JP2017163370A - Phase error detector, inter-polarized interference elimination system, and phase error detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase error detector capable of more extensively handling, a polarization interfering interference elimination system, and a phase error detection method.SOLUTION: The phase error detector includes a difference calculating unit 13 and a phase difference detecting unit 14. The difference calculating unit 13 calculates a difference between a signal transmitted and demodulated by one polarization system out of the plurality of polarization systems and a signal from which a noise component is removed. On the basis of the difference calculated by the difference calculating unit 13, the phase difference detecting unit 14 detects a phase difference between the demodulated signal and a signal transmitted in another polarization system.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a phase error detector, an inter-polarization interference cancellation system, and a phase error detection method corresponding to a phase error of signals transmitted by different polarization systems.

  There is a dual polarization transmission device that transmits signals in two different polarization systems (for example, horizontal polarization and vertical polarization). In both polarization transmission apparatuses, the signals received in the respective polarization systems may be synchronized based on local signals generated by different PLLs (Phase Locked Loops). Such a synchronization method is called a reference synchronization method. In the reference synchronization method, the frequency is synchronized, but the phase is not synchronized.

  Patent Document 1 describes means for suppressing phase noise caused by the reference synchronization method in such a dual-polarization transmission device.

  FIG. 5 is a block diagram showing a configuration example of the phase noise suppression circuit described in Patent Document 1. In FIG. In the phase noise suppression circuit shown in FIG. 5, the error detector 26 calculates the phase difference between the normal phase rotation angle of the own polarization signal in the complex multiplier 18 and the input signal. Then, the error detector 26 inputs an error signal indicating the calculated phase difference to the phase noise detector 27.

  In addition, a signal for removing interference by the adder 19 output from an XPIC (Cross Polarization Interference Cancer) 24 is input to the phase noise detector 27 after being phase-rotated by a complex multiplier 18 ′.

  Then, the phase noise detector 27 calculates a phase noise difference that is a difference in the phase direction of the phase noise component based on the input error signal and the cross polarization interference cancellation signal. The calculated phase noise difference is fed back to the complex multiplier 18 ′ via the adder 29 and the like.

  Patent Document 2 describes a circuit that extracts a phase difference based on a received signal.

  Patent Document 3 describes a phase noise control system in which feedforward control and feedback control are combined.

International Publication No. 2007/046427 JP 2002-158630 A Special table 2009-545277

  In recent years, signals modulated by a larger multi-level modulation scheme have been transmitted and received. Then, as described in FIG. 6 of Patent Document 1, it is becoming difficult to cope with the circuit described in Patent Document 1.

  The circuit described in Patent Document 2 performs a process of extracting a phase difference directly from a received signal. In order to realize the process at a lower cost, the process is performed at a lower frequency. Is preferably performed.

  The system described in Patent Document 3 is a combination of feedforward control and feedback control, and there is a problem that it takes time to make appropriate adjustments according to the use environment of the system.

  Therefore, an object of the present invention is to provide a phase error detector, an inter-polarization interference cancellation system, and a phase error detection method that can be applied more widely.

  The phase error detector according to the present invention includes a difference calculation means for calculating a difference between a signal transmitted by one polarization method among a plurality of polarization methods and demodulated, and a signal from which a noise component has been removed. Phase difference detection means for detecting a phase difference between a demodulated signal and a signal transmitted by another polarization method based on the difference calculated by the difference calculation means is provided.

  An inter-polarization interference cancellation system according to the present invention includes a phase error detector according to any aspect, a signal corresponding to a phase difference detected by a phase difference detection unit, and a signal transmitted from the signal transmitted by another polarization method. Multiplication means for calculating a multiplication result with a signal based on a signal subjected to feedback processing for removing interference, and a calculation result by the multiplication means from a signal based on a signal transmitted and demodulated by one polarization method Subtracting means for generating a signal from which interference from a signal transmitted by another polarization method is removed by subtracting a signal corresponding to

  According to another aspect of the present invention, an inter-polarization interference cancellation system includes a phase error detector according to any one of the aspects, a signal corresponding to the phase difference detected by the phase difference detection unit, and the signal transmitted in another polarization method. A multiplication unit for calculating a multiplication result with a signal based on a signal whose interference from the compensated signal is compensated, and a signal based on a signal transmitted and demodulated with one polarization method, in accordance with the calculation result by the multiplication unit. And subtracting means for generating a signal from which interference from a signal transmitted by another polarization method is removed by subtracting the signal.

