JP2973952B2 - Interference wave removal method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing interference waves, and more particularly to a method and an apparatus for removing interference waves by a power inversion adaptive array circuit to optimally combine a desired signal wave. About.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing the configuration of a conventional example of this type of interference wave removing apparatus.

[0003] FIG. 2 shows a communication system based on spatial double diversity. The left side of the figure is defined as a first wireless station, and the right side is defined as a second wireless station.

[0004] A first wireless station has a transmission baseband circuit 2.
01, a modulator 202, and two transmitters 203 and 2
04, two antennas 205 and 206, two receivers 207 and 208, a power inversion adaptive array circuit 209, and a demodulator 210.
, A decision unit 211 and a reception baseband circuit 212.

[0005] The second radio station has a transmission baseband circuit 2
21, a modulator 222, and two transmitters 223 and 2
24, two antennas 225 and 226, receiver 2
27 and 228 and one power inversion
An adaptive array circuit 229, a demodulator 230,
It comprises a decision unit 231 and a reception baseband circuit 232.

[0006] In a long-distance wireless communication line using microwaves or the like, good quality communication may be hindered by fading in general, and diversity reception is used to reduce the influence of fading. In the transmission data signal of the first wireless station, an overhead signal such as a frame synchronization signal is time-division multiplexed in the transmission baseband circuit 201 to perform speed conversion. Transmission baseband circuit 201
Is modulated by the modulator 202. The modulated wave is further branched into two, input to the transmitters 203 and 204, respectively, frequency-converted from the intermediate frequency band to the radio frequency band, and subjected to power amplification processing. Transmitters 203 and 20
4 are input to antennas 205 and 206, respectively. It is assumed that the first wireless station emits a radio wave by the vertically polarized wave V. The radio wave radiated from the first wireless station spreads and propagates spatially according to the radiation pattern of the antenna. From the antenna 205 to the antenna 225 of the second wireless station
Is the propagation constant (complex number) from the antenna 205 to the antenna 226 of the second wireless station (complex number).
H12, the propagation constant (complex number) from the antenna 206 to the antenna 225 of the second wireless station is h21, and the antenna 20
The propagation constant (complex number) from No. 6 to the antenna 226 of the second wireless station is h22.

The microwave communication line has a problem that the quality of the communication line deteriorates due to various interference waves or communication becomes impossible. Examples of these interference waves include an interference wave from an adjacent channel, a radar interference wave, a jamming radio wave, and the like.

In FIG. 2, an interference wave source 240
Is incident on antennas 225 and 226 of the second wireless station. From the interference wave source 240 to the antenna 225
The propagation constant (complex number) to the antenna 226 is J1 and the propagation constant (complex number) from the interference wave source 240 to the antenna 226 is J2. Since the transmission polarization plane at the first radio station is vertical,
The second polarization direction of the second radio station is also vertical.
The signal waves received from antennas 225 and 226 are input to receivers 227 and 228, respectively, and are subjected to low noise amplification and frequency conversion processing from a radio frequency band to an intermediate frequency band. Here, if the received signals output by the receivers 227 and 228 are denoted by r1 and r2, these signals can be expressed by the following equations. r1 = h11 · S + h21 · S + J1 · J (1) r2 = h12 · S + h22 · S + J2 · J (2) In the above equation, S indicates a transmission signal, and this signal is a desired wave on the reception side. The received signals of the above two branches are power
The inversion adaptive array circuit 229 receives a linear synthesis process. The power inversion adaptive array circuit 229 is a well-known prior art used for interference wave cancellation, and is a power inversion adaptive circuit.
The output y of the adaptive array circuit 229 is expressed by the following equation. y = W1 · r1−W2 · r2 (3) By substituting Equations (1) and (2) into Equation (3), y = {W1 (h11 + h21) −W2 (h12 + h22)} · S + (W1 · J1) −W2 · J2) · J (4) is obtained. Here, a necessary condition for removing the interference wave J is W1 · J1−W2 · J2 = 0 (5). The power inversion adaptive array circuit 229 obtains W1 = 1 / J1 (6) W2 = 1 / J2 (7) as a solution of the above equation (5) and performs linear synthesis to remove unnecessary interference waves.

