JPS5856545A - Eliminating circuit for polarized wave interference - Google Patents

Abstract

PURPOSE:To speed up the control, by controlling the compensation coefficient through the change of combinations of addition and subtraction of the real and imaginary parts of a discrimination error signal in response to a quadrant where the signal exists, when the value of the real and imaginary parts of an interference polarized wave reception signal is equal. CONSTITUTION:Horizontal and vertical polarized wave reception signals HO and VO are inputted to a polarized wave interference subtraction circuit 6 and the signal VO is inputted to an interference discriminator 3''. A compensation coefficient OMEGA is multiplied with the signal VO at the circuit 6, and the result is summed up with the signal HO to output an interference wave eliminating signal He. The signal He is inputted to a discrimination error detector 1 to output a discrimination error signal (e) from a detector 1. The real and imaginary parts eR and eI of the signal (e) are respectively inputted to correlation devices 2-2''' to calculate eR+eI and eR-eI and each correlation device outputs a signal corresponding to each quadrant to a switch 4'. The discriminator 3'' detects that the absolute value of the real and imaginary parts of the signal VO is equal and gives a control signal to select the output of the correlation devices 2-2''' depending to which quadrand the signal belongs, to a switch 4 and gives the signal selected at the switch 4 to the circuit 6 via an LPF 5 as the coefficient OMEGA.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cross-polarization interference compensation technology that occurs due to orthogonal polarization sharing in wireless transmission.

Wireless communications in the microwave band are rapidly developing, centering on terrestrial communications and satellite communications. The demand for wireless communications is expected to further increase in the future due to the expansion of mobile communication services, etc., and along with the development of sub-millimeter wave and higher frequency bands, so-called frequency reuse of current frequency bands with high practical value is expected. Thoughts are growing. The CCIR (Consultative Committee on International Radiocommunications) recommendations regarding FM radio frequency allocation from 4 to 6 GH2 clearly specify the use of orthogonal polarization.

In addition, in satellite communications, IN-5AT (International Telecommunication Satellite Organization) is expected to commercialize technology for sharing orthogonal polarization in the 4 to 6 GH band, which has been used with single polarization on V related satellites. It is.

Originally, free space is independent of two orthogonal polarizations, and is a transmission line that can simultaneously transmit both polarized waves. However, in actual propagation paths, it is difficult to determine which medium has anisotropy to transmit rainfall, and whether the orthogonal polarization If a shared system is adopted, coupling between polarized waves due to the generation of cross-polarized waves will cause interference between channels of different polarizations.

In order to achieve this shared use of orthogonal polarization, it is important to improve the polarization characteristics of antennas and power supply equipment, as well as develop cross-polarization compensation circuits that compensate for deterioration of polarization characteristics during radio wave propagation due to rain, etc. It has become a challenge.

Cross polarization compensation technology automatically compensates for such coupling between polarized waves by providing a compensation circuit within an antenna feeder or wireless device.

Conventionally, microwave band communication has centered on analog transmission, mainly FM, but in recent years, digital transmission has come to be used in the microwave band as well, and the cross-polarization compensation method has also been developed to take advantage of the characteristics of digital transmission. Proposals for more efficient methods are requested.

Conventionally, this type of circuit receives two mutually orthogonal polarized waves, multiplies the received signal of one (interference @) by a compensation coefficient, and subtracts it from the received signal of the other (desired reception 1111) to remove the interference component. I am trying to remove it. For example, considering horizontal polarization and vertical polarization, each has independent data H and V.
, the horizontally polarized received signal and the seasonal polarized received signal V@
is Ho2H+αV・・・・・・・・・・・・
・・・・・・・・・(1) ■・=V+βH・−・・・・・・・
...-...-...(2). Now, if we consider the case where we want to receive data H, the vertically polarized received signal va
It is common to multiply K'mi by the inertia coefficient Ω and add it to the horizontal received signal to obtain an interference cancellation signal H.

