JP2016021686A - Cross polarization interference compensation device and cross polarization interference compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cross polarization interference compensation device capable of preventing divergence of phase noise suppression control.SOLUTION: The cross polarization interference compensation device is configured to compensate for an interference between one polarized wave and another polarized wave, and includes: a transversal filter which multiplies the other polarized wave by a plurality of tap coefficients correspondingly to a plurality of signals delayed at predetermined time intervals and outputs a value obtained by adding multiplication results as a cross polarization interference compensation signal; a tap coefficient control circuit by which the plurality of tap coefficients are generated and supplied to the transversal filter on the basis of an amplitude difference between regular one polarized wave and actual one polarized wave, an error signal indicating a phase difference and the other polarized wave; and a phase noise compensator for calculating phase noises of the one polarized wave and the other polarized wave on the basis of the cross polarization interference compensation signal and the error signal. The tap coefficient control circuit fixes a phase of any one tap coefficient among the plurality of tap coefficients.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cross-polarization interference compensation device and a cross-polarization interference compensation method in a receiver of both polarization transmission devices.

In microwave communication, as a method for improving frequency utilization efficiency, there is a dual polarization transmission method in which two orthogonal polarizations (vertical polarization (V polarization) and horizontal polarization (H polarization)) are transmitted at the same frequency. Are known.
In both polarization transmission systems, since the V polarization and the H polarization are the same frequency, interference signals are generated by reflection or scattering in the propagation path. The other polarization with respect to one polarization is called “cross-polarization”, and the fact that one polarization interferes with the other polarization is called “cross-polarization interference”. On the receiving side, cross polarization interference compensation is required to suppress this cross polarization interference. An example of a cross polarization interference canceller (XPIC: cross polarization interference canceller) provided in a receiving apparatus is disclosed in Patent Document 1.
In order to compensate for cross polarization interference, there is a method of synchronizing the local oscillation frequencies of V polarization and H polarization in XPIC. As the method, a local synchronization method and a reference synchronization method are known. The local synchronization method has a problem that signals of both polarizations cannot be output when the local oscillator fails. On the other hand, in the reference synchronization method, there is a problem that the phase noise causes the characteristic deterioration of the cross polarization interference compensation.

An example of a method of suppressing phase noise in reference-synchronized dual polarization transmission is disclosed in Patent Document 2. FIG. 5 is a block diagram showing a configuration example of a receiving apparatus including a related cross-polarization interference compensating apparatus.
As shown in FIG. 5, the receiving apparatus includes antennas 3 and 3 ′ that receive an RF (Radio Frequency) signal, mixers 4 and 4 ′ that convert the RF signal into an IF (Intermediate Frequency) signal, and mixers 4 and 4. Local oscillators 45 and 45 'for supplying an RF local signal to', a reference oscillator 46 for supplying a reference signal to the local oscillators 45 and 45 'for synchronizing the frequency, a demodulator 5 on the V polarization side, and H And a demodulator 5 'on the polarization side.
The demodulator 5 includes quadrature demodulators 41 and 43, a local oscillator 42, a DEM (demodulator) 10, an XPIC 130, an error detector 11, a phase noise compensator 12, a complex multiplier 15, And an adder 14. The demodulator 5 ′ has the same configuration as the demodulator 5.
FIG. 6 is a block diagram showing a configuration example of the phase noise compensator shown in FIG. The phase noise compensator 12 includes a phase noise detector 21, a multiplier 22, an accumulator 23, an adder 24, and a SIN / COS table 25. In addition, since the structure similar to the structure shown in FIG. 5 and FIG. 6 is disclosed by patent document 2, the detailed description is abbreviate | omitted.
In the apparatus disclosed in Patent Document 2, the XPIC 130 corrects phase noise that changes slowly in time, and the phase noise compensator 12 corrects phase noise that changes quickly in time.

JP 2000-165339 A International Publication No. 2007/046427 (paragraph 0069)

In the apparatus disclosed in Patent Document 2, two circuits, an XPIC and a phase noise compensator, are provided as circuits for suppressing phase noise. Since these two circuits have different tracking speeds with respect to phase, control is diverged (competition). )there's a possibility that. This problem will be described with reference to FIG.
Of the arrows shown in FIG. 7, regarding the suppression of the phase noise for the cross polarization interference compensation signal, either the control indicated by the upper arrow or the control indicated by the lower arrow can be performed. As described above, there are a plurality of solutions for the suppression of the phase noise, and there is a possibility that the control may diverge (compete).
In recent years, digital signal processing has been heavily used for communication processing, and processing has become time consuming.There is a risk of control divergence (competition) caused by correction at multiple locations based on feedback data. There is a need to consider countermeasures.

