RU132588U1 - DEVICE FOR CORRELATION-FILTER PROCESSING OF MULTI-FREQUENCY LINEAR-FREQUENCY-MODULATED PHASE-CODO-MANIPULATED SIGNAL WITH SINGLE-FREQUENCY HETERODINING - Google Patents

Abstract

A correlation-filter processing device for a multi-frequency linear-frequency-modulated phase-code-manipulated signal with a single-frequency heterodyning, containing from the 1st to the Nth bandpass filter, the outputs of which are connected to the inputs from the 1st to the Nth amplifiers, respectively, the outputs which are connected to the inputs from the 1st to the Nth phase shifter, respectively, the outputs of which are connected to the input of the adder, the output of which is the output of the device, characterized in that the mixer, LFM local oscillator, phase modulate are additionally introduced p, an M-sequence generator, while the M-sequence generator is connected to the first input of the phase modulator, the second input of which is the LFM output of the local oscillator, while the output of the phase modulator is the second input of the mixer, the first input of which is the input of the device, and its output is the input from 1st to Nth bandpass filters.

Description

The proposed device relates to the field of radio engineering and can be used in radar systems for detection, recognition and selection.

.A device is known that allows for incoherent processing of a multi-frequency linear frequency-modulated (MF LFM) signal, comprising a 1st amplifier, a bandpass filter, a preselector, a 2nd amplifier, a dispersion filter, an envelope detector and an integrating element, as well as a unit for generating heterodyne frequency -modulated (FM) oscillations [1, p. 409, Fig. 6.38]. The operation of the device lies in the fact that the reflected from the target MF LFM signal containing N partial linear frequency-modulated (LFM) radio pulses, which, in turn, is fed through a microwave amplifier and preselector to the mixer, to which heterodyne frequency modulated oscillations. They are formed either by single or double phase modulation. In the mixer (LFM), the radio pulses of the multi-frequency (MF) signal, in addition to the central one, are shifted by a certain amount relative to the frequency of the receiver dispersion filter. As a result, interference fading is excluded and for non-quasi-pointed purposes, with an increase in the broadband frequency of the MF signal, the losses become less than

.

The disadvantage of this device is the limited functionality for processing complex signals with intrapulse modulation, as well as the presence of losses of the processed signal in comparison with optimal filtering.

Also known is a small-channel (by the number of N partial LFM radio pulses) device that performs coherent processing of a quasi-noise MF LFM signal, containing a microwave amplifier, an intermediate frequency amplifier, two bandpass filters, N + 1 (by the number of partial LFM radio pulses) phase modulators, N dispersion filters, N detectors, N attenuators and a multi-tap delay line [1, p. 409, Fig. 6.39].

, а отводы следуют через ΔT₃=1/NΔf_со. Зависимости частоты от времени МЧ ЛЧМ сигнала f_с(t), отраженного от квазиточечной цели, и гетеродинных МЧ колебаний f_г(t), например на первом и втором отводах линии задержки, изображены в [1, стр.401, рис. а, б, в соответственно]. Для изображенной ситуации на выходе смесителя 2 гармоническая составляющая частотной модуляции МЧ ЛЧМ сигнала демодулируется и на дисперсионный фильтр ДФ2 поступает согласованный с ним ЛЧМ радиоимпульс частоты f_см(t)=f_с(t)-f_г2(t) [1, стр.401, рис.6.40, г]. Тогда на выходе второго канала в момент t₀+τ_с получается сжатый импульс [1, стр.401, рис.6.40, д] с длительностью

и амплитудой, равной максимуму функции неопределенности МЧ ЛЧМ сигнала при τ=0 [1, стр.26, рис.1.23, г]. На выходах остальных смесителей (1-го, 3-го, 4-го, … N-го) указанная демодуляция не происходит, а нелинейная частотная модуляция еще более увеличивается. Поэтому на выходах соответствующих дисперсионных фильтров получаются остаточные сигналы [1, стр 401, график 1 на рис.6.40, д], максимальные выбросы которых в моменты (t₀+τ_с)±NΔT_з соответствуют амплитудам боковых лепестков функции неопределенности МЧ ЛЧМ сигнала при τ=1/iΔf_со, где i=1, 2, …, N. Если отраженный МЧ ЛЧМ сигнал смещается на Δt=1/iΔf_со, то сжатый импульс сдвигается на эту же величину, появляясь на выходе соседнего канала обработки. В свою очередь, следующие сжатые импульсы на выходе каждого канала обработки появляются при смещении отраженного МЧ ЛЧМ сигнала на Δt=1/Δf_со. Энергетические потери при такой обработке отсутствуют.The operation of the device is as follows. The heterodyne MF voltage is generated either by a single phase modulation of a continuous microwave signal of frequency f _g = f _{0 by} harmonic oscillation of the intermediate frequency F ₀₁ = F ₀ -F _cm , or by twice phase modulation, but by harmonic oscillations and with frequencies F ₀₁ and NF ₀₁ (this depends on the method of generating sounding MF LFM radio pulses, where F ₀ and NF ₀ are the frequencies of harmonic modulating oscillations used in the transmitter), but at F ₀₁ = F ₀ (F _cm = 0) and is fed to N processing channel mixers through a delay line with bends. Total line delay