  The phase error detection method according to the present invention calculates a difference between a signal transmitted and demodulated by one polarization method among a plurality of polarization methods and a signal from which a noise component has been removed from the signal. Based on this, a phase difference between a demodulated signal and a signal transmitted by another polarization method is detected.

  According to the present invention, it is possible to deal with phase noise more widely.

It is a block diagram which shows the structural example of the phase noise detector of the 1st Embodiment of this invention. It is explanatory drawing which shows the range of the frequency which a phase noise detector and a feedforward part can respond | correspond. It is a block diagram which shows the structural example of the feedforward part of the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the phase error detector of the 3rd Embodiment of this invention. 10 is a block diagram illustrating a configuration example of a phase noise suppression circuit described in Patent Document 1. FIG.

Embodiment 1. FIG.
A phase noise detector 100 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a phase noise detector 100 according to the first embodiment of this invention. Each component including the phase noise detector 100 of the first embodiment of the present invention illustrated in FIG. 1 is mounted on, for example, both polarization transmission apparatuses. Each component is a component corresponding to one of the two polarization signals received by both polarization transmission apparatuses.

  As shown in FIG. 1, the phase noise detector 100 according to the first embodiment of the present invention is connected to a feedback unit 200, a feedforward unit 300, a demodulator 401, and a post-demodulation signal delay adjuster 402.

  The demodulator 401 receives a received signal by one polarization method (for example, horizontal polarization). The demodulator 401 demodulates the input received signal. Further, demodulator 401 inputs the demodulated signal after demodulation to phase noise detector 100 and demodulated signal delay adjuster 402, respectively. The demodulator 401 and the feedforward unit 300 are connected to each other via a post-demodulation signal delay adjuster 402. The post-demodulation signal delay adjuster 402 delays the input post-demodulation signal by a predetermined time and inputs the delayed signal to the feedforward unit 300. The predetermined time will be described later.

  The phase noise detector 100 is connected to the XPIC unit 403 via the feedback unit 200.

  The XPIC unit 403 is an intersection for removing an interference component with a received signal of the other polarization method (for example, vertical polarization) from a received signal of one polarization method (horizontal polarization in this example). The polarization interference cancellation signal X is input to the feedback unit 200.

  As shown in FIG. 1, the phase noise detector 100 includes a subtractor 110, a hard decision device 120, a subtractor 130, and a phase difference detector 140.

  The signals after demodulation by demodulator 401 are input to subtractor 110 and subtractor 130, respectively.

  In addition, the subtractor 110 and the phase difference detector 140 receive a temporary interference removal signal X ′ described later from the feedback unit 200.

  The subtractor 110 generates a signal after removing the temporary interference which is a signal indicating a difference between the signal obtained by subtracting the signal X ′ for removing the temporary interference from the demodulated signal. Then, the subtractor 110 inputs the generated temporary interference removal signal to the hard decision unit 120.

  The hard decision unit 120 makes a hard decision based on the input signal after removing the temporary interference. Then, the hard decision device 120 generates a hard decision signal indicating the result of the hard decision. Further, the hard decision unit 120 inputs the generated hard decision signal to the subtractor 130.

  The subtractor 130 generates a cross polarization interference signal indicating a difference between the result of subtracting the hard decision signal from the demodulated signal. Then, the subtractor 130 inputs the generated cross polarization interference signal to the phase difference detector 140.

  The phase difference detector 140 detects a phase difference between signals having different polarization schemes based on the input cross-polarization interference signal and provisional interference removal signal X ′. Then, the phase difference detector 140 generates an interference cancellation signal phase error signal indicating the detected phase difference. Furthermore, the phase difference detector 140 inputs the generated interference cancellation signal phase error signal to the feedback unit 200 and the feedforward unit 300, respectively.

  The configuration of the feedback unit 200 will be described. The feedback unit 200 includes a low-pass filter 210, a numerically controlled oscillator 220, and a multiplier 230.

  The low-pass filter 210 receives an interference cancellation signal phase error signal. Then, the low-pass filter 210 performs a filtering process that removes noise components (phase noise). The interference cancellation signal phase error signal is input to the numerically controlled oscillator 220 after the filtering process.

