CN114114249A

CN114114249A - Omnidirectional coverage multi-beam detection radar system

Info

Publication number: CN114114249A
Application number: CN202111308817.1A
Authority: CN
Inventors: 刘海波; 崔莹莹; 曾大治; 于冲
Original assignee: Bit Raco Electronic Information Technology Co ltd
Current assignee: Bit Raco Electronic Information Technology Co ltd
Priority date: 2021-11-05
Filing date: 2021-11-05
Publication date: 2022-03-01

Abstract

The invention relates to an omnidirectional coverage multi-beam detection radar system, which is used for solving the detection problem of low-altitude low-speed small targets such as flying birds and the like. The frequency synthesis module generates a radio frequency excitation signal and sends the radio frequency excitation signal to the cylindrical phased array antenna array, and the cylindrical phased array antenna array is used for transmitting and receiving signals; when a target exists, the cylindrical phased array antenna array receives an echo and transmits multi-channel data to the digital receiving beam forming module to receive a beam DBF, the obtained data is transmitted to the digital signal processing module after the beam DBF is received, the digital signal processing module processes the obtained data to obtain target information, and a target trace is output and displayed through the comprehensive control module. The method has the advantages of flexible and quick beam forming, strong anti-interference capability, omnidirectional coverage in the direction and capability of effectively capturing the low-slow small target.

Description

Omnidirectional coverage multi-beam detection radar system

Technical Field

The invention relates to an omnidirectional coverage multi-beam detection radar system, which is suitable for detecting low-altitude slow-speed small (low-slow small) targets such as flying birds and the like and belongs to the technical field of detection radars.

Background

Bird strikes are events in which birds collide with aircraft, causing damage to the aircraft. On one hand, with the development of aviation technology, more and more people choose to take airplanes for traveling. According to the statistical data of the Chinese civil aviation, the number of the passenger traffics in the national aviation in 2018 reaches 6.1 hundred million people, the total number of airlines is 4206, and compared with 2017, the number of the passenger traffics is increased by 10.9%, and 167 international airlines are newly added. On the other hand, with the gradual restoration of ecological environment, up to now, the number of birds in China reaches up to 1200, which accounts for 1/8 of the total number of the world, and the number of birds keeps the first in Asia for years. In the face of increasing aviation passenger volume and bird species and number, aviation safety not only reflects important standards of aviation development, but also is a significant problem concerning national civilization.

By using the radar technology, all-weather detection can be theoretically carried out on birds near an airport all day long. The principle of the method is that radar equipment is arranged at an airport, scene targets in the coverage range of the radar are detected, the targets are found in time, and corresponding bird repelling measures are taken.

However, bird targets have the characteristics of low observability, low flying speed, low flying height, small RCS (radar cross section), strong maneuverability and the like, are typical 'low-slow small' targets, and are complex in modern urban environment, so that great challenges are brought to detection of the targets. In view of the situation, research and development of equipment with strong bird target detection capability is urgent.

The development of foreign bird-detecting radar technology has been in progress for over thirty years, and great achievements have been achieved. Relatively mature bird detection radars have been developed in the united states, canada, and the netherlands. The development in this field lags abroad due to late start in China.

The Merlin radar in the United states is provided with two radars with different wave bands, one X-band radar is used for scanning in the vertical direction, the other S-band radar is used for horizontal scanning, and the whole radar adopts a T-shaped waveguide array antenna. However, the radar does not belong to a three-coordinate radar in a strict sense because the beam coverage of two radar devices which scan horizontally and vertically is small. The Merlin radar is most often deployed near runways at airports. The horizontal scanning radar is responsible for scanning the surrounding environment in the coverage area, but does not provide the height information of the target, only plays a role in early warning, and the other radar device in the vertical direction and the airport runway form a straight line, so that the scanning area can cover the takeoff and landing of the airplane, and the three-coordinate radar can play a role at the moment to obtain the height of the target.

