JP2687691B2 - Cross polarization interference cancellation circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cross polarization interference canceling circuit, and more particularly to a cross polarization interference canceling circuit, in which a reception signal of the same frequency is interfered with other polarizations in a dual polarization transmission system. The present invention relates to a cross polarization interference canceling circuit that cancels a transversal filter that is an interference canceling equalizer.

[Conventional technology]

A conventional cross polarization interference canceling circuit of this type will be described with reference to the block diagram of FIG. The conventional example shown in FIG. 3 is a received signal 101, which is obtained by converting a digitally modulated signal transmitted in two polarized waves orthogonal to each other at the same frequency into an intermediate frequency band.
Compensation created by transversal filters 12 and 22 which are waveform equalizers for cross polarization elimination that input 201 by dividing it into 201, the other received signal 101 and 201 that is divided into two, and transversal filters 12 and 22 described later. Combiners 15 and 25 that combine the signals 107 and 207, and demodulators 11 and 21 that demodulate the output signals 102 and 202 of the combiners 15 and 25 and output baseband signals 103 and 203.
And the two inputs of the baseband signals 103 and 203 are compared, the correlation for each bit is detected, and the transversal filter 12 and 2 is detected.
Weighting control signals 104,2 that control the weighting of the two taps
It is composed of control signal generators 13 and 23 that output 04. When the received signals 101, 201 include cross polarization interference components, the transversal filters 105, 205 output weighted compensation signals 107, 207. In the steady state when cross polarization interference components are not included, transversal filter
The weighting amount of each tap of 12 and 22 becomes zero, and the compensation signal 10
7,207 is the minimum, and received signals 101,201 are demodulators as they are.
It was entered in 11,21.

[Problems to be solved by the invention]

In the conventional cross polarization interference cancellation circuit described above, in order to increase the cross polarization interference cancellation capability, the maximum level of the compensation signal,
That is, it is necessary to increase the maximum output level of the transversal filter. However, since the dynamic range of the output level of the transversal filter is finite, if the maximum output level of the transversal filter is increased, even if the tap weight is set to zero in the steady state without cross polarization interference, There is a drawback that a signal of a minute level is output and the quality of the main signal in a steady state is deteriorated.

[Means for solving the problem]

The cross polarization interference canceling circuit of the present invention is a demodulator for inputting each cross polarization reception signal which transmits two digital modulation signals orthogonal to each other at the same frequency through a coupler and demodulating the digital modulation signal. A control signal generator that compares the baseband signals output from each of the demodulators with each other to detect the amount of interference from other polarizations and outputs a weighting control signal corresponding to the amount of interference; And a waveform equalizer for cross polarization interference cancellation, which is a transversal filter provided with terminals for inputting the branched signals of the wave reception signals and outputting the signals adaptively controlled by the weighting control signals to the combiner. In the cross polarization interference canceling circuit, the residual error component contained in the demodulator output signal on the own polarization side generated in the control signal generator and the demodulator output signal on the other polarization side are included. Having the result of the correlation operation value and was multiplied with the signal from the terminal multiplier to be input to the combiner as a compensation signal.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention. In this embodiment, a received signal 101 in the intermediate frequency band, which is a digital modulation signal transmitted in two polarized waves having the same frequency and orthogonal to each other,
Compensation is performed by multiplying transversal filters 12 and 22 that are equalizers for cross-polarization interference cancellation that inputs 201 and transversal filter output signals 105 and 205 with multiplier weighting signals 106 and 206 of control signal generators 13 and 23 described later. Signal 107,207
Multipliers 14 and 24 that output the received signals 101 and 201 and compensation signals
Couplers 15 and 25 for coupling 107 and 207, and the coupler output signal 102,
Demodulator that demodulates 202 and outputs baseband signals 103 and 203
11, 21 and two signals of the baseband signals 103, 203 are input, and weighting control signals 104, 204 for controlling the tap weighting of the transversal filters 12, 22 and multiplier weighting signals 106, 206 for controlling the weighting amounts of the multipliers 14, 24 are set. It is composed of output control signal generators 13 and 23. Here, the control signal generators 13 and 23 perform the correlation calculation of the residual error component after polarization interference signal compensation between the output signal of the demodulator 11 on the own polarization side and the output signal of the demodulator 21 on the other polarization side. The calculation result signal is sent to the multiplier 14. If the cross polarization interference components of the received signals 101, 201 are included, the multiplier 1
The weighted amounts of 4, 24 are controlled, and the compensation signals 107, 207 for removing the cross polarization interference component are output. In the steady state where cross polarization interference components are not included, the transversal filters 12, 2
The weighting amount of each tap of 2 and the weighting amounts of the multipliers 14 and 24 are both zero.

