RU2615996C1 - Super-wide band radar with active multi-frequency antenna array - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: desired operating frequency band with a width B is divided into N non-overlapping sub-bands in the frequency B_k, k=1…N, so that

. The carrier frequency sub-bands are mutually coherent (derived from a common reference oscillator) ƒ_k=ƒ₁Δƒ (k-1), where ƒ₁ - lower the carrier frequency;

- the interval between carrier frequencies not exceeding the maximum signal band width B_k. In order to increase the working distance is performed in each sub-band phase modulation (keying) signal (linear or nonlinear frequency modulation, phase-shift keying), and when receiving the signal is compressed. The resultant signal is obtained by summing the despread signals in accordance with their carrier phase. To reduce the sidelobes in the resulting phase modulation signal (manipulation) can be performed on an individual law for each carrier frequency.

EFFECT: increase of the range resolution.

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Description

The invention relates to radar and can be used in various radar systems where high range resolution is required.

Known short-pulse radars in which drift diodes with sharp recovery are used as a pulse generator [1]. The disadvantage of such radars is the short range (several tens of meters with the parameters of the generator diode close to the limiting ones - a pulse voltage of 1 kV at a load of 50 Ohms). In addition, the range resolution of these radars is limited by the minimum duration of the emitted pulse (leading edge duration is 0.6 ns).

Known short-pulse radars built on relativistic backward wave lamps [2]. Such radars have a pulse duration of more than 1 ns, which is their main disadvantage.

There are suggestions for using short video pulses generators in high-resolution radars with a range of operation, the principle of which is based on cutting a short pulse from a longer one using a gas spark gap (slider) [2]. Using such a device, pulses of 1-5 ns were obtained with an output power of up to 400 MW, with the prospect of increasing to 1 GW, with a repetition frequency of 100 Hz, with a stability of no more than 3%; the stability of the pulse duration turned out to be less than 10%, which is insufficient to detect objects with low ESR. In addition, the maximum energy in the spectrum of the emitted signal is concentrated in the decimeter and low-frequency parts of the centimeter wavelength range, so the resolution is limited to a few nanoseconds.

A common drawback for all known devices is the problem of matching the antenna system with the transmitter and receiver in a wide and ultra-wide (UW and UWB) frequency band, and therefore, the difficulty of obtaining a high antenna gain in the working frequency band. Also, the method of forming pulses in these devices eliminates the possibility of using known methods of pulse compression [3].

As a prototype selected radar with an active phased array (AFAR) [4]. In the AFAR channels, traditional microwave amplification devices (klystrons, amplitrons, transistor amplifiers) can be used, while the required radar range is achieved by selecting the required number of AFAR channels. However, the disadvantage of the prototype is the limited frequency band of power amplifiers, and therefore, limited resolution. For example, the band of one of the powerful broadband amplification devices — continuous traveling wave tubes (TWTs) —does not exceed one octave in the frequency range 1 ... 4 GHz, and becomes even smaller with an increase in the operating frequency [5]. The frequency band of powerful pulsed TWT does not exceed 1 GHz at an operating frequency of 15 GHz [5].

The technical result of the invention is the expansion of the working frequency band of the radar in order to increase the resolution in range.

Obtaining a technical result is provided by a combination of essential features of the prototype and the present invention.

The block diagram of the proposed device is presented in FIG. one.

The block diagram of the prototype is shown in FIG. 2.

The prototype includes a pathogen (1), a receive-transfer switch (SPT) of the distribution system (2), a distribution system (PC) (3), which in reception mode works as an adder of received signals, and in transmission as a distribution device exciter signal, active modules (AM) (4), consisting of IFR (6 and 13), phase shifters (5) and receiving and transmitting paths. The AM transmission path includes the first and second preamplifiers (7 and 9), the first controlled attenuator (8) and the power amplifier (10), which receives the pulse modulation signal U _m (t) from the pulse modulation signal generator (11) through PC modulating signal (12). The emitted signal through the SPT (13) and matching device (14) is fed to the transceiver element of the antenna array (15).

