIC output signal to the self-polarized digital signal, thereby removing interference components from the different polarized waves. Then, the intersymbol interference on the self-polarization side is removed by the equalizer 56, and the frequency of the LO 51 is controlled from the output thereof. Note that the demodulation device 48 'on the different polarization side operates in the same manner as the demodulation device 48 on the own polarization side described above, and a detailed description thereof will be omitted. In this way, the V / H demodulated signal is output from terminals 3 and 4, respectively.

In the transmission LO synchronization method, as shown in FIG. 9, the LOs 40, 40 'and the 44, 44' of the modulators 41, 41 'and the transmitters 42, 42' are made common or synchronized. I have. Thereby, the interference component from the different polarization in the space is synchronized with the signal of the own polarization. Receiver 47, 4
Although the LOs 46 and 46 'of the 7' are independent, when the carrier synchronization is established in the respective demodulators 50 and 50 ', the frequency difference between the LOs of the receivers 47 and 47' becomes irrelevant. A / D converter 52 ′ of different polarization with carrier wave synchronization established
Is input to the self-polarization demodulator 48, and the signal sampled by the self-polarization clock and the A /
The phase relationship with the output signal of the D converter 52 is the same as the phase relationship between the interference component in space and the self-polarized signal. Therefore, it is possible to obtain an interference component between different polarizations from the two BB signals.

FIG. 10 is a block diagram showing a configuration of a transmission / reception system of the dual polarization transmission system using the reception LO synchronization system.
In the figure, V / H signals are input from terminals 1 and 2 to modulation devices 41 and 41 ', respectively. Modulation devices 41, 4
The IF output 1 ′ becomes an RF signal in the transmitters 42 and 42 ′ and is radiated from the transmission antennas 43 and 43 ′. At this time, the LO4 of the modulators 41 and 41 'and the transmitters 42 and 42'
0, 40 'and 44, 44' are each asynchronous between V / H.

On the other hand, when the orthogonality of the plane of polarization is maintained on the receiving side, each of the receiving antennas 45 and 45 'receives only the signal of the self-polarized wave. The signal on the wave side is also received and becomes an interference component. The received signals are converted into IF signals at the receivers 47 and 47 'and input to the demodulators 48 and 48'. At this time, the receiver 47,
The LO 46 at 47 'is synchronized between V / H.

In the demodulator 48 on the self-polarization side, the LO
When 51 is synchronized with the carrier frequency, the eye opens at the output of the demodulator 50 and is converted into a digital signal by the A / D converter 52. The output of the receiver 47 'is also input to the self-polarized wave demodulator 48, demodulated by the demodulator 53 at the carrier frequency of the self-polarized wave, and the A / D converter 52 converts the digital signal with the same clock as the self-polarized wave. Is converted to And the A / D converter 5
The output of 2 is input to the XPIC 55, and the inverse characteristic of the interference component in space is output. This X
By adding the PIC output signal by the adder 54,
Interference components from different polarizations are removed. The intersymbol interference on the self-polarization side is removed by the equalizer 56, and the output of the equalizer 56 controls the frequency of the LO 51. V / H demodulated signals are output from terminals 3 and 4, respectively. The demodulation device 4 on the different polarization side
The operation of 8 'is the same as the operation described above, and the description is omitted.

In the reception LO synchronization method, the transmission side LO4
Since 0, 40 'and 44, 44' are asynchronous, the interference component in space is also shifted from the self-polarized signal by the difference of the transmission LO frequency. Assuming that the LOs 46 of the receivers 47 and 47 'are common or synchronous, the frequency difference between the IF signal of the self-polarization and the IF signal of the different polarization is the frequency difference of the transmission LO. Further, the frequency when the IF signal of the different polarization is converted into the BB signal at the carrier frequency of the own polarization is also the frequency difference of the transmission LO. Therefore, the self-polarized signal with carrier synchronization established and the different-polarized IF signal are separated by BB at the regenerated carrier frequency of self-polarization.
The phase relationship with the dropped signal matches the phase relationship between the self-polarized signal and the different-polarized signal in space. Therefore, also in this case, it is possible to obtain an interference component between different polarizations from the two BB signals.

