RU2480788C2 - Radar system of remote earth sensing - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method is carried out by inclusion of an unmanned aircraft, a low-speed radio channel of data transfer into the composition of the structural circuit of the available radar system and by variation of the mode of operation of the generator that generates signals with linear-frequency modulation with a modulation period equal to the interval of antenna aperture synthesising, which simultaneously performs functions of the clock pulse oscillator of the wide-band carrier of the radar data transfer channel. The proposed system makes it possible to produce radar data from a board segment of the synthetic aperture radar NI along a noise-immune low-speed communication channel, to process them and to produce radar images with the required resolution in the real time mode.

EFFECT: improved noise immunity relative to active noise.

1 dwg

Description

The invention relates to radio engineering and can be used in radar systems with a synthesized aperture of the antenna and continuous emission of signals (SAR NI) to solve various problems of remote sensing of the Earth using aircraft and spacecraft.

Known monopulse radar system (radar) with a pulsed phase-manipulated probe signal used on mobile carriers, mainly on unmanned aerial vehicles (UAVs) (1).

This invention solves the problem of radar reliability when installed on an UAV, which will increase the noise immunity with respect to passive interference, for example, in the form of reflections from local objects.

Known radar system with the adjustment of the carrier frequency and the regime of the SDC (2). It is used in the development of noise-resistant radar systems that maintain operability in a complex electromagnetic environment, and in the presence of intense interfering reflections from passive interference, local objects and meteorological conditions.

The technical result consists in increasing the noise immunity with respect to active interference.

The closest analogue in technical essence and the achieved effect, adopted as a prototype, is proposed a radar system with a synthesized aperture of the antenna and continuous emission of signals from an unmanned aerial vehicle [3]; the on-board segment of which includes: an on-board digital control computer (BCM), a navigation system, a linearly-frequency-modulated signal generator, controlled by a BCM, a transmitter, a transmitting antenna, a receiving antenna, a receiver, a balanced mixer, to the second input of which through an attenuator a signal comes from a linear-frequency modulation generator, an analog-to-digital converter, a radar data recording device, where navigation is also recorded nnye data from the navigation system; the ground segment includes serially connected: a buffer storage device, a digital spectrum analyzer, a trajectory instability compensation unit and autofocus, an azimuth compression unit that implements antenna aperture synthesis algorithms based on the Fourier transform [3]; an information display device and a radar image recording device.

The indicated radar system is capable of obtaining a radar image of the area with high detail in any weather conditions around the clock, in the presence of smoke and dust, to solve navigation problems. However, to obtain real-time radar images, a high-speed channel for transmitting radar data to the ground segment of the radar system is required, for which it is technically difficult to provide an acceptable level of noise immunity.

An object of the invention is to reduce the required transmission speed and increase noise immunity when transmitting radar data from the airborne segment of the radar system SAR NI to the ground segment.

The solution to this problem is achieved by taking into account the spectral characteristics of the radar data.

To achieve the claimed technical result, it is proposed to introduce into the RSA radar system additionally in the airborne segment: sequentially connected radar data forming device, the input of which is connected to the output of the analog-to-digital converter and the output of the navigation system; a pulse-width modulated signal modulator, a multiplier, the second input of which is connected through an attenuator to the output of the linear frequency modulation signal generator, a high-frequency module of the radio link transmitter, an antenna of the radio link transmitter; in the ground segment: serially connected antenna of the radio line receiver, pulse-width modulation decoder, shift register; in addition, change the operating mode of the linear frequency modulation signal generator, generating signals with linear frequency modulation with a modulation period equal to the synthesis aperture synthesis interval of the antenna aperture.

Such a construction of a remote sensing radar scheme allows you to receive radar data from the airborne segment via an noise-resistant low-speed communication channel, process them and obtain radar images with the required resolution in real time.

The invention is illustrated by a further description and drawing, which shows a structural diagram of a remote sensing radar, which includes:

1 - transmitter antenna,

2 - transmitter

3 - signal generator linear frequency modulation,

4 - managed by a computer,

5 - receiving antenna,

6 - receiver

7 - balanced mixer,

8 - navigation system,

9 - device for recording radar data,

10 - analog-to-digital Converter,

11 is a device for forming a frame of radar data,

12 - signal modulator with pulse width modulation,

13 - multiplier

14 - high-frequency module of the transmitter of the radio line,

15 - antenna of the transmitter of the radio link,

16 - the antenna of the receiver of the radio link,

17 - high-frequency module of the receiver of the radio link,

18 - decoder pulse width modulation,

19 - shift register

20 - buffer storage device,

21 is a digital spectrum analyzer,

22 - block compensation of trajectory instabilities and autofocus,

23 - block compression in azimuth,

24 is a display device information

25 is a device for recording radar images.

A radar system for remote sensing of the Earth with a synthesized aperture and continuous radiation works as follows.