  The present invention has been made to solve the above-described problems of the technology, and provides a cross-polarization interference compensation device and a cross-polarization interference compensation method capable of preventing divergence of phase noise suppression control. The purpose is to do.

In order to achieve the above object, the cross polarization interference compensation device of the present invention is a cross polarization interference compensation device for compensating for interference between the own polarization and the different polarization,
A transversal filter that multiplies a plurality of tap coefficients corresponding to a plurality of signals obtained by delaying the different polarizations at a predetermined time interval, and outputs a value obtained by adding the multiplication results as a cross polarization interference compensation signal;
Tap coefficients that generate the plurality of tap coefficients based on the error signal indicating the amplitude difference and phase difference between the normal polarization and the actual polarization and the cross polarization and supply the tap coefficients to the transversal filter A control circuit;
A phase noise compensator for obtaining phase noise of the own polarization and the different polarization based on the cross polarization interference compensation signal and the error signal;
The tap coefficient control circuit is configured to fix the phase of any one of the plurality of tap coefficients.

Further, the cross polarization interference compensation method of the present invention is a cross polarization interference compensation method for compensating for interference between the own polarization and the different polarization,
A plurality of tap coefficients are generated based on the error signal indicating the amplitude difference and phase difference between the normal self polarization and the actual self polarization and the cross polarization,
Multiplying the plurality of tap coefficients corresponding to a plurality of signals obtained by delaying the different polarizations at a predetermined time interval, and generating a value obtained by adding the multiplication results as a cross polarization interference compensation signal,
Based on the generated cross-polarization interference compensation signal and the error signal, the cross-polarization interference compensation signal is corrected by obtaining phase noise of the own polarization and the different polarization,
When generating the plurality of tap coefficients, the phase of any one of the tap coefficients is fixed.

  According to the present invention, it is possible to prevent the phase noise suppression control from diverging.

It is a block diagram which shows the example of 1 structure of the cross polarization interference compensation apparatus of this embodiment. It is a figure for demonstrating operation | movement of the phase fixing method by the tap coefficient control circuit of this embodiment. It is a flowchart which shows the operation | movement procedure of the phase fixing method by the tap coefficient control circuit of this embodiment. It is a flowchart which shows the procedure of the cross polarization interference compensation method of this embodiment. It is a block diagram which shows one structural example of the receiver containing the related cross polarization interference compensation apparatus. FIG. 6 is a block diagram illustrating a configuration example of a phase noise compensator illustrated in FIG. 5. It is a figure for demonstrating the subject of the related cross polarization interference compensation apparatus.

The configuration of the cross polarization interference compensation device of this embodiment will be described. FIG. 1 is a block diagram showing a configuration example of the cross polarization interference compensation device of the present embodiment.
The cross polarization interference compensation device of the present embodiment includes an XPIC 13, an error detector 11, a phase noise compensator 12, an adder 14, and a complex multiplier 15. In this embodiment, an XPIC 13 shown in FIG. 1 is provided instead of the XPIC 130 shown in FIG.
In this embodiment, in each of the demodulators 5 and 5 ′ shown in FIG. 5, the polarization that is the source of the main signal is referred to as self-polarization, and the other polarization that is orthogonal thereto is referred to as cross-polarization. . For example, for the demodulator 5, the V polarization is a self polarization and the H polarization is a different polarization. In the present embodiment, the description of the same configuration as that shown in FIGS. 5 and 6 is omitted, and the description of the demodulator 5 ′ is also omitted.