In either system, the transmitters 42, 4
The above-described phase relationship holds even when considered at the stage of the IF signal where 2 ′ and the receivers 43 and 43 ′ are omitted. Therefore, I
Only the F signal will be described.

In the receiving LO synchronization method, there is no need to synchronize the LO on the transmitting side, so that there is an advantage that the circuit configuration on the transmitting side is simplified. However, on the contrary, the original different polarization side for demodulating a signal is used. Since a demodulator for estimating cross-polarization interference is required in the demodulator for self-polarization separately from the demodulator of the above, there is a demerit that the circuit scale on the receiving side increases.

On the other hand, in the transmission LO synchronization system, the demodulator only needs to demodulate the original signal, so that the configuration on the reception side is simple, but the LO synchronization circuit is required on the transmission side, and the circuit configuration becomes complicated. In addition to the above, there is a problem that a procedure for preventing the influence on the different polarization side during maintenance on the transmission side is complicated.

As described above, each of the two systems has advantages and disadvantages, and is used properly according to the conditions required for each system.

The demodulators 50, 50 ', 53,
The XPIC method has been described on the assumption that 53 'is constituted by an analog circuit and is a synchronous detection method.

However, in recent years, a quasi-synchronous detection system in which a demodulator is configured by a digital circuit and a carrier frequency deviation in an analog unit is compensated by a digital circuit has been realized.

FIG. 11 shows the configuration of a quasi-synchronous detection type demodulator.

In FIG. 11, the input IF signal of the carrier frequency fc demodulator input from the terminal 6 is the output signal of the LO 11 having the frequency fc 'which is close to but not the same as the carrier frequency fc after passing through the bandpass filter 23. And the multiplier 10, 1
By orthogonally multiplying by 0 ', the signal is converted into a BB signal in which the phase rotation of a slight frequency (fc-fc') remains. The BB signal is converted into a digital signal by the A / D converters 12 and 12 ', and then input to the demodulator 22.
The demodulator 22 gives the input BB signal a rotation in a direction opposite to that of the input BB signal. As a result, the phase rotation of the BB signal is eliminated, and carrier synchronization is established.

In a conventional synchronous detection type demodulator, the analog LO oscillator is a VCO, which requires manual adjustment. Further, there is a problem such as temperature compensation of the oscillating frequency in order to secure the carrier wave synchronizing frequency range, and it has been difficult to maintain constant characteristics.

On the other hand, the quasi-coherent detection type demodulator has the effect of solving these problems of the conventional demodulation device.

[0027]

In the conventional transmission LO-synchronous XPIC described above, the analog BB signal on the different polarization side in a state where the carrier is synchronized (the eye is open) is reproduced by its own polarization. It is necessary to sample with a clock.

However, in a quasi-synchronous detection type demodulator,
Since the carrier wave is not synchronized at the stage of the analog BB signal, an XPIC of the transmission LO synchronization method cannot be configured.

An object of the present invention is to configure a transmission LO synchronous XPIC using a quasi-synchronous detection type demodulator.

[0030]

In order to solve the above-mentioned problem, a dual-polarization transmission system using a transmission LO synchronization system of the present invention synchronizes a local oscillator with two orthogonal polarization signals at the same frequency. Means for transmitting and receiving, means for receiving the transmitted signals and quasi-synchronous detection, means for converting the quasi-synchronous detected signals into digital signals and demodulating each, and Means for compensating interference between different polarizations based on a correlation between an error signal obtained from the demodulation signal on the own polarization side and a demodulation signal on the different polarization side.

[0031]

(First Embodiment of the Invention) A first embodiment of the demodulation device of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a demodulator having a cross-polarization interference compensator of a transmission LO synchronization system according to an embodiment of the first invention.

FIG. 2 shows demodulators on the own polarization side and the different polarization side because signals are exchanged between different polarizations. However, signals between different polarizations are actually bidirectional, but are completely symmetrical, so only one direction from the different polarization to the own polarization is shown. In the case of the quadrature modulation system, a mixer for converting an IF signal to a BB signal and an A / D converter for converting an analog signal to a digital signal are provided for each of the I channel and the Q channel. Shall be represented.

