RU2765484C2 - Method for direction finding and device implementing thereof - Google Patents

Abstract

FIELD: physics.SUBSTANCE: group of inventions relates to radio engineering and can be used in radio direction-finding equipment. During direction finding, the received signal is delayed in the entire operating frequency band for the time of frequency determination. Band in the vicinity of the measured frequency is selected from the band of the delayed signal. Direction finding is performed in this band. Device comprises a multichannel direction finder with a delay line and a frequency converter in each channel. Adjustment of frequency converters is carried out using a frequency determination device. Delay lines are adjusted for the frequency determination time, but not less than the duration of the received pulse.EFFECT: reduced probability of missing a signal.3 cl, 1 dwg

Description

SUBSTANCE: group of inventions relates to radio engineering and can be used in radio direction finding equipment.

Known methods of amplitude direction finding [1, p. 27–28], at which the energy maximum or minimum per radio emission source (RES) is measured, or the equisignal direction is determined by comparing the signal amplitudes at the outputs of two or more direction finder channels. A common disadvantage of these methods is the low accuracy of direction finding for a wide sector of work. For the equal-signal method, which has the highest accuracy of the listed ones, the error is approximately 0.05 of the antenna beamwidth [2, p. 309-312]. When taking direction finding, for example, in a sector of 30 °, the width of the radiation pattern of each antenna in the general case is also at least 30 °, and the direction finding error, respectively, is at least 15 °.

где

– разность фаз сигналов, принятых антеннами,

– рабочая длина волны принимаемого сигнала, D – база пеленгования (расстояние между антеннами). Согласно выражению пеленг зависит от частоты и может быть однозначно измерен только при изменении разности фаз

не более чем на 360 °, что достигается в относительно узком диапазоне частот. Таким образом, недостатком метода является узкий диапазон рабочих частот.The phase direction finding method using two antennas is based on measuring the phase difference of a signal received by two identical antennas and passing through two identical channels. This method has a smaller error with a wide sector of work, reaching 120 ° [3, p. 10]. The direction to IRI α is determined in accordance with the expression

where

is the phase difference of the signals received by the antennas,

is the operating wavelength of the received signal, D is the direction finding base (the distance between the antennas). According to the expression, the bearing depends on the frequency and can be unambiguously measured only when the phase difference changes

no more than 360 °, which is achieved in a relatively narrow frequency range. Thus, the disadvantage of the method is the narrow range of operating frequencies.

The disadvantage of the phase direction finding method with two antennas is eliminated by using a multi-antenna system with several bases of different sizes and determining the bearing by the “refinement method” [3, p. 8–15]. In this case, the direction finding accuracy is determined by the largest base, and the rest serve to eliminate the ambiguity of measurements. The disadvantage of this method is the need to use multiple antennas, the number of which increases with the expansion of the frequency range and sector of work. Also, the disadvantage is the decrease in the sensitivity of the direction finder, which implements this method of direction finding, with the expansion of the operating frequency range. This is due to the increase in noise power and, accordingly, the deterioration of the signal-to-noise ratio with the expansion of the operating frequency range.

There is also a method of direction finding using a correlation interferometer with frequency tuning [2, p. 326-334], taken as a prototype. With this method, phase differences are theoretically calculated for elements of the antenna array at different angles of wave arrival. During direction finding of a radio emission source, the measured phase differences are compared with previously calculated ones, and the correlation coefficients of a set of measured and theoretical data are calculated. The direction for which the correlation coefficient is maximum is selected as the bearing to the target. Such a direction finder makes it possible to provide high accuracy with a compact arrangement of antenna array elements. Frequency tuning provides both a wide operating frequency band and high sensitivity due to a narrow operating frequency band, in which the integrated noise power is lower, which means that the signal-to-noise ratio required for processing can be achieved with a lower signal power.

The disadvantage of this method is the possibility of skipping the signal when scanning by frequency, if the frequency of the direction-finding signal is not known in advance.

The purpose of the group of inventions is to provide the possibility of direction finding at low input signal power, a wide band of operating frequencies and high direction finding accuracy.

The technical result is to reduce the probability of signal skipping.

The goal is achieved by the fact that frequency conversion is performed in the direction finding channels. In addition to this, the received signal is preliminarily delayed in the operating frequency band for a time not less than t. During the time t, the frequency of the signal in the operating frequency band is determined and a band with a center frequency equal to the frequency of the received signal is selected for direction finding. Then, a band is selected from the band of the delayed signal with the help of frequency conversion and direction finding is performed in it.

In addition, the proposed method differs in that the delay time t is greater than the duration of the received pulse.

High accuracy of direction finding is ensured by using the method necessary to achieve it - correlation-interferometric, phase or other. The method is selected based on the given accuracy. Assuming that the distribution of noise power in the operating frequency band is uniform, the integrated noise power in the narrow band is lower than the noise power in the wide band. Therefore, by using a narrow band allocated according to the measured frequency, direction finding of a low power signal is achieved. At the same time, the bandwidth of the operating frequencies in the proposed method is determined by the bandwidth in which the delay and frequency determination are performed, as well as the bandwidth of the operating frequencies of the direction finding equipment that implements one or another method. In the practical implementation of all these actions, the bandwidth is preserved, which was not already originally used in direction finding methods.

In addition, if the pulse duration is greater than the time t, a part of the pulse may be lost. Therefore, when receiving long pulses, it is advisable to choose the delay time t greater than the duration of the received pulse.

Another goal of the group of inventions is to offer a variant of the device for implementing the proposed direction finding method.