The configuration of the XPIC 13 of this embodiment will be described with reference to FIG.
As shown in FIG. 1, the XPIC 13 includes a transversal filter 30 and a tap coefficient control circuit 35. The XPIC 13 is an adaptive control type filter including a FIR (Finite Impulse Response) filter. When the cross polarization signal is input, the XPIC 13 refers to the error signal received from the error detector 11 and generates a cross polarization interference compensation signal that is a signal for canceling the cross polarization interference wave mixed in the self polarization. To do.
Transversal filter 30 includes delay units 31-1 to 31-4 connected in series, multipliers 32-1 to 32-5 provided corresponding to delay units 31-1 to 31-4, and multiplications. And adders 33-1 to 33-4 for adding the output results of the devices 32-1 to 32-5. The delay units 31-1 to 31-4 delay the demodulated signals of different polarizations at a predetermined time interval. The adder 33-4 outputs a value obtained by adding the multiplication results of the multipliers 32-1 to 32-5 to the complex multiplier 15 as a cross polarization interference compensation signal.
The tap coefficient control circuit 35 generates each tap coefficient by correlating the error signal obtained from the input demodulated signal of the own polarization and the input demodulated signal of the different polarization. In the present embodiment, the tap coefficient is a complex number composed of a real part and an imaginary part. The real part corresponds to the coefficient of the I (in-phase) component, and the imaginary part corresponds to the coefficient of the Q (quadrature phase) component. In FIG. 1, tap coefficients input to the multipliers 32-1 to 32-5 are represented by (a1 + jb1) to (a5 + jb5).
If time is t, the signal input to the transversal filter 30 is x (t), the output of the transversal filter 30 is y (t), and the error signal is e (t), y (t) It is represented by Moreover, it is known that each tap coefficient wk (k is an arbitrary integer of 0 to 4) of the real part and the imaginary part is expressed by Expression 2. However, the LMS (Least Mean Square) algorithm is used to correct the tap coefficient, and μ is the correction coefficient.

  As shown in Equation 2, the tap coefficient wk at time (t + 1) is expressed by adding the correlation calculation result between the demodulated signal of different polarization and the error signal to the tap coefficient wk at time t. From this, it is understood that the tap coefficient at a certain time is obtained by adding the correlation calculation result to the sum (integral value) of the previous tap coefficients.

  The tap coefficient control circuit 35 of the present embodiment determines one tap coefficient for fixing the phase among the tap coefficients (a1 + jb1) to (a5 + jb5), and controls the real part of the determined tap coefficient. Fix to zero. For other tap coefficients, the tap coefficient control circuit 35 controls both the real part and the imaginary part. FIG. 1 shows a case where the imaginary part of the tap coefficient (a3 + jb3) is fixed to zero.

Next, a method for fixing one phase of the tap coefficient by the tap coefficient control circuit 35 of the present embodiment will be described.
FIG. 2 is a diagram for explaining the operation of the phase fixing method by the tap coefficient control circuit of this embodiment. FIG. 3 is a flowchart showing the operation procedure of the phase fixing method by the tap coefficient control circuit of this embodiment.
The tap coefficient control circuit 35 determines a tap coefficient for fixing the phase among the tap coefficients (a1 + jb1) to (a5 + jb5). Here, it is assumed that the tap coefficient having the largest amplitude is (a3 + jb3) shown in FIG. 1 and is selected as the tap coefficient for fixing the phase. Subsequently, the tap coefficient control circuit 35 calculates the correlation between the demodulated signal of different polarization and the error signal (step 101). Then, the tap coefficient control circuit 35 compares only the imaginary part with the sum (integral value) of the previous tap coefficients and the sign of the correlation calculation result (step 102).
If the correlation calculation result and the sign of the integral value match as a result of the comparison in step 102, the tap coefficient control circuit 35 inverts the sign of the correlation calculation result (× −1) (step 103), and then proceeds to step 104. move on. As a result of the comparison in step 102, when the correlation calculation result and the sign of the integral value are different, the tap coefficient control circuit 35 adds the correlation calculation result to the integral value (step 104). As a result of the process of step 104, the imaginary part of the tap coefficient becomes zero, and only the real part a3 remains. The tap coefficient control circuit 35 calculates a real part and an imaginary part for other tap coefficients.

Usually, a plurality of tap coefficients change according to other tap coefficients. As in this embodiment, when the imaginary part of one tap coefficient among the plurality of tap coefficients is set to zero, the tap coefficient becomes only the real part and is fixed with respect to the phase. With respect to the imaginary part, when one place is fixed, the imaginary part of other tap coefficients is not changed by other tap coefficients. As a result, in XPIC, the phase noise suppression function is abandoned.
Although the case where the tap coefficient having the largest amplitude is selected as the tap coefficient for fixing the phase has been described, the tap coefficient for fixing the phase is not limited to the one having the largest amplitude. The tap coefficient with the largest amplitude has the advantage of higher reliability than other tap coefficients.