The self-polarized IF signal input from the terminal 1 is multiplied by the output signal of the receiving LO 11 by the mixer 10, converted into a BB signal, and subjected to quasi-synchronous detection.

However, at this stage, since the frequency of the LO 11 on the receiving side is asynchronous with the frequency of the LO on the transmitting side, the carrier is still in an asynchronous state. Therefore, the eyes are not open.

The BB signal is supplied to an A / D converter (A / D) 1
2, the modulation speed (fs) supplied from the voltage controlled oscillator (VCO) 13 is 2n times (n = 1, 2, 3,...)
) Is converted into a digital signal by a sampling clock having a frequency (2 nfs), and a complex multiplication circuit (COMP M
ULTI) and a demodulation circuit (DEM) 14 composed of a numerically controlled oscillator (NCO).

FIG. 2 is a block diagram of the demodulation circuit 14. In the figure, a demodulation circuit 14 receives an output from the A / D converter 12 and passes a signal having a speed of 2 fs (ROLL-OFF FILTE).
R) 31 and carrier A from the control circuit (CONT) 18
Carrier loop filter (CARRL) for inputting PC signal
PF) 34, NCO 33, and complex multiplication circuit (COMP
MULTI) 32.

The demodulation circuit 14 multiplies the sine wave represented by the digital signal generated by the NCO 33 in accordance with the carrier APC signal supplied from the control circuit 18 to remove the remaining phase rotation, thereby achieving carrier synchronization. Is established. The speed of the output signal of the demodulation circuit 14 is 2 fs, which is the same as the output of the roll-off filter 31.

A voltage controlled oscillator (VCO) 13 for generating a sampling clock for the A / D converter 12 is controlled by a clock recovery circuit 15 for generating clock phase information from an output signal of the demodulation circuit 14.

After the clock phase information is extracted, the output of the demodulation circuit 14 is decimated in half and the speed is fs, resulting in only the opening of the eye. demodulation circuit 1 with fs speed
The output signal of No. 4 is added to the output of the XPIC 19 which is the inverse characteristic of the interference component from the different polarization side, thereby compensating for the interference component between the different polarizations contained therein. Further, the equalizer 17 compensates for waveform distortion of the self-polarization due to fading.
And the final demodulated signal is output to the terminal 3.

The equalizer 17 is used for a communication path in which interference occurs as the object of the present invention and for compensating for cross-polarization interference. For this reason, the demodulator of the present invention can be configured without the equalizer 17 when the occurrence of interference is small.

The XPIC 19 receives the output of the demodulation circuit on the different polarization side at a speed of 2 fs as an input, and correlates the error signal supplied from the control circuit 18 on the own polarization side with the signal on the different polarization side. Thus, an inverted replica of the interference component from the different polarization side at the speed of fs is generated.

The demodulation device on the different polarization side composed of the input terminal 2 to the output terminal 4 has exactly the same configuration, and the description is omitted.

Although not shown in the figure, the modulation device corresponding to the present demodulation device uses the transmission LO synchronization system, so that the LO on the self-polarization side and the LO on the different polarization side are common. Alternatively, it is assumed that the LO on the different polarization side is synchronized with the LO on the own polarization side. It is assumed that clocks input to the respective modulation devices are synchronized.

Further, the main configuration of the present demodulator will be specifically described below with reference to FIGS.

A modulated wave (IF) having a carrier frequency fc and a modulation speed fs is multiplied by an LO signal having a frequency fc ',
It becomes a BB signal of frequency fc-fc '. This BB signal has a frequency of 2 nf synchronized with the modulation speed of the BB signal which is an output signal from the VCO 13 in the A / D converter 12.
It is converted into a digital signal by a sampling clock of s (n = 1, 2, 3,...).

