RU2510685C2 - Synthetic-aperture and quasicontinuous radiation radar station - Google Patents

Synthetic-aperture and quasicontinuous radiation radar station Download PDF

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RU2510685C2
RU2510685C2 RU2012107268/07A RU2012107268A RU2510685C2 RU 2510685 C2 RU2510685 C2 RU 2510685C2 RU 2012107268/07 A RU2012107268/07 A RU 2012107268/07A RU 2012107268 A RU2012107268 A RU 2012107268A RU 2510685 C2 RU2510685 C2 RU 2510685C2
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radar
processor
signal
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Анатолий Иванович Канащенков
Анатолий Сергеевич Матюшин
Владимир Никитович Антипов
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Открытое акционерное общество "Корпорация "Фазотрон-Научно-исследовательский институт радиостроения"
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Abstract

FIELD: physics, navigation.
SUBSTANCE: invention relates to radar and can be used in radar systems mounted on mobile objects for mapping the earth's (sea) surface and the surface of other planets. The technical result is designing a synthetic-aperture and quasicontinuous radiation radar station, which increases the range of the radar station while maintaining a small "dead area".
EFFECT: radar station design using composite quasicontinuous radiation is disclosed.
2 cl, 4 dwg

Description

The invention relates to radar and can be used in radio systems installed on moving objects, for mapping the earth (sea) surface or the surfaces of other planets.
Known:
1) Pulse radar with synthesizing aperture (V.N. Antipov, V.T. Goryainov, A.N. Kulik and others. Radar stations with digital synthesis of the aperture of the antenna. - M .: Radio and communication, 1988, p. 304), containing a coherent transceiver path with one antenna (transceiver with a circulator for receiving and transmitting) and a digital signal processing system;
2) Holographic radar (TIME FREQUENCY ANALYSIS - AN APPLICATION TO FMCW RADARS by BALAJI NAGARAJAN BE, Electronics and Communication Engineering Hindustan College of Engineering, University of Madras Chennai, India - 2001), containing a small transmitting antenna and a linear receiving antenna array, as well as a memory unit and a signal processing processor;
3) Side-view radar (G.S. Kondratenkov, V.A. Potekhin, A.P. Reutov, Yu.A. Feoktistov. Radar stations for land survey. - M: Radio and communications, 1983, p. 272 ; A.A. Komarov, G.S. Kondratenkov, N.N. Kurilkin and others. Airborne reconnaissance radars. - M.: Military Publishing House, 1983, p. 152) with a large antenna along the fuselage.
4) a continuous radiation radar with aperture synthesis, containing a coherent transceiver path with two antennas (receiving and transmitting) and a digital signal processing system (Antipov V.N., Koltyshev E.E., Mukhin V.V., Pechennikov A.V. , Frolov A.Yu., Yankovsky VT Radar system of an unmanned aerial vehicle. Radio engineering, 2006) (prototype);
The disadvantages of these devices are the short range of a radar with continuous radiation, or a large "dead" zone for a radar with pulsed radiation of the same level. Other types of radars have low azimuth resolution, a high level of pulsed power of the transmitting device, high demands on the computing system in terms of memory and speed, and low efficiency of receiving radar image (RLI) of the terrain.
Of the known technical solutions, the closest (prototype) is a continuous-wave radar with synthesizing an aperture (Antipov V.N., Koltyshev E.E., Mukhin V.V., Pechennikov A.V., Frolov A.Yu., Yankovsky V. T. Radar system of an unmanned aerial vehicle. Radio engineering, 2006). Figure 1 shows a radar - prototype, contains a mixer (1), the first input of which is connected to the output of the frequency-modulated signal generator (2) and is connected to a transmitting antenna (4) through a transmitter (power amplifier) (3). The second input of the mixer through the receiver (high-frequency amplifier) (5) is connected to the output of the receiving antenna (6), and the output of the mixer (1) is connected in series with a low-pass filter (7), an analog-to-digital converter (ADC), and a signal processor ( 8). The ADC and the signal processing processor implement the synthesis of the antenna aperture by compressing the signal in range, compensating for path instabilities and harmonic analysis, while the second processor input is connected to the aircraft navigation system (9), and the output is connected to the operator indicator (10).
The known device operates as follows. A highly stable generator of a frequency-modulated signal (usually linear in the law - LFM) generates high-frequency oscillations that enter the transmitter (Rx) and one of the inputs of the mixer. In the LFM transmitter, the signal is amplified to the required power and radiated into the space by the transmitting antenna.
Electromagnetic waves reflected from all objects in the radar field of view are received by the receiving antenna and fed to the receiver (PFP), where it is amplified and fed to the second input of the mixer. From the output of the mixer, the signal is filtered and fed to the input of an analog-to-digital converter (ADC) and a digital signal processor. Depending on the problem being solved, the processing system (digital processor) implements various algorithms for processing the trajectory signal, but the main operations are: synthesis of the aperture, compression of the signal by distance, compensation of trajectory instabilities, and harmonic analysis. On the operator’s indicator, a radar image of the observed part of the earth’s surface and other information (coordinates of targets, marks of moving targets, results of target classification, etc.) are formed.
