JP2663906B2 - Cross polarization interference compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross polarization interference compensator used in digital radio communication, and more particularly to a cross polarization interference compensator using a digital transversal filter.

[0002]

2. Description of the Related Art In a dual-polarization transmission system in which a data signal is transmitted using two orthogonal polarizations having the same frequency and orthogonal to each other, a data signal transmitted with its own polarization is cross-polarized from a different polarization. To eliminate wave interference, a cross-polarization interference compensator that creates an interference component from a data signal transmitted with a different polarization using a transversal filter and subtracts from the data signal transmitted with its own polarization Used.

A normal transversal filter used by such a cross-polarization interference compensator integrates the output of each tap and the error component of the cross-polarization interference-compensated data signal, and outputs the integrated value and the immediately preceding addition output. Further, the output of the adder to be added is set as the latest tap weighting coefficient of the corresponding tap. This adder integrates the integrated value from time 0 to time t and expresses the integrated value as a tap weighting coefficient at time t + 1 when the time is represented by the symbol period of the data signal (for example, Japanese Patent Laid-Open No. 55-133156). .

In such tap weight control, when a minute bias is superimposed on an integrated value, which is an integrand, due to incompleteness of hardware or the like, a minute bias is added as a result of long-time integration. As a result, the tap weighting coefficients may continue to grow and overflow, and correct tap weight control may not be performed.

In order to avoid such a situation,
There is known tap weighting control in which a correction value, which is a constant value of a sign corresponding to a sign of a tap weighting coefficient at time t, is subtracted from an integrated value, which is an integrand, and then input to an adder. By performing this correction to reduce the influence of the integrand value accumulated in the past, the influence of the accumulation of the minute bias can be eliminated.

[0006]

By the way, as described above, a transversal for tap weighting control for eliminating the influence of the accumulation of minute bias on a data signal obtained by demodulating a coded digitally modulated reception signal transmitted wirelessly. When decoding by cross-polarization interference compensation using a conventional cross-polarization interference compensator that uses a filter, it takes time to re-lock the synchronization if the carrier synchronization, clock synchronization of the demodulator, or code synchronization of the decoder is lost. There is. An object of the present invention is to make it possible to shorten the re-locking time of the demodulator or the decoder, and to eliminate the influence of the accumulation of the minute bias from the tap weighting coefficient as described above after the pull-in. It is an object of the present invention to provide a cross polarization interference compensator that can be used.

[0007]

The cross-polarization interference compensator of the present invention has been wirelessly transmitted using the first of the first and second polarizations having the same frequency and orthogonal to each other as a carrier. A combiner combines a first data signal and an output signal of a transversal filter that inputs a second data signal wirelessly transmitted using the second polarization as a carrier, and receives the first data signal. A cross polarization interference compensator for compensating for cross polarization interference, wherein each of the tap weighting coefficient generation means of the transversal filter outputs an output signal of a corresponding tap and an output signal of the combiner. An integrator that generates and outputs a signal corresponding to an integrated value of the error component including the error component, a first adder that adds a correction value to an output signal of the integrator, an output signal of the first adder, The integration And a second adder for further adding the output signal of the selector and the output signal immediately before the selector and outputting the same as the latest tap weighting coefficient. A correction value generator that has a polarity corresponding to the polarity of the output signal of the second adder, generates the correction value whose absolute value is a predetermined value, and outputs the correction value to the first adder. Including.

In the present invention, the first data signal is a coded signal, and the output signal of the first adder is selected when a decoder for decoding the output signal of the synthesizer is code-synchronized. The selector may be controlled so as to select an output signal of the integrator when code synchronization is lost.

When the first demodulator that generates the first data signal by using the reference carrier reproduced based on the error component included in the output signal of the synthesizer to generate the first data signal is out of synchronization with the carrier, the integration is performed. The selector may be controlled to select an output signal of the detector.

Further, a first demodulator for generating the first data signal by sampling / analog digitally sampling a baseband signal at a timing of a clock reproduced based on an error component included in an output signal of the synthesizer. The selector may be controlled to select an output signal of the integrator when clock synchronization is lost.