An Accipiter series radar developed in Canada adopts an X-waveband parabolic antenna to detect bird targets, a pitching wave beam is narrow (the width of a main lobe is only 4 degrees), and the pitching coverage range is 0-30 degrees. Therefore, although the target accurate height can be obtained by having a narrower beam, the coverage area is small, and the limitation is large.

The netherlands Robin radar, like the us Merlin radar, consists of multiple radars. In the horizontal direction, the Robin radar adopts S-band horizontal scanning, and the rotating speed (45r/min) of the Robin radar is in a very fast level in a mechanical scanning radar; the vertical direction adopts an X-band antenna to vertically scan the airspace, but the beam width is wide (20 degrees), so the height information of the target is not accurate enough. Meanwhile, the Robin radar is provided with an FMCW radar, and the working modes of the Robin radar are three types: (1) scanning mode: simultaneously scanning the pitch and azimuth; (2) staring mode: observing a range specified by a user; (3) tracking mode: and tracking the target specified by the user in real time.

In summary, the advanced countries such as the united states, canada and the netherlands have conducted intensive research to develop mature bird detection radar systems, so as to detect the bird situation in airports, and the main technical indexes and functional characteristics are shown in table 1.

TABLE 1 main technical indexes of foreign bird detection radar

In recent years, the domestic research on bird-detecting radar is gradually increased, and related researches are carried out in many colleges and universities, but most of the research results still cannot be practically applied to airports.

Disclosure of Invention

The invention provides a radar system capable of realizing omnidirectional coverage of directions and obtaining accurate Doppler and angle information of a target, aiming at solving the obvious problems that the performance is reduced under a large scanning angle because all the existing bird-detecting radars cannot perform omnidirectional coverage on the surrounding environment, and the problems that the birds belong to a typical low-slow small target and the effective residence time of a radar beam at the target is short due to a traditional scanning mode, so that the speed is fuzzy.

The invention relates to a multi-beam detection radar system based on omnidirectional coverage. The connection among the modules of the whole radar system is shown in fig. 1, and the modules are connected in sequence to form the whole radar system.

The frequency synthesis module generates a radio frequency excitation signal and sends the radio frequency excitation signal to the cylindrical phased array antenna array, and the cylindrical phased array antenna array is used for transmitting and receiving signals; when a target exists, the cylindrical phased array antenna array receives an echo and transmits multi-channel data to the digital receiving beam forming module to receive a beam DBF, the obtained data is transmitted to the digital signal processing module after the beam DBF is received, the digital signal processing module processes the obtained data to obtain target information, and a target trace is output and displayed through the comprehensive control module.

The cylindrical phased array antenna array provided by the invention has M x N array elements, and all the array elements are uniformly distributed on the cylindrical array surface. Wherein, totally N rings are evenly distributed on the cylindrical surface on the cylindrical array surface, and totally M array elements are arranged on each ring (also can be understood as totally M vertically arranged linear arrays are evenly distributed on the cylindrical surface, and each linear array is composed of N array elements). All array elements of the whole array can complete the receiving and transmitting of signals. In the design, each array is regarded as one TR component, so that the whole array works, and M TR components work simultaneously. When the TR component is in operation, the strength and direction of the transmitted signal is controlled by amplitude and phase weighting.

The comprehensive control module is used for realizing the control of an operator on a radar system, and comprises a working mode for setting a radar, a control unit (TR) module to work and close, a control unit (DBF) module and a digital signal processing module to work, so that the point track and track information of a target is obtained and output.

The frequency synthesis module is used for generating a DA clock, a baseband signal, a local oscillator and a calibration signal and providing an antenna unit on the TR component to radiate electromagnetic waves in the air. Wherein, the frequency synthesizer generates an original baseband signal through a DA clock; the baseband signal is subjected to up-conversion through a local oscillator signal generated by frequency synthesis to generate a radio frequency excitation signal; the calibration signal is used to achieve phase calibration for each channel.

The digital receiving beam forming module is used for carrying out DBF on received data, thereby realizing the functions of sum/difference beams, low side lobe antennas, self-adaptive zero points, shadow-hiding antennas and the like, and transmitting the synthesized digital beams to the digital signal processing module.