The signal reflected from the location object and received by the antenna array element (15) through the matching device (14) and the IFR (13) enters the AM receiving path, consisting of a protection device (16), the first and second low-noise amplifiers (17 and 19), matched filter (18) and a second controlled attenuator (20). Further, the signal through the IFR (6) and the phase shifter (5) goes to the AM output. The signals from the outputs of all AMs are sent to a PC (3) that performs the function of an adder, and then the received amount through the IFR (2) goes to the output device (21).

.All prototype AM transceiver AM modules operate on the same signal carrier frequency

.

In order to solve the problem for the formation and reception of radar signals, it is proposed to use multi-frequency antenna arrays (MCHAR) [6]. The possibility of generating pulsed UWB signals using the MCAR is described in [7], the possibility of phase modulation of the MCAR signals is shown in [8].

In FIG. 1 shows a structural diagram of the proposed device.

To solve this problem, the UWB spectrum of a radar signal with a bandwidth of B is divided into N non-overlapping subbands with a frequency band of In _k , k = 1 ... N:

The signal in each subband is generated and received in a separate AM (4), radiated and received by a separate element of the antenna array (15). The carrier frequencies of the subbands are mutually coherent (formed from a common reference oscillator):

- нижняя несущая частота;

- интервал между несущими частотами, не превышающей максимальной полосы сигнала В_k.Where

- lower carrier frequency;

- the interval between carrier frequencies, not exceeding the maximum signal band In _k .

. В связи с этим из схемы исключены ППП (2) и (6). Взаимная когерентность обеспечивается общим для всех AM опорным генератором (22), сигнал с которого поступает на возбудители (1) через PC опорного сигнала (23). При этом полосы частот могут быть одинаковыми В_k=В_k+1 или иметь разную ширину.Thus, in contrast to the prototype, the pathogen (1) is located in each AM and generates a signal with a frequency

. In this regard, SPP (2) and (6) are excluded from the scheme. Mutual coherence is ensured by the common reference oscillator (22) common to all AMs, the signal from which is supplied to the exciters (1) via the PC reference signal (23). In this case, the frequency bands can be the same In _k = In _{k + 1} or have a different width.

In each subband, unlike the prototype, in order to obtain a signal with a large base and subsequent compression of the pulse in the receiving path, the signal is angularly modulated - frequency (linear or non-linear) or phase-pulse. The use of pulse compression increases the range of the radar or reduces its power consumption at a given range [3]. For this, a phase modulator (24) is introduced into the transmitting path of each AM, controlled by the phase modulation (manipulation) signal generator U _{fm k} (t) (25). All phase modulation (manipulation) signal generators are synchronized by a reference modulating signal generator (26). Moreover, in order to reduce the level of side lobes in the received AFAR signal, angular modulation (manipulation) in the subbands can be performed according to various laws.

The phase shifter (5) has been moved to the AM transmission path. A controlled delay line (28) is introduced into the receiving path, which ensures the maximum radiation pattern in a given direction.

Unlike the prototype, the device (3) works only as an adder and ceases to fulfill the functions of a distribution system, the SPP (2) is excluded from the circuit, and the received AFAR signal is sent directly to the output device (21).

могут работать не один, a L_k каналов АФАР.Since the carrier frequencies in the subbands are mutually coherent, the UWB signal is formed from N narrow-band or wide-band signals. As a result, in addition to the fact that a signal with a frequency band exceeding the passband of transmitting and receiving amplifying devices can be radiated and received, the task of matching the transmitting and transmitting paths and antenna systems is simplified. For example, antennas with individual sizes or even different types of antennas may be used in each subband. Moreover, in order to obtain the required amplitude-frequency characteristics of the radar and the given power at each frequency

not one, but L _k AFAR channels can work.

In FIG. 1 shows a structural diagram of the proposed device, in FIG. 2 is a structural diagram of a prototype.