  The numerically controlled oscillator 220 inputs a signal having a predetermined power (gain: gain) and phase to the multiplier 230 according to the input interference cancellation signal phase error signal.

  The multiplier 230 multiplies the signal and the cross polarization interference cancellation signal X input by the XPIC unit 403, and generates a temporary interference cancellation signal X ′ indicating the multiplication result. The multiplication of the signal and the cross polarization interference cancellation signal X means a complex operation, and the phases are added to each other. Then, the multiplier 230 inputs the generated temporary interference removal signal X ′ to the subtractor 110 and the phase difference detector 140 of the phase noise detector 100 and the feedforward unit 300.

  The feedforward unit 300 will be described. The feedforward unit 300 includes a low-pass filter 310, a numerically controlled oscillator 320, an interference cancellation signal delay adjuster 330, a multiplier 340, and a subtractor 350.

  The low-pass filter 310 receives the interference cancellation signal phase error signal. Then, in the low-pass filter 310, a filtering process for removing noise components (phase noise) is performed. Then, the interference removal signal phase error signal after the filtering process is input to the numerically controlled oscillator 320.

  Note that the low-pass filter 310 has a longer delay time than the low-pass filter 210, but has higher reliability. Specifically, the low-pass filter 310 has a longer delay time than the low-pass filter 210, but has a characteristic that the frequency of a signal to be passed is lower.

  The numerically controlled oscillator 320 inputs a signal having a predetermined power (gain: gain) and phase to the multiplier 340 in accordance with the input interference cancellation signal phase error signal.

The interference cancellation signal delay adjuster 330 performs a delay process for delaying the input temporary interference cancellation signal X ′ for a predetermined time. Then, the interference cancellation signal delay adjuster 330 inputs the provisional interference cancellation signal X ′ _z after the delay processing to the multiplier 340. The predetermined time will be described later.

Multiplier 340, a numerically controlled oscillator 320 multiplies the temporary interference removing signal X _'z where signal interference cancellation signal delay adjuster 330 entered entered, generates a new interference removing signal multiplication results are shown . Incidentally, the multiplication of the numerical control signal oscillator 320 is inputted and the temporary interference removing signal X _'z means a complex operation, the phase is added up together. Then, multiplier 340 inputs the generated new interference removal signal to subtractor 350.

  The subtractor 350 generates and outputs a post-interference removal signal obtained by subtracting the new interference removal signal from the signal based on the post-demodulation signal input by the post-demodulation signal delay adjuster 402.

  Next, the operation of the phase noise detector 100 according to the first embodiment of the present invention will be specifically described.

  It is assumed that the post-demodulation signal obtained by demodulating the reception signal by the demodulator 401 includes the cross-polarization interference signal x in the main signal D. Therefore, the demodulated signal is represented as D + x.

  The subtractor 110 generates a signal after removing temporary interference (D + x−X ′), which is a signal indicating a difference between the result of subtracting the signal X ′ for removing temporary interference from the demodulated signal (D + x).

  Here, when phase noise is appropriately detected by the phase noise detector 100 and compensation processing based on the detection result is appropriately performed by the feedback unit 200, x≈X ′, so provisional interference removal The rear signal is (D + x−X ′) ≈D. Therefore, the signal after provisional interference removal has the content corresponding to the main signal D, and is therefore represented as the signal D after provisional interference removal.

  The hard decision unit 120 generates a hard decision signal d from which noise components have been removed from the input signal D after removing temporary interference. Then, the hard decision device 120 inputs the generated hard decision signal d to the subtractor 130.

  Then, the subtracter 130 generates a cross-polarization interference signal (D + x−d) indicating a difference between the results of subtracting the hard decision signal d from the demodulated signal (D + x). Here, if D≈d, the content of the cross-polarization interference signal is the cross-polarization interference signal x as described above.

  The phase difference detector 140 detects a phase difference between signals having different polarization methods based on the cross-polarization interference signal x and the temporary interference removal signal X ′. Then, the phase difference detector 140 generates an interference cancellation signal phase error signal x ′ that is a signal indicating the phase difference.