Power Inversion Adaptive
The array circuit 229 shows a case of two-branch diversity combining. For a general system using an N-element antenna array, Compton describes "The Power Inversion Adaptive Array: Concept and Performance". ETransaction on Aerospace and Electronic Systems, Vol. 15, No. 6, January 1979. In this power inversion adaptive array, the weighting factors W1 and W2 are problematic. However, in the above document, the weight coefficient is obtained by the correlation between the error signal between the array combined output and the reference signal and each of the array branch received signals. What is the reference signal Or adopted to become a problem.

For a microwave signal using diversity, the prior art shown in FIG. 3 is employed as a practical configuration method of a power inversion adaptive array.

In FIG. 3, AGC amplifiers 301 and 3
02 receives the input r1 and the input r2 of each branch, respectively, and the complex multipliers 303 and 304 output the AGC signals respectively.
The outputs of the amplifiers 301 and 302 are multiplied by weighting factors W1 and W2. Correlators 305 and 306 determine weighting factors W1 and W2 for each branch. Each complex multiplier 3
03 and 304 are output from a subtractor 307 and an adder 308.
And an AGC amplifier 309 to combine them, and a switch 310 selects and outputs one of them.

In FIG. 3, diversity combining of the inputs r1 and r2 is performed by an adder 308, and the combining method is based on maximum ratio combining. Each of the diversity inputs r1 and r2 is first filtered by AGC amplifiers 301 and 302 to remove level fluctuation due to flat fading. Next, the multiplier 30 performs the maximum ratio synthesis in the adder 308.
3 and 304 are multiplied by weighting factors W1 and W2 (complex numbers), respectively. These weighting factors are calculated by the correlator 30
In steps 5 and 306, the output is obtained by the correlation between the output of the AGC amplifier 309 after the diversity combining and the outputs of the AGC amplifiers 301 and 302, respectively. When there is no interference wave J, the switch 310 selectively outputs the output of the AGC amplifier 309. When there is a strong interference wave J such that the D / U ratio (the ratio of the interference wave to the desired wave) is negative, the switch 310 selectively outputs the output of the subtractor 307. The subtracter 307 subtracts the output of the complex multiplier 304 from the output of the complex multiplier 303, and the adder 308 performs in-phase synthesis on the phase, whereas the subtractor 307 performs anti-phase synthesis to obtain interference. Performs wave removal.

FIG. 4 illustrates the operation of interference removal by the diversity combining circuit. (A) and (d) show the inputs r1 and r2 of the diversity branches 1 and 2 as complex vectors on a complex plane. Here, the desired waves of each branch are S1 and S2, respectively, and the interference waves are J1 and J2, respectively. When the interference wave is so large that D / U becomes minus, AGC amplifiers 301 and 302 normalize the interference wave. In the initial initial state, the phases of the interference wave vectors of the multipliers 303 and 304 are not in phase, but most of the output components of the adder 308 are occupied by the interference waves. This is further added to the AGC amplifier 30
9 and the correlation with the outputs of the AGC amplifiers 301 and 302, the phase information of the interference wave vector of each branch can be obtained as a complex conjugate based on the interference wave at the output of the AGC amplifier 309. These are the weighting factors W1 and W2 of each branch. By multiplying these by each branch, the interference wave vector can be controlled to have the same phase as the phase of the normalized interference wave vector output from the AGC amplifier 309. That is, in the adder 308, each interference wave can be combined in phase, and as shown in FIGS. 4B and 4E,
The interference wave J1 is output from the output of each of the multipliers 303 and 304.
And J2 have the same amplitude and phase. In this case, (c) shows the in-phase synthesis of the interference waves in the adder 309. On the other hand, as shown in (f), the subtractor 307 removes the interference waves by inverse-phase synthesis and synthesizes and extracts only the desired wave. Here, in-phase synthesis is not performed for the desired waves S1 and S2. In particular, the desired wave S may disappear due to the phase relationship between the desired wave S and the interference wave J.