In FIG. 3a shows the maximum envelope of the signal normalized at the output of one of the matched filters, calculated in the time interval of ± 0.075 μs for synchronous LFM in all subbands, with the following AFAR signal parameters: B = 2 GHz; N = 21, T = 1 μs. In FIG. 3b shows the envelope of the signal at the output of the summing device for time intervals of ± 0.075 μs, normalized to the maximum of the envelope at the output of the matched filters.

The block diagram of the proposed device is shown in FIG. one.

The device contains transceiver elements AFAR (15), matching devices (14), active modules (4), adder (3), output device (21), reference generator (22), distribution system of the reference signal (23), reference modulating signal generator (26), modulating signal reference signal distribution system (27), pulse modulation signal generator (11), pulse modulating signal distribution system (12) and active modules, which include the pathogen (1), phase shifter (5) phase modulator (24), generator phase modulation (manipulation) ator (25), first and second preamplifiers (7) and (9), first controlled attenuator (8), power amplifier (10), receive-transmit switch (13), receive path protective device , the first and second low-noise amplifiers (17) and (19), a matched filter (18), a second controlled attenuator (20), a controlled delay line (28) and a controlled phase shifter (5).

. Несущие частоты определяются выражением (2). Для обеспечения взаимной когерентности частоты возбудителей формируются от общего опорного генератора (22), сигнал с частотой

поступает на возбудители через распределительную систему опорного сигнала (23).The device operates as follows. The causative agent (1) of each active module (2) generates a signal with a carrier frequency

. Carrier frequencies are determined by expression (2). To ensure mutual coherence, the frequencies of pathogens are formed from a common reference generator (22), a signal with a frequency

enters the pathogens through the distribution system of the reference signal (23).

увеличивается до B_k так, чтобы выполнялось выражение (1), при этом, как указывалось ранее, условие В_k=В_k+1 может не выполняться. Закон модуляции U_{фм k} может быть одинаковым для всех частот

или индивидуальным для каждой частоты с целью уменьшения боковых лепестков в принятом сигнале, получаемом при совместной обработке сигналов всех каналов РЛС. Генераторы фазовой модуляции (манипуляции) (25) используют опорный сигнал, поступающий с опорного генератора модулирующих сигналов (26) через распределительную систему опорного сигнала модулирующих сигналов (27). ЛЧМ и нелинейную ЧМ в данном случае будем рассматривать как частный случай фазовой модуляции.The signal from the output of the pathogen (1) goes to the controlled phase shifters, which (5) are needed in order to control the radiation pattern of the multi-frequency AFAR, and then to the phase modulator (24). The law by which modulation is carried out is set using the phase modulation (manipulation) generator (25). As a result of modulation, the frequency band of the signal

increases to B _k so that expression (1) is satisfied, while, as mentioned earlier, the condition B _k = B _{k + 1} may not be satisfied. The modulation law U _{fm k} may be the same for all frequencies

or individual for each frequency in order to reduce side lobes in the received signal obtained by joint processing of signals of all radar channels. Phase modulation (manipulation) generators (25) use the reference signal coming from the base modulating signal generator (26) through the distribution system of the base signal of modulating signals (27). In this case, the LFM and nonlinear FM will be considered as a special case of phase modulation.

As a result of phase modulation (manipulation), a signal with a base B _k T is created in each AFAR channel, where T is the pulse duration during which phase modulation (manipulation) is performed. A pulse is formed by modulating power amplifiers (10) of all active modules, to which a modulating voltage U _m (t) is supplied through a distribution system of a pulse modulation signal (12) from a pulse modulation signal generator (11).

The signal from the output of the power amplifier through the receive-transmit switch (13) and matching device (14) is fed to the transmit-receive antenna element (15).