, and taps follow through ΔT ₃ = 1 / NΔf _with . Dependences of the frequency on time of the MF LFM signal f _s (t) reflected from the quasi-point target and heterodyne MF oscillations f _g (t), for example, on the first and second taps of the delay line, are shown in [1, p .011, Fig. a, b, c, respectively]. For the situation shown, at the output of mixer 2, the harmonic component of the frequency modulation of the MF LFM signal is demodulated and the dispersion filter DF2 receives a radio frequency pulse f _cm (t) = f _s (t) -f _g 2 (t) matched with it LFM [1, p. 401, Fig. 6.40, d]. Then, at the output of the second channel at the moment t ₀ + τ _s , a compressed pulse is obtained [1, p.401, Fig.6.40, d] with a duration

and an amplitude equal to the maximum of the uncertainty function of the MF LFM signal at τ = 0 [1, p. 26, Fig. 1.23, d]. At the outputs of the remaining mixers (1st, 3rd, 4th, ... Nth), this demodulation does not occur, and the nonlinear frequency modulation is further increased. Therefore, residual signals are obtained at the outputs of the corresponding dispersion filters [1, p. 401, graph 1 in Fig. 6.40, d], the maximum emissions of which at the moments (t ₀ + τ _s ) ± NΔT _s correspond to the amplitudes of the side lobes of the uncertainty function of the MF LFM signal at τ = 1 / iΔf _co , where i = 1, 2, ..., N. If the reflected MF chirp signal is shifted by Δt = 1 / iΔf _co , then the compressed pulse is shifted by the same amount, appearing at the output of the adjacent processing channel. In turn, the following compressed pulses at the output of each processing channel appear when the reflected MF chirp signal is offset by Δt = 1 / Δf _co . Energy losses during such processing are absent.

However, in this small-channel device for coherent processing of quasi-noise MF LFM signal, like in other known devices for coherent processing of MF LFM signals, an independent phase modulator (FM) made on a traveling wave lamp (TWT) or its solid-state analogue is usually used to generate the MF heterodyne signal. Obviously, the use of, although identical in structure, separate FM in devices for processing and generating MF chirp signals, due to the spread of the FM parameters and differences in destabilizing factors, will lead to differences in the harmonic modulation indices of the probe M _φ1 and heterodyne M _φ2 signals. This affects the quality of coherent processing of the MF LFM signal and leads to a distortion of the shape of the compressed pulse at the output of the matched filter and increases the level of the side lobes of the autocorrelation function (ACF).

The closest technical solution to the proposed one is a device built on the basis of a multi-channel matched filter [2, p. 348, Fig. 21.3], which is selected as a prototype.

The device contains N bandpass filters, N amplifiers, N phase shifters and a common adder.

The input of the device is the input of 1 ... N bandpass filters, which are connected through 1 ... N amplifiers and 1 ... N phase shifters to a common adder, the output of which is the output of the device.

The operation of this device consists in filtering the frequency components of a multi-frequency signal along frequency channels, processing them separately, followed by coherent summation. Bandpass filters pass signals in each of the N channels, highlighting the desired frequency band. The passband of each filter is approximately equal to F / N, where F is the width of the spectrum, N is the number of elements in the signal and the number of channels in the filter.

At the output of the bandpass filters, the signal will have the form (1).

Next, the signal of each of the N channels is fed to an amplifier with a gain K _y , and then to the phase shifter φ, providing a phase shift of -θ _n or 2π-θ _n .

