JP2894088B2 - Interference wave canceller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference wave removing apparatus,
In particular, the present invention relates to an interference wave removing apparatus capable of removing a wideband interference wave which is a strong near-end interference wave such that D / U (desired wave to interference wave ratio) becomes negative in a line-of-sight microwave communication line employing angle diversity. .

[0002]

2. Description of the Related Art In general, a line-of-sight microwave communication line employing angle diversity is irradiated with microwaves from a transmission antenna 301 via a transmission horn 302 from a transmission point A and scattered at a scattering point P as shown in FIG. The main beam received by the main beam horn 304 from the antenna 303 at the receiving point B and the angle beam scattered at the scattering points Q having different path differences, and the so-called multipath radio wave is received by the angle beam horn 305. Forming a communication line. The propagation time of the angle beam taking the path of AQB and the propagation time of the main beam taking the path of APB fluctuate with the elevation angle of the angle beam horn 305 and propagation conditions. On the other hand, when there is a strong interference wave J called a near-end interfering wave at the receiving point B, interference from an FM line near the receiving point on a digital line-of-sight microwave line using PSK or QAM, or an adjacent channel Interference such as interference from the vehicle may be a problem. In particular, when digital transmission is performed at high speed, the FM interference wave can be regarded as a narrow band interference wave, but other interference waves may have a wide band. Particularly, since the reception signal level in the non-line-of-sight communication is low, the interference wave level tends to be higher.

On the other hand, in addition to the interference from the vicinity, the transmission point A
In a non-line-of-sight communication line in which multipath fading of a strength generated between the receiving points B and B occurs, an angle diversity system and an adaptive equalization technique for eliminating intersymbol interference are indispensable, and the propagation distance is large as in non-line-of-sight communication. In a line, a matched filter (MF) and a decision feedback equalizer (DFE) have been developed as important techniques for canceling intersymbol interference.

Conventionally, there is a conventional technique using a power inversion adaptive array in order to remove the former broadband interference wave near the receiving point. As shown in the block diagram of FIG. 4, this system comprises a main antenna 102 for a receiving antenna, an angular beam horn 103, receivers 104 and 105 including a PSK demodulator, and AGC amplifiers 106 and 107 for baseband level stabilization. , Multipliers 110 and 111, correlators 112 and 113, and adder 11
5, a subtractor 116, AGC amplifiers 108 and 109, a switch 117, an adaptive matched filter (AMF) 118, a decision feedback equalizer 119, and a switch controller 122.

Next, the operation of the conventional example will be described. Each diversity input is demodulated at receivers 104, 105 and AGC
After the level fluctuation due to fading is removed by the amplifiers 106 and 107, the signal is passed through multipliers 110 and 111.
The multipliers 110 and 111 are multiplied by the complex tap coefficients from the correlators 112 and 113, respectively. These tap coefficients are correlation values between the outputs of the AGC amplifiers 106 and 107 and the outputs of the AGC amplifier 108 after the diversity synthesis.
These correlation values are complex conjugates of transfer coefficients with respect to the input signals of the multipliers 110 and 111.
The outputs of 111 are in phase with respect to the phase and the square of the input with respect to the amplitude. Therefore, the output of the multiplier 110 and 11
By combining the outputs of 1 with the adder 115, maximum ratio combining is performed. When there is no interference wave, the switch 117
Selects and outputs the maximum ratio combining route of the outputs of the AGC amplifiers 108 and 109. The switching controller 122 normally selects the side of the adder 115. However, the line monitor monitors the bit error rate or S / N indicating the line quality and greatly increases the bit error rate due to strong interference. When the deterioration or the like is recognized, switching is performed by the switching controller 122 so as to select the side of the subtractor 116 described below. This subtractor 116 is a multiplier 1
The output of the multiplier 111 is subtracted from the output of 10, and the adder 115 performs in-phase synthesis on the phase, while the subtractor 116 performs anti-phase synthesis to remove the interference wave. That is, the output of the subtractor 116 is equivalent to the output of the power inversion adaptive array.

Next, the operation of removing the interference wave will be described with reference to FIG. 5 which is an explanatory diagram of the vector synthesis of the desired waves S1, S2 and the interference waves J1, J2. FIGS. 5A to 5C show the input 1, that is, the angle beam horn 103, the multiplier 110, and the adder 1.
5 (d) to 5 (f) show the input 2, namely the main beam horn 102, the multiplier 111, and the subtractor 11
6 is shown. 5 (g) to 5 (i) and FIG.
(J) to (l) correspond to the above-described input 1 and input 2, respectively, and show a case where the desired wave and the interference wave are at special vector positions.