The signal reflected from the location object and received by the antenna element (15) passes through the matching device (14) the receive-transmit switch (13) and the protective device (16) to the input of the receiving path and is amplified by the first low-noise amplifier (17). Next, the signal is fed to the input of a matched filter (18), which compresses the phase-modulated (phase-shifted signal), and is amplified by a second low-noise amplifier (19). The controlled attenuators (20) allow performing the weighted processing of the received signal in the entire band of radiated frequencies B. The controlled delay lines (28) provide scanning of the AFAR radiation pattern if the AFAR size in the scanning plane is greater than s / V, where c is the speed of light in free space.

From the output of all active modules, the signals are sent to the adder (3) and then the sum of the signals goes to the output device (21).

We define the envelope of the signal at the output of the summing device for the case of synchronous LFM in all channels of the AFAR. In this case, the sweep bands In _k in all channels are the same, and the rate of change of frequency in each subband is determined as β = 2πV _k / T [rad / s].

может быть представлен как свертка аналитического сигнала на входе фильтра

и импульсной характеристики фильтра

, где τ - время задержки, а T - длительность излучаемого импульса. Огибающая при расчетах с аналитическими сигналами получается как половина действительной части свертки:We assume that the signal is reflected from a point source, the amplitudes of signal A at the output of the matched filters are the same, and the number of AFAR channels is equal to the number of frequency subbands, that is, L _k = 1. Then the signal at the output of the matched filter at the cyclic frequency

can be represented as a convolution of the analytical signal at the input of the filter

and impulse response of the filter

where τ is the delay time and T is the duration of the emitted pulse. The envelope in the calculations with analytical signals is obtained as half the real part of the convolution:

Using simple transformations, one can obtain [9]:

Given that the signal maximums are time-aligned using delay lines (28) and made in-phase using phase shifters (5), we determine the signal at the output of the summing device

;

.Where

;

.

, где q=е^-jΔωτ:The sum of the exponentials in this expression can be calculated as the sum of the geometric progression

where q = e ^-jΔωτ :

Thus, for the case under consideration, the signal at the output of the summing device can be represented as:

- средняя частота многочастотного сигнала.Where

- the average frequency of the multi-frequency signal.

The normalized envelope of the signal at the output of each matched filter and the envelope of the signal at the output of the summing device can be described by the following expressions, respectively:

In FIG. 3a shows the maximum envelope of the signal normalized at the output of one of the matched filters, calculated in the time interval of ± 0.075 μs for synchronous LFM in all subbands, with the following AFAR signal parameters: B = 2 GHz; N = 21, T = 1 μs. In FIG. 3b shows the envelope of the signal at the output of the summing device for time intervals of ± 0.075 μs, normalized to the maximum of the envelope at the output of the matched filters.

Thus, the amplitude of the resulting pulse entering the output device is N times greater than the amplitude of the pulse at the output of the matched filter, and the duration of this pulse, which determines the resolution of the proposed device, is N times smaller than the pulse width at the output of the matched filter and is inversely proportional to the working band of the generated UWB signal B.

Literature

1. Golovachev M.V., Kochetov A.V., Mironov O.S., Panfilov P.S., Sarychev V.A., Khomyakov I.M. Ultrashort pulse radar of a decimeter range. // IV All-Russian Armand readings "Radiophysical methods in remote sensing of media", Murom, 2014, p. 255-260.

2. Bystrov R.P., Cherepenin V.A. Theoretical justification of the possibilities of applying the method of generating powerful nanosecond pulses of electromagnetic radiation when creating radar systems of electronic warfare (RE) to destroy objects. - Journal of Radio Electronics (electronic journal), 2010, No. 4. from. 9.

3. Reference radar. / Under. ed. M.I. Skolnik. Per. from English under the general ed. B.C. Willow. In 2 book Prince 1, Ch. 8. M .: Technosphere, 2014.

4. Gostyukhin V.L., Trusov V.N., Gostyukhin F.V. Active Phased Antenna Arrays / Ed. V.L. Gostyukhina. Ed. 3rd, rev. and add. - M .: Radio engineering, 2011, p. 19.