The voltage at a high frequency from the output of the signal generator by linear frequency modulation 3, the modulation period and deviation of which is set by the controlled BCMF 4, is supplied to the input of the transmitter 2, the output of which is the signal emitted by the antenna of the transmitter 1 in the direction of the capture band of the terrain.

Reflected from the terrain, the radio signals are received by the receiving antenna 5, amplified in the receiver 6 and passed to the 1st input of the balanced mixer 7. At the same time, the signals from the output of the linear-frequency modulation signal generator 3, respectively, are fed to the 2nd input of the mixer 7 as a result, at the output of the balanced mixer 7 there are beat signals whose frequencies are proportional to the ranges to the targets within the capture band of the terrain. Next, the real and imaginary part of the beat signals is subjected to analog-to-digital conversion in a two-channel ADC 10. The signals from the ADC output are stored in the radar data recording device 9, where the navigation data from the navigation system 8 is simultaneously and synchronously recorded, which is the coordinate information about the center of mass of the aircraft . To transmit radar and navigation data to the ground segment of the remote sensing radar in the device for generating a frame of radar data 11, a frame of radar data is formed, which includes radar data (beating signals) and navigation data from the navigation system 8, which is the coordinate information about the center of mass of the aircraft and used in further processing in the compression block in azimuth 23. A frame of radar data is converted into a serial code, each binary symbol of which encoded in a pulse-width modulator 12 and fed to the 1st input of the multiplier 13, the second input of which is fed through the attenuator signal from the output of the signal generator by linear frequency modulation 3. Thus, at the output of the multiplier 13 a high-frequency signal with a broadband carrier is formed, which amplified in the high-frequency module of the transmitter of the radio line 14 and is emitted by the antenna of the transmitter of the radio line 15 of the airborne segment of the DZZ radar.

The signals received by the antenna of the receiver of the radio link 17 on the ground segment of the remote sensing radar are transmitted through the high-frequency module of the transmitter of the radio link 17, to the pulse-width modulation decoder 18, where the received signals are processed in a coordinated manner, which are stored in the buffer memory 20 and simultaneously transmitted to the register input in a serial code shift 19. Where the incoming radar data of the beat signals with a sampling frequency of the analog-to-digital Converter 10 are accumulated during the interval ablyudeniya equal interval synthetic aperture antenna. After the shift register 19 is completely filled in, the accumulated data is read in parallel to the digital spectrum analyzer 21, which implements the direct Fourier transform operation. At the output of the digital spectrum analyzer 21, a range band is formed in the spectral region with a resolution inversely proportional to the observation interval. Range strips with an interval equal to the sampling period of the digital spectrum analyzer 21 are fed to the compression unit in azimuth 23 and to the compensation unit for path instabilities and autofocus 22, where a consistent (optimal) processing in the spectral region and the inverse Fourier transform are performed. The result of the processing is a radar image, which is visually displayed in the information display device 24 and stored in the device for recording radar images 25.

Based on the above description and drawing, the proposed radar system can be manufactured using well-known components and technological equipment known in the electronics industry and used on unmanned aerial vehicles as a radar system for remote sensing of the Earth.

Information sources

1. RF patent No. 2309430, IPC G01S 13/44 "Monopulse radar system".

2. RF patent №2245562, IPC G01S 13/58 "Radar system with the adjustment of the carrier frequency and the regime of SDC".

3. Antipov V.N., Koltyshev E.E., Mukhin V.V., Pechennikov A.V., Frolov A.Yu., Yankovsky V.T. The radar system of an unmanned aerial vehicle // Radio Engineering, 2006, No. 7. S.14-20 (prototype).

Claims (1)

Earth remote sensing radar system, the onboard segment of which includes an onboard digital control computer (BCM), a navigation system, a linearly coupled linear frequency modulation (LFM) signal generator controlled by a BCM, a transmitter, a transmitting antenna, a receive antenna in series, a receiver, balanced a mixer, the second input of which through the attenuator receives a signal from the chirp generator, an analog-to-digital converter, a radar registration device data, where navigation data from the navigation system is also recorded, and the ground segment includes a serially connected buffer memory, a digital spectrum analyzer, a trajectory instability compensation unit and autofocus, an azimuth compression unit where consistent (optimal) processing in the spectral region is performed and the inverse Fourier transform , an information display device and a radar image registration device, characterized in that it is additionally introduced into the boron a new segment of a radar data frame forming device, the input of which is connected to the output of the analog-to-digital converter and the output of the navigation system, a pulse-width modulated signal modulator, a multiplier, the second input of which is connected through the attenuator to the output of the LFM generator, a high-frequency module of the radio line transmitter, the antenna of the radio link transmitter, in the ground segment - sequentially connected the antenna of the receiver of the radio link, pulse-width modulation decoder, output which is associated with the output of the buffer memory, a shift register connecting the buffer memory and a digital spectrum analyzer, the output of which, in turn, is associated with the input of the compression unit in azimuth, and the modulation period of the generator generating the signals with linear frequency modulation is equal to the synthesis interval antennas.