The disadvantage of the prototype is the short range radar. The fact is that to obtain a long range of action, a high radar energy potential is needed. With limited antenna sizes, to achieve high potential it is necessary to increase the transmitter power. However, with increasing transmitter power, the amount of the penetrating signal (interference) from the transmitting antenna to the receiving one increases. Therefore, until the power of the penetrating signal does not exceed the level of the internal noise of the receiver with increasing transmitter power, the range increases. If the penetrating signal from the transmitter exceeds the internal noise power of the receiver, a further increase in the transmitter power leads to an increase in both the useful (reflected) signal and the interference power (penetrating signal) and the signal-to-noise ratio for a given range remains constant. With an increase in the mapping range, the useful signal decreases, and the interference power remains the same, and thereby the detection characteristics and the quality of the radar image of the area are deteriorated. In addition, the presence of a penetrating signal requires expanding the dynamic range of the receiver in order to pass the useful signal without distortion.
Even after decoupling between the receiving and transmitting antennas, α p = -80 dB, choosing the suppression coefficient of the bandpass filter, which is specially introduced into the receiving path circuit to attenuate the penetrating signal at α pf = -80 dB and at the level of the side lobes of the compression filter in range α pf = -42 dB, the range is limited to 10 ... 15 km. This regularity is illustrated in FIG. 2 by the dependence of the mapping range on the transmitter power when decoupling between the receiving and transmitting antennas at 80 dB. Dependencies are constructed on the basis of the range formula for the radar with the directivity gain of the transmitting antenna G = 0.6 (4πS A / λ 2 ) = 370; the area of the receiving antenna S A = 0.045 m 2 (0.3 × 0.15), the noise figure of the receiver is 4 dB, the carrier speed V = 30 m / s, α p = minus 80 dB; α bl = minus 42 dB; α pf = minus 80 dB.
Thus, the object of the invention is to increase the range of the radar while maintaining a small "dead" zone.
The problem is achieved in that in the continuous-wave radar with synthesizing the aperture, the following are additionally introduced: a “receive-transmit” circulator, a second receiving channel, which includes a high-frequency amplifier of a second receiver, a second mixer, a second low-pass filter; also introduced controlled attenuator, synchronizer and drive antenna system.
Figure 3 presents a structural diagram of a radar with quasi-continuous radiation and synthesizing aperture, where;
1 - first and second mixers, in the first and second receiving channel, 2 - master frequency-modulated signal generator, 3 - transmitter power amplifier, 4 - transceiver antenna, 5 - high frequency amplifiers of the first and second receivers, 6 - receiving antenna, 7 - first and second low-pass filters, 8 - first and second analog-to-digital converters and a processor, 9 - aircraft navigation system, 10 - operator indicator, 11 - processor-controlled synchronizer, 12 - receive-transmit circulator with protective device in orogo receivers 13 - controllable attenuator 14 - Antenna system with reducible stabilization.
The second additionally introduced receiving channel includes a transmit-receive circulator 12, which is connected between the power amplifier of the transmitter 3 and the input-output of the transceiver antenna 4, while the second output of the circulator 12 is connected in series with the input of the high-frequency amplifier of the second receiver 5, by the second mixer 1 , the second low-pass filter 7. The second input of the second mixer 1 is connected to the third output of the master oscillator 2.
The controlled input of the attenuator 13 is connected to the first output of the synchronizer 11, the second input of the attenuator is connected to the output of the receiving antenna 6, and the output of the attenuator is connected to the input of the high-frequency amplifier of the first receiver 5.
The controlled input of the synchronizer 11 is connected to the second output of the ADC and the processor 8, and the second input of the synchronizer 11 is connected to the first output of the master oscillator 2. The synchronizer 11 is connected by the second and third outputs to the second inputs of the high-frequency amplifiers of the first and second receivers 5, respectively.
The master oscillator 2 is connected by a second output to the input of the power amplifier of the transmitter 3, and the third and fourth outputs of the generator 2 are connected to the second inputs of the first and second mixers, respectively.
The first output of the processor 8 is connected to the input of the indicator of the operator 10, and the third output is connected to the stabilization drive 14 of the antennas 4 and 6, the third input of the processor 8 is connected to the output of the navigation system 9.
The invention is represented by the following graphic materials:
- in FIG. 1 shows a structural diagram of a continuous-wave radar with synthesizing an aperture (prototype);
- in FIG. 2 shows the dependence of the range of a continuous-wave and quasi-continuous radiation radar on the power of the transmitter in aperture synthesis mode;
- in FIG. 3 shows a structural diagram of a quasi-continuous radiation radar with aperture synthesis;
- figure 4 shows a timing diagram of the operation of a radar with quasi-continuous radiation with asymmetric (sawtooth) frequency modulation inside the pulse.
In quasi-continuous radiation radars, pulsed signals with symmetric or asymmetric linear frequency modulation of the probe signal are usually used. As an example, consider the timing diagram of the radar with asymmetric (sawtooth) frequency modulation inside the pulse (figure 4).
A probe signal with asymmetric frequency modulation can be represented as:
Figure 00000001
= 0, for other values of t.
