RU2305295C1 - Phase method for direction finding - Google Patents

Abstract

FIELD: radio electronics, applicable for passive radio monitoring in multi-channel system designed for direction finding of several sources of radio emission simultaneously getting into the reception zone.

SUBSTANCE: expanded functional potentialities by way of direction finding in two planes of several sources of radio emission simultaneously getting into the reception zone.

EFFECT: expanded functional potentialities.

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Description

The proposed method relates to the field of radio electronics and can be used for passive radio monitoring in multichannel systems intended for direction finding of several sources of radio emission that simultaneously fall into the reception band.

Known methods of direction finding (RF patents No. 2003131, 2006872, 2010258, 2012010, 2155352, 2207583, 2175770, Kinkulkin I.E. et al. Phase method for determining coordinates. M: Sov. Radio, 1979; Space radio engineering complexes. Edited by C. .I. Bychkova. - M .: Sov. Radio, 1967, p.134-138, fig. 2.3.9, and others.)

Of the known methods, the closest to the proposed one is (Space Radio Engineering Complexes. Edited by S. I. Bychkov. - M .: Sov. Radio, 1967, p.134-138, Fig. 2.3.9, and others), which and selected as a prototype.

The specified method provides direction finding of only one source of radio emission and only in one plane.

An object of the invention is to expand the functionality of the method by direction finding in two planes of several sources of radio emission, simultaneously falling into the reception band.

The problem is solved in that according to the phase direction finding method, based on receiving signals on two antennas spaced apart in space, amplifying and limiting the amplitude of the received signals in the first and second receivers, use a third receiving antenna and a third receiver, in which the received signals also amplify and limit in amplitude, while the receiving antennas are arranged in the form of a geometric right angle, at the top of which a third receiving antenna is placed, common to the other two receiving antennas signals in the azimuthal and elevation planes, the signals received by the first and second receivers are passed through n-tap delay lines, forming n channels of correlation processing in each plane, and in each processing channel, the delayed signal is multiplied with the signal of the third receiver, the low-frequency voltage is extracted, compared it with a threshold voltage and if the threshold voltage is exceeded, this excess is recorded and a decision is made on the number and numbers of processing channels in which the thresholds are exceeded ie voltage, the number of emitters, and their elevations.

The structural diagram of a device that implements the proposed phase method of direction finding is presented in figure 1. The relative position of the receiving antennas is shown in figure 2. The device contains three receiving channels, each of which consists of series-connected: receiving antenna 1 (2, 3), receiver 4 (5, 6). The n-tap delay line 7.i (8.i), the multiplier 9.i (10.i), the second input of which is connected to the output of the receiver 6, filter 11.i (12.i) are connected in series to the output of the receiver 4 (5). ) low-frequency threshold block 13.i (14.i), blocks 15.i (16.i) registration (i = 1, 2, ..., n).

The proposed phase direction finding method is implemented as follows.

The signals of several sources of radio emissions are simultaneously captured by receiving antennas 1, 2, 3, amplified and limited in amplitude at receivers 4, 5, 6, respectively. In this case, the receiving antennas 1, 2, 3 are located in the form of a geometric right angle, at the top of which the third receiving antenna 3 is placed, common to the other two receiving antennas 1 and 2 located in the elevation and azimuthal planes. Then, the signals received by the first 4 and second 5 receivers are passed through the n-tap delay lines 7.i and 8i (i = 1, 2, ..., n), respectively.

It should be noted that according to the phase method of direction finding, the phase differences Δφ ₁ and Δφ _{2 of the} signals received by antennas 1 and 2, 1 and 3 are determined by the expressions:

where d is the distance between spaced antennas (measuring base);

λ is the wavelength;

β, α - elevation angle and azimuth of the radiation source.

. Но с ростом

уменьшаются значения угловых координат β и α, при которых разности фаз Δφ₁, и Δφ₂ превосходят значение 2π, т.е. наступает неоднозначность отсчета.However, the phase method of direction finding is characterized by a contradiction between the requirements for the accuracy of measurements and the uniqueness of the reference angles β and α. Indeed, according to the above expressions, the phase system is the more sensitive to changes in the angles β and α, the longer the relative size of the measuring base

. But with growth

the values of the angular coordinates β and α decrease at which the phase differences Δφ ₁ and Δφ ₂ exceed the value 2π, i.e. ambiguity of counting occurs.

The ambiguity of the phase method of direction finding of radio sources can be eliminated by two classical methods: using antennas with a sharp radiation pattern and using several measuring bases (multichannel) in each plane.

Direction finding systems with highly directional antennas have a long range and high resolution in direction. However, they require a search for a source of radio emission before the start of measurements and its automatic tracking in the direction of the antenna beam during measurements, and also deprive the phase method of direction finding of one of its advantages - the possibility of using directional (isotropic) antenna systems.