Next, a case where a desired signal wave disappears due to synthesis will be described with reference to FIG.

When the inputs r1 and r2 are the same in the amplitude and phase relationship between the desired wave S and the interference wave J as shown in (g) and (j), the outputs of the multipliers 303 and 304 are (h) and (k). )
Match as shown. At this time, as shown in (i), the adder 3
As for the output 08, both the desired wave S and the interference wave J are synthesized in phase, and the output of the subtracter 307 is formed such that the desired wave S and the interference wave J are synthesized in opposite phases.
That is, although the interference wave J has been removed, the desired wave S also disappears. This is the case where the coefficient of the desired wave S in the first term on the right side in equation (4) is zero. That is, when W1 (h11 + h21) = W2 (h12 + h22) (8), the desired wave output from the power inversion adaptive array circuit disappears.

In FIG. 2, the signal from which the interference wave has been removed is input to the demodulator 230, where the carrier is synchronized and demodulation is performed. The demodulated signal is in a band-limited eye pattern state, and is reproduced as a digital signal by the determiner 231. The determination data signal is input to the reception baseband circuit 232, where frame synchronization and the like are taken, and a signal such as an order wire signal is separated and extracted. Note that the above description describes the transmission of a signal from the first wireless station to the second wireless station, but the signal from the second wireless station to the first wireless station in the opposite direction is also described. The same operation as described above is performed. However, in this case, the horizontal polarization H is used for the polarization planes of the transmission signal at the second radio station and the reception signal at the first radio station.

[0017]

As described above, when an interference wave is to be removed by the conventional power inversion adaptive array circuit, diversity in-phase synthesis is not performed on a desired wave. Has a problem that even a desired wave is eliminated.

An object of the present invention is to solve this problem, to prevent the disappearance of a desired wave due to the elimination of an interference wave, to remove an intense broadband interference wave, and to make it possible to optimally combine the desired wave. It is to provide a removal method and apparatus.

[0019]

SUMMARY OF THE INVENTION An interference wave elimination method according to the present invention is an interference wave elimination method for eliminating the mixing of an interference wave from a received signal in a spatial duplex diversity communication system. The transmission signal is branched into two, one transmission signal is multiplied by a complex coefficient, and the transmission signal is transmitted together with the other transmission signal in the vertical polarization or the horizontal polarization, and the reception side performs diversity combining of the two reception signals, The combined output is demodulated, the demodulated signal is determined, and an error generated before and after the determination when the interference signal is included in the demodulated signal is different from the transmission side of the vertically polarized wave or the horizontally polarized wave as an error signal. Transmitted by polarization, the mean square value of the error signal received on the transmitting side is determined, and the complex coefficient to be multiplied is determined so that the square mean value is minimized. Remove more interference waves It is set to be.

Further, the interference wave removing apparatus of the present invention extracts and separates, at the time of transmission, a complex multiplying means for multiplying one of the modulated and branched transmission signals by a complex coefficient and an error signal transmitted from the other side. Means for obtaining a complex coefficient for minimizing the root mean square value of the error signal, and diversity reception of the received signal is performed at the time of reception, and when the interference signal is included in the demodulated signal obtained by demodulating the synthesized signal, the demodulated signal is And a means for transmitting the difference signal generated before and after the determination as an error signal to the other party.

In any of the method and the apparatus, the diversity combining at the receiving side can be performed by a power inversion adaptive array, and the transmission of the error signal from the receiving side to the transmitting side is performed at the time of transmission. Feedback can be provided as part of the overhead signal by the division multiplexing means.

[0022]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of an interference wave removing apparatus according to the present invention.

FIG. 1 shows a communication system based on spatial double diversity. The left side of the figure is defined as a first wireless station, and the right side is defined as a second wireless station.
Wireless station.

The first radio station includes a transmission baseband circuit 1
01, modulator 102, and two transmitters 103 and 1
04, two antennas 105 and 106, two receivers 107 and 108, a power inversion adaptive array circuit 109, and a demodulator 110.
, A determiner 111, a reception baseband circuit 112,
A subtractor 113, a root mean square error control circuit 114,
It comprises a complex multiplier 115.