where a 0 is the amplitude of the probe signal, f 0 is the center frequency; k LChM = ΔF / T p - frequency modulation coefficient; ΔF is the frequency deviation; τ And is the pulse duration; Tp is the pulse repetition period (Fig. 4), where n is the number of the sensing period; N is the number of pulses in the synthesis interval.
The signal reflected from the target is described by the expression
s about t R ( θ , t ) = ε ˙ ( θ ) exp { j 2 π ( f 0 + k l h m 2 ( t - τ ( θ ) ) ) ( t - τ ( θ ) ) } , ( 2 )
Figure 00000002
Where ε ˙ ( θ )
Figure 00000003
is the complex amplitude of the signal, θ is the azimuthal coordinate of the target; τ (θ) = 2r (θ) / s - signal delay caused by the propagation of the signal to the target and vice versa; r (θ) is the distance from the phase center of the antenna to the target.
The signal reflected from the i-th reflector at the mixer output has the form:
Figure 00000004
In the expression (3) for simplicity of further calculations, it is assumed that a 0 = 1.
The first exponential factor in expression (3) determines the frequency of the signal at the output of the mixers. This frequency is proportional to the propagation time of the signal to the target and vice versa:
Figure 00000005
The second factor describes the constant phase of the signal.
The dependence of the frequency of the signal at the output of the mixers on the range to the target is used to resolve targets in range. The frequency resolution is determined by the signal accumulation time T n : δf = 1 / T n . Then the resolution in range will be determined by the expression:
Figure 00000006
For example, with a frequency deviation ΔF = 120 MHz, a period of frequency modulation T n = 1 kHz and small distances from the radar to the target (τ i << T p ), when it can be assumed that T n ≈ T p the range resolution is 1 , 25 m. The radar works similarly when measuring flight altitude (distance to the ground), providing high accuracy. To reduce the level of the side lobes in range, various weight functions can be used. For example, the use of the Hamming weight function leads to a decrease in side lobes to -42.8 dB with a decrease in range resolution by 1.3 times.
Thus, the procedure for compressing the signal by range in each modulation period consists in multiplying the received signal by the probing signal, followed by the Fourier transform (spectral analysis). As a result, a line of high-resolution range signal samples is formed within a given range of range viewing. Further processing of the packet obtained in neighboring periods of modulation is similar to synthesizing an aperture with a periodic pulsed sounding signal. It should be noted that the receiver can be performed according to a superheterodyne circuit and instead of one UHF and mixer, several frequency conversion schemes can be used.
The proposed device provides surveillance of targets in a wide range of ranges due to the use of a higher energy potential of the radar without increasing the dead zone. The control of the modes (mapping zones) is provided by the processor 8 and the synchronizer 11. With a short mapping range, when the reflected signal enters the receiver 5 at the time of transmitter 3 emission (timing diagram in Fig. 4), the synchronizer 11 introduces the attenuation of the attenuator 13 to protect the receiver and save its dynamic range, reducing the power of the penetrating signal of the transmitter to the level of the internal noise of the receiver, unlocks the first UHF 5 (the second UHF is locked) and the radar operates according to the scheme with continuous radiation.
On the contrary, with a long mapping range, when the reflected signal enters the receivers 5 after the radiation from the transmitter 3 (Fig. 4), the synchronizer 11 unlocks both receivers and the signals received by the two antennas 4 and 6 (to increase the overall directional coefficient of the antenna system), are processed by analogy with processing in radar with synthesizing an aperture with a pulse signal. By controlling the gating modes of the first and second UHF 5 and controlled attenuator 13, you can map the terrain at various ranges: from almost zero, which is limited by the altitude of the carrier, to maximum, which is limited by the power of the transmitter.
In real flight, an aircraft (LA) is subject to fluctuations in heading, roll and pitch. These oscillations lead to random wandering of the antenna over the earth's surface and modulation of the reflected signal in amplitude, which leads to brightness modulation of the image. To stabilize the antenna system in space, the aircraft navigation system measures the magnitude of the oscillations along the heading, roll and pitch, and the processor generates control signals for the stabilization drive of the antenna system to parry these oscillations, eliminating the amplitude modulation of the reflected signal. We also note that for small fluctuations of the carrier in the direction (the magnitude of the oscillations does not exceed the width of the radiation pattern in azimuth), the antenna drive may not be available.
To perform the claimed device can be used elemental base, currently produced by domestic industry.
The use of the invention in comparison with the prototype due to the introduction of a "transmit-receive" circulator, a second receive channel and a signal processing system at times when the transmitter does not emit, provides a longer range. The introduction of a controlled attenuator attenuates the power of the signal penetrating from the transmitter and thereby protects the receiver and reduces the requirements for its dynamic range. The control of the gating modes of the receivers provides the required mapping range. The introduction of the drive of the antenna system associated with the navigation system of the carrier through the computer eliminates the brightness modulation of the terrain image caused by the fluctuations of the carrier in flight.