That is, He = Ha + ΩVo...
...・・・・・・・・・・・・
・・・・・・・・・(4) That is, by setting α=−Ω, He:H・・・・・・・・・・・・・・・・
...(5), and polarization interference is removed. At this time, the control of Ω is generally performed in the Ω direction1)-Ω"-kV@ ・(He-'Ae)-
−= (6). Here 9. is H
is the identification value of . . , and He−e is the identification error e, which includes interference from vertical polarization. Therefore, if Ω is controlled in a direction that minimizes the correlation between numbers 8 and 7, α=−Ω, and interference will be removed.

However, -... is a complex multiplication and requires an expensive analog multiplier, which is very expensive especially when the transmission rate is high.

An object of the present invention is to provide an inexpensive polarization interference cancellation circuit that can solve the above-mentioned conventional input problem and obtain a value proportional to the above-mentioned ■♂・e without using a complex multiplier. .

The interference cancellation circuit of the present invention receives two mutually orthogonal polarized waves, multiplies one received signal by a compensation coefficient, and adds it to the other received signal to remove the polarization interference component. , the received signal after compensation and its identification number 1
an adder and a subtracter that output the sum and difference between the real part and the imaginary part of the identification error signal output by the error detector; an interference side discriminator that detects that the absolute values of the real part and the imaginary part are equal and outputs a control signal according to which quadrant they belong to; and the adder in response to the control signal output from the interference 9JA discriminator. A switch that changes the sign combination of the output signal of the subtracter and outputs it, and a low-frequency P-wave device that smoothes the output of the switch, and the compensation coefficient is obtained by the output of the low-frequency P-wave device. It is characterized by the following.

Next, the present invention will be explained in detail with reference to the drawings.

First, the principle of the present invention will be explained. Now, the received signal■
. Let VR be the real part of
No V!・・・・・・・・・・・・・・・
...... (7) 6=el+noe1...
・・・・・・・・・・・・・・・(8) Therefore, v:e ” (VB-)Vl ) (15R+7'@I
)-(VRe R+ VIe 1) 10' (Vuet VIeR)
It is. Here, V-Vx>0 ・・・・・・・・・
・・・・・・・・・・・・ When (9), Ve eoc(sB+eH) +) (el
eB)・・・・・・・・・・・・・・・・・・・・・
・a・ Therefore, the above α1 formula can be obtained using only an adder. Therefore, u(
By outputting the value of Equation 1 and controlling the compensation coefficient using this value, it is possible to eliminate the interference wave component by K.

For example, as shown in FIG.
Among the m (16QAM) signals, the signal marked with a black circle is (9)
satisfies the formula.

FIG. 2 is a circuit diagram showing a row of interference side discriminators that output an output signal when formula (9) is satisfied. That is, the real part vR and imaginary part vl of the interfering side received signal are respectively input to the terminals 300 and 301, subtracted by the subtracter 31, outputted as the absolute value of the difference by the folding circuit 32, and outputted by the comparator circuit 33. In comparison, lVt1 in lVal is detected from K. vR>0 is detected by comparator 30. Both outputs of the comparators 30 and 34 are ANDed by an AND circuit 34 and output to an output terminal 302.

Figure 3 is a block diagram showing an example of a polarization interference removal circuit using the above-described circuit. That is, for example, the horizontally polarized received signal Ha is input to the input terminal 600 of the polarization interference subtraction circuit 6, and the vertically polarized received signal Va is inputted to the input terminal 601. The vertically polarized received signal (1) is multiplied by a compensation coefficient Ω in a multiplier 61 and added to the horizontally polarized received signal (1) in an adder 60. Therefore, the interference cancellation signal H6 is output to the output terminal CO2. In other words, equation (3) is realized. The interference canceled signal HeFi is connected to the input terminal 100 of the discrimination error detector 1 and is outputted via the discrimination value by the discriminator 10. is output, and the subtracter 11 takes the difference from the above-mentioned H, and the discrimination error e is output from the terminal 101. Real part @R and imaginary part e of identification error e! is the adder 2 built in the correlator 2
2 and subtracted by the subtracter 23.

The output of the adder 22 is ((eB + el
), and the output of the subtractor 23 is ((e,
-el) is given. These outputs are supplied to integrators 50 and 51, respectively, when the switch 4 (switch 40, 41) is closed, and are subjected to the integration operation shown in equation (6) and smoothed.