In the demodulation circuit 14, a digital carrier APC (Automatic Phase Control) corresponding to the carrier frequency shift outputted from the control circuit 18 is provided.
rol) signal is converted to a phase amount and then input to the carrier loop filter 34. The output of the carrier loop filter 34 is input to the NCO 33, and a sine wave represented by a digital signal corresponding to the phase is generated.

The complex multiplying circuit 32 uses the sine wave and A / D
Multiplication with the output of the converter 12 is performed. By performing the multiplication, a rotationally symmetric transformation is performed, and by rotating the input signal of the demodulation circuit 14 in a direction opposite to the phase rotation direction, the phase rotation of the output signal of the demodulation circuit 14 is removed. That is,
Carrier synchronization is established. The frequency of the sine wave becomes fc−fc ′ when carrier synchronization is established.

In the case of the orthogonal transform method, the output of the A / D converter 12 is for two channels, and the corresponding sine waves are also two waves of a sin wave and a cos wave. For this reason, since each is represented by a real part and an imaginary part of a complex number, the demodulation circuit 1
Reference numeral 4 denotes a complex multiplier.

The output signal of the demodulation circuit 14 has a speed of 2 fs. The self-polarized clock recovery circuit 15 and the thinning circuit 20
And the XPIC 19 'on the different polarization side.

The clock recovery circuit 15 detects the phase difference between the BB signal in the A / D converter 12 and the sampling clock from the output signal of the demodulation circuit 14 at a speed of 2 fs, and controls the VCO 13 so that the phase difference becomes zero. Control. Thereby, the phase of the sampling clock of the A / D converter 12 is synchronized with the eye opening and the zero-cross portion of the BB signal.

A method for extracting clock phase information from a signal sampled at twice the modulation speed is described in, for example, "Development of Digital Demodulation LSI for Satellite Communication", IEICE Technical Report SAT 90-48 (1990). Details are provided.

The decimation circuit (DECIM) 20 does not need a signal of 2 fs for the eye opening of the BB signal, and therefore performs decimation to obtain a signal of fs corresponding to the eye opening of the BB signal. It should be noted that phase information for performing the thinning can be obtained from the clock recovery circuit 15, so that phase uncertainty does not occur at the time of thinning.

As a configuration of the thinning circuit 20, for example,
It can be easily configured using flip-flops. That is, the output signal (2fs) of the demodulation circuit 14 is input to the data terminal of the flip-flop, and the signal of fs is input to the clock terminal of the flip-flop, so that the output of the signal is f.
s signal can be obtained.

The signal on the self-polarization side having the speed fs is added to the output of the XPIC 19 at the same speed fs, and the interference component from the different polarization is removed. If you use an adder here,
The output of the XPIC 19 has the inverse characteristic of the interference component from the different polarization. When the subtracter is used, the output of the XPIC 19 becomes the interference component itself from the different polarization.

FIG. 3 is a block diagram showing the configuration of the XPIC 19.

In this figure, the XPIC 19 comprises a tap control circuit 64 and a transversal equalizer 60. The difference from the conventional XPIC shown in FIG. 8 is that each output of the delay circuit 61 of each tap is input to each multiplier 62 via the delay circuit 65.

The output signal of the demodulation circuit 14 ′ on the different polarization side is input and correlated with the error signal output from the control circuit 18 on the own polarization side, whereby interference components from the different polarization side are removed. Output.

Here, the input signal speed of the XPIC 19 is f
If s, the equalization characteristics of the XPIC will be degraded due to the phase difference between the signals on the own polarization side and the different polarization side. In the present invention,
In order to prevent this characteristic deterioration, a 2 fs signal is input. This is called fractional spacing (fractiona
l spacing).

In a synchronous detection type demodulation device constituted by a conventional analog circuit, BB before A / D conversion on the different polarization side is used.
The signal was passed, and this was sampled by the clock on the self-polarization side. However, in the quasi-synchronous detection composed of a digital circuit, A / D in which carrier synchronization has not yet been established
Since the BB signal before the conversion cannot be used, the digital signal after sampling with the clock on the different polarization side and synchronizing with the carrier has to be used. In this case, since the clocks are synchronized between the polarizations, the frequencies match, but the optimal phase on the different polarization side is not necessarily the optimal phase of the XPIC input signal on the own polarization side. However, in the present invention, in consideration of the phase difference with the self-polarization side, the XPI
The input signal speed of C is 2 fs.

