阅读说明：本技术 一种提高低慢小目标搜索雷达空域覆盖的方法 (Method for improving airspace coverage of low-slow small-target search radar ) 是由 王昊 朱一鸣 徐达龙 徐文文 王岩 权双龙 陶诗飞 于 2020-12-29 设计创作，主要内容包括：本发明涉及一种提高低慢小目标搜索雷达空域覆盖的方法,包括以下步骤：步骤S1,在俯仰维度上将搜索低慢小目标空域划分为不同区域；步骤S2,对不同区域的发射波束进行不同半功率波束宽度的宽波束赋形,并根据波形赋形得到投影系数以及对应的激励矩阵；步骤S3,对不同区域的接收波束进行不同波束宽度的和-差波束混合赋形；步骤S4,定各区域内波束个数,在俯仰维按照半功率宽度方向图进行交叠,在方位维按照交错波束排列方式确定所有波束位置。(The invention relates to a method for improving the airspace coverage of a low-slow small target search radar, which comprises the following steps: step S1, dividing the low-slow searching small target airspace into different areas in the pitching dimension; step S2, carrying out wide beam forming of different half-power beam widths on the emission beams in different areas, and obtaining a projection coefficient and a corresponding excitation matrix according to waveform forming; step S3, carrying out sum-difference beam mixed forming of different beam widths on the receiving beams in different areas; and step S4, determining the number of wave beams in each area, overlapping according to a half-power width directional diagram in a pitching dimension, and determining the positions of all the wave beams according to a staggered wave beam arrangement mode in an azimuth dimension.)

1. A method for improving the airspace coverage of a low-slow small target search radar is characterized by comprising the following steps:

step S1, dividing the low-slow searching small target airspace into different areas in the pitching dimension;

step S2, carrying out wide beam forming of different half-power beam widths on the emission beams in different areas, and obtaining a projection coefficient and a corresponding excitation matrix according to waveform forming;

step S3, carrying out sum-difference beam mixed forming of different beam widths on the receiving beams in different areas;

and step S4, determining the number of wave beams in each area, overlapping according to a half-power width directional diagram in a pitching dimension, and determining the positions of all the wave beams according to a staggered wave beam arrangement mode in an azimuth dimension.

2. The method according to, wherein the step S1 is divided into low elevation area, middle elevation area and high elevation area; wherein

A low elevation area with a pitch angle less than 10,

the pitch angle is in the middle elevation area between 10 degrees and 20 degrees,

pitch angles greater than 20 are in the high elevation region.

3. The method according to claim 2, wherein in step S2, the wide beamforming with larger half-power width is used for the transmission beam in the high elevation angle region, and the wide beamforming with smaller half-power width is used for the transmission beam in the middle elevation angle region and the low elevation angle region.

4. The method according to claim 2, wherein in step S3, sum-difference beamforming is used for high elevation area receive beamforming, and a wide beamforming with smaller half-power width is used for medium elevation area receive beamforming; and for the low elevation angle area receiving beamforming, the beamforming with uniform weighting of all channels is adopted.

Technical Field

The invention relates to a radar technology, in particular to a method for improving the airspace coverage of a low-slow small target search radar.

Background

The search radar is also called as a search early warning radar, and is a classical radar with wide application scenes. Search radars typically implement 360 ° scans in the azimuth dimension using a mechanical turntable. With the development and the increasing maturity of phased array technology, most advanced search radars adopt a phased array system. Compared with the traditional mechanical scanning radar, the phased array radar has the advantage of faster wave beam scanning speed, but a reasonably designed work flow is required. In phased array radar resource management, data rate is an important index for reflecting radar system performance, which not only reflects the relationship among some indexes of phased array radar, but also is one of important contents of time resource management. The importance of the radar searching task is increasingly shown due to the self characteristics of low and slow small targets.