Now, when the interference wave is so large that the D / U becomes minus, the interference waves are controlled so as to be in-phase combined with each other, as shown in FIGS. 5B and 5E.
At the 0 and 111 outputs, the interference waves J1 and J2 have the same amplitude and phase. In this case, FIG.
Five outputs show in-phase synthesis of interference waves. On the other hand, as shown in FIG. 5 (f), in the subtractor 116, the interference waves are subjected to antiphase synthesis with each other, the interference wave is removed, and only the desired signal wave is extracted. However, for the desired waves S1 and S2, not only the maximum ratio combining but also the in-phase combining is not performed. In particular, the desired signal wave may disappear due to the phase relationship between the desired wave S and the interference wave J. When the inputs 1 and 2 have the same amplitude and phase relationship between S and J as shown in FIGS. 5 (g) and 5 (j),
The outputs of the multipliers 110 and 111 match as shown in FIGS. 5 (h) and 5 (k). At this time, as shown in FIG.
The output is in-phase synthesis for both S and J, and the output of the subtractor 116 is
Is also reversed-phase synthesis. That is, although the interference wave has been removed, the desired signal wave also disappears.

The adder 11 when the interference wave is large
5, the operation of the subtractor 116 will be described in further detail.
With five outputs, the interference wave level is higher than the desired wave level, and the interference wave is used as a reference signal by the correlators 112 and 113.
Will be returned to That is, the multipliers 110 and 111 are multiplied by a weighting factor that combines the interference waves between the diversity branches at the maximum ratio. On the other hand, the subtractor 116 is
5 performs the reverse operation of the maximum ratio combination. Since the interference wave level at the input of the subtractor 116 is normalized by the AGC amplifiers 106 and 107, the interference wave is removed at the output of the subtracter 116, and the desired wave is output. In the above description, the operation of adding or subtracting the desired wave S and the interference wave J has been described using a vector. Of the desired wave S and the interference wave J, particularly the desired wave S has a time difference between the main beam horn and the angle beam horn. Therefore, the symbols a0, a-1, a-2, a-3 (one symbol corresponds to two bits in the case of four-phase PSK) of the time-series digital reception signal are received.
A temporal correlation shift occurs between the main beam and the angle beam. That is, as shown in FIG. 6, the time-series signal format of the desired wave S1 at the output of the multiplier 110 in the angle beam reception has a period T and the symbols a1, a0, a-1 to a
-4, the multiplier 1 in the main beam reception
If the time-series signal format of the desired wave S2 at 11 outputs is shifted by a period T and arranged like symbols a2, a1, a0 to a-3, for example, the symbols a0 are shifted by a period T, No state is shown. However, when the time difference between the main beam and the angle beam reception is less than half of the period T, for example, the correlation between the symbols a0, a1 and the like becomes large. As shown in (f) and (l), interference between desired waves and elimination of symbols of the desired wave occur in the worst case. In the case of the interference wave, as shown in FIG. 6, since the interference is from the vicinity, there is no time lag between the angle beam reception and the main beam reception, and the target interference wave cancellation is performed normally. When the time lag between the desired waves is τ due to multipath fading or the like without the above-mentioned interference wave, the impulse response due to the two-wave propagation is centered on the main response by the adaptive matching filter 118 as shown in FIG. Symmetrized. The main response 312 is 311 by a matched filter.
Is the main response resulting from focusing the dispersed energy on the main response 310, and its amplitude level is higher than 310. This is SN by matched filtering
Interpreted as a ratio maximizing operation. Note that the delay response of 311 is dispersed to a small level of the delay-advance response of 314 and 313, and the load on the adaptive equalization operation of the decision feedback equalizer 119 can be reduced.

[0009]

As described above, in the conventional interference wave canceling apparatus, when trying to cancel the interference wave, the maximum ratio combining of the diversity or the in-phase combining is not performed for the desired wave. However, there is a drawback that optimal reception and interference wave elimination are not compatible with adaptive equalization in a line having a problem, and a desired signal is lost in the worst case.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an interference wave canceling apparatus capable of preventing a desired wave from disappearing due to interference cancellation and removing strong broadband interference waves without impairing the diversity effect.

[0011]