Multichannel is usually achieved using several measurement bases. At the same time, a smaller base forms a rough but unambiguous reference frame for the corner, and a large base forms an accurate but ambiguous reference frame.

In the proposed phase direction finding method, the contradiction between the requirements for measurement accuracy and the uniqueness of the reading of angles β and α is resolved by correlation processing of the received signals.

The phase differences of the high-frequency oscillations received by antennas 1 and 2, 1 and 3 are determined by the relation (1). On the other hand, the indicated phase differences are determined as follows:

- время запаздывания сигнала, приходящего на антенну 1, по отношению к сигналу, приходящему на антенну 3;Where

- the delay time of the signal arriving at the antenna 1, in relation to the signal arriving at the antenna 3;

- время запаздывания сигнала, приходящего на антенну 2, по отношению к сигналу, приходящему на антенну 3;

- the delay time of the signal arriving at the antenna 2, in relation to the signal arriving at the antenna 3;

Therefore, equating these ratios, we get:

By measuring the delays τ ₁ and τ ₂ and knowing the measuring base d, we can unambiguously determine the true elevation angle and azimuth of the radio source:

The distances traveled by the signals from the radiation source to the receivers 4, 5 and 6 are not the same, and therefore, differ in the phases received by the signals. The delay of one of the signals depends on the position of the radio source and the measurement base d.

Since the signal in the three reception channels is the same, and the noise and interference in the channels are independent, then in each channel there will be oscillations of the form:

,

,

- входные колебания в первом, втором и третьем каналах приема, представляющие собой аддитивную смесь сигнала u_c(t) и шума u_ш1(t), u_ш2(t), u_ш3(t) в каждом канале приема.Where

,

,

- input vibrations in the first, second and third reception channels, which are an additive mixture of the signal u _c (t) and noise u _w1 (t), u _w2 (t), u _w3 (t) in each receive channel.

In the correlators, the signals are multiplied, and the interference signals are mutually suppressed. The implementation of the cross-correlation function of signals from one radio source in two independent channels takes maximum values in the case of compensation of the delay time of a signal in one of the channels due to the inclusion of a delay line. The number of correlators equal to n is determined by the convenience of using n delay lines with a fixed delay time τ _i (i = 1, 2, ..., n). The number of correlators is determined by the required accuracy of determining the elevation angle and azimuth to the source of radio emission.

In the general case, it is necessary to provide a total signal delay in the range from −Δτ to Δτ using n delay lines. The time interval Δτ is determined from the expression:

where c is the propagation velocity of radio waves.

The presence at the outputs of several correlators of local maxima of the mutual correlation function corresponds to the situation when several sources of radio emission are present at the boundary. On this basis, the number of sources of radio emission in the controlled area is estimated.

The mutual correlation function of a signal from a single source of radio emission, received by two identical channels, and formed by the correlator, is nothing more than an autocorrelation function, but with different signal delay times.

The first and second reception channels include multi-tap delay lines 7.i and 8.i (i = 1, 2, ..., n) and the same number of correlators consisting of multipliers 9.i (10.i) and filters 11.i (12.i) low frequencies. The output voltages of the correlators are compared with a threshold voltage U _then in the threshold blocks 13.i and 14.i. The threshold voltage U _{then is} exceeded only at the maximum value of the output voltage of the correlator. If there are several sources of radio emission, maxima can be observed at the outputs of several correlators. In case of exceeding the threshold voltage U _then , this excess is recorded by the corresponding registration blocks 15.i and 16.i. By the number and numbers of processing channels in which the threshold voltage U _then is exceeded, a decision is made on the number of sources of radio emission, their azimuths and elevation angles.

Thus, the proposed method in comparison with the prototype provides direction finding in two planes of several sources of radio emission, simultaneously falling into the reception band.

In addition, the proposed method allows to resolve the contradiction between the requirements for the accuracy of measurements and the uniqueness of counting elevation angles and azimuths to radiation sources of radio emissions. This is achieved by correlation processing of the received signals.

Thus, the functionality of the method is expanded.

Claims (1)

Phase direction finding method based on receiving signals on two antennas spaced apart in space, amplifying and limiting the amplitude of the received signals in the first and second receivers, characterized in that they use a third receiving antenna and a third receiver, in which the received signals are also amplified and limited in amplitude wherein the receiving antennas are arranged in the form of a geometric right angle, at the top of which a third receiving antenna is placed, common to two other receiving antennas located in the azimuthal and of the natural planes, the signals received by the first and second receivers are passed through the n-tap delay lines, forming n channels of correlation processing in each plane, and in each processing channel the delayed signal is multiplied with the signal of the third receiver, the low-frequency voltage is extracted, it is compared with the threshold voltage and in case of exceeding the threshold voltage, record this excess and decide on the number and numbers of processing channels in which the threshold voltage is exceeded, on the number Source radio emissions, their azimuth and elevation angles.

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