Next, a cross polarization interference compensation method by the cross polarization interference compensation device of this embodiment will be described. FIG. 4 is a flowchart showing the procedure of the cross polarization interference compensation method of this embodiment.
The tap coefficient control circuit 35 generates a plurality of tap coefficients based on the error signal detected from the amplitude difference and phase difference between the normal own polarization and the actual own polarization and the different polarization. At that time, the tap coefficient control circuit 35 fixes the phase of any one of the plurality of tap coefficients. Then, the transversal filter 30 multiplies the plurality of tap coefficients corresponding to the plurality of signals generated by delaying the different polarizations at a predetermined time interval, and adds the multiplication result to the cross-polarization interference. A compensation signal is generated and output (step 201).
The phase noise compensator 12 obtains the phase noise difference between the own polarization and the different polarization based on the cross polarization interference compensation signal and the error signal, and outputs the difference to the complex multiplier 15 serving as a phase rotator. The complex multiplier 15 controls the phase of the cross polarization interference compensation signal output from the transversal filter 30 in a direction to suppress the phase noise difference. In this way, the phase noise of the cross polarization interference compensation signal is corrected (step 202).

  As described above, in the phase noise suppression method of the present embodiment, the phase noise suppression function is abandoned in XPIC. For this reason, since there is only one circuit capable of suppressing the phase noise, the solution is uniquely determined, and there is no possibility that control will diverge (compete).

  In general, cross polarization interference compensation is performed simultaneously by controlling the amplitude direction and the phase direction by using complex tap coefficients. In the present embodiment, one of the plurality of tap coefficients is controlled only by a real number. As a result, the cross-polarization interference compensator cannot suppress the phase noise, and the phase noise obtained by the phase noise compensator is suppressed by the phase rotator. Since there is no competition for phase noise correction between the cross polarization interference compensator and the phase rotator, it is possible to prevent the phase noise suppression control from diverging (competing).

13 Cross polarization interference compensator (XPIC)
30 Transversal filter 35 Tap coefficient control circuit

Claims (6)

A cross-polarization interference compensator that compensates for self-polarization and cross-polarization interference,
A transversal filter that multiplies a plurality of tap coefficients corresponding to a plurality of signals obtained by delaying the different polarizations at a predetermined time interval, and outputs a value obtained by adding the multiplication results as a cross polarization interference compensation signal;
Tap coefficients that generate the plurality of tap coefficients based on the error signal indicating the amplitude difference and phase difference between the normal polarization and the actual polarization and the cross polarization and supply the tap coefficients to the transversal filter A control circuit;
A phase noise compensator for obtaining phase noise of the own polarization and the different polarization based on the cross polarization interference compensation signal and the error signal;
The tap coefficient control circuit is a cross polarization interference compensation device that fixes a phase of any one of the plurality of tap coefficients. In the cross polarization interference compensation device according to claim 1,
The tap coefficient is a complex number;
The cross polarization interference compensation device, wherein the tap coefficient control circuit sets an imaginary part of any one of the tap coefficients to zero in order to fix the phase. In the cross polarization interference compensation device according to claim 2,
The cross-polarization interference compensating apparatus, wherein the tap coefficient control unit selects a tap coefficient having the largest amplitude among the plurality of tap coefficients as a tap coefficient for setting the imaginary part to zero. A cross-polarization interference compensation method that compensates for self-polarization and cross-polarization interference,
A plurality of tap coefficients are generated based on the error signal indicating the amplitude difference and phase difference between the normal self polarization and the actual self polarization and the cross polarization,
Multiplying the plurality of tap coefficients corresponding to a plurality of signals obtained by delaying the different polarizations at a predetermined time interval, and generating a value obtained by adding the multiplication results as a cross polarization interference compensation signal,
Based on the generated cross-polarization interference compensation signal and the error signal, the cross-polarization interference compensation signal is corrected by obtaining phase noise of the own polarization and the different polarization,
A cross polarization interference compensation method for fixing a phase of any one tap coefficient when generating the plurality of tap coefficients. In the cross polarization interference compensation method according to claim 4,
The tap coefficient is a complex number;
A cross-polarization interference compensation method for setting the imaginary part of any one of the tap coefficients to zero in order to fix the phase. In the cross polarization interference compensation method according to claim 5,
A cross-polarization interference compensation method for selecting a tap coefficient having the largest amplitude among the plurality of tap coefficients as a tap coefficient for setting the imaginary part to zero.

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