The low-slow small target is short for the low-altitude low-slow small target. Targets with flying height not exceeding 1000m, flying speed not exceeding 50m/s and radar reflection cross-sectional area less than two squares are generally considered low-slow small targets. In recent years, the number of low-speed and small-target objects is rapidly increased and widely applied to various fields of military and civil use, so that great convenience is brought, and meanwhile, various security threats such as 'black fly', out-of-control or malicious reconnaissance and attack are brought. Low and slow small objects may pose significant security threats to 1) airport runways, 2) hazardous areas such as prisons, power stations, oil fields, etc., and 3) crowded places such as train stations, squares, sports halls, etc. The characteristics of short flying distance, low height, low speed and small radar reflection sectional area of the low-slow small target enable the detection effect of the traditional search radar to be obviously poor. The traditional search radar has a large short-range blind area in the detection range, so that the unmanned aerial vehicle moving at a short distance cannot be detected. Because the unmanned aerial vehicle has low flying height, low speed and small radar cross section, the unmanned aerial vehicle is easily covered by strong ground clutter.

Disclosure of Invention

The invention aims to provide a method for improving the airspace coverage of a low-slow small target search radar, which comprises the following steps:

step S1, dividing the low-slow searching small target airspace into different areas in the pitching dimension;

step S2, carrying out wide beam forming of different half-power beam widths on the emission beams in different areas, and obtaining a projection coefficient and a corresponding excitation matrix according to waveform forming;

step S3, carrying out sum-difference beam mixed forming of different beam widths on the receiving beams in different areas;

and step S4, determining the number of wave beams in each area, overlapping according to a half-power width directional diagram in a pitching dimension, and determining the positions of all the wave beams according to a staggered wave beam arrangement mode in an azimuth dimension.

Further, in step S1, the airspace for searching for the low and slow small targets is divided into a low elevation angle region, a medium elevation angle region and a high elevation angle region; wherein

A low elevation area with a pitch angle less than 10,

the pitch angle is in the middle elevation area between 10 degrees and 20 degrees,

pitch angles greater than 20 are in the high elevation region.

Further, in step S2, the wide beam forming with a large half-power width is used for the transmission beam in the high elevation angle region, and the wide beam forming with a small half-power width is used for the transmission beam in the middle elevation angle region and the low elevation angle region.

Further, in step S3, sum-difference beam hybrid forming is adopted for the high elevation angle region receive beam forming, and a wide beam forming with a smaller half-power width is adopted for the medium elevation angle region receive beam forming; and for the low elevation angle area receiving beamforming, the beamforming with uniform weighting of all channels is adopted.

Compared with the prior art, the invention has the following advantages: (1) the received wave beam at high elevation angle adopts the mixed forming of the sum wave beam and the difference wave beam; (2) and designing a self-adaptive radar signal processing flow according to different beamforming and arranging strategies.

The invention is further described below with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic flow chart of a method for improving the airspace coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 2 is a flow chart of adaptive radar signal processing of a method for improving the spatial coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 3 is a technical flowchart of wide beam forming of the method for improving the spatial coverage of the low-slow small-target radar according to the embodiment of the present invention.

Fig. 4 is an array directional diagram of sum beams and difference beams of a method for improving the spatial coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of sum-wave-difference beam hybrid forming under two different forming conditions of a method for improving the airspace coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 6 is a search airspace pitch dimension coverage map of the method for improving the airspace coverage of the low-slow small-target radar provided by the embodiment of the present invention.

Fig. 7 is a schematic flow chart of a frequency domain Pulse Compression (PC) technique for improving the spatial coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 8 is a schematic flow chart of a Moving Target Detection (MTD) technique for improving the airspace coverage of a low-slow small-target radar according to an embodiment of the present invention.

Fig. 9 is a schematic flow chart of a constant false alarm detection (CFAR) technique for improving the coverage of a low-slow small-target radar airspace according to an embodiment of the present invention.