As the self-polarized wave equalizer 17, a linear equalizer such as a transversal type equalizer or a decision feedback type equalizer is used.

The equalizer 17 correlates the error signal output from the self-polarization control circuit (same as the error signal output to the XPIC) with the self-polarization signal to obtain the self-polarization signal. An inverse characteristic of the intersymbol interference, which is a cause of deterioration of the polarization frequency characteristic, is generated and given to the self-polarized demodulated signal, thereby removing the intersymbol interference in the demodulated signal. The signal after the equalization becomes an output of the demodulation device and an input signal of the control circuit 18.

The control circuit 18 outputs an error signal corresponding to the difference between the ideal signal point position and the received signal, and a carrier APC signal to the demodulator 14.

The operation of each section of the demodulation device has been described above, but the same applies to the demodulation circuit on the different polarization side.

(Second Embodiment) As described above, in the first embodiment of the present invention, when there is a phase difference between the signal on the self-polarization side and the signal on the different polarization side, deterioration of the XPIC characteristics is prevented. To prevent this, the speed of the input signal of the XPIC was set to 2 fs.

However, even if the configuration shown in FIG. 1 is adopted, if there is a deviation between the phase of the clock signal of the self-polarization side demodulation circuit 14 and the phase of the clock signal of the different polarization side demodulation circuit 14 ', the phase difference As a result, the XPIC deteriorates.

The cause of the phase difference between the clock signal of the self-polarized wave and that of the differently-polarized wave is, for example, the case where fading occurs on only one side of the polarization or the length of the IF connection cable length between the self-polarized wave and the differently polarized wave. It is considered that a phase difference occurs due to a difference or the like. In the former case, the probability of fading occurring on only one side is very small, so there is almost no problem.

However, the latter can be solved by adjusting the cable length and the connector type for both polarized waves so that no phase difference occurs between the self-polarized wave and the different polarized wave when the demodulator is installed. And had problems with cost.

The second embodiment of the present invention provides a configuration in which self-polarization and different polarization delay absorbing means are provided in the configuration of FIG. 1 in order to solve the above problem.

FIG. 4 is a block diagram showing a demodulator according to the second embodiment of the present invention. This drawing differs from FIG. 1 in that a delay difference absorber (DADE) 71 (71 ′) is added to the output of the demodulation circuit 14 (14 ′).

The delay difference absorber 71 can be composed of, for example, a memory which is written at the output of the demodulation circuit 14 ′ of the different polarization and is read at the output of the demodulation circuit 14 of the own polarization. With such a configuration, it is possible to absorb the phase difference between the clock signal of the self-polarization and the clock signal of the different polarization.

As a result, it is possible to prevent a phase difference between the self-polarized wave and the different polarization without having to perform a special operation such as matching the IF cable or the connector of the demodulator between the self-polarization and the different polarization. This has the effect of facilitating installation work and maintenance.

(Third Embodiment) As described above, in the first embodiment of the present invention, when there is a phase difference between the signal on the self-polarization side and the signal on the different polarization side, deterioration of the XPIC characteristics is prevented. To prevent this, the speed of the input signal of the XPIC was set to 2 fs.

However, when the phase difference between the signal of the self-polarized wave and the signal of the different polarized wave is within a certain range, the input signal speed may be set to fs since the characteristics of the XPIC cannot be deteriorated. Also, the output of the XPIC is fs regardless of the speed of the input signal because only the signal corresponding to the signal of the eye opening on the self-polarization side is required.

FIG. 5 is a diagram showing a block diagram of a demodulator when the input signal speed of the XPIC is fs. In this figure, the input signal speed of the XPIC shown in FIG.
The description of the same configuration as that of the block diagram of the demodulation device to be fs is omitted.