The digital signal processing module is used for processing digital signals after DBF, including pulse compression, pulse Doppler processing and CFAR detection to extract distance and speed information of a target, realizing angle measurement of the target by using a single-pulse angle measurement technology, and finally realizing output of a target point track and a track through point track condensation, track initiation, prediction and management.

The target detection process of the bird condition detection radar system follows the following steps:

s01: in the cylindrical phased array radar, M N-element uniform linear arrays distributed on a cylindrical surface are numbered in sequence, wherein the number of the N-element uniform linear arrays is 1M, 2M and 3 … … M. As previously described, each uniform linear array corresponds to a TR assembly, so the TR assembly number is the same as the linear array number. Because each uniform linear array is completely the same, array elements in one uniform linear array are numbered as 1, 2 and 3 … … N respectively.

S02: the cylindrical phased array radar of the invention is different from the traditional scanning phased array radar, and is characterized in that: the azimuth adopts a staring working mode and the elevation adopts a beam scanning mode. Controlling the phase of a transmission signal of each channel in the column antenna, controlling the beam in the pitching direction to point at different pitching angles in a time-sharing manner, for example, when the wave positions of 6 pitch dimensions are required to point at 2 °, 10 °, 18 °, 27 °, 36 ° and 45 ° at the time of T1, T2, T3, T4, T5 and T6, respectively, controlling the phase of each channel in the column antenna, and when all the column antennas point at 2 °, 10 °, 18 °, 27 °, 36 ° and 45 ° at the time of T1, T2, T3, T4, T5 and T6, respectively; by controlling each column of antennas in the 360 ° azimuth to use the same amplitude phase, a 360 ° omnidirectional radiation pattern is formed in the azimuth direction.

S03: if a target exists in the detection range of the radar, the electromagnetic wave is transmitted after meeting the target, and the generated echo is received by an array element on the radar. The invention adopts the single pulse technology to obtain the angle information of the target, so the sum and difference beams are obtained through the DBF technology.

Single TR and differential beamforming: according to the previous description. Each TR is a column of uniform linear arrays with N array elements. And dividing each TR into an upper half array and a lower half array, when the array receives echoes, firstly carrying out pitching low side lobe processing on the echoes, and then adding and subtracting the upper and lower half arrays to respectively obtain the TR and the difference beam.

Sub-array sum and difference beamforming: first, the formation of the reception direction diagram will be described. And after the sum and difference beams of each TR are obtained, selecting K adjacent TRs to form a subarray (marked as subarray 1) and difference beams, after the formation of the subarray and the difference beams is completed, performing sliding window processing with the step length of 1 array element on the selected TR, marking the obtained new subarray as subarray 2, performing the formation of the sum and difference beams by the same method, continuing sliding window processing, and so on to finally obtain M subarrays. To achieve angular measurement of the target, the sum and difference beams for each sub-array need to be obtained. Each subarray comprises a subarray sum beam and two subarray difference beams (a pitch difference beam and a azimuth difference beam). Firstly, dividing each subarray into a left semi-array and a right semi-array (the left semi-array is marked as A, and the right semi-array is marked as B), wherein the forming method of the subarrays and the beams is to add TR and beams contained in the A and B semi-arrays; the subarray pitching difference wave beam is that TR difference wave beams contained in the A and B semi-arrays are added; the sub-array azimuth difference beam is the subtraction of the TR and beam contained in the A and B half-arrays. Thus, a subarray sum beam, a subarray pitch difference beam and a subarray azimuth difference beam can be obtained.

S04: further, digital signal processing is carried out according to the subarray and the difference beam, and the distance, speed and direction information of the target can be obtained.

S05: and outputting the point track and the flight track of the target according to the result of the S04.

Advantageous effects

Compared with the prior application, the invention has the following advantages and characteristics:

(1) by adopting a phased array system, beam forming is flexible and rapid, and the anti-interference capability is strong;

(2) the cylindrical array form is adopted, so that the omnidirectional coverage of the direction can be realized, the detection power is uniform, and the detection performance is stable;

(3) the staring system is adopted to realize wide-sending and narrow-receiving of the wave beams, long-time accumulation is achieved by long-time residence at the target position, and the signal-to-noise ratio of the echo is improved.