Detailed Description

With reference to fig. 1, a method for improving the airspace coverage of a low-slow small-target search radar includes the following steps:

step S100, dividing a low-slow searching target airspace into a low elevation angle area, a middle elevation angle area and a high elevation angle area in the elevation dimension according to the size of the elevation angle;

step S200, determining radar beam residence time T according to radar azimuth beam width delta theta, search data rate delta r and speed resolution delta v, determining radar emission pulse width tau according to a search radar equation, and determining a radar emission pulse repetition period PRT according to a maximum unambiguous distance d;

step S300, performing wide beam forming of different half-power beam widths on the transmitting beams in different areas, and obtaining a projection coefficient and a corresponding excitation matrix according to waveform forming; the shaping method is as follows: the transmitting wave beam of the high elevation angle area adopts wide wave beam shaping with larger half-power width, and the transmitting wave beam of the middle elevation angle area and the transmitting wave beam of the low elevation angle area adopt wide wave beam shaping with smaller half-power width;

step S400, sum-difference beam mixed forming is adopted for the receiving beam forming of the high elevation angle area, and wide beam forming with smaller half-power width is adopted for the receiving beam forming of the medium elevation angle area; adopting full-channel uniformly weighted beam forming for the low elevation angle area receiving beam forming;

and S500, determining the number of wave beams in each area, overlapping according to a half-power width directional diagram in a pitching dimension, and determining the positions of all the wave beams according to a staggered wave beam arrangement mode in an azimuth dimension.

Specifically, in step S100, the low and slow small target airspace to be searched is divided into a low elevation angle (< 10 °), a medium elevation angle (10 ° to 20 °), and a high elevation angle region (>20 °) in the pitch dimension according to the size of the elevation angle. In step S100 of this embodiment, for the phase-scanning radar, the azimuth dimension rotates 360 ° at a constant speed, and the elevation dimension changes the phase through the TR module to scan the beam rapidly. The low-slow small target flight altitude is usually lower than 1km, the movement distance is usually less than 4km, and the movement speed is usually less than 20 m/s. The radar pitch dimension coverage area is a sector area, so that the area is divided into three parts according to the elevation angles of 10 degrees and 20 degrees, and different beam forming requirements of different areas can be met.

Specifically, in step S200, the radar beam dwell time T, the radar emission pulse width τ, and the radar emission pulse repetition period PRT are respectively:

wherein R is power, P_tFor radar peak transmit power, G_t、G_rRespectively the gains of the radar antenna array transmission and reception, sigma is the radar reflection sectional area, lambda is the radar working wavelength, I is the radar pulse accumulation number, k is the Boltzmann constant, T₀Is standard room temperature, F_nFor the receiver noise figure, L_sFor system losses, C_BFor bandwidth calibration factor, D₀For the detection factor, d is the maximum unambiguous distance.

Specifically, with reference to fig. 2, the detailed steps of performing wide beamforming with different half-power beamwidths on the transmission beams in different areas in step S300 are as follows:

step S301, a group of independent high-gain narrow beams is obtained by using amplitude weighting coefficients of Taylor distribution;

step S302, projecting the target wide beam forming directional diagram on the group of beams to obtain a projection coefficient;

step S303, based on the obtained projection coefficient, the excitation matrix vector of the free radical beam is superposed to obtain an excitation matrix of a target wide beam forming directional diagram;

in step S304, the wave controller uses the excitation matrix to control the phase shift of the TR component so as to form a final wave beam.

Specifically, in step S400, the principle of forming sum beam and difference beam by the phased array radar is as follows:

for an N (even) element array, the weighting coefficients of the sum beams are:

w_Σ＝[w_Σ1·e^{j*2πλ*sinθ/d},w_Σ2·e^{j*2πλ*2sinθ/d},...,w_ΣN·e^{j*2πλ*Nsinθ/d}]^T

w_Σ1，w_Σ2，...，w_ΣN＝1

the weighting coefficients of the difference beams are:

w_Δ＝[w_Δ1·e^{j*2πλ*sinθ/d},w_Δ2·e^{j*2πλ*2sinθ/d},...,w_ΔN·e^{j*2πλ*Nsinθ/d}]^T

w_Δ1，w_Δ2，...，w_Δ(N/2-1)＝-1

w_ΔN/2，w_Δ(N/2+1)，...，w_ΔN＝1

in the above formula, λ is the radar operating wavelength, θ is the radar control beam pointing angle, and d is the radar antenna array unit spacing.