The switch 4 is a switch that closes according to the output of the gait discriminator 3, and the interference side discriminator 3 has a K14 structure as shown in Fig. 2, and outputs only when formula (9) is satisfied. issue. Therefore, since the switch 4 is electrically conductive only when the formula (9) is satisfied, the output of the correlator 2 at this time is proportional to the above-mentioned -41e according to the formula.

The output of the adder 22 is smoothed by an integrator 50 to become the real part Ω of the compensation coefficient Ω, and the output of the subtracter 23 is smoothed by the integrator 51 to become the imaginary part Ω of the compensation coefficient Ω.
It is said that Integrator 50; complex low plate p-wave unit 5 with s1
The committee is comprised of members. That is, Ω in equation (6) can be obtained without using a multiplier.

The compensation coefficient Ω is multiplied by the vertically polarized received signal ve K by the above-mentioned multiplier 61 and added to the peak of the horizontally polarized received signal, thereby canceling polarization interference.

The remaining compensation becomes the identification error signal e and corrects the next compensation coefficient by the above-described operation.

However, in the above method, only two points of the 16-value amplitude phase shift signal (16QAM) shown in FIG. 1 are used, so the control speed is slow. In order to increase control speed, it is necessary to use many signals. Therefore, in the present invention, 1Viz I = lVx I
We aimed to increase the control speed by using all the signal points that satisfy the following. For example, in the case of 16QAM,
In Fig. 4, 8 points (4 sets) indicated by ・, mu, gig, and ma are used. It was mentioned earlier that the signal marked with ・ satisfies the above equation (9), and a signal proportional to input 1e can be obtained from the right side of the OI equation.In the signal marked with 9-, the real number is negative and the imaginary number is positive, so Vo 'el (X: -('ea el)-) (@
m +”1)・・・・・・・・・・・・・・・・・・
...αυ, and the signal marked with a mark is -1oc - (@Tomi+61) 10 (e-e-ri...
・・・・・・・・・・・・・・・・・・ α Rim mark signal is Vo”e” Cen ew) + ) (el 6
1)・・・・・・・・・・・・・・・・・・・・・I
becomes. Detection of a signal point group for which equations 01 to u3 hold can be performed, for example, by an interference gJA discriminator as shown in FIG. That is, for example, the real part vR of the vertically polarized received signal part is inputted to the terminal 300, and the imaginary part V! is input to the terminal 301. Real part V at positive/negative comparator 35°36
The signs of R and the imaginary part v1 are determined, and the output thereof is input to AND circuits 39a to 39, d.

The AND circuit 39m outputs a NO level for the signal in the first quadrant, and the AND circuits 39b to 39dij output a NO level for the signals in the second to fourth quadrants, respectively. On the other hand, the real part vR and the imaginary part v■ are folded back 37.38
and their outputs are input to the subtracter 31 and subtracted. The output of the subtracter 31 is compared with a constant level by a comparator 33 via a folding circuit 32, and the IVRI key! V
Xl is determined, and the output of the comparator 33 is used as one input of AND circuits 34-34d. AND circuits 34a to 34
The other input KH1 of d is connected to the AND circuit 39.
Outputs 1 to 39d are connected. Therefore, the AND circuit 34a outputs a high level for the signal indicated by the symbol * in FIG. 4, and the AND circuits 34b to 34d each output a high level.
Outputs high level for the signals indicated by marks, marks, and marks. Therefore, by using these outputs as control signals and combining the identification error signals, it is possible to create the right side of the equation (1(strange~(1,1).

FIG. 6 is a block diagram showing one embodiment of the present invention.

That is, the horizontally polarized received signal peak is inputted to the terminal 600, and the vertically polarized received signal VD is inputted to the interference side separator 3' via the terminals 601 and 603. The interference side identification booklet has the configuration shown in FIG. 5, and controls the opening and closing of the switch 4' by outputting a control signal according to the conditions of the input signal.