, где c - коэффициент пропорциональности (в дальнейшем без ущерба для общности примем c=1; f₀ - средняя частота МЧ сигнала; t₀ - некоторое время запаздывания;

- комплексная огибающая когерентного МЧ сигнала).From the outputs of the phase shifters, the signals of all channels enter the adder. The complex envelope of the impulse response of a matched filter can be represented as:

, where c is the proportionality coefficient (hereinafter, without loss of generality, we take c = 1; f ₀ is the average frequency of the MF signal; t ₀ is the delay time;

- complex envelope of a coherent MF signal).

The above-described device provides multi-frequency signal processing, and its main disadvantage is the limited functionality for processing complex signals with intrapulse phase-code-shift keying.

The main purpose of the proposed utility model is to expand the functionality of the prototype for processing complex multi-frequency signals with intrapulse phase-code manipulation. One of such complex signals is a multi-frequency linear-frequency-modulated phase-code-manipulated signal (MF LFM FKM), consisting of N number of partial LFM radio pulses having the same frequency deviation Δf ₀ and emitted simultaneously at different carrier frequencies, while inside the partial The LFM of the radio pulses the phase changes according to the law of the generated M-sequence (Fig. 2).

This goal is achieved by the fact that in the known device for processing a multi-frequency signal containing from the 1st to the Nth bandpass filter, the outputs of which are connected to the inputs from the 1st to the Nth amplifier, respectively, the outputs of which are connected through the 1st to The Nth phase shifter with the input of the adder, the output of which is the output of the device, an additional mixer, an LFM local oscillator, a phase modulator, an M-sequence generator are introduced, while the M-sequence generator is connected to the first input of the phase modulator, the second input of which the first is the LFM output of the local oscillator, while the output of the phase modulator is the second input of the mixer, the first input of which is the input of the device, and its output is the input from the 1st to the Nth bandpass filter.

This device under the conditions in practice, allows to achieve the following technical effect: to expand the functionality of the prototype, that is, to provide correlation-filter processing of a multi-frequency LFM signal with binary phase-code manipulation according to the M-sequence code with single-frequency heterodyning.

The technical effect in the proposed device is achieved by introducing a mixer 1, the chirp of the local oscillator 6, the phase modulator 7, the generator of the M-sequence 8, which allows, unlike the prototype, using the binary code of the M-sequence to manipulate the phase of the chirp signal, and then the phase and frequency demodulation of the multi-frequency linear-frequency-modulated phase-code-manipulated (MF LFM FKM) signal input to the input, followed by filtering and coherent summation of the frequency components.

The implementation of the proposed utility model does not require structural changes in the equipment of existing radars and is reduced to the introduction of an additional device for the coherent processing of multi-frequency LFM FCM signals.

The block diagram of the developed device for correlation and filter processing of MF LFM FKM signal with single-frequency heterodyning is shown in figure 1.

This device is designed to work in conjunction with a device for generating multi-frequency LFM FKM signal.

The structure of the correlation-filter processing device for MF LFM FKM signal with single-frequency heterodyning includes: mixer 1, bandpass filters 2-1, 2-2, ..., 2-N, amplifiers 3-1, 3-2, ..., 3-N, phase shifters 4-1, 4-2, ..., 4-N, adder 5, chirp heterodyne 6, phase modulator 7, generator of the M-sequence 8.

Consider the connection of the elements of a correlation-filter processing device for a multi-frequency lazy-frequency-modulated phase-code-manipulated signal with single-frequency heterodyning.

The M-sequence generator 8 whose output is connected to the first input of the phase modulator 7, the second input of which is connected to the LFM output of the local oscillator 6, and the output is the second input of the mixer 1, the first input of which is the first input of the device, and its output is the inputs from the 1st on the N-th bandpass filter 2-1, 2-2, ..., 2-N, the outputs of which are connected respectively to the input of the 1st, 2nd, ..., N-th amplifier 3-1, 3-2, ..., 3-N, the outputs of which are connected respectively to the input of the 1st, 2nd, ..., Nth phase shifter 4-1, 4-2, ..., 4-N, the outputs of which are connected to the adder 5, the output which is the output of the device.

The operation of the device consists in phase and frequency demodulation of the received multi-frequency linear-frequency-modulated signal with binary phase-shift keying, coordinated processing of the frequency components and their coherent summation.