The second radio station includes a transmitting baseband circuit 121, a modulator 122, two transmitters 123 and 124, two antennas 125 and 126, and two receivers 127 and 128. , A power inversion adaptive array circuit 129 and a demodulator 130
, A determiner 131, a reception baseband circuit 132,
A subtractor 133, a root mean square error minimum control circuit 134,
And a complex multiplier 135.

The configuration diagram shown in FIG. 1 is different from the configuration diagram of the prior art shown in FIG. 2 in that components 113, 114, 115, 1
33, 134 and 135 are added. A feature of the present invention is that one branch of the diversity transmission signal is multiplied by a complex coefficient C using the complex multipliers 115 and 135, and the mean square of the decision error signal of the partner station is minimized. That is to control. A description will be given of how this method can simultaneously realize interference wave removal and optimal synthesis of a desired wave by the power inversion adaptive array circuit 129.

Now, consider a case where a signal is transmitted from the first wireless station and received by the second wireless station. Here, the complex multiplier 115
Is multiplied by the complex coefficient C, the received signals r1 and r2 described in the prior art are expressed by the following equations. r1 = h11 ・ S + h21 ・ C ・ S + J1 ・ J (9) r2 = h12 ・ S + h22 ・ C ・ S + J2 ・ J (10) Therefore, the output of the power inversion adaptive array circuit 129 is y = ｛W1 (h11 + h21 ・ C) ) −W2 (h12 + h22 · C)｝ · S + (W1 · J1−W2 · J2) · J (11) In order to eliminate the interference wave J in the above equation, the power inversion adaptive array circuit 129 performs a correlation operation on the weight coefficients W1 and W2 given by the equations (6) and (7), and the interference wave J is removed. You. That is, the power inversion adaptive array circuit 12
The nine outputs are y = {W1 (h11 + h21 · C) −W2 (h12 + h22 · C)} · S (12) Here, the difference from the prior art is that a weight coefficient C multiplied on the transmission side is included as is clear from the above equation (12). In the above equation (12), the condition under which the signal of the two branches is optimally combined with respect to the desired wave S is that the coefficient portion of the desired wave S is 1
It is to become. This is equivalent to taking the transmission path as an impulse response and setting the main response to 1 in order to satisfy the Nyquist distortion-free condition. Therefore, there exists a weight coefficient Copt that satisfies W1 (h11 + h21 · C) −W2 (h12 + h22 · C) = 1 (13). When the complex coefficient C deviates from the optimal solution Copt, the Nyquist no distortion condition is not satisfied, and the error signal ε before and after the decision unit 131 is obtained.
Take a certain value. If the optimal solution is satisfied, the error signal ε
Becomes zero. Therefore, if the transmission-side weighting coefficient C is controlled so that the root mean square value of the error signal ε is minimized, the optimum synthesis is always performed on the desired wave. In this case, it is possible to solve the problem of the prior art, that is, the extinction of the desired wave in reverse phase synthesis. In this embodiment, the error signal ε of the second wireless station output from the subtracter 133 is time-division multiplexed into an overhead portion together with a frame synchronization signal and the like by the transmission baseband circuit 121 and transmitted to the first wireless station of the partner station. . The first radio station demodulates and reproduces the error signal ε transmitted from the second radio station, and
After the frame synchronization in step 2, the separation and extraction are performed. The extracted error signal ε is converted into an error signal ε by a root mean square error control circuit 114.
The complex coefficient C is controlled such that the root mean square value of is minimized. The control method is performed by calculation using a microcomputer or a DSP. Specifically, the error signal ε is squared and integrated. Next, C is perturbed from the initial value on the complex plane, the mean square value at that time is obtained, and the increase / decrease from the initial value is obtained. These processes are sequentially repeated, and an optimal solution is obtained by Newton's method or the like.
Although some convergence time from the initial value to the optimal solution is required, once the optimal solution is reached, the optimal solution can be maintained as adaptive processing by introducing a calculation algorithm such as sequential correction.