  The operation of each unit in the feedback unit 200 will be specifically described. In the feedback unit 200, the interference removal signal phase error signal x ′ is input to the low-pass filter 210 to remove a noise component. The numerically controlled oscillator 220 inputs a signal having a predetermined power and phase to the multiplier 230 in accordance with the phase difference indicated by removing the noise component from the interference cancellation signal phase error signal x ′.

  The multiplier 230 multiplies the signal and the cross polarization interference cancellation signal X input by the XPIC unit 403, and generates a temporary interference cancellation signal X ′ indicating the multiplication result. Note that the numerically controlled oscillator 220, for example, in accordance with the multiplication result by the multiplier 230, causes the inter-polarization interference cancellation signal X to rotate so as to cancel the cross-polarization interference signal x in the complex plane. Generate '.

  The generated temporary interference cancellation signal X ′ is input to the subtractor 110, the phase difference detector 140, and the interference cancellation signal delay adjuster 330.

  The operation of each part of the feedforward unit 300 will be specifically described. In the feedforward unit 300, the low-pass filter 310 receives the interference removal signal phase error signal x 'and removes noise components. Then, the numerically controlled oscillator 320 inputs a signal of predetermined power and phase to the multiplier 340 in accordance with the phase difference indicated by removing the noise component from the interference cancellation signal phase error signal x ′.

Here, is input to the multiplier 340, 'is is _z, both temporary interference removing signal X generated by the multiplier 230' the signal and the temporary interference removing signal X is a signal based on. However, the signal is delayed by the subtractor 110, the hard discriminator 120, the subtractor 130, the phase difference detector 140, the low-pass filter 310, and the numerically controlled oscillator 320 according to the processing time of each unit, and the multiplier. 340 is input. Therefore, the interference cancellation signal delay adjuster 330 performs a delay process for delaying the input temporary interference cancellation signal X ′ by a predetermined time corresponding to the processing time of each part. Then, the interference cancellation signal delay adjuster 330 inputs the provisional interference cancellation signal X ′ _z after the delay processing to the multiplier 340.

The multiplier 340 multiplies the signal input from the numerically controlled oscillator 320 by the temporary interference cancellation signal X ′ _z input from the interference cancellation signal delay adjuster 330, and a new interference cancellation signal x ′ _z indicating the multiplication result. Is generated. Incidentally, the multiplication of the numerical control signal oscillator 320 is inputted and the temporary interference removing signal X _'z means a complex operation, the phase is added up together. Then, the multiplier 340 inputs the generated new interference removal signal x ′ _z to the subtractor 350.

Here, the new interference removal signal x ′ _z input to the subtractor 350 is a signal based on the demodulated signal (D + x), but the subtractor 110, the hard decision device 120, the subtractor 130, and the phase difference detector. 140, a low-pass filter 310, a numerically controlled oscillator 320, and a multiplier 340, and are input to the subtracter 350 after being delayed according to the processing time of each unit. Therefore, the post-demodulation signal delay adjuster 402 inputs to the subtractor 350 a signal obtained by delaying the input post-demodulation signal (D + x) by a predetermined time corresponding to the processing time of each unit.

The subtractor 350 receives the new interference removal signal x ′ _z from the signal obtained by delaying the post-demodulation signal (D + x) input by the post-demodulation signal delay adjuster 402 by a predetermined time corresponding to the processing time of each unit. A signal after interference removal obtained by subtracting is generated and output.

  According to the present embodiment, when the phase noise is appropriately detected by the phase noise detector 100 and the phase noise is appropriately compensated for by the feedback unit 200, the subtractor 130 receives the demodulated signal (D + x) and the hard signal. The determination signal d is input. Here, the hard decision signal d is a signal obtained by removing noise components from the signal D after provisional interference removal. Therefore, the hard decision signal d≈the signal D after provisional interference removal. Then, in the subtractor 130, there is a difference between the post-demodulation signal (D + x) and the hard decision signal d, that is, the cross-polarization interference signal x. Therefore, even when the phase noise is appropriately detected by the phase noise detector 100 and the phase noise is appropriately compensated for by the feedback unit 200, the signals input to the subtractor 130 are different from each other. A cross polarization interference signal (D + x−d) corresponding to the result is output. Then, the cross-polarized wave interference signal (D + x−d) is input to the phase difference detector 140. The phase difference detector 140 detects the phase difference between the input cross-polarization interference signal (D + x−d) and the temporary interference removal signal X ′.