The difference from FIG. 1 is that, first, the output signal speed of the demodulation circuit in this figure is fs, so that the thinning circuit 20 (20 ') in FIG. 1 is not required. Second, the demodulation circuit 14 (14 ') and the XPIC 19 (1
9 '), the clock synchronization circuit 15 (15') is
s.

FIG. 6 is a block diagram showing the demodulation circuit 14 (14 ') of FIG. In the figure, a demodulation circuit 14 is provided with a roll-off filter (ROLL-OFF) that receives an output of the A / D converter 12 and passes a signal having a speed of fs.
FILTER 31, a carrier loop filter (CAR LPF) 34 for inputting a carrier APC signal from the control circuit (CONT) 18, an NCO 33, and a complex multiplication circuit (COMP MULTI) 32.

The demodulation circuit 14 removes the remaining phase rotation by multiplying the sine wave represented by the digital signal of the speed fs generated by the NCO 33 according to the carrier APC signal supplied from the control circuit 18. , Carrier synchronization is established. The speed of the output signal of the demodulation circuit 14 is the same fs as the output of the roll-off filter 31.

(Fourth Embodiment) When the system on the self-polarization side and the system on the different polarization side are physically separated, a high-speed and large-number of digital signals are transferred between the systems. Can be difficult.

In this case, the demodulation function of the self-polarization is provided in the demodulation device of the self-polarization, as in the reception LO synchronization system, or the demodulation function of the self-polarization is provided in the demodulation device of the heteropolarization. It can also be configured as shown in FIG.

FIG. 7 is a block diagram of a demodulation device showing a fourth embodiment of the present invention.

In this figure, terminal 1 is a self-polarized IF signal input, terminal 2 is a differently polarized IF signal input, terminal 3 is a self-polarized demodulator output, and terminal 4 is a differently polarized demodulator. Output, 9
Reference numeral 0 denotes a self-polarization demodulator, and reference numeral 90 ′ denotes a different polarization demodulator having the same configuration as that of the demodulator 90.

LO for converting IF signal to BB signal
Reference numeral 11 is shared by self-polarization and different polarization.

The self-polarization demodulator 90 has A / D converters 12 and 12 ′, demodulation circuits 14 and 14 ′, and clock recovery circuits 15 and 15 ′ for self-polarization and cross-polarization, respectively. And
The sampling clock VCO 13 is shared. However, since the optimum sampling phase is different between the self-polarized wave and the different polarization, there is a phase shifter 20 for shifting the phase of the sampling clock on the different polarization side from the phase on the self-polarization side.

For this reason, the demodulation circuit 14 ′ on the different polarization side is
Carrier synchronization can be established from the signal sampled by this sampling clock.

The XPIC 19 correlates the error signal output from the control circuit 18 on the own polarization side with the demodulation circuit 14 'on the different polarization side.

The equalizer 17 ′ on the different polarization side is essentially unnecessary, but since the received signal is being interfered now, the carrier on the different polarization side is considered. Required to improve synchronization characteristics.

Similarly, the demodulator for differential polarization 90 ′ is also the mixer 1
The outputs 0 and 10 ′ are input via cables 91 and 92.

As a result, according to the present invention, the self-polarization demodulator 90 and the hetero-polarization demodulator 90 'can be used even when the self-polarization side system and the opposite polarization side system are physically separated. And independently connected by cables 91 and 91 '.

[0090]

According to the present invention, it is possible to configure the transmission LO synchronous XPIC even when using a quasi-synchronous detection type demodulator composed of digital circuits.

On the receiving side, the demodulator can be digitized without deteriorating the advantage of the transmission LO synchronization system that there is no need to have a demodulator for different polarizations for the XPIC. No adjustment and stable characteristics can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a first invention of a demodulation device of the present invention.

FIG. 2 is a block diagram of a demodulation circuit 14 of FIG.

FIG. 3 is a block diagram of the XPIC 19 of FIG.

FIG. 4 is a block diagram showing a second embodiment of the demodulation device of the present invention.

FIG. 5 is a block diagram showing a demodulation device according to a third embodiment of the present invention.