Further, the selector may be controlled so as to select an output signal of the integrator when carrier synchronization or clock synchronization of a second demodulator for generating the second data signal is out of synchronization. .

Further, the tap interval of the transversal filter is n times the symbol interval of the second data signal.
/ M (m and n are positive integers).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

Referring to FIG. 1 showing an embodiment of the present invention, a received signal 101 on the self-polarized side and a received signal 102 on the different-polarized side are both digitally modulated by a data signal at a transmitting end, and have the same radio frequency. Are received signals in the intermediate frequency band transmitted using horizontal and vertical polarizations orthogonal to each other. The data signal on the own polarization side is error-correction-coded at the transmitting end.

The demodulator 1 reproduces a reference carrier in synchronization with the reception signal 101 on the self-polarization side, and synchronously detects the reception signal 101 using the reference carrier to obtain a baseband signal. Then, a reproduction clock is generated in synchronization with the clock, a baseband signal is sampled using this reproduction clock, converted from analog to digital, and output as a data signal 103 on the self-polarization side. If the carrier synchronization and the clock synchronization are normal, the logic "0",
If the carrier synchronization or the clock synchronization is lost, a synchronization state signal 111 which becomes logic "1" is output. Similarly, the demodulator 2 performs the data signal 104 and the synchronization state signal 1 on the different polarization side.
12 is output. The data signal 104 on the different polarization side is input to the transversal filter 3.

The transversal filter 3 converts the input data signal 104 on the different polarization side into 1/1 of the symbol interval.
Weighting devices 33, 34, 35 for weighting data lines 104, 104-1 and 104-2, which are tap outputs, based on given tap weighting coefficients C1, C2 and C3. And a synthesizer 36 for synthesizing the output signals of the weighters 33, 34, 35.

The data signal 104 on the different polarization side is
1, and also to the weighter 33 and the tap weighting coefficient generator 7 as the first tap output. Data signal 104-1 which is an output signal of delay line 31
Is input to the delay line 32 and also to the weighter 34 and the tap weighting coefficient generator 8 as the second tap output. The data signal 104-2, which is the output signal of the delay line 32, is input to the weighter 35 and the tap weighting coefficient generator 9 as a third tap output. The weighters 33, 34, and 35 input the data signals 104, 10
4-1 and 104-2 and tap weighting coefficient generator 7,
Tap weighting coefficients C1, C2, C generated in 8 and 9
3, and the synthesizer 36 calculates the weights 33, 3
The total sum of the integrated outputs of 4, 35 is calculated and output as a cross polarization interference compensation signal 105.

The coupler 4 outputs the data signal 103 on the self-polarization side.
And the cross polarization interference compensation signal 105,
06, it is output to the demodulator 1, the error detector 5, and the decoder 6. The cross-polarization interference compensation signal 105 is a signal having the same amplitude and opposite polarity as the cross-polarization interference component received by the data signal 103 on the own polarization side, and the data signal 106 is a signal from which the cross-polarization interference has been removed. It is.

The error detector 5 receives the data signal 106, detects an error component remaining in the data signal 106, and outputs it as an error signal 107 to the demodulator 1 and the tap weighting coefficient generators 7, 8, and 9. Demodulator 1 receives data signal 106
The control signal for carrier synchronization and clock synchronization is obtained by logically operating the error signal 107. These logical operations are described in JP-A-57-131151 and JP-A-59-161149. Decoder 6
Performs error correction decoding of the data signal 106 and performs
08, and outputs a code synchronization state signal 113 which becomes logic "0" when code synchronization is normal and becomes logic "1" when code synchronization is lost.

The tap weighting coefficient generators 7, 8, 9
Tap output 1 input from transversal filter 3
04, 104-1 and 104-2 are correlated with the error signal 107 input from the error detector 5 to generate tap weighting coefficients C1, C2 and C3.
34 and 35. Tap weighting coefficient generator 7,
8 and 9 have two operation modes.
2. OR gate 1 for inputting the code synchronization state signal 113
The operation mode is switched according to the state of the output signal 114 of 0.