SUMMARY OF THE INVENTION An interference wave removing apparatus according to the present invention comprises a first receiver for demodulating a received signal from an angle beam horn in angle diversity, and a first receiver for removing a fluctuation in the output level of the first receiver. AGC amplifier and the first
Receiving means having a first multiplier for multiplying an output signal of the AGC amplifier corresponding to a coefficient signal inputted from a first external terminal, and receiving from the main beam horn in the angle diversity A second receiver for demodulating the signal and a second receiver for removing the output level fluctuation of the second receiver.
AGC amplification of the second AGC amplification, a second multiplier for multiplying an output signal of the second AGC amplification by a coefficient signal inputted from a second external terminal, and the first reception means, And an adder that receives the output signal of the second receiving means and performs addition and synthesis, the output signal of the adder, and the first A
A first correlator for supplying a coefficient corresponding to a correlation value correlated with an output signal of the GC amplifier to the first external terminal, an output signal of the adder, and an output signal of the second AGC amplifier; The coefficient corresponding to the correlation value obtained by taking the correlation
A subtractor for inputting the output signals of the first and second receiving means and synthesizing the interfering interference signal mainly in reverse phase, and the adder or the subtractor. And an adaptive matching filter and a decision feedback equalizer connected to the output of the switch to select the output signal of the diversity output signal. In the interference wave canceling device for monitoring the judgment data for judging the quality and selecting the switch, an output signal of the judgment data and the first AGC increase signal are output.
At the time of relative delay greater than the relative delay time difference τ1 from the width output
A delay element for setting the interval τ (τ1 <τ) in advance, a third correlator for correlating an output signal of the delay element with an output signal of the first AGC amplifier, and an output from the third correlator. Angle beam horn control means for controlling the elevation angle of the angle beam horn by inputting a coefficient corresponding to a correlation value signal, and controlling the line quality of the determination data output in response to the elevation angle change of the angle beam horn. Control is performed so that the correlation value of the third correlator is maximized in order to improve the correlation.

[0012]

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, and FIG.
It is operation | movement explanatory drawing of an Example of this. 1, the same reference numerals as those in the conventional example of FIG. 4 have the same configuration and function. That is, in this embodiment, the correlator 114 and the angle beam horn controller 1
20, a delay element 121, and an angle beam horn 103A that can change the angle in the elevation direction by control.

Next, the operation of this embodiment will be described. In FIG. 1, the angle beam horn 103A and the main beam horn 10A
2 from receivers 104 and 10 respectively.
The signal is converted from a radio frequency into an intermediate frequency signal or a baseband signal by 5 and the level is standardized by AGC amplifiers 106 and 107. AGC amplifiers 106 and 10
7, 108, 109, multipliers 110, 111, correlators 112, 113, adder 115, and subtractor 116.
Constitutes the same power inversion adaptive array as the conventional configuration. The output of the adder 115 corresponds to the maximum ratio combined output of diversity, and the subtractor 11
Six outputs correspond to the power inversion adaptive array output. Now, the relative delay time difference between the main beam and the angle beam signal in FIG. 2 will be described with reference to FIG. By adjusting and controlling the setting direction of the angle beam horn, the delay difference due to the angle beam can be kept constant. However, the decision data signal 320 of the decision feedback equalizer 119 is now delayed by τ in advance by the delay element 121, Judgment data signal 321
The cross-correlation is taken by the correlator 114 with the output signal 322 of the AGC amplifier 106.

Assume that the relative delay difference between the determination signal 320 and the output signal 322 before the angle horn adjustment is τ1. When the direction of the angle beam horn approaches the direction of the main beam horn and the delay difference of the desired wave between the diversity branches is smaller than τ (τ1 <τ), the correlation output of the correlator 114 is small. On the other hand, when the direction of the angle beam horn is changed so as to increase the angle difference of the reception horn, τ2 in FIG.
As shown in the figure, the angle beam reception wave is delayed from the main beam reception wave. That is, the output of the correlator 114 increases, and the correlation value becomes maximum when the delay of the angle beam reception wave becomes τ. Therefore, the angle beam horn controller 120 controls the correlator 11
The direction adjustment of the angle beam horn is automatically controlled so that the correlation value of 4 becomes maximum. This operation makes it possible to always delay the angle beam reception wave by τ. By the way, the correlation value of the correlator 114 causes a short-term amplitude / phase fluctuation due to Rayleigh fading. Therefore, if the angle beam horn 103 is directly controlled from now on, the adjustment of the direction of the angle beam horn is performed by short-term fading, and the angle beam horn 103 does not correspond to the propagation path length difference between the angle diversity branches shown in FIG. Accordingly, the angle beam horn controller 120 averages the correlation value of the output of the correlator 114 to obtain the median value,
Control is performed to maximize this. When τ is set to T of the transmission symbol period, the desired wave components at the outputs of the multipliers 110 and 111 correspond to τ = T in FIG.
On the other hand, when a broadband interference wave is applied near the receiving point,
The delay difference of the interference wave between the diversity branches can be ignored as described in the conventional example. The interference wave components at the outputs of the multiplier 110 and the multiplier 111 are removed by the subtractor 116 because the interference waves between the diversity branches are controlled to have the same amplitude and the same phase at the outputs of the multipliers 110 and 111. You. For the desired wave, a symbol shift occurs due to a delay difference between the diversity branches, and the signal does not disappear even if the desired waves are combined in opposite phases.

