JPS5856544A - Eliminating circuit for polarized wave interference - Google Patents

Abstract

PURPOSE:To obtain an inexpensive polarized wave interference eliminating circuit, by providing a means correcting a compensation coefficient when the real and imaginary parts of an interference signal for a circuit where the compensation coefficient is multiplied to the interference signal of an orthogonal polarized signal and the polarized interference component is eliminated. CONSTITUTION:Horizontal and vertical polarized reception signals HO and VO are inputted to an input terminal of a polarized wave interference subtraction circuit 6. The signal VO is multiplied with a compensation coefficient OMEGA at a multiplier 61 and added to the signal HO at an adder 60 and an interference eliminating signal He is outputted at a terminal 602. The signal He is inputted to a discrimination error detector 1 and a discriminated error (e) is detected. The real part eR and imaginary part eI of the error (e) are added and subtracted at an adder 22 and a subtractor 23 of a correlation device 2 and the output is applied to a switch 4. In case the real part VR is equal to the imaginary part VI of the signal VO, an interference discriminator 3 produces an output, the switch 4 is closed and signals eR+eI and eR-eI are respectively inputted to integrators 50 and 51 of an LPF 5 for smoothing to form the real part OMEGAR and the imaginary part OMEGAI of the compensation coefficient. The coefficients OMEGAR and OMEGAI are multiplied with the signal VO at a multiplier 51, the compensation coefficient is corrected and optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technology for compensating for cross-polarization interference that occurs when orthogonal polarizations are shared in wireless transmission.

Microwave band wireless communications 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 the development of frequency bands beyond quasi-T waves is expected, as well as the so-called so-called current frequency bands that have no practical value. The idea of frequency reuse is growing.

Originally, free space is independent of two orthogonal polarized waves, and is a transmission line that can simultaneously transmit both polarized waves. When a wave sharing method is adopted, the coupling between polarized waves due to the generation of cross-polarized waves causes interference between channels of different polarizations.

Therefore, in order to achieve orthogonal polarization sharing, it is necessary to improve the polarization characteristics of antennas and power supply devices, as well as develop a cross-polarization compensation circuit that compensates for the deterioration of polarization characteristics during radio wave propagation due to rain, etc. This has become an important issue.

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

Conventionally,! Ita 0R band communication is mainly analog transmission centered on FM, but in recent years, microwave band has also been used.
As digital transmission is increasingly used, there is a need to propose a more efficient cross-polarization compensation method that takes advantage of the characteristics of digital transmission.

Conventionally, this type of circuit receives two mutually orthogonal polarized waves, multiplies the received signal of one (the interfering side) by a compensation coefficient, and eliminates the interference component from the received signal of the other (the desired receiving side). For example, if we consider horizontally polarized waves and vertically polarized waves, and put independent data H and V on each, the horizontal -
The received wave signal H0 and the vertically polarized received signal V.
(1) ■, -V+/H... (7) Considering the case where we want to receive data H now, we multiply the received signal VoK of the vertical wave by the VoK compensation coefficient Ω and then Received signal H8
In addition to this, it is common to obtain an interference cancellation signal. That is, He == H, +ΩV,
−・Strike−・(3) Therefore, He=H+αV+Ω(V+βH) =H0(α+Ω)V+Ω・β・H KiH−)(α10Ω)V ・・・・・・
...(4) That is, by setting α=-Ω, H
H mountain in e... (5) As a result, polarization interference is removed. At this time, the control of Ω is
In general, Ω□i+1>=i′>−hv knee<kle−Fb)
, -, , -, , ,H). Here, He is a value for each iron, He - He ij is an identification error e, and includes interference from flIjL polarized waves. Therefore, if Ω is controlled in a direction that minimizes the correlation between C and V, α=−Ω, and interference is eliminated.

However, Vo-e is a complex multiplication and requires expensive analog multipliers, which are very expensive, especially at high transmission rates.

An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide an inexpensive polarization interference cancellation circuit that can obtain a value proportional to the above-mentioned V...C without using a multiple 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 the multiplied signal to the other received signal, thereby removing the polarization interference component. In the circuit, there is an identification error detector that detects the error between the compensated received signal and its identification value, and an interference detector that outputs when the real and imaginary components of the interfering received signal are both positive and equal in magnitude. a side discriminator, an adder and a subtracter that output the sum and difference between the real component and the imaginary component of the output value of the discrimination error detector, and an output of the adder and subtracter that outputs the output of the interference side discriminator The present invention is characterized in that it includes a switch that conducts by the switch, and a low-frequency P#L device that smooths the output of the switch and outputs the compensation coefficient.

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■
The real part of 0 is ■8. The imaginary part is Vl, the knowledge error signal C
Let the real part of be eR + the imaginary part be CI, then Atsushi = V, → -
jVr ・−・・・・−・(7)
e=eB+ノe■...
・・・・・・ Since (8), V-e=(V鼠-)°VI)(e凰+)el)=(Vg
eiz+VI el) -1-)(VlcI Vlet). Here, ■凰=Vx>0
・・・・・・・・・ At the time of (9), V−e oc (el+e■)+j(eI elL)
・・・・・・・・・(11) Therefore, the above slope equation can be obtained only by an adder.In other words, the present invention outputs the value of equation (11) only when equation (9) is satisfied. The interference wave component is removed by controlling the compensation coefficient.