This goal is achieved by the fact that in a device containing direction finding channels, the outputs of which are connected to the calculator, and each channel contains an antenna, a frequency converter and a filter, additionally, a series-connected antenna, a delay line and a frequency determination device are used. Moreover, the signals from the output of the frequency determination device set the heterodyne frequencies in the frequency converters.

The figure shows a variant of the device that implements the proposed method of direction finding.

The essence of the group of inventions is illustrated by the example of a device that contains: 1 - antenna; 2 - frequency determination device (UOCH); 3 – frequency synthesizer (MF); 4.1 - 4.N - direction finding channels, 5 - calculator. Each direction finding channel 4.1 - 4.N contains identical antenna 6, delay line (LZ) 7, mixer (Sm) 8 and filter (F) 9.

The device works as follows. The RF signal in the operating frequency band is received by all antennas (antenna 1 and antennas 6.1–6.N of direction finding channels 4.1–4.N). From the antenna output 1, the signal enters the frequency determination device 2, and from the antenna outputs 6.1–6.N, the signal enters the delay lines 7.1–7.N. In the frequency determination device 2, the frequency determination of the signal is performed. In accordance with the measured frequency, the frequency determination device 2 generates a control command "Control" and sends it to the frequency synthesizer 3. All operations in the frequency determination device 2 are performed in time t. By the command "Control" the output frequency is tuned, generated by the frequency synthesizer 3. In the delay lines 7.1–7.N, the signal is delayed for a time not less than t. The signal from the outputs of the delay lines 7.1–7.N enters the mixers 8.1–8.N. By this time, with the help of the “Control” control command, frequency synthesizer 3 already outputs a signal with such a frequency f _Г that mixers 8.1–8.N from the entire delayed frequency band carry out signal transfer to an intermediate frequency from the signal frequency that was measured in the device frequency determination 2. The signal from the outputs of mixers 8.1–8.N in a single range of intermediate frequencies is fed to filters 9.1–9.N, which select the intermediate frequency band. Those. by transferring the signal to the intermediate frequency range from the frequency of the received signal, a narrow band is selected for direction finding from the entire operating frequency range, and a narrow band for direction finding is selected using filters 9.1–9.N. The filtered signal from the outputs of the direction finding channels 4.1 - 4.N enters the calculator 5 to determine the bearing by a method that provides the required direction finding accuracy.

Broadband frequency detection device 2 in practice can be made on the basis of a matrix receiver (according to the schemes described, for example, in [4, 5]), a subsampling receiver (according to the schemes described, for example, in [6, 7]), or other well-known schemes described, for example, in the literature [8, 1].

The delay line 7 can be implemented on the basis of signal transfer from the radio frequency range to the optical one, the signal delay in the fiber optic cable and the reverse transfer to the radio frequency range using the technical solution described, for example, in [9].

The remaining elements of the device are implemented using well-known means.

Sources of information

1. Kupriyanov A. I., Sakharov A. V. Radio-electronic systems in the information conflict // M.: Vuzovskaya kniga. 2003. 528 p.

2. Rembovsky A. M., Ashikhmin A. V., Kozmin V. A. Radio monitoring. Tasks, methods, means // Hotline-Telecom. 2010. 624 p.

3. Denisov V.P., Dubinin D.V. Phase radio direction finders: monograph // Tomsk: Tomsk state. University of control systems and radio electronics. 2002. 251 p.

4. Patent RU 155553 U1. Receiving device / A.I. Bezzub, A.S. Podstrigaev; No. 2014151261/08; dec. 12/17/2014; publ. 10.10.2015, Bull. No. 28.

5. Patent RU 2422845 C2. Matrix receiver / V.D. Anokhin, E.V. Anokhin, V. G. Kildyushevskaya, Simokhammed Fauzi. No. 2009131254/09; dec. 08/17/2009; publ. 27.02.2011, Bull. No. 18.

6. Patent US 5109188 A. Instantaneous frequency measurement receiver with bandwidth improvement through phase shifted sampling of real signals / R. B. Sanderson, J. B. Y. Tsui. No. 672309; dec. 03/06/1991; publ. 04/28/1992.

7. Patent RU 2516763 C1. Receiving device / A. N. Krenev et al. No. 2012143923/08; dec. 10/15/2012; publ. May 20, 2014, Bull. No. 14.

8. Tsui J., Cheng Ch.-H. Digital techniques for wideband receivers. 3rd ed. // New York, SciTech Publishing Inc, 2015. 608 p.

9. Patent RU 2715366 C2. Microwave signal delay method and delay line implementing it / A. S. Podstrigaev, A. A. Galichina. No. 2019122980; dec. 07/19/2019; publ. 02/26/2020, Bull. No. 6.

Claims (3)

1. The direction finding method, which consists in the fact that the received signal in a wide band of operating frequencies is delayed for a time of at least t, in time t the frequency of the received signal in a wide band of operating frequencies is determined, the delay signal is transferred from a wide band of frequencies to an intermediate frequency from a frequency a signal equal to the measured frequency of the received signal, a narrow frequency band with a center frequency corresponding to the measured frequency of the received signal is selected from the signal in a single range of intermediate frequencies, and direction finding is performed in the selected narrow frequency band. 2. The method according to p. 1, characterized in that the delay time t is greater than the duration of the received pulse. 3. A radio direction finding device containing direction finding channels, the outputs of which are connected to the calculator, characterized in that each direction finding channel contains a direction finding channel antenna, a delay line, a mixer and a filter connected in series, while additionally using a series connected antenna, a broadband frequency determination device and a synthesizer frequencies, and the signals from the output of the broadband frequency determination device in accordance with the measured frequency of the received signal in the frequency synthesizer sets the heterodyne frequency, which is fed to the mixers of the direction finding channels.

Images