5. Microwave generators and amplifiers. / Ed. I.V. Lebedev. - M .: "Radio Engineering", 2005, p. 123 table 3.3., P. 47 table 1.9.

6. Vorobyov N.V., Gryaznov V.A. Multi-frequency antenna array for forming a sequence of pulsed signals in space: Patent RU 2267838. Priority dated January 27, 2004.

7. Vorobyov I.N., Vorobyev N.V., Gryaznov V.A., Neplyuev O.N. Spatial formation of ultra-wideband pulse signals by multi-frequency antenna arrays with a random distribution of signal frequencies // Conflict-resistant, electronic systems. Vol. 159. 2011, No. 18, p. 21-26.

8. Vorobyov N.V., Gryaznov V.A., Korol O.V., Lobanov B.S., Multi-frequency antenna array for forming a sequence of radio pulses in space. Patent RU 2456723. Priority dated 04/11/2011.

9. Gonorovsky I.S. Radio engineering circuits and signals: Textbook for universities. 4th ed., Revised and add. - M.: Radio and Communications, 1986, p. 98-106.

Claims (1)

An ultra-wideband radar with an active multi-frequency antenna array, consisting of active modules, the input-output of each of which is connected via a matching device to the transmitter-receiver element of the antenna array and pulse modulation signal generator, the output of which is connected to the input of the distribution system of the pulse modulation signal, signals from the outputs active modules enter the inputs of the summing device, the output of which is connected to the input of the output device; active modules include a receive-transmit switch, the input-output of which is the input-output of the active module, the receiving and transmitting paths; the transmitting path of the active module consists of a first pre-amplifier, the output of which is connected to the input of the first controlled attenuator, the output of the first controlled attenuator is connected to the input of the second pre-amplifier, the output of the second pre-amplifier is connected to the input of the power amplifier, the output of the power amplifier is connected to the input of the “receive- transmission ”, and a pulse modulation signal from each output of the distribution elitelnoy system width modulation signal; the receiving path of the active module consists of a protective device, the input signal of which comes from the output of the receive-transfer switch, the output of the protective device is connected to the input of the first low-noise amplifier, the output of the first low-noise amplifier is connected to the input of the matched filter, the output of the matched filter is connected to the input of the second low-noise amplifier, the output of which is connected to the input of the second controlled attenuator, characterized in that the spectrum of the signal emitted and received by the proposed device, having a frequency bandwidth B is divided into N non-overlapping subbands with a frequency band B _k , k = 1 ... N, so that the condition

, a signal in each subband is generated and received in a separate active module, radiated and received by a separate element of the antenna array, while the carrier frequencies of the subbands are mutually coherent and form a frequency grid

where

- lower carrier frequency,

- the interval between the carrier frequencies, not exceeding the maximum signal bandwidth In _k , in addition, to obtain a signal with a large base for compression, a phase modulation (manipulation) of the signal is carried out according to the same for all subbands or individual for each subband law; for these purposes, a pathogen generating a signal with a frequency of

a controlled phase shifter, a phase modulator and a phase modulation (manipulation) generator, so that the signal from the pathogen output goes to the input of the controlled phase shifter, the output of the controlled phase shifter is connected to the input of the phase modulator, the output of the phase modulator is connected to the input of the first pre-amplifier, the control input of the phase modulator is connected with the output of the phase modulation generator; mutual coherence of the carrier frequencies is provided by a reference generator, the output of which is connected to the input of the distribution system of the reference signal, and each output of the distribution system of the reference signal is connected to the input of each pathogen; phase modulation (manipulation) in all subbands is synchronized with a reference modulating signal generator, the output of which is connected to the input of the distribution system of the reference signal of modulating signals, and each output of this distribution system is connected to the input of each phase modulation generator; controlled delay lines are introduced into the receiving path of each active module, the output of which serves as the output of the active module, and the input is connected to the output of the second controlled attenuator.

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