Next, a second embodiment of the present invention will be described with reference to the block diagram of FIG. In FIG. 2, circuits having the same reference numerals as those in FIG. 1 have the same configuration and operation. That is, in the second embodiment, level detectors 16 and 26 are provided which input the transversal filter output signals 105 and 205 respectively and output the multiplier weighting signals 106A and 206A for controlling the multipliers 14 and 24 respectively. . Therefore, the connection between the control signal generators 13 and 23 and the multipliers 14 and 24 in the first embodiment is not made.

Next, the operation of the second embodiment will be described. Received signal 101,20
When the cross polarization interference component is included in 1, the level detectors 16 and 26 detect an increase in the transversal filter output signals 105 and 205 and output multiplier weighting signals 106A and 206A, respectively, according to the increase. To do. The multipliers 14 and 24 multiply the multiplier weighting signals 106A and 206A and the transversal output signals 105 and 205, respectively, and output compensation signals 107 and 207. At steady time when cross polarization interference component is not included,
Since the weighting amount of each tap of the transversal filters 12 and 22 and the weighting amount to the multipliers 14 and 24 are both zero,
The compensation signals 107 and 207 are not output.

As described above, according to the first and second embodiments, the compensation amounts of the compensation signals 107 and 207 can be changed significantly depending on the magnitude of the interference component. Therefore, the compensation signal in a steady state where there is no interference is greatly reduced and is hardly output.

In this embodiment, the example in which the cross polarization interference canceling circuit is configured in the intermediate frequency band is shown, but the same effect can be obtained when it is configured in the base band.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention provides a control signal generator or level detector that outputs a weighting amount change signal according to the amount of cross polarization interference at the output of a transversal filter, a weighting amount change signal, and a transformer. By providing a multiplier that multiplies the output signal of the Versal filter, the range of the dynamic range of the compensation signal level can be increased. In addition, there is an effect that a large cross polarization interference removal capability can be obtained without degrading the quality of the main signal in a steady state without cross polarization interference.

[Brief description of the drawings]

1 and 2 are block diagrams of the first and second embodiments of the present invention, and FIG. 3 is a block diagram of a conventional cross polarization interference canceling circuit. 11,21 …… Demodulator, 12, 22 …… Transversal filter, 13, 23 …… Control signal generator, 14, 24 …… Multiplier, 15, 2
5 …… Combiner, 16, 26 …… Level detector.

Claims (2)

(57) [Claims] 1. A demodulator for inputting, via a combiner, two cross-polarized reception signals that transmit two digital modulation signals that are orthogonal to each other at the same frequency, and demodulates the digital modulation signals. A control signal generator that compares the baseband signals output from each and detects the amount of interference from other polarizations with each other, and outputs a weighted control signal corresponding to this amount of interference; Cross-polarization interference elimination circuit having a waveform equalizer for cross-polarization interference elimination which is a transversal filter provided with terminals for respectively inputting the signals and adaptively controlling the signals by the weighting control signal to the coupler. In, the residual error component included in the demodulator output signal of the own polarization side generated in the control signal generator and the correlation calculation value of the demodulator output signal of the other polarization side and the Cross polarization interference cancellation circuit, characterized in that it comprises a multiplier for inputting a result of the multiplication of the signal from the child to the coupler as a compensation signal. 2. In the case of inputting a signal from the terminal of the cross polarization interference canceling waveform equalizer, which is the transversal filter, and detecting a minute signal which is determined not to include a cross polarization interference component. A residual error component included in the output signal of the demodulator of the self-polarization side generated in the control signal generator in the multiplier and a demodulator of the other polarization side having a level detector that outputs at least a coefficient of zero. 2. The cross polarization interference canceller according to claim 1, wherein, in place of the correlation calculation value with the output signal, the coefficient of at least zero and the signal from the terminal are multiplied and output as a compensation signal to the coupler. circuit.