The tap weighting coefficient generator 7 includes an integrator 71 which receives the data signal 104 input from the transversal filter 3 as the first tap output and the error signal 107 input from the error detector 5 as an integration input, Bowl 71
, A first adder 73 that takes the output signal of the integrator 72 as one of the additional inputs, an adder output of the first adder 73, and an adder. AND gate 1
When the state of the 0 output signal 114 is logic "0", the selector 74 selects and outputs the added output of the first adder 73, and when the state of the output signal 114 is logic "1", selects and outputs the output signal of the integrator 72. ,
The selected output of the selector 74 is used as one addition input, and its own output is used as the tap weighting coefficient C1.
To the other, and as the other addition input of its own
, The polarity of the tap weighting coefficient C1 is determined, and if the polarity is positive, a predetermined negative value −β is calculated.
If it is negative, it comprises a correction value generator 76 which generates a positive value + β and outputs it to the first adder 73 as the other addition input, and a reset circuit 77. Reset circuit 77
Outputs the tap weighting coefficient C1 input from the second adder 75 to the weighting unit 33 as it is when the state of the output signal 115 of the OR gate 11 for inputting the synchronization state signals 111 and 112 is logic "0". When the logic value is "1", the tap weighting coefficient C1 is intermittently reset to the value "0". The configuration of the tap weighting factor generators 8 and 9 also indicates that the tap outputs input from the transversal filter 3 are the data signals 104-1 and 104-2, and the tap weighting factors to be output are the tap weighting factors C2 and C3. Except for this, the configuration is the same as that of the tap weighting coefficient generator 7.

The received signal 101 on the own polarization side and the received signal 102 on the different polarization side are normally received, and the demodulator 1
2 is normal and the cross-polarized interference received by the data signal 103 on the self-polarization side is small, the error rate of the data signal 106 output from the coupler 4 is small, and the Operates normally and the synchronization status signal 1
The states of 11, 112 and the code synchronization state signal 113 are all logic "0", and both the signals 114 and 115 are logic "0".
Becomes In this case, tap weighting factor generators 7, 8,
The selector 74 selects and outputs the added output of the first adder 73, and the reset circuit 77 stops the reset operation.

In this case, the tap weighting coefficient generator 7,
When the operations of 8 and 9 are expressed by equations, tap weighting coefficients C1, C2, and C3 at time t are represented by C (t) and tap output 10
4, 104-1 and 104-2 are D (t), error signal 10
7 is E (t), and sgn (X) is a function indicating the polarity of X.

C (t + 1) = C (t) −α {E (t) · D (t)} − βsgn {C (t)} (1) The first term and the first term on the right side of equation (1) The second term indicates an operation in which the output of the integrator 72 is integrated by the second adder from time 0 to time t. The effect of accumulation of minute vias received by the output of the integrator 72 due to the integration over a long time is eliminated by the correction of the third term. The correction operation indicated by the third term is performed by the correction value generator 76 and the first adder 73.

The deterioration of the error rate characteristic of the data signal 106 due to the deterioration of the radio wave propagation state on the self-polarization side or the different polarization side, and the code synchronization of the decoder 6 is lost due to the loss of the code synchronization of the decoder 6. If the state of the signal 114 is logic "1", the tap weighting factor generator 7,
Tap output D (t) input to 8, 9 and error signal E
At least the error signal E (t) of (t) contains many errors, and thus the generated tap weighting coefficient C
Since (t) also includes many errors, the transversal filter 3 operates incorrectly. In such a state, even if the correction shown in the third term of Expression (1) is performed based on the tap weighting coefficient C (t) having many errors, it is not effective. When the deterioration of the error rate characteristic of the data signal 106 decreases again and the decoder 6 is in the process of re-locking, the error of the tap weighting coefficient C (t) also decreases with time. Weighting coefficient C (t)
And the latest tap weighting coefficient C (t +
When 1) is generated, the adverse effect of the erroneous correction becomes larger than the effect of the correction.
, Erroneous operation is prolonged, so that the re-synchronization of the decoder 6 is delayed. Therefore, when the code synchronization of the decoder 6 is lost and the state of the signal 114 becomes logic “1”, the selector 74 selects the output of the integrator 72 and outputs it directly to the second adder 75 to generate the correction value. The correction operation by the adder 76 and the first adder 73 is bypassed. This control of the selector 74 by the code synchronization state signal 113 and the signal 114 can prevent the synchronization re-pulling time of the decoder 6 from becoming long.