With the above operation, it is possible to simultaneously realize the optimum combining of the diversity with respect to the desired wave simultaneously with the elimination of the interference wave by the power inversion adaptive array.

[0029]

As described above, according to the present invention, one of two diversity transmission signals transmitted from the transmission side is multiplied by a complex coefficient, and an error signal generated between the input and output of the decision unit on the reception side is transmitted to the transmission side. By transmitting and using the optimal solution of the complex coefficient that minimizes the root mean square value of this error signal on the transmitting side and using this, even if interference wave removal by the conventional power inversion adaptive array is performed, In addition, it is possible to prevent the desired signal wave from disappearing due to the reverse-phase synthesis, which has been impossible in the related art, and it is also possible to simultaneously achieve the optimum diversity combining for the desired wave in the fading channel.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a spatial double diversity communication system to which an embodiment of an interference wave removing method according to the present invention is applied.

FIG. 2 is a configuration diagram of a spatial double diversity communication system according to a conventional interference wave removing method.

FIG. 3 is a configuration diagram of the power inversion adaptive array circuit of FIGS. 1 and 2;

FIG. 4 is a diagram illustrating diversity combining of received signals on the receiving side.

FIG. 5 is an explanatory diagram in a case where a desired wave disappears due to diversity combining of received signals on a receiving side.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Transmitting baseband circuit 102 Modulator 103, 104 Transmitter 105, 106 Antenna 107, 108 Receiver 109 Power inversion adaptive array circuit 110 Demodulator 111 Judge 112 Receiving baseband circuit 113 Subtractor 114 Square mean Error minimum control circuit 115 Complex multiplier 121 Transmit baseband circuit 122 Modulator 123, 124 Transmitter 125, 126 Antenna 127, 128 Receiver 129 Power inversion adaptive array circuit 130 Demodulator 131 Judge 132 132 Receiving base Band circuit 133 Subtractor 134 Minimum mean square error control circuit 135 Complex multiplier

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) H04B 7/00 H04B 7/02-7/12 H04L 1/02-1/06

Claims (6)

(57) [Claims] An interference wave removing method for removing interference waves from a received signal in a spatial duplex diversity communication system, wherein a transmitting signal modulated on a transmitting side is branched into two signals to be converted into one transmitting signal. Multiplied by the complex coefficient and transmitted together with the other transmission signal in vertical polarization or horizontal polarization, and the receiving side performs diversity combining of the two received signals, demodulates the combined output, and determines the demodulated signal. Performing, when the demodulated signal contains an interference wave, the error that occurs before and after the determination as an error signal, transmitted with a polarization different from the transmission side of the vertical polarization or horizontal polarization, received at the transmission side An interference wave elimination method for obtaining a root-mean-square value of an error signal, obtaining the complex coefficient to be multiplied so as to minimize the root-mean-square value, and thereafter performing an iterative operation during communication to remove an interference wave from a received signal. 2. The interference wave removing method according to claim 1, wherein the diversity combining at the receiving side is performed by a power inversion adaptive array circuit. 3. The method according to claim 1, wherein the transmission of the error signal from the receiving side to the transmitting side is fed back as a part of an overhead signal by a transmission time division multiplexing unit. 4. An interference wave eliminator installed on each of a transmission side and a reception side in a spatial duplex diversity communication system, wherein at the time of transmission, one of a modulated and bifurcated transmission signal is multiplied by a complex coefficient. Complex multiplying means and means for extracting and separating the error signal transmitted from the other party and obtaining the complex coefficient for minimizing the root mean square value of the error signal; and at the time of reception, diversity combining of the received signal is performed. When an interference wave is included in the demodulated signal obtained by demodulating the synthesized signal,
An interference wave removing apparatus comprising: means for detecting an error occurring before and after the determination of the demodulated signal as an error signal; and means for transmitting the error signal to a partner. 5. The apparatus according to claim 4, wherein the diversity combining at the receiving side is performed by a power inversion adaptive array circuit. 6. The interference wave canceling apparatus according to claim 4, wherein the transmission of the error signal from the receiving side to the transmitting side is fed back as a part of an overhead signal by the transmission time division multiplexing means.