The specific process of the sum-difference beam mixed forming adopted for the high elevation angle area receiving beam forming is as follows:

step S401, acquiring a sum beam and a difference beam of a receiving beam, and normalizing;

step S402, overlapping the normalized sum beam and the difference beam, and taking an overlapped signal with a certain beam width by taking the peak value of the sum beam as the center.

In fig. 3, the sum-difference beam hybrid forming of different beam widths for the receiving beam requires the array pattern of the sum beam and the difference beam to be used simultaneously. In fig. 4, the normalized sum beam is overlapped with the difference beam, and then the overlapping curve segment of 3dB beam width is taken with the peak of the sum beam as the center, and the result is shown in the sum-difference curves in fig. 4a) and b).

With reference to fig. 5, in step S500, the number of beams configured in the high, medium and low airspace is further determined by the transmitted beams that have completed beamforming with different beam widths, and in an embodiment, in the elevation-dimensional radar power diagram, two beams are configured in a 0 ° region to 10 °, one beam is configured in a 10 ° region to 20 °, and two beams are configured in a 20 ° region to 40 °. Wherein, the two receiving beams configured in the angle of 20-40 degrees are sum-difference mixed shaped beams. In the radar power diagram in the azimuth dimension, all beam positions are determined in a classical staggered beam arrangement (0.886 times beam width interval).

Referring to fig. 6, in step S600, the radar signal processor performs adaptive radar signal processing on the detected signal according to the methods in steps S100 to S500, and the detailed steps include:

step S601, under the control of a wave control machine, a power division sum-difference network outputs sum-difference two-path analog radio frequency echo signals;

step S602, the receiver performs analog down-conversion processing on the radio frequency signal to intermediate frequency, and outputs two paths of digital intermediate frequency echo signals of sum and difference after intermediate frequency sampling;

step S603, the signal processor performs digital down-conversion on the sum and difference two paths of intermediate frequency signals to a baseband and then performs frequency domain pulse compression processing;

step S604, the signal processor determines whether to detect only the target in the sum beam or the target of the sum beam and the difference beam according to the sequence number of the receiving beam;

step S605, the signal processor carries out moving target detection and constant false alarm detection on the echo data output by pulse compression, and extracts information such as a target distance gate, a speed gate and the like;

step S606, the data processor processes the target number in the sum and difference echo data reported by the signal processor at the same time,

and outputting motion information such as target motion track, target actual measurement distance, speed, height and the like.

With reference to fig. 7, in step S603, the frequency domain pulse compression processing is based on the working principle that first, N (number of coherent accumulation points) point discrete fourier transform is performed on the digital IQ path echo signal, then, the digital IQ path echo signal is complex-multiplied by the coefficient of the matched filter in the frequency domain, and finally, N point inverse discrete fourier transform is performed on the product result.

With reference to fig. 8, in step S605, the moving target detection is performed according to the working principle that firstly, the distance-time two-dimensional data matrix output by pulse compression is rearranged, then, the chebyshev window function weighting is performed in the time dimension, and finally, the N-point discrete fourier transform is performed in the time dimension to output the distance-doppler two-dimensional data matrix.

With reference to fig. 9, in step S605, the constant false alarm detection processing is based on the working principle that first, data rearrangement is performed on the range-doppler two-dimensional data matrix, then, the reference units on both sides of the target unit are averaged and compared, and then, the average value is increased, then, the average value is multiplied by the set threshold factor to serve as a discrimination threshold, the amplitude of the target unit is compared with the decision threshold, and finally, trace point information exceeding the threshold is output to complete the constant false alarm detection.