RU2726937C2 - Method for analyzing composite signals in an autocorrelation receiver - Google Patents

Abstract

FIELD: radio equipment.SUBSTANCE: invention relates to methods and equipment for radio monitoring of radio-frequency sources. Technical result is achieved by the fact that the received signal is filtered, delayed for a given time, multiplies the signal with its delayed copy, estimates the differential signal frequency, selecting signal component at difference frequency and low-frequency component of signal, obtaining their amplitude-frequency spectra (AFS), frequency of received signal after filtration is doubled, double frequency signal is delayed for a predetermined time, multiplied with a delayed copy, differential signal frequency is evaluated, a signal component is determined on the difference frequency and a low-frequency signal component, obtaining their AFS, obtained signal spectra are compared with given threshold values and based on the comparison results, a decision is made on the type of the received radar signal, according to the invention, additionally: if it was decided to receive a chirp signal, then a low-frequency envelope of the signal component at the difference frequency is determined, from which the pulse duration and repetition period is determined, determining the rate of change of frequency inside the chirp pulse and the width of the spectrum of the chirp pulses; if it was decided to receive a simple signal, then duration and pulse repetition period is determined by low-frequency component; if it has been decided to receive a phase-coded signal, then the signal at double frequency is fed for phase automatic frequency tuning, generating a reference signal and multiplying it with the received signal after filtering, method includes selecting a low-frequency component from which the law of phase alternation, number of discrepancies, duration and repetition period of pulses are determined, duration of one code discrete and width of the spectrum of the phase-coded signal are determined. In the proposed method of analyzing complex signals in an autocorrelation receiver, the novel essential features of the invention are newly introduced procedures for processing radar signals after determining their type.EFFECT: technical result, achievement of which is the claimed invention, is expressed in improvement of accuracy of determination of parameters of chirp pulse, phase-coded signal and simple radio pulses, having carrier frequencies in the band of the high-frequency input filter of the receiver, when receiving the chirp, the phase-coded signal, or simple radio pulses, as well as with simultaneous reception of the chirp and simple radio pulses.1 cl, 1 dwg

Description

The invention relates to the field of radio engineering, in particular, to methods and techniques for radio engineering monitoring of radio emission sources.

The following methods and methods of measuring the parameters of signals with frequency modulation are known [Smirnov Yu.A. Radio-technical intelligence - M .: Voenizdat, 2001. - p. 129-133]: using a non-tunable and tunable radio receiver, functional method, method of convolution of the signal spectrum.

The closest in technical essence (prototype to the alleged invention) is a method for determining the parameters of chirp signals in radio monitoring equipment (RTM), which consists in comparing the signal with its delayed copy at the output of the autocorrelation circuit [Smirnov Yu.A. Radio-technical intelligence - M .: Voenizdat, 2001. - p. 125-128, Patent RU 2578041 C1, IPC G01S 13/00, publ. 03/20/2016. bul. No. 8], based on the reception of a signal by an autocorrelation receiver (ACP), determination of the pulse duration τ _u by the method of a generator-conversion scheme [Smirnov Yu.A.

Radio-technical intelligence - M .: Voenizdat, 2001. - p. 108-111] and determining the width of the signal spectrum Δƒ _s according to the expression:

where ƒ _p is the difference frequency of the signal at the ACP output, τ _s is the duration of the signal delay.

The disadvantages of the method of technical analysis of complex signals in the means of RTM [Smirnov Yu.A. Radio-technical intelligence - M .: Voenizdat, 2001. - p. 125-128, Patent RU 2578041 C1, IPC G01S 13/00, publ. 03/20/2016. bul. No. 8] are the definition of parameters only for signals with chirp modulation with possible errors in the simultaneous presence of PCM and simple signals having close (identical) carrier frequencies.