  On the other hand, when the subtractor 130 is configured to receive the signal D after temporary interference removal and the hard decision signal d, the phase noise detector 100 appropriately detects the phase noise, and the feedback unit 200. When the phase noise is appropriately compensated for by the above, the hard decision signal d≈the signal D after provisional interference removal, so that signals having no difference are input to the subtractor 130. Then, a signal corresponding to the 0 vector is input from the subtractor 130 to the phase difference detector 140. Therefore, the signal corresponding to the zero vector and the temporary interference removal signal X ′ are input to the phase difference detector 140. However, the phase difference detector 140 cannot detect a phase difference between a signal corresponding to the 0 vector and another signal. Therefore, the phase difference detector 140 does not operate properly, and the feedback unit 200 or the like cannot operate properly.

  That is, according to the present embodiment, the phase noise detector 100 appropriately detects the phase noise and the phase noise detector corresponding to a wide range of situations including the case where the feedback unit 200 appropriately compensates the phase noise. 100 and the feedback unit 200 and the like can be appropriately operated as a whole.

  Further, according to the present embodiment, the phase noise is appropriately detected by the phase noise detector 100, and the phase noise is appropriately compensated by the feedforward control by the feedforward unit 300. Therefore, compared with the case where the feedforward unit 300 is not provided, it is possible to cope with a reception signal having a higher frequency.

  FIG. 2 is an explanatory diagram showing a range of frequencies that the phase noise detector 100 and the feedforward unit 300 can handle. In FIG. 2, the range in which the phase noise is compensated by feedback control is indicated by hatching, and the range in which the phase noise is compensated by feedforward control is indicated by shading. In other embodiments described later, the same range can be dealt with.

  As shown in FIG. 2, according to the present embodiment, the feedforward unit 300 compensates for phase noise by feedforward control. Therefore, in addition to the case where phase noise is compensated by feedback control, reception of higher frequencies is performed. The phase noise of the signal can be compensated.

Embodiment 2. FIG.
The feedforward part 302 of the 2nd Embodiment of this invention is demonstrated with reference to drawings. FIG. 3 is a block diagram illustrating a configuration example of the feedforward unit 302 according to the second embodiment of this invention. As shown in FIG. 3, in the feedforward unit 302 of the second embodiment of the present invention, an adder 352 is disposed between the low pass filter 310 and the numerically controlled oscillator 320 in the feedforward unit 300 shown in FIG. ing. Further, the cross polarization interference cancellation signal X is input to the interference cancellation signal delay adjuster 330 by the XPIC unit 403. The other elements are the same as those shown in FIG. 1, and thus the same reference numerals as those in FIG.

  The adder 352 receives the interference-removed signal phase error signal x ′ from which noise components have been removed by the low-pass filters 210 and 310, and adds them to each other. A signal corresponding to the addition result is input to the numerically controlled oscillator 320.

  The numerically controlled oscillator 320 inputs a signal having a predetermined power (gain: gain) and phase to the multiplier 340 in accordance with the input signal corresponding to the addition result.

  The interference cancellation signal delay adjuster 330 performs a delay process for delaying the cross polarization interference cancellation signal X by a time obtained by adding the processing time in the adder 352 to the predetermined time described above. Then, the interference cancellation signal delay adjuster 330 inputs the delayed signal to the multiplier 340.

The multiplier 340 multiplies the signal input by the numerically controlled oscillator 320 and the delayed signal, and generates a new interference removal signal x ′ _z indicating the multiplication result. Then, the multiplier 340 inputs the generated new interference removal signal x ′ _z to the subtractor 350.

According to the present embodiment, cross polarization interference cancellation signal X, the multiplier through before it is input to the subtracter 350 becomes the new interference cancellation signal x _'z is only multiplier 340. Therefore, in the first embodiment shown in FIG. 1, it is possible to reduce errors generated in the multiplication process as compared with the case where the data passes through the multiplier 230 and the multiplier 340.

  In addition, the same effects as in the first embodiment can be obtained.

Embodiment 3. FIG.
Next, a phase error detector according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram illustrating a configuration example of the phase error detector according to the third embodiment of the present invention.