Claims (2)

1. Radar station with synthesizing aperture and quasi-continuous radiation, comprising a first mixer, the first input of which is connected to the output of the master oscillator of the frequency-modulated signal, which is connected to the transmitting antenna through the transmitter power amplifier, and the second input of the first mixer is connected through the high-frequency amplifier of the first receiver with the output of the receiving antenna, while the output of the mixer is connected in series with a low-pass filter, an analog-to-digital converter and a processor, in the otor has synthesized the antenna aperture by compressing the signal by range, compensating for trajectory instabilities and harmonic analysis, as well as containing a navigation system connected to the second input of the processor and an operator indicator, the input of which is connected to the first output of the processor, characterized in that the circulator is inserted into it transmit-receive ”, connected between the transmitter power amplifier and the transmit-receive antenna, the second output of the circulator is connected in series with the second high-frequency amplifier The second receiver, the second mixer, the second low-pass filter, the second analog-to-digital converter and the third input of the processor, also introduced an attenuator connected between the receiving antenna and the high-frequency amplifier of the first receiver, and a synchronizer, the controlled input of which is connected to the second output of the processor, and the second input is connected to the master oscillator, while the first output of the synchronizer is connected to the control input of the attenuator, and the second and third outputs of the synchronizer are connected to the second inputs of the amplifiers Oka frequency of the first and second receivers.
2. The aperture synthesized radar according to claim 1, characterized in that the transmitting and receiving antennas are mounted on a platform with a stabilization drive connected to the third output of the processor.
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Cited By (3)

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RU2590900C1 (en) * 2015-06-16 2016-07-10 Борис Григорьевич Татарский Method of producing detailed radar image of limited section of earth's surface
WO2017083827A1 (en) * 2015-11-12 2017-05-18 Texas Instruments Incorporated Buffer sample size control for variable chirp radar
RU2660450C1 (en) * 2017-05-29 2018-07-06 Акционерное общество "Уральское проектно-конструкторское бюро "Деталь" Device of radar location station with continuous linear-frequency-modulated signal and synthesis of aperture

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Publication number Priority date Publication date Assignee Title
RU2590900C1 (en) * 2015-06-16 2016-07-10 Борис Григорьевич Татарский Method of producing detailed radar image of limited section of earth's surface
WO2017083827A1 (en) * 2015-11-12 2017-05-18 Texas Instruments Incorporated Buffer sample size control for variable chirp radar
US9759808B2 (en) 2015-11-12 2017-09-12 Texas Instruments Incorporated Buffer sample size control for variable chirp radar
US10281562B2 (en) 2015-11-12 2019-05-07 Texas Instruments Incorporated Buffer sample size control for variable chirp radar
RU2660450C1 (en) * 2017-05-29 2018-07-06 Акционерное общество "Уральское проектно-конструкторское бюро "Деталь" Device of radar location station with continuous linear-frequency-modulated signal and synthesis of aperture

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