The technical result, which the claimed invention is aimed at, is expressed in increasing the accuracy of determining the parameters of the chirp, FCM and simple radio pulses having carrier frequencies in the band of the input high-frequency filter of the receiver, when receiving separately chirp, FCM or simple radio pulses, as well as with simultaneous reception of chirp and simple radio pulses.

The specified technical result is achieved by the fact that the received signal is filtered, delayed for a specified time, the signal is multiplied with its delayed copy, the difference frequency of the signal is estimated ƒ _times1 , the signal component at the difference frequency ƒ _times1 and the low-frequency component of the signal are isolated, their amplitude-frequency spectra are obtained ( AFR), the frequency of the received signal after filtering is doubled, the signal at the doubled frequency is delayed for a specified time, multiplied with the delayed copy, the difference frequency of the signal is estimated ƒ _times2 , the signal component at the difference frequency ƒ _times2 and the low-frequency component of the signal are obtained, their AFC obtained signal spectra are compared with predetermined threshold values and, based on the comparison results, a decision is made on the form of the received radar signal, according to the invention, additionally: if a decision was made to receive a chirp signal, then the low-frequency envelope of the signal component at a difference frequency ƒ _times2 , n about which the duration and repetition period of the pulses are determined, the rate of change of the frequency within the chirp pulse and the width of the chirp pulse spectrum are determined; if a decision was made to receive a simple signal, then the duration and repetition period of the pulses are determined from the low-frequency component; if a decision was made to receive a PCM signal, then the signal at a doubled frequency is fed to a phase automatic frequency control (PLL), a reference signal is generated and multiplied with the received signal after filtering, a low-frequency component is isolated, according to which the law of phase rotation is determined, the number of samples, the duration and repetition period of the pulses, determine the duration of one sample of the code and the width of the spectrum of the PCM signal.

The essence of the invention lies in the fact that if it was decided to receive the chirp signal, then the low-frequency envelope of the signal component at the difference frequency ƒ _times2 is determined, according to which the duration and repetition period of the pulses are determined, the rate of change of the frequency within the chirp pulse and the width of the spectrum of the chirp pulses are determined; if a decision was made to receive a simple signal, then the duration and repetition period of the pulses are determined from the low-frequency component; if a decision was made to receive a PCM signal, then the signal at a doubled frequency is fed to the PLL, a reference signal is formed and multiplied with the received signal after filtering, a low-frequency component is isolated, according to which the law of phase rotation, the number of samples, the duration and the pulse repetition period are determined, determine the duration of one sample of the code and the spectrum width of the PCM signal.

It is known [Likhachev V.P., Veselkov A.A., Nguyen Chong N. Characteristics of detection of linear-frequency-modulated, phase-code-keyed and simple radio pulses in an autocorrelation receiver // Radiotekhnika, 2018. No. 8, P. 71- 76], that to determine the type of the received radar signal, the presence or absence of the AFR low-frequency component is checked, which is the component at the difference frequency of the resulting signal after multiplication and similar signal components at the doubled frequency after multiplication with its delayed copy at a given threshold. Considering the result of determining the type of signal, various procedures for processing and determining the frequency-time parameters of the signal are used: for the chirp signal, the low-frequency envelope of the signal component at the difference frequency ƒ _times2 is determined, according to which the time parameters of the chirp signal are determined, knowing the estimate of the difference frequency of the signal ƒ _times2 , the value of the delay time and the value of the pulse duration determine the rate of change of the frequency inside the chirp pulse and the width of the spectrum of the chirp pulses [Likhachev V.P., Semenov V.V., Veselkov A.A. Experimental testing of the algorithm for determining the frequency-time parameters of chirp signals // Telecommunications, 2016. No. 5. S. 2-7]; for a simple signal by the low-frequency component, which, like the component of the chirp signal at the difference frequency ƒ _times2, is a simple radio pulse, the duration and repetition period of the pulses are determined; for the PCM signal, a signal is supplied at a doubled frequency at the PLL, a reference signal is formed and multiplied with the received signal after filtering, the low-frequency component of the signal is isolated, according to which the law of phase rotation, the number of samples, the duration and the pulse repetition period are determined, knowing the number of samples and the pulse duration determine the duration of one sample of the code and the spectrum width of the PCM signal. This achieves the technical result specified in the invention.

