RU2529184C2 - Radio signal direction-finding method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to radio receiving engineering and can be used in radio-frequency source direction-finding systems. The result is achieved by measuring phase difference between signals from the output of a non-directional antenna having a circular beam pattern and from the output of a 90° phase changer-adder, which forms a circular beam pattern from two orthogonal antennae with a beam pattern in the form of a figure eight, and using existing receiving communication antennae having all elements necessary to carry out said method.

EFFECT: high accuracy of direction-finding with weak signals and easy implementation.

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Description

The invention relates to radio technology and can be used in direction finding systems of radio emission sources.

A known method of direction finding of radio signals [1, p. 33, 2], in which the phase shifts of signals received by several antennas spaced apart in space are measured and processed. To obtain acceptable azimuth accuracy, at least three antennas are required. The disadvantage of this method is the need to place several receiving antennas on the object.

The closest in technical essence to the proposed (prototype) is the direction finding method used in the direction finder [1, Fig.8.41].

In the prototype, the received signals from two orthogonal loop antennas are fed to the goniometer inputs, which ensures the azimuthal rotation of the total “eight” radiation pattern and its adjustment to the signal reception minima (two-digit bearing). To resolve the bearing uncertainty 0/180 degrees. an additional signal from an omnidirectional (pin) antenna is supplied to the input of the direction-finding receiver, which eliminates the second minimum. The disadvantage of this method is the decrease in direction finding accuracy with weak signals, comparable in level with interference. In this case, the minimum radiation patterns are filled with noise (“blurry”), and the accuracy of determining the direction from the minimum is significantly reduced. In addition, this method is quite difficult to implement even when using an electronic goniometer.

The purpose of the invention is to improve the accuracy of the bearing with weak signals and simplify the implementation.

In the proposed method, the signals from the orthogonal frames are fed to the input of the adder-phase shifter 90 °. Using the auxiliary emitter located in the far zone in the azimuth of do, a control signal is emitted and the phase difference between the received signals is measured from the output of the omnidirectional (pin) antenna and from the output of the adder, which is remembered and taken as the reference phase φ ₀ . The phase difference between the same outputs is measured, but for the direction finding signal φ _{p the} azimuth of the direction finding signal (radio source) α is defined as

α = α ₀ + (φ ₀ -φ _n ).

Consider the method in more detail. When adding signals from 2 orthogonal frames with a phase shift of 90 °, the total antenna pattern from “eight” turns into a circular one. In this case, the phase of the received signal changes in proportion to the azimuth of the arrival of the signal. At the same time, the phase of the signal coming from an omnidirectional antenna is constant and does not depend on azimuth. Figure 1 shows the experimental dependence of the phase difference of the signals coming from the omnidirectional (pin) antenna and the output of the adder Δφ on the angle of rotation in the horizontal plane α of the combined action "KV-K" antenna manufactured by NPM Rosmorservice.

As can be seen from the graph, the dependence Δφ (α) is close to linear. The error is determined mainly by the phase error of the phase shifter in the adder. Figure 2 shows the experimental dependence of the error of the phase shifter (differences from 90 °) of the adder Delta 90 from the frequency of the same antenna. The error in the operating range does not exceed 2 °.

Figure 3 shows a block diagram of a possible embodiment of a device that implements the proposed method. It contains:

1 - receiving non-directional (pin) antenna;

2` and 2`` - two receiving antennas (loop) with orthogonal radiation patterns in the form of “eights”;

3 - adder-phase shifter (RVR) at 90 °;

4 - radios with the same transmission coefficients;

5 - phase difference meter;

6 - analog-to-digital converter ADC;

7 - control unit BU;

8 - memory device;

9 - phase difference calculator;

10 - auxiliary radiating antenna;

11 - high-frequency generator.

The auxiliary antenna is located in the far zone of the receiving antennas, at a distance of not less than the wavelength of the received signals, preferably from the north side (α ₀ = 0 °).

The device operates as follows.

By an external command, the control device 8 is transferred to the "Calibration" mode, in which:

- the control device 7 supplies the control signals of the frequency tuning of the generator 11, and the auxiliary antenna sequentially emits monoharmonic signals in the operating frequency range;

- the radios 4 sequentially receive signals at these frequencies, and the phase difference meter 5 measures the phase difference φ ₀ between the signals received by the omnidirectional antenna 2` and with the PDF 3;

- the values of φ _{0 are} digitized in ADC 6, and the entire array of φ ₀ (f) is stored in memory 8;

- the generator turns off (radiation stops).

Usually in the KB range it is enough to measure φ ₀ at 20-30 frequencies uniformly distributed (logarithmically) over the range.

By an external command, the control device 8 is transferred to the "Measurement" mode, in which:

- the control device tunes the radios to the frequency specified by the external command, at which the signal for direction finding is located;

- the phase difference meter determines the phase difference φ _p between the signals received by the omnidirectional antenna 2` and from the output of the PDF 3;

- the value of φ _{p is} digitized in the ADC 6 and is fed to the input of the memory 8;

- the signal from the control unit 7 to one of the outputs of the memory 8 receives the previously stored value φ ₀ at a frequency closest to the frequency of the direction-finding signal, and to the other output - the value of φ _p ;

- in the calculator 9 is determined by the difference φ ₀ -φ _p , which is the azimuth of the signal. If the difference φ ₀ -φ _n > 0, then the azimuth is positive, i.e. to the right of the direction to the auxiliary antenna (0 ... 180 °). If φ ₀ -φ _n <0, then the azimuth is negative, i.e. to the left of the direction to the auxiliary antenna (0 ... -180 °). If φ ₀ -φ _p = 0, then the direction of arrival of the signal coincides with the direction of location of the auxiliary antenna. If the azimuth of the auxiliary antenna is α ₀ ≠ 0 °, then α = α ₀ + (φ ₀ -φ _p ).

The technical result - improving the accuracy of direction finding with weak signals - is provided by the proposed method due to the fact that the levels of the compared signals are always maximum. In the prototype, the direction of arrival of the signal is determined by the minimum signal, which can be very fuzzy ("blurry") due to the presence of interference.

In addition, the implementation of the proposed method does not require special direction-finding antennas. Here you can use serial communication receiving antennas (for example, Aktsiya-KV-K antennas), in which there are already two orthogonal loop antennas, a pin omnidirectional antenna and a 90 ° IDF used to obtain a circular radiation pattern of loop antennas.

Literature

1. Kukes I.S., Old man M.E. Basics of direction finding. - M .: Owls. Radio, 1964 .-- 640 s.

2. US patent No. 6989789.

Claims (1)

A method of direction finding radio signals, which consists in receiving and processing radio signals from two orthogonal antennas with "figure eight" radiation patterns in the horizontal plane and from one antenna with an omnidirectional (circular) radiation pattern, characterized in that the signals from the orthogonal frames are added in the adder-phase shifter 90 °, the phase difference φ ₀ is measured between the output of the omnidirectional antenna and the output of the adder-phase shifter of the signal from the auxiliary emitter located in the far zone in the azimuth α ₀ , the phase difference φ _p between the same outputs is measured, but for the direction-finding signal, the azimuth of the direction-finding signal α is calculated by the formula
α = α ₀ + (φ ₀ -φ _n ).

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