FIG. 6 is a block diagram of the demodulation circuit of FIG. 5;

FIG. 7 is a block diagram showing a fourth embodiment of the demodulation device of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional XPIC in which an input signal speed is a modulation speed (fs).

FIG. 9 is a block diagram of a transmission LO synchronization system constituted by a conventional synchronous detection demodulator.

FIG. 10 is a block diagram of a reception LO synchronization system constituted by a conventional synchronous detection demodulator.

FIG. 11 is a block diagram of a conventional quasi-coherent detection type demodulator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 own polarization IF input terminal 2 different polarization IF input terminal 3 own polarization demodulation output 4 different polarization demodulation output 10 (10 ′) mixer 11 (11 ′) local oscillator 12 (12 ′) A / D converter 13 (13 ') VCO 14 (14') Demodulation circuit 15 (15 ') Clock recovery circuit 16 (16') Adder 17 (17 ') Equalizer 18 (18') Control circuit 19 (19 ') XPIC 20 ( 20 ') Thinning circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (11)

[Claims] 1. A means for transmitting signals of two orthogonal polarized waves at the same frequency by synchronizing a local oscillator, a means for receiving each transmitted signal and performing a quasi-synchronous detection, and the quasi-synchronous detection. Means for converting each signal obtained into a digital signal and demodulating each of the digital signals, and differently demodulating the respective demodulated signals based on a correlation between an error signal obtained from a demodulation signal on the self-polarization side and a demodulation signal on the different polarization side. A dual polarization transmission system using a transmission LO synchronization method, comprising: means for compensating for inter-wave interference. 2. The demodulation means inputs an APC signal corresponding to a shift of a carrier frequency from a control circuit.
A numerically controlled oscillator that converts a PC signal into a phase amount to generate a sine wave corresponding to the phase amount, and a digital signal having a speed of 2n times (n is an integer of 1 or more) the modulation speed detected by the quasi-synchronous detection. A roll-off filter that limits the band and outputs a signal having a rate twice as high as the modulation rate, and a complex multiplier that performs complex multiplication of the output of the roll-off filter and the output of the numerically controlled oscillator. A dual polarization transmission system using the transmission LO synchronization method according to claim 1. 3. The transmission LO according to claim 2, further comprising means for reducing the speed of the demodulated signal to a modulation speed.
Dual polarization transmission system using a synchronous method. 4. The means for compensating for interference between different polarizations comprises a transversal filter and a tap coefficient control circuit, inputs a demodulation signal of a different polarization twice as fast as the modulation speed, and outputs a signal of the modulation speed. 2. The dual polarization transmission system according to claim 1, wherein the transmission LO synchronization system is used. 5. The dual-polarization transmission system according to claim 1, wherein said transmitting means further comprises a modulation clock synchronized between the two polarizations. 6. A dual-polarization transmission system using a transmission LO synchronization system for transmitting signals of two orthogonal polarizations at the same frequency by synchronizing a local oscillator, wherein the transmission signal is received and the polarization A quasi-synchronous detection circuit that performs quasi-synchronous detection for each wave, first and second A / D converters that sample the detection output at a predetermined frequency for each of the polarizations and convert them into a digital signal; , The second A
A first and a second demodulation circuit for receiving the output of the / D converter to generate demodulated signals at twice the modulation speed, and clock phase information from the outputs of the first and the second demodulation circuits, respectively. First and second clock recovery circuits for extracting the first and second clock recovery circuits; first and second voltage-controlled oscillators for respectively generating the sampling clocks based on the outputs of the first and second clock recovery circuits; A first and a second thinning circuit for thinning out the output of the second demodulation circuit and outputting a signal of the modulation speed, a first error signal of the output of the first demodulation circuit, and an output of the second demodulation circuit. A first inter-polarization interference compensator for compensating for interference to its own polarization based on the interference between different polarizations based on a correlation between an error signal of an output of the second demodulation circuit and an output of the first demodulation circuit; A second inter-polarization interference compensator that compensates for First, transmission LO, characterized in that it comprises a second control circuit for outputting the error signal, respectively