  As shown in FIG. 4, the phase error detector according to the third embodiment of the present invention includes a difference calculation unit 13 and a phase difference detection unit 14.

  The difference calculation unit 13 corresponds to the subtractor 130 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG.

  The phase difference detector 14 corresponds to the phase difference detector 140 in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG.

  The difference calculation unit 13 calculates a difference between a signal transmitted and demodulated by one polarization method among a plurality of polarization methods and a signal from which the noise component has been removed.

  Then, the phase difference detection unit 14 detects a phase difference between the demodulated signal and a signal transmitted by another polarization method based on the difference calculated by the difference calculation unit 13.

  According to this embodiment, a signal corresponding to the difference calculated by the difference calculation unit 13 is input to the phase difference detection unit 14. And the said signal is a signal according to the difference of the signal which was transmitted and demodulated by one polarization system among several polarization systems, and the signal from which the noise component was removed from the said signal. Then, the signal is not a signal corresponding to the zero vector.

  Therefore, the phase difference detection unit 14 is based on the signal between the signal transmitted and demodulated by one polarization method among the plurality of polarization methods and the signal transmitted by another polarization method. A phase difference can be detected.

13 Difference calculation unit 14 Phase difference detection unit 100 Phase noise detector 110, 130, 350 Subtractor 120 Hard decision unit 140 Phase difference detector 200 Feedback unit 210, 310 Low-pass filter 220, 320 Numerically controlled oscillator 300, 302 Feed forward unit 330 Interference Rejection Signal Delay Adjuster 340 Multiplier 352 Adder 401 Demodulator 402 Demodulated Signal Delay Adjuster 403 XPIC Unit

Claims (7)

Difference calculating means for calculating a difference between a signal transmitted and demodulated in one polarization method among a plurality of polarization methods and a signal obtained by removing a noise component from the signal;
Phase difference detection means for detecting a phase difference between the demodulated signal and a signal transmitted by another polarization method based on the difference calculated by the difference calculation means. Phase error detector. A difference between the demodulated signal and a signal subjected to feedback processing for removing interference from a signal transmitted according to another polarization method to a signal corresponding to the phase difference detected by the phase difference detection unit The phase error detector according to claim 1, further comprising: a noise component removal signal generation unit that generates a signal from which the noise component has been removed from the demodulated signal based on. A phase error detector according to claim 1 or claim 2;
A signal corresponding to the phase difference detected by the phase difference detection means, and a signal based on a signal subjected to feedback processing for removing interference from the signal transmitted by the other polarization method to the signal. Multiplication means for calculating a multiplication result;
By subtracting the signal according to the calculation result by the multiplication means from the signal based on the signal transmitted and demodulated by the one polarization method, interference from the signal transmitted by the other polarization method is removed. And a subtracting means for generating a received signal. A noise component removing unit for removing a noise component from a signal corresponding to the phase difference detected by the phase difference detecting unit, which is input to the multiplying unit;
A feedback process for removing interference from a signal transmitted by the other polarization method is delayed based on a processing time in the noise component removing means based on a signal applied to a signal corresponding to the phase difference The inter-polarization interference cancellation system according to claim 3, further comprising: a delay unit that inputs to the multiplication unit. A phase error detector according to claim 1 or claim 2;
Based on a signal corresponding to the phase difference detected by the phase difference detecting means and a signal for compensating interference from a signal transmitted by the other polarization method in the signal transmitted by the one polarization method Multiplication means for calculating a multiplication result with the signal;
By subtracting the signal according to the calculation result by the multiplication means from the signal based on the signal transmitted and demodulated by the one polarization method, interference from the signal transmitted by the other polarization method is removed. And a subtracting means for generating a received signal. A noise component removing unit for removing a noise component from a signal corresponding to the phase difference detected by the phase difference detecting unit, which is input to the multiplying unit;
6. A delay unit that delays a signal in which interference from a signal transmitted by the other polarization method is compensated based on a processing time in the noise component removing unit and inputs the delayed signal to the multiplying unit. The described polarization interference cancellation system. Calculating a difference between a signal transmitted and demodulated in one polarization method among a plurality of polarization methods and a signal from which a noise component has been removed from the signal;
A phase error detection method, comprising: detecting a phase difference between the demodulated signal and a signal transmitted by another polarization method based on the calculated difference.

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