When the carrier state or the clock synchronization of the demodulator 1 on the self-polarization side is lost due to the deterioration of the radio wave propagation state on the self-polarization side and the synchronization state signal 111 becomes logic "1", Becomes indefinite and the error signal 10
7 is also undefined, and the tap weighting coefficient generators 7, 8, 9
Is unstable, and the control of the transversal filter 3 diverges. In this case, the signal 115 is set to logic "1" via the OR circuit 11, and the tap coefficients C1, C
2. C3 is intermittently reset to the value "0" to promote re-pull of the control of the transversal filter 3, and as a result, control signals of carrier wave synchronization and clock synchronization are generated from the data signal 106 and the error signal 107. The re-locking of the carrier synchronization or the clock synchronization of the demodulator 1 is promoted. During this re-locking, the code synchronization of the decoder 6 is lost, the code synchronization state signal 113 and the signal 114 become logic "1", and the selector 74 selects the output of the integrator 72 and directly sends it to the second adder 75. And the correction operation by the correction value generator 76 and the first adder 73 is bypassed, so that the adverse effect of this correction operation causes the re-pull-in time of the control of the transversal filter 3 and, consequently, the re-pull-in time of the demodulator 1. , Decoder 6 can be prevented from becoming long.

When the synchronization state signal 112 becomes logic "1" due to the loss of carrier or clock synchronization of the demodulator 2 on the different polarization side due to deterioration of the radio wave propagation state on the different polarization side, etc. Data signal 104, cross polarization interference compensation signal 10
5 is undefined, the error signal 107 is also undefined, and the control of the transversal filter 3 diverges. As a result, an OR circuit 11 is provided to prevent the data signal 106 from being disturbed via the coupler 4 by the indeterminate cross-polarization interference compensation signal 105 and to promote re-pulling of the control of the transversal filter 3. To make the signal 115 logic "1", causing the reset circuit 77 to perform a reset operation. During this reset operation period, the signal 114 is set to logic "1" by using the OR circuit 10, and the selector 74 selects the output of the integrator 72, and the correction value generator 76 and the first adder 7
Bypassing the correction operation by the control unit 3 prevents the re-pull-in time of the control of the transversal filter 3 and, consequently, the re-pull-in time of the decoder 6 from becoming long due to the adverse effect of the correction operation.

As described above, when the error rate characteristic of the data signal 106 output from the coupler 4 is significantly deteriorated, it is better not to perform the correction by the correction value generator 76 and the first adder 73 on the transversal filter 3. Fewer incorrect operations. Therefore, even if the data signal 103 on the self-polarization side is not coded, if the error rate of the data signal 106 is monitored and an alarm is generated when the error rate exceeds the threshold value, the alarm is generated. The selector 74 is input to the OR circuit 10 instead of the synchronization state signal 113 to control the selector 74. During the occurrence of the alarm, the selector 74 selects the output of the integrator 72 to output the correction value generator 76 and the first If the correction by the adder 73 is not performed, the erroneous operation of the transversal filter 3 during this period is reduced. When such an alarm is not obtained, the synchronization state signal 111 of the demodulator 1 is input to the OR circuit 10, and during the synchronization re-locking of the carrier synchronization or the clock synchronization of the demodulator 1, the correction value generator 76 and the By bypassing the correction operation by the 1 adder 73, it is possible to prevent the re-locking time of the demodulator 1 from being lengthened due to the adverse effect of the correction operation.