Drawings

FIG. 1 is a schematic diagram of a layout of a cylindrical phased array radar array unit according to the present invention;

FIG. 2(a) -schematic illustration of an azimuth beam launch of a radar system according to the present invention in gaze mode;

FIG. 2(b) -a schematic view of a azimuth beam receive beam of the radar system of the present invention in gaze mode;

figure 3-block diagram of an omnidirectional coverage multi-beam detection radar system according to the present invention;

figure 4-a flow chart of the operation of the omnidirectional coverage multi-beam detection radar system of the present invention;

FIG. 5 is a signal processing flow diagram of the radar system of the present invention;

Detailed Description

The composition and operation of the system of the present invention will be further explained with reference to the drawings.

Fig. 1 is a schematic layout diagram of a cylindrical phased array radar array unit according to the present invention. The radar system adopts a cylindrical two-dimensional active phased array system and consists of M multiplied by N same array elements. Each layer of circular rings has M array elements, and N layers of circular rings are uniformly distributed on the cylindrical array surface. The height difference h and the radius R between adjacent layers of the cylindrical array are required to be large enough to ensure that a directional diagram of the array does not generate grating lobes (h is less than or equal to lambda/2, M is more than or equal to 4 pi R/lambda, wherein lambda is the wavelength) when the array scans.

Fig. 2 is a schematic view of azimuth beam transmission and reception in gaze mode of the radar system of the present invention.

In forming the azimuth transmit beam: as shown in fig. 2(a), the cylindrical array radar transmits M linear arrays simultaneously in the same amplitude and direction, and forms omnidirectional coverage in azimuth.

During reception, as shown in fig. 2(b), M linear arrays simultaneously receive, and form a plurality of azimuth beams after passing through the DBF, covering the whole azimuth. The mode has the advantages that the holographic staring processing mode is adopted, the beam dwell time for the target position is long, the speed resolution ratio is high, and the slow target detection capability and the target identification capability can be greatly improved. Fig. 3 is a block diagram of an omni-directional coverage multi-beam detection radar system according to the present invention.

When the radar works, firstly, the frequency synthesizer generates an original baseband signal through a DA clock, the baseband signal is subjected to up-conversion through a local oscillator signal generated by the frequency synthesizer to generate a radio frequency excitation signal and is sent to the cylindrical array, and the cylindrical array completes radiation of electromagnetic waves to a target airspace through the array antenna.

When a target is present, the emitted electromagnetic waves may generate echoes due to reflection. After the echo reaches the array antenna, the array antenna receives the echo and transmits multi-channel data to the DBF module to receive the beam DBF, the obtained data is transmitted to the digital signal processing module after the beam DBF is received, the digital signal processing module performs operations such as pulse compression, pulse Doppler processing and CFAR detection on the obtained data to obtain target information, and a target point trace is output to a display screen through the comprehensive control module.

In the whole process, the comprehensive control module plays a control role in other modules. Such as controlling the switches of the TR module, the operation of the DBF module and the DSP module, etc.

Fig. 4 is a flow chart of the operation of the omnidirectional coverage multi-beam detection radar of the invention. The specific working process is as follows:

s01: and when the radar is in a working mode, the comprehensive control module controls the frequency synthesizer and the cylindrical array and radiates electromagnetic waves to an airspace through the array antenna to transmit.

The transmission beam forming scheme is as follows: controlling the phase of a transmission signal of each channel in the column antenna, controlling the beam in the pitching direction to point at different pitching angles in a time-sharing manner, for example, when the wave positions of 6 pitch dimensions are required to point at 2 °, 10 °, 18 °, 27 °, 36 ° and 45 ° at the time of T1, T2, T3, T4, T5 and T6, respectively, controlling the phase of each channel in the column antenna, and when all the column antennas point at 2 °, 10 °, 18 °, 27 °, 36 ° and 45 ° at the time of T1, T2, T3, T4, T5 and T6, respectively; by controlling each column of antennas in the 360 ° azimuth to use the same amplitude phase, a 360 ° omnidirectional radiation pattern is formed in the azimuth direction.