The method for analyzing complex signals in the ACP can be implemented, for example, using a device, the diagram of which is shown in the drawing, where it is indicated: 1 - bandpass filter; 2 - frequency multiplier; 3 - delay line; 4 - multiplier; 5 - low-pass filter; 6 - a block for obtaining a spectrum, designed to obtain a spectrum of chirp, PCM and simple radio pulses; 7 - threshold device; 8 - decision block; 9 - key; 10 - meter of frequency-time characteristics of the signal; 11 - envelope detector; 12 - PLL. Meter 10.1 is designed to determine the time-frequency characteristics of the chirp signal. Meter 10.2 is designed to determine the temporal characteristics of a simple signal. Meter 10.3 is designed to determine the time-frequency characteristics of the PCM signal. The purpose of the remaining elements of the device is clear from their names.

и перемножается с его задержанной копией. Полосовым фильтром 1.2, выделяется составляющая сигнала на разностной частоте ƒ_раз1 (может быть оценена, например, по максимальной составляющей спектра сигнала в диапазоне частот [ƒ_{p min} ƒ_{p max}], который определяется минимальным и максимальным значениями скорости изменения частоты внутри ЛЧМ импульса). Для простого сигнала полученная составляющая сигнала близка к нулю. Низкочастотным фильтром 5.1 выделяется низкочастотная составляющая на выходе перемножителя 4.1, которая близка к нулю для ЛЧМ сигнала. Сигнал на выходе полосового фильтра 1.1 подается на вход умножителя частоты 2, где удваивается частота сигнала, производится задержка сигнала в линии задержки на время, определяемое как

и перемножение сигнала с его задержанной копией. Полосовым фильтром 1.3, выделяется составляющая сигнала на разностной частоте ƒ_раз1 (может быть оценена аналогично ƒ_раз1). Для простого сигнала и ФКМ сигнала полученная составляющая близка к нулю. Низкочастотным фильтром 5.2 выделяется низкочастотная составляющая на выходе перемножителя 4.2, которая близка к нулю для ЛЧМ сигнала. Для сигналов на выходе фильтров 1.2, 5.1, 1.3, 5.2 получают АЧС, максимальные значения которых сравниваются в пороговых устройствах 7.1, 7.2, 7.3 и 7.4 соответственно. Пороговое значение G_П может быть определено, например, по критерию Неймана-Пирсона при заданной вероятности ложной тревоги и вероятности правильного обнаружения [Смирнов Ю.А. Радиотехническая разведка - М.: Воениздат, 2001. - с. 237-240]. Принятые в пороговых устройствах 7.1, 7.2, 7.3, 7.4 решения подаются на первый, второй, третий и четвертый входы блока принятия решения 8. Блок принимает решение о виде принятого сигнала [Лихачев В.П., Веселков А.А., Нгуен Чонг Н. Характеристики обнаружения линейно-частотно-модулированных, фазо-кодо-манипулированных и простых радиоимпульсов в автокорреляционном приемнике // Радиотехника, 2018. №8, С. 71-76].The device works as follows: the received signal is fed to the input of the bandpass filter 1.1 with a bandwidth Δƒ _HF which can be set, for example, by the limiting width of the spectrum of signals of radio electronic systems in a given frequency range RTM [Radio electronic systems; Basics of construction and theory. Directory. / Ed. POISON. Shirman. - M .: Radiotekhnika, 2007 .-- p. 297]. The selected signal is delayed in the delay line for a time defined as