The transversal filter 3 includes a delay line 3
The data signal 10 on the different polarization side to which the delay amounts of 1, 32 are input
4 is set to の of the symbol interval. If the symbol interval is the same between the data signal 103 on the own polarization side and the data signal 104 on the different polarization side, this fineness of the delay amount is sufficient. If the symbol interval of both data signals is different,
The fineness of the delay amount needs to be about 1/2 of the symbol interval of the data signal 103 on the self-polarization side. Since the delay line is usually realized by a flip-flop, the amount of delay of the delay lines 31 and 32 is set to n / m of the symbol interval of the data signal 104 on the different polarization side to be input, from the viewpoint of ease of clock generation.

[0030]

As described above, the present invention eliminates the influence of the accumulation of the minute bias superimposed on the integrated value of the output of each tap and the error component of the data signal subjected to the cross polarization interference compensation. Compensation for cross-polarization interference using a transversal filter that performs tap weighting control to perform correction enables stable tap weighting control, and
A selector was added to stop the correction to eliminate the effect of the accumulation of minute bias, so the correction was stopped when the error rate characteristics of the data signal for which cross polarization interference compensation was significantly deteriorated. The erroneous operation of the transversal filter can be reduced, and the demodulator on the self-polarization side that performs carrier synchronization or clock synchronization loses synchronization based on the error component of the data signal compensated for cross-polarization interference, or Stopping the correction when the decoder that decodes the data signal in which the signal is encoded and decoding the cross-polarized interference compensated data signal is out of synchronization can prevent the demodulator and the decoder from having a longer re-locking time. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

 1, demodulator 3 transversal filter 4 synthesizer 5 error detector 6 decoder 7, 8, 9 tap weighting coefficient generator 71, 72 integrator 73 first adder 74 selector 75 second adder 76 Correction value generator 77 Reset circuit

Claims (6)

(57) [Claims] 1. A first data signal wirelessly transmitted using a first polarization as a carrier among first and second polarizations having the same frequency and orthogonal to each other, and the second polarization as a carrier. A cross-polarization interference compensator for compensating for cross-polarization interference received by the first data signal by synthesizing in a synthesizer an output signal of a transversal filter for inputting a second data signal wirelessly transmitted. Wherein each of the tap weighting coefficient generation means of the transversal filter generates a signal corresponding to an integrated value of an output signal of the corresponding tap and an error component included in an output signal of the combiner. An integrator to be output, a first adder for adding a correction value to an output signal of the integrator, and one of an output signal of the first adder and an output signal of the integrator is selected and output. Selection Selector, a second adder that further adds the output signal of the selector and the output signal immediately before the selector and outputs the result as the latest tap weighting coefficient, and a polarity of the output signal of the second adder. Generating the correction value having a corresponding polarity and an absolute value being a predetermined value;
A cross-polarization interference compensator comprising: a correction value generator that outputs the correction value to the adder. 2. The method according to claim 1, wherein the first data signal is an encoded signal, and the decoder selects an output signal of the first adder when a decoder for decoding an output signal of the synthesizer is code-synchronized. 2. The cross polarization interference compensator according to claim 1, wherein the selector is controlled so as to select an output signal of the integrator when code synchronization is lost. 3. The first carrier using a reference carrier reproduced based on an error component included in an output signal of the combiner for synchronous detection.
2. The cross polarization interference compensation according to claim 1, wherein said selector is controlled so as to select an output signal of said integrator when a carrier of said first demodulator for generating said data signal is out of carrier synchronization. vessel. 4. A clock synchronization of a first demodulator which generates the first data signal by sampling / analog-digital sampling a baseband signal at a timing of a clock reproduced based on an error component included in an output signal of the synthesizer. The cross-polarization interference compensator according to claim 1, wherein the selector is controlled so as to select an output signal of the integrator when the distance is deviated. 5. The method according to claim 1, wherein the selector is controlled so as to select an output signal of the integrator when carrier synchronization or clock synchronization of a second demodulator for generating the second data signal is lost. The cross polarization interference compensator according to claim 1. 6. The tap interval of the transversal filter is n / m of the symbol interval of the second data signal.
2. The method according to claim 1, wherein (m, n are positive integers).
A cross-polarization interference compensator as described.