Next, a second embodiment of the present invention will be described with reference to FIG. That is, the delay element 24 described in the first embodiment
2, correlators 229 and 230, angle horn controller 211,
212, angle horns 205 and 20 that can be changed in the elevation direction
6 is an embodiment in which space diversity used in combination with angle diversity, that is, quadruple diversity, is applied. In FIG. 3, spatial diversity reception is performed by reception antennas 201 and 202, and main beam horn 203 is received.
And 204 and the angle beam horns 205 and 206 perform angle diversity to obtain four uncorrelated diversity branch signals. The interference cancellation by the power inversion adaptive array is performed between the angle diversity branches, and the adaptive diversity filters 237 and 238 perform the adaptive diversity combination between the respective spatial branches. In these adaptive matched filters, maximum ratio combining is performed for both the implicit diversity combining in the time domain and the ordinary spatial diversity combining. Therefore, a strong signal-to-noise ratio improvement is performed on the desired signal, and at the same time, the waveform distortion due to multipath fading is reduced and removed by the decision feedback equalizer 240.

Since the propagation by the main beam and the angle beam undergoes Rayleigh fading independent of each other, the respective responses 310 and 311 also have level phase fluctuations that are uncorrelated with each other. Even after the main response of 310 drops in level, 3 after matched filtering
Since the eleven delayed waves can be converted to the main wave, they can be used as desired signals. That is, the diversity effect in the time domain can be realized by the matched filter. This effect is called an implicit diversity gain. Therefore, even if interference diversity is removed by this method, even if the apparent diversity branch is degenerated, the diversity gain is preserved as implicit diversity due to the delay difference between the angle diversity branches. From the above, it is possible to solve the problem that the diversity effect cannot be obtained by the conventional interference cancellation method using diversity.

[0017]

As described above, according to the present invention, by controlling the direction of the angle beam receiving horn in the angle diversity reception, a delay difference is generated between the received waves of the main beam and the angle beam. Even if interference is removed by the power inversion adaptive array, it is possible to eliminate strong signal and eliminate wideband interference and multipath distortion while preserving the diversity effect without losing the desired signal wave. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional interference wave removing apparatus.

FIG. 5 is an operation explanatory diagram of a conventional example.

FIG. 6 is an operation explanatory diagram of a conventional example.

FIG. 7 is a schematic diagram of a general angle diversity system.

[Explanation of symbols]

101 Receiving antenna 102, 203, 204 Main beam horn 103, 103A, 205, 206 Angle beam phone 104, 105, 207-210 Receiver 106-109, 213-220 AGC amplifier 110, 111, 221-224 Multiplier 112-114 , 225-230 Correlator 115,231,232 Adder 116,233,234 Subtractor 117,235,236 Switch 118,237,238 Adaptive matched filter (AM
F) 119, 240, 241 Decision feedback equalizer 120, 211, 212 Angle beam horn controller 121, 242 Delay element

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 7/00 H04B 7/02-7/12 H04L 1/02-1/06

Claims (2)

(57) [Claims] 1. A first receiver for demodulating a received signal from an angle beam horn in angle diversity, a first AGC amplifier for removing the output level fluctuation of the first receiver, and an output of the first AGC amplifier A first multiplication corresponding to a coefficient signal input from a first external terminal to the signal;
, A second receiver for demodulating a received signal from the main beam horn in the angle diversity, and a second AGC amplifier for removing the output level fluctuation of the second receiver. A second receiving means having a second multiplier for multiplying the output signal of the second AGC amplification by a coefficient signal input from a second external terminal; An adder that inputs the output signal of the receiving means and performs addition and synthesis; and a coefficient corresponding to a correlation value obtained by correlating the output signal of the adder with the output signal of the first AGC amplifier. First to supply to external terminal
And a second correlator that supplies a coefficient corresponding to a correlation value obtained by correlating the output signal of the adder and the output signal of the second AGC amplifier to the second external terminal. A subtractor that receives the output signals of the first and second receiving means and synthesizes the interfering interference signal mainly in reverse phase, a switch that selects the output signal of the adder or the subtractor, and a switch of the switch. The decision data for judging the quality such as the bit error rate or S / N of the diversity combined signal outputted via the adaptive matching filter and the decision feedback equalizer connected to the output is monitored, and In the interference wave canceling device for performing selection, an output signal of the determination data and an output signal of the first AGC amplifier are output.
Relative delay time τ greater than force relative delay time difference τ1
(Τ1 <τ), a third correlator for correlating an output signal of the delay element with an output signal of the first AGC amplifier, and a correlation value output from the third correlator. Angle beam horn control means for controlling the elevation angle of the angle beam horn by inputting a coefficient corresponding to the signal, if the line quality of the determination data output in response to the elevation angle change of the angle beam horn is good. An interference wave eliminator, wherein a control is performed such that a correlation value of the third correlator is maximized. 2. A receiver for non-line-of-sight communication that uses both an angle diversity system and a space diversity system includes at least the angle beam horn control means for the space diversity system receiver. Item 2. The interference wave removing device according to Item 1.