and multiplied with its delayed copy. With a bandpass filter 1.2, the signal component at a difference frequency ƒ _{times1 is selected} (it can be estimated, for example, by the maximum component of the signal spectrum in the frequency range [ƒ _{p min} ƒ _{p max} ], which is determined by the minimum and maximum values of the frequency change rate within the chirp pulse). For a simple signal, the received signal component is close to zero. A 5.1 low-pass filter selects the low-frequency component at the output of the 4.1 multiplier, which is close to zero for the chirp signal. The signal at the output of the bandpass filter 1.1 is fed to the input of the frequency multiplier 2, where the signal frequency is doubled, the signal is delayed in the delay line for a time defined as

and multiplying the signal with its delayed copy. With a bandpass filter 1.3, the signal component at the difference frequency ƒ _times1 (can be estimated similarly ƒ _times1 ) is _selected . For a simple signal and a PCM signal, the resulting component is close to zero. The low-pass filter 5.2 selects the low-frequency component at the output of the multiplier 4.2, which is close to zero for the chirp signal. For the signals at the output of filters 1.2, 5.1, 1.3, 5.2, ASF is obtained, the maximum values of which are compared in the threshold devices 7.1, 7.2, 7.3 and 7.4, respectively. The threshold value G _P can be determined, for example, by the Neumann-Pearson criterion at a given probability of false alarm and the probability of correct detection [Smirnov Yu.A. Radio-technical intelligence - M .: Voenizdat, 2001. - p. 237-240]. The decisions made in the threshold devices 7.1, 7.2, 7.3, 7.4 are fed to the first, second, third and fourth inputs of the decision making block 8. The block decides on the form of the received signal [Likhachev V.P., Veselkov A.A., Nguyen Chong N Characteristics of detection of linear-frequency-modulated, phase-code-shift keyed and simple radio pulses in an autocorrelation receiver // Radiotekhnika, 2018. No. 8, pp. 71-76].

If a decision is made to receive a chirp signal, then a signal appears at the first output of the decision block 8, which turns on the operation of the meter 10.1. The envelope detector 11 selects the low-frequency envelope of the signal component at the difference frequency ƒ _times2 , which is fed to the input of the meter 10.1, according to which the pulse duration is determined (for example, by the maximum of the linear convolution of the low-frequency envelope with a series of rectangular pulses (PI)) and the pulse repetition period [Likhachev V.P., Semenov V.V., Veselkov A.A. Experimental testing of the algorithm for determining the frequency-time parameters of chirp signals // Telecommunications, 2016. No. 5. P. 2-7], knowing the estimate of the difference frequency of the signal ƒ _paz2 , the value of the delay time and the value of the pulse duration, the rate of change of the frequency inside the chirp pulse and its spectrum width are determined [Kupryashkin I.F., Likhachev V.P., Semenov V.V. ., Lozhkin A.L. Polarimetric and interferometric modes of operation of radar with a synthetic aperture of the antenna in interference conditions: Monograph. - Voronezh: VUNC VVS "VVA", 2015. - p. 173, 174].

If from the second output of the decision block 8 to the key 9.1 a decision is given that only a simple signal is received or a simple signal and a chirp signal are received, then the key turns on the operation of the meter 10.2. The meter determines the pulse duration (similar to the 10.1 meter, for example, by the maximum of the linear convolution of the low-frequency signal component at the output of the 5.1 filter with a series of PI) and the pulse repetition period [Likhachev VP, Semenov VV, Veselkov AA. Experimental testing of the algorithm for determining the frequency-time parameters of chirp signals // Telecommunications, 2016. No. 5. S. 2-7].