Dual polarization transmission system using a synchronous method. 7. The first and second demodulation circuits each receive an APC signal corresponding to a difference in carrier frequency from the control circuit, convert the APC signal into a phase amount, and correspond to the phase amount. A numerically controlled oscillator for generating a sine wave, a roll-off filter for limiting the digital signal to twice the modulation speed, a complex multiplier for complex-multiplying the output of the roll-off filter and the output of the numerically controlled oscillator, 7. The dual-polarization transmission system using a transmission LO synchronization system according to claim 6, comprising: 8. The first and second inter-polarization interference compensators each include a transversal filter and a tap coefficient control circuit, each of which receives a demodulation signal of a different polarization at twice the modulation speed, and The dual-polarization transmission system according to claim 5, wherein a signal of a speed is output. 9. The input of the demodulated signals of the first and second inter-polarization interference compensators includes a delay difference absorber that absorbs a clock phase difference between the own polarization and the different polarization. 9. A dual polarization transmission system using the transmission LO synchronization method according to claim 8. 10. A dual-polarization transmission system using a transmission LO synchronization system for transmitting signals of two orthogonal polarizations at the same frequency by synchronizing a local oscillator, wherein: A quasi-synchronous detection circuit that performs quasi-synchronous detection for each wave, first and second A / D converters that sample the detection output at a predetermined frequency for each of the polarizations and convert them into a digital signal; , The second A
First and second demodulation circuits for receiving outputs of the / D converter and generating demodulated signals at the respective modulation speeds; and the first and second demodulation circuits.
First and second clock recovery circuits for extracting clock phase information from the outputs of the demodulation circuits of the first and second, respectively;
A first and a second voltage-controlled oscillator for respectively generating the sampling clock based on the output of the clock recovery circuit; and a first error signal of the output of the first demodulation circuit and an output of the second demodulation circuit. A first inter-polarization interference compensator for compensating for interference to its own polarization based on the interference between different polarizations based on a correlation between an error signal of an output of the second demodulation circuit and an output of the first demodulation circuit; A second inter-polarization interference compensator that compensates for
A dual-polarization transmission system using a transmission LO synchronization method, comprising first and second control circuits for outputting the first and second error signals, respectively. 11. A dual-polarization transmission system using a transmission LO synchronization system for transmitting signals of two orthogonal polarizations at the same frequency by synchronizing a local oscillator, wherein the transmitted signal is received and the respective polarizations are received. A quasi-synchronous detection circuit that performs quasi-synchronous detection for each wave, and first and second A / Ds that sample each detection output at a predetermined frequency and convert it into a digital signal with respect to its own polarization.
A converter and first and second A / D converters which receive the outputs of the first and second A / D converters and generate demodulated signals having respective modulation rates.
, A first and a second clock recovery circuit for extracting clock phase information from the outputs of the first and second demodulation circuits, respectively, and the sampling clock based on the output of the first clock recovery circuit. A first voltage-controlled oscillator that is generated, a phase shifter that generates the sampling lock by controlling a phase of an output of the first voltage generation control circuit based on an output of the second clock recovery circuit, A first inter-polarization interference compensator for compensating for interference to its own polarization based on a first error signal output from the first demodulation circuit and an output from the second demodulation circuit, and outputting the first error signal Third and fourth A / D converters for sampling different detection outputs at a predetermined frequency and converting them into digital signals with respect to different polarized waves; 4. Input the output of the A / D converter Third and fourth demodulation circuits for respectively generating demodulated signals at modulation speeds; third and fourth clock recovery circuits for extracting clock phase information from outputs of the third and fourth demodulation circuits, respectively; A second voltage-controlled oscillator for generating the sampling clock based on the output of the third clock recovery circuit, and a phase of the output of the second voltage generation control circuit based on the output of the fourth clock recovery circuit. A phase shifter for generating the sampling clock, and a second differential signal for compensating for interference with its own polarization based on a second error signal of the output of the third demodulation circuit and an output of the fourth demodulation circuit. A dual polarization transmission system using a transmission LO synchronization method, comprising: an inter-wave interference compensator; and a second control circuit that outputs the second error signal.