S02: when a target appears in the radar radiation range, the array antenna receives an echo of the target. At this time, the array antenna transmits echo data received by the M TRs to the DBF module for DBF processing. Firstly, the DBF module forms sum and difference beams of each TR for echoes of M TRs, and the process comprises low side lobe processing of a pitch dimension in the implementation process.

S03: after generating the TRs and the difference beams, K adjacent TRs are selected as a receiving subarray. A new subarray is formed along the subarray sliding window once (the step length is one TR), and M sliding windows are needed to be performed in total to form M subarrays.

S04: in order to obtain accurate angle information of the target, the system adopts a sum-difference single pulse angle measurement method to measure the angle of the target. Thus, to obtain the subarray sum and difference beams, the subarray sum and difference DBF needs to be performed on the M subarrays in S503. Firstly, forming a subarray and a beam, when the ith (i is 1, 2 and 3 … … M) subarray is subjected to beam forming, the subarray is divided into a left half array and a right half array, and the TR and the beam of the left half array and the right half array are added to obtain the subarray and the beam. And then forming a subarray pitching difference beam, dividing the subarray into a left half array and a right half array, and adding the TR difference beams of the left half array and the right half array to obtain the subarray pitching difference beam. And finally, forming a sub-array azimuth difference beam, dividing the sub-array into a left half array and a right half array, and subtracting the TR and the beam of the left half array and the TR and the beam of the right half array to obtain the sub-array azimuth difference beam (in the process of forming the azimuth receiving beam, the processing of the azimuth low side lobe is included).

The above steps S03, S04 are implemented by a digital receive beamforming module (DBF module in fig. 3).

S05: and respectively performing pulse compression and pulse Doppler processing on the subarray and the difference beam. After the processing, a P-D plane (pulse-Doppler plane) can be obtained from the processed sum channel data, CFAR detection is carried out on the P-D plane, and the point trace is condensed, so that the point trace of the target can be obtained.

S06: and after the step of S05, calculating the distance and speed information of the target according to the obtained target point trace. And obtaining the azimuth and the pitch angle of the target by a sum-difference single pulse angle measurement method.

S07: and obtaining a plurality of traces of the target through the processing of a plurality of CPIs. And obtaining the point track and the flight track of the target through the flight track initiation, prediction and management, and outputting the point track and the flight track to a display screen.

Fig. 5 is a signal processing flow chart of an omnidirectional coverage multi-beam detection radar system according to the present invention, and the process is implemented by a digital signal processing module.

The specific signal processing steps are as follows:

and S01, performing fast time dimension pulse compression (namely performing matched filtering on a time domain echo signal and a reference signal) on the subarray and difference channel data obtained by the DBF, and improving the signal-to-noise ratio of the echo.

And S02, after pulse compression is finished, performing PD (pulse Doppler) processing on the obtained data in a slow time dimension (a common method is to perform FFT processing on the pulse compressed data along the slow time dimension). After pulse compression and pulse doppler processing, the P-D (pulse-doppler) plane is obtained from the sum channel data.

And S03, after the P-D plane is obtained, Constant False Alarm Rate (CFAR) detection and trace aggregation can be further carried out on the P-D plane to obtain a target trace.

And S04, calculating a target point trace obtained after CFAR detection and trace coagulation treatment to obtain the slant range and radial velocity information of the target.

And S05, obtaining angle information (including an azimuth angle and a pitch angle) of the target by a sum-difference monopulse angle measurement method, and obtaining the coordinate position of the target relative to the radar by matching with the target information obtained in the previous step.

And S06, obtaining a point track and a flight track of the target through radar data processing.