Consider in more detail the operation of the device. From the output of the generator of the M-sequence 8, which can be performed as shown in [3, p.145-150], the binary M-sequence arrives at the first input of the phase modulator 7. Its second input receives a signal from the LFM of the local oscillator, the phase of which, in turn, is modulated by the generated M-sequence in the phase modulator.

At the first input of the mixer 1 receives MF LFM FKM signal with phase manipulation binary M-sequence (figure 2):

- крутизна фазовой модуляционной характеристики модулятора, Δf₀, τ_u - девиация частоты и длительность парциального ЛЧМ радиоимпульса, θ_i(t) - фазовая манипуляция внутри СВЧ ЛЧМ радиоимпульса, F_м - частота гармонического модулирующего напряжения, φ₀(t) - начальная фаза парциального ЛЧМ радиоимпульса. Используя известное равенство:where U ₀ is the amplitude of the input microwave oscillations, M _φ = S _φ U _m is the index of phase harmonic modulation,

is the steepness of the phase modulation characteristic of the modulator, Δf ₀ , τ _u is the frequency deviation and the duration of the partial LFM radio pulse, θ _i (t) is the phase manipulation inside the microwave LFM radio pulse, F _m is the frequency of the harmonic modulating voltage, φ ₀ (t) is the initial phase partial LFM radio pulse. Using the well-known equality:

where J _n (z) is the first-order Bessel function of the nth order of the real argument z, expression (3) can be transformed to:

where n is the number of the partial LFM radio pulse.

The second input of the mixer 1 receives a local oscillator LFM PCM signal, shown in figure 2, with phase manipulation of the same M-sequence, in general form, the expression of which can be written as:

where θ _i (t) is the phase shift keying inside the microwave LFM radio pulse, φ ₀ is its initial phase.

In the mixer 1 is the multiplication of the signals supplied to its inputs, while the low-frequency components are filtered out, thus the frequency and phase demodulation of the signal received at the input of the MF LFM FKM is performed. At the output of the mixer there is a multi-frequency simple signal (figure 2) of the form:

This multi-frequency signal can be represented on the frequency axis as the sum of harmonics (Fig. 3), which are amplified in amplifiers with a gain proportional to the harmonic amplitude, then are aligned in the initial phases using adjustable phase shifters for their coherent summation in the adder 5. The signal at the output of the adder 5 is shown in FIG.

The prototype was chosen as the base object, since it meets the necessary requirements for such devices at present.

Unlike the base object, in which it is possible to process a multi-frequency signal, the proposed device allows correlation-filter processing of a multi-frequency LFM signal with binary phase-code manipulation according to the M-sequence code with single-frequency heterodyning. This became possible by turning on the mixer, the LFM of the local oscillator, the phase modulator, as well as the M-sequence generator. In this case, the inclusion of additional elements does not significantly complicate the algorithm of the proposed device as a whole, but it allows you to process a multi-frequency LFM signal with binary phase-code manipulation using the M-sequence code with single-frequency heterodyning.

Thus, the proposed device allows for correlation filter processing of a multi-frequency LFM signal with binary phase-code keying according to the M-sequence code with single-frequency heterodyning and can be made on a known element base and known industrial means.

BIBLIOGRAPHY

1. N.G. Baturin, A.V. Gomozov, V.I. Gomozov, A.V. Zyuzin. The dynamic theory of the formation of complex microwave signals with high modulation speed: Monograph. - Yaroslavl, 2010 .-- 552 p.

2. L.E. Varakin. Communication systems with noise-free signals. - M .: Radio and communications, 1985 .-- 384 p.

3. V. B. Pestryakov, V.P. Afanasyev, V.L. Hurwitz. Noise-like signals in information transmission systems. - M., “Owls. Radio ”, 1973, 424 p.

Claims (1)

A device for correlation filter processing of a multi-frequency linear-frequency-modulated phase-code-manipulated signal with a single-frequency heterodyning, containing from the 1st to the Nth bandpass filter, the outputs of which are connected to the inputs from the 1st to the Nth amplifiers, respectively, the outputs which are connected to the inputs from the 1st to the Nth phase shifter, respectively, the outputs of which are connected to the input of the adder, the output of which is the output of the device, characterized in that the mixer, LFM local oscillator, phase modulate are additionally introduced p, an M-sequence generator, while the M-sequence generator is connected to the first input of the phase modulator, the second input of which is the LFM output of the local oscillator, while the output of the phase modulator is the second input of the mixer, the first input of which is the input of the device, and its output is the input from 1st to Nth bandpass filters.

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