For example, as shown in FIG.
6QAM) signals, the signals marked with black circles satisfy equation (9).

FIG. 2 is a circuit diagram showing an example of a nine-interference side discriminator that outputs an output signal when formula (9) is satisfied. That is, the real number s of the interfering side received signal is sent to the terminals 300 and 301.
vl and the imaginary part v■ are respectively input, subtracted by the subtracter 31, outputted the absolute value of the difference by the folding circuit 32, and compared by the comparator circuit 33) l v凰1 * l V
I l Force detection level b -V3B > On Comparison 1m
Detected at 30. Both outputs of comparators 30 and 34 are ANDed in AND circuit 34 and output to output terminal 302.

3 is a block diagram showing an embodiment of the present invention; FIG.

That is, the input terminal 600K of the polarization interference subtraction circuit 60 is inputted with, for example, the horizontally polarized received signal #.
i Input the vertically polarized received signal vo. The multiplier polarization received signal v0 is multiplied by a compensation coefficient Ω in a multiplier 61 and sent to an adder 6.
0 to the horizontally polarized received signal H6. Therefore, the interference cancellation signal He is output to the output terminal 602. In other words, equation (3) is realized. The interference cancellation signal He is connected to the input terminal 100 of the identification error detector 10 and
0, the identification value He is output, the subtracter 11 takes the difference from the above He, and the identification error C is output from the terminal 101. The real part eB and the imaginary part el of the discrimination-difference C are added by the adder 22 built in the correlator 2, and the subtracter 2
Subtracted by 3. The output of the adder 22 provides (ei+er) on the right side of the H equation, and the output of the subtracter 23 provides (e, eH) on the right side of the aQ equation. These outputs are supplied to integrators 50 and 51, respectively, when the switch 4 (switches 40, 41) are closed, and the integral operation shown in (6) 2 is performed and smoothed. The switch 4 is a switch that closes according to the output of the interference side discriminator 3, and is configured as shown in FIG.
9) The output is output only when the formula (9) is satisfied. Therefore, the switch 4 is conductive only when the formula (9) is satisfied. e
K is proportional. The output of the adder 22 is smoothed by the integrator 50 to form the real part Ω wing of the compensation coefficient Ω,
The output of is smoothed by an integrator 51 to give a compensation coefficient Ω
The imaginary part of Ω! It is said that Complex low frequency V with integrator 50°51
This constitutes a wave device 50. That is, Ω in equation (6) can be obtained without using a multiplier. As described above, the compensation coefficient Ω is multiplied by the vertically polarized received signal v by the multiplier 61 and added to the horizontally polarized received signal v, thereby canceling polarization interference. The remaining compensation becomes identification error No. 16C, and the next compensation coefficient is corrected by the above-described operation.

Furthermore, the condition for the output of the interference side discriminator is not limited to equation (9); it can also be achieved by detecting a signal that satisfies 1Vit I = IVt l and changing the polarity of the correlator depending on the quadrant to which vo belongs. .

As described above, in the present invention, an interference cancellation signal is obtained by multiplying the polarization signal by a compensation coefficient and adding it to the signal on the receiving side, and the difference between the interference cancellation signal and the identification signal, In other words, the compensation coefficient is modified only when the interfering signal satisfies certain conditions using the sum and difference signals of the real and imaginary parts of the identification error signal, so no multiplier is used. The compensation coefficient can be changed automatically and appropriately. That is, there is an effect that a good interference wave cancellation signal can be obtained and the quality of received data is improved. According to the present invention, changes in polarization interference caused by Faraday rotation in outer space in satellite communications can be quickly and precisely followed.

[Brief explanation of drawings]

Fig. 1 is a diagram showing each signal point of the Fi16 value oscillation phase change'#I4 signal and a signal point that satisfies specific conditions; Fig. 2 is a circuit diagram showing an example of an interference side discriminator used in the present invention; FIG. 3 is a block diagram showing an embodiment of the present invention. -, 1... Dislike job difference detector, 2... Correlator. 3... Interference side discriminator, 4... Switch, 5... Low frequency ν wave device, 6... Polarization interference subtraction circuit, 10... Discriminator, 11... Subtractor, 22...-Adder, 23...Subtractor, 30.33...-Comparator, 31...Subtractor, 3
2... Return circuit, 34... AND circuit, 40.4
1...Switch, 50°551...Integrator, 60...
- Adder, 61... Multiplier.

Claims (1)

[Claims] In a polarization interference removal circuit that receives two mutually orthogonal polarized waves and removes polarization interference components by multiplying one received signal by a compensation coefficient and adding it to the other received signal, the received signal after compensation is an interference side discriminator that outputs an error when both the real component and the imaginary component of the interfering side received signal are positive and equal in magnitude, and the above identification error. an adder and a subtracter that output the sum and difference between the real component and the imaginary component of the output value of the detector;
It is characterized by comprising a switch that conducts the outputs of the wrinkle adder and the subtracter by the output of the interference side discriminator O, and a low-frequency p-wave generator that smoothes the output of the switch and outputs the compensation coefficient. polarization interference removal circuit.