On the other hand, the vertically polarized received signal Ve is multiplied by the compensation coefficient Ω input from the terminal 604 in the polarization interference cancellation circuit 6, and then added to the horizontally polarized received signal H9, and the interference wave canceled signal He is outputted from the terminal 602. be done. Interference wave cancellation signal 1 (6ij
: Input to terminal 100 of #separate error detector 1,
The identification error signal C is output from 01. The lifetime part eB and the imaginary part e1 of the identification error signal e are respectively sent to the correlator 2. Z,
(eR+ ex ) and (ei
t 6r) is calculated, and each correlator outputs a signal corresponding to the right side of equation 0I-00. The switch 4' selectively selects the output of each of the correlators in response to the control signal output from the interference side discriminator r,
input to the input terminal 500 of. The low-pass p-wave generator 5 smoothes the input signal and outputs it from the output terminal 501 as a compensation coefficient Ω.

In this embodiment, 8 signals out of 16 signals shown in FIG. 4 can be used to control the coefficient Ω, so rapid control is possible. In other words, it is possible to react even when the interference polarization fluctuates rapidly, and a control speed approximately four times faster than in the configuration shown in FIG. 3 can be obtained. Therefore, for example, Faraday in space in satellite communications
It is also possible to quickly and accurately follow polarization interference changes due to rotation.

Note that in the above description, correlators 2, 2', ! , 2' were provided with an adder and a subtracter 'ft, respectively, and the right side of equation u3 was found in each correlator. If the switch 4' is configured to add or subtract according to the control signal, the correlator z,! , γ can be omitted.

As described above, in the present invention, an adder that adds the real part and the imaginary part of the identification error signal and a subtracter that subtracts the real part and the imaginary part of the interference polarization reception signal are provided, so that the magnitude of the real part and the imaginary part of the interference polarization received signal is When they are equal, the above 7J[] X corresponds to the quadrant to which they belong.
Since the compensation coefficient is controlled by changing the combination of outputs of the subtractor and the subtractor, the number of signal points that can be used for compensation coefficient control is increased, and rapid control speed can be obtained. Furthermore, the configuration is simple because the compensation coefficient can be optimally and automatically changed without using a multiplier.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing each signal point of a 16-value silkworm width phase modulation signal and a signal point that satisfies a specific condition, and Fig. 2 is a circuit diagram showing an example of a separate device for the interference 1111# that detects the above-mentioned specific condition. , Fig. 3 is a block diagram showing an example of a polarization interference cancellation circuit that changes the compensation coefficient in the above-mentioned specific case, and Fig. 4 shows the magnitude of the real part and imaginary part of the tilS value amplitude phase modulation signal. FIG. 5 is a circuit diagram showing an example of an interference side discriminator for detecting the above conditions for use in the present invention, and FIG. 6 is a block diagram showing an embodiment of the present invention. It is a diagram. In the figure, 1-...Identification error detector, 212Z
z, r...-correlator, 3, 3'...interference @
Discriminator, 4゜4'...Switch, 5...Low frequency Pt& device, 6...Polarization interference subtraction circuit, 10...
...-Discriminator, 11...Subtractor, 22...
...Adder, 23...Subtractor, 30,33゜35.36...Comparator, 32,37,38...
...Folding circuit, 34.34a to 34d, 39
a ~ 39d...-AND circuit, 40.41...
...Switch, 50゜51...-Integrator, 60-...
... Adder, 61 ... Multiplier. Agent Patent Attorney Resident 1) Bonds Cold Figure 1 Figure 2

Claims (1)

[Claims] In a polarization interference cancellation circuit that receives two mutually orthogonal polarized waves and removes the polarization interference component by multiplying one received signal by a compensation coefficient and adding it to the other received signal, the received signal after compensation and An identification error detector that detects an error with the identification value, an adder and a subtractor that output the sum and difference between the real part and imaginary part of the identification error signal output from the error detection story, and an interference polarization side an interfering side discriminator that detects that the feed values of the real part and the imaginary part of a received signal are equal and outputs a control signal according to which quadrant it belongs to; and a control signal corresponding to the output of the interfering side discriminator. a switch that changes the sign combination of the output signals of the adder and the subtracter and outputs the same; and a low-frequency P-wave device that smoothes the output of the # switch; A polarization interference removal circuit that obtains a compensation coefficient by t%.