Claims

1. An omnidirectional coverage multi-beam detection radar system comprises a cylindrical phased antenna array module, a comprehensive control module, a frequency synthesis module, a digital receiving beam forming module and a digital signal processing module, wherein all the modules are connected in sequence to form the whole radar system;

the cylindrical phased antenna array is provided with M × N array elements, all the array elements are uniformly distributed on a cylindrical array surface, the cylindrical array surface is provided with N rings longitudinally and uniformly distributed on a cylindrical surface, each ring is provided with M array elements, namely M linear arrays vertically arranged are uniformly distributed on the cylindrical surface, and each linear array is composed of N array elements; all array elements of the whole array can complete the receiving and transmitting of signals; each array is regarded as a TR component, and when the whole array works, the M TR components work simultaneously;

2. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the cylindrical phased antenna array adopts a staring working mode in the azimuth direction and adopts a beam scanning mode in the pitching mode;

the transmitting wave beam adopts the working principle of omnidirectional radiation in the azimuth direction and time-sharing scanning in the pitching direction; controlling the wave beams in the pitching direction to point to different pitching angles in a time-sharing manner by controlling the phase of a transmitting signal of each channel in the array antenna; by controlling each column of antennas in the 360 ° azimuth to use the same amplitude phase, a 360 ° omnidirectional radiation pattern is formed in the azimuth direction.

3. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the digital beam forming of the digital receiving beam forming module to the receiving data comprises:

single TR and differential beamforming: each TR is a column of uniform linear array with N array elements, each TR is divided into an upper half array and a lower half array, when the array receives echoes, the arrays are subjected to pitching low side lobe processing at first, and then the upper and lower half arrays are added and subtracted to obtain sum beams of single TRs and difference beams of single TRs respectively;

sub-array sum and difference beamforming: firstly, explaining the formation of a receiving direction diagram, after obtaining sum and difference beams of each TR, selecting K adjacent TRs to form a sub-array and difference beams, marking the sub-array as a sub-array 1, after completing the formation of the sub-array 1 and the difference beams, performing sliding window processing with the step length of 1 array element on the sub-array, marking the obtained new sub-array as a sub-array 2, performing the sum and difference beam formation on the new sub-array according to the same method, continuing sliding window processing, and so on to finally obtain M sub-arrays, wherein each sub-array comprises a sub-array sum beam and two sub-array difference beams, and the two sub-array difference beams are namely a sub-array pitch difference beam and a sub-array difference beam; the forming method of the subarray sum beam is to add the sum beams of all the single TRs contained in each subarray; the subarray elevation difference beam is formed by adding difference beams of all single TRs contained in the subarray, and the subarray azimuth difference beam is formed by carrying out difference on sum beams of all the TRs contained in the subarray in a symmetrical mode of the subarray.

4. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the TR element operates to control the strength and directionality of the transmitted signal by amplitude and phase weighting.

5. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the comprehensive control module is used for realizing the control of an operator on the radar system, and comprises a working mode for setting the radar, a control TR component to work and close, and a control digital beam forming and digital signal processing module to work, so that the point track and track information of the target is obtained and output.

6. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the frequency synthesis module is used for generating a DA clock, a baseband signal, a local oscillator and a calibration signal and providing an antenna unit on the TR component to radiate electromagnetic waves in the air; wherein, the frequency synthesizer generates an original baseband signal through a DA clock; the baseband signal is subjected to up-conversion through a local oscillator signal generated by frequency synthesis to generate a radio frequency excitation signal; the calibration signal is used to achieve phase calibration for each channel.

7. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the digital receiving beam forming module is used for carrying out digital beam forming on the received data so as to realize the functions of sum/difference beams, low side lobe antennas, self-adaptive zero points, shadow-hiding antennas and the like, and transmitting the synthesized digital beams to the digital signal processing module.

8. An omnidirectional coverage multi-beam sounding radar system according to claim 1, wherein: the digital signal processing module is used for performing signal processing on digital signals after digital beam forming, and comprises pulse compression, pulse Doppler processing and CFAR detection so as to extract distance and speed information of a target, angle measurement of the target is realized by using a single pulse angle measurement technology, and finally output of a target point track and a track is realized through point track condensation, track initiation, prediction and management.