If from the third output of the decision block 8 to the key 9.2 a decision is made that only the FCM signal is received, then the key turns on the operation of the meter 10.3. The signal at the doubled frequency is fed to the input of the PLL 12, operating at the doubled frequency [Zimarin V.I., Illarionov B.V., Koziratsky A.Yu., Kozlov S.V. Devices for receiving and processing signals / Textbook. - Voronezh: VUNC VVS "VVA", 2015. - p. 197, 198]. The reference signal at the output of the PLL is multiplied with the signal at the output of the filter 1.1. The low-frequency filter 5.3 selects the low-frequency component of the signal at the output of the multiplier 4.3, according to which the law of phase rotation of the PCM signal is determined in meter 10.3: if the amplitude of the received signal at the output of filter 5.3 is greater than zero, then symbol 0 is transmitted, if less than zero, then symbol 1 is transmitted. Then the number of samples, the pulse duration are determined (similar to the meter 10.1, for example, according to the maximum of the linear convolution of the low-frequency component at the output of the filter 5.3 with a series of PI) and the pulse repetition period [Likhachev V.P., Semenov V.V., Veselkov A.A. Experimental testing of the algorithm for determining the frequency-time parameters of chirp signals // Telecommunications, 2016. No. 5. P. 2-7], knowing the number of samples and the pulse duration, the duration of one sample of the code and the spectrum width of the PCM signal are determined [Smirnov Yu.A. Radio-technical intelligence - M .: Voenizdat, 2001. - p. 124, 137].

Thus, in the proposed method for analyzing complex signals in the automatic transmission system, the new essential features of the invention are the newly introduced procedures for processing radar signals after determining their type.

The proposed technical solution is new, since from the publicly available information methods are not known that allow, after recognizing chirp, FCM and simple radio pulses having carrier frequencies in the passband of the input filter, to determine their time-frequency parameters when receiving separately chirp, FCM or simple radio pulses, while receiving Chirp and simple radio pulses, as well as allowing, in the case of simultaneous reception of chirp and FKM or LFM, FKM and simple radio pulses, to determine the time-frequency parameters of the chirp signal.

The proposed technical solution is practically applicable, since standard electronic devices and means can be used for its implementation. For example, bandpass filter 1.1 can be implemented as a waveform analog filter (WAF); bandpass filters 1.2 and 1.3, low-pass filters 5.1-5.3 can be implemented as filters on surface acoustic waves (SAW) or filters on resonators [Ulahovich D.A. Fundamentals of the theory of linear electrical circuits: Textbook. allowance. - SPb .: BHV-Petersburg, 2009 .-- p. 586-603, 746-780]. Spectrum acquisition units 6.1 - 6.4 can be implemented on the basis of an analog-to-digital converter (ADC) and a programmable logic integrated circuit (FPGA), or using a spectrum analyzer; decision block 8, keys 9.1 and 9.2 can be implemented in analog form based on a set of logic elements AND, NOT, or in digital form using a microcontroller. Time-frequency meters 10.1 - 10.3 can be implemented digitally using a microcontroller or FPGA.

Claims (1)

A method for analyzing complex signals in an autocorrelation receiver, which consists in filtering and delaying the received signal for a given time, multiplying the received signal with its delayed copy, estimating the difference frequency of the signal, separating the signal component at the difference frequency and the low-frequency component of the signal, obtaining their amplitude-frequency spectra ( ASF), doubling the frequency of the received signal after filtering, delaying the signal at a doubled frequency for a specified time, multiplying the signal at the doubled frequency with its delayed copy, estimating the difference frequency of the signal, isolating the signal component at the difference frequency and the low-frequency component of the signal, obtaining their ASF, comparing the obtained signal spectra with given threshold values and making a decision on the form of the received radar signal, characterized in that additionally: if a decision was made to receive the chirp signal, then the low-frequency envelope of the signal component at the difference frequency is determined, by which the duration and repetition period of the pulses are determined, the rate of change of the frequency within the chirp pulse and the width of the chirp pulse spectrum are determined; if it was decided to receive a simple signal, then the duration and repetition period of the pulses are determined from the low-frequency component; if it was decided to receive a PCM signal, then the signal at the doubled frequency is fed to the phase automatic frequency control, a reference signal is generated and multiplied with the received signal after filtering, the low-frequency component is isolated, according to which the law of phase rotation, the number of samples, duration and period are determined pulse repetition, determine the duration of one sample of the code and the spectrum width of the PCM signal.

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