阅读说明：本技术 一种近场空间网状结构聚焦波束形成方法 (Near-field space mesh structure focusing beam forming method ) 是由 余尚江 陈晋央 曹运合 陈显 王徐华 周会娟 孟晓洁 于 2020-12-17 设计创作，主要内容包括：本发明涉及一种近场空间网状结构聚焦波束形成方法,包括以下步骤：步骤S1.确定雷达天线系统参数；步骤S2.将M个阵元划分为N个子阵,每个数字子阵由L个阵元组成；步骤S3.根据子阵相对参考子阵的回波延时和阵元相对参考阵元的回波延时得到目标回波信号；步骤S4.设定参考信号；步骤S5.将目标回波信号与参考信号做去斜脉冲压缩处理得到各个通道的回波信号；步骤S6.对子阵接收到的信号进行孔径渡越补偿；步骤S7.根据延时补偿后的信号聚焦形成多个空间网状波束覆盖多个目标。本方法可有效的聚焦形成多个空间网状波束覆盖目标,无需扫描、改善对目标距离像的处理,适用于宽带信号下雷达检测目标的实际位置。(The invention relates to a near-field space mesh structure focusing beam forming method, which comprises the following steps: s1, determining parameters of a radar antenna system; s2, dividing M array elements into N sub-arrays, wherein each digital sub-array consists of L array elements; s3, obtaining a target echo signal according to the echo delay of the subarray relative to the reference subarray and the echo delay of the array element relative to the reference array element; s4, setting a reference signal; s5, performing deskew pulse compression processing on the target echo signal and the reference signal to obtain echo signals of all channels; s6, carrying out aperture transit compensation on the signals received by the subarrays; and S7, forming a plurality of spatial mesh beams to cover a plurality of targets according to the signal focus after the delay compensation. The method can effectively focus to form a plurality of spatial mesh-shaped wave beams to cover the target, does not need scanning, improves the processing of the target range profile, and is suitable for the actual position of the radar detection target under the broadband signal.)

1. A near-field space network structure focusing beam forming method is characterized in that: the method comprises the following steps:

step S1, determining parameters of a radar antenna system, wherein the radar system comprises 1 transmitting array element and M receiving array elements, the transmitting array element is a directional antenna, a directional diagram of the M array elements is an isotropic omnidirectional antenna, and a radar transmitting signal is a linear frequency modulation signal with the wavelength of lambda;

step S2, dividing M receiving array elements into N sub-arrays, each sub-array is composed of L array elements, the first sub-array is set as a reference sub-array, the first array element of the reference sub-array is set as a reference array element, and the distance from the target center to the reference array element is set as R₀Dividing Q points at equal intervals in an airspace covered by the transmitted wave beam at the distance to form a mesh structure, wherein each point reflects signals transmitted by the radar, the signals reflected by each point are linear frequency modulation broadband signals with the wavelength of lambda, and the signals reflected by each point have different time delays;

step S3, obtaining an echo signal of the qth point (Q-1 … Q) of the ith array element (L-1 … L) in the nth sub-array (N-1 … N) according to the delay of each sub-array relative to the reference sub-array and the delay of each array element relative to the reference array elementThen analog summation is carried out on the array elements of each subarray to form echo signals of the q point of the nth subarray

Step S4, setting the distance from the target center to the radar antenna reference array element as R₀Time is a time reference point, and the time delay of the emission sample is set to be tau₀(τ₀≈τ_r) With a delay error of Δ τ with respect to the reference subarray and the time reference point₀To obtain a reference signal S₀(t)；

Step S5, theAnd a reference signal S₀Conjugation of (t) S₀ ^*(t) performing deskew pulse compression processing to obtain echo signals after all receiving subarray pulse compression

Step S6, echo signal received by the subarrayCarrying out aperture transition compensation to obtain a q point aperture transition compensated signal vector B of N sub-arrays^q(t)，

Step S7, according to the aperture transition compensated signal B obtained in step S6^q(t) mixing B^q(t) and the N-dimensional weight vector of the q-th pointMultiplying, i.e. focusing to form a beam at Q points, and obtaining Q point compensated signals and corresponding N-dimensional weighting vector W (t) respectively, wherein W (t) is [ W ═ W¹(t)…W^q(t)…W^Q(t)]And then the Q points are respectively focused to form a spatial mesh beam covering the whole transmitting airspace.

2. The method of claim 1, wherein the near field spatial mesh focused beam forming comprises: in step S3, the echo signal of the q-th point of the nth sub-arrayThe method is obtained by the following specific method:

the emission signal S (t) of the radar is:

whereinf₀Is the carrier frequency, mu is the chirp rate, T_pRepresents the pulse width;

establishing a space rectangular coordinate system by taking a first array element of a first subarray as a reference point, wherein the space position of the ith array element is (x)_l,y_l,z_l) L is equal to {1,2, …, M }, and the spatial positions of the N sub-arrays are (x) respectively_n,y_n,z_n) N is equal to {1,2, …, N }, and the spatial position of the reference subarray is (x)_a,y_b,z_c)；

Because the distance of the target relative to the radar antenna reference array element is R₀Then its delay isThe airspace azimuth angle corresponding to the q-th point is assumed to be theta_qAngle of pitch isThe coordinates of the q-th point are

Range radar R₀The distance from the reflector of the q-th point to the l-th array element is recorded as r_l,

Its distance to the reference array element is denoted as r₁，

The relative envelope delay of the signal received at the 1 st array element with respect to the reference array element is τ_l,1，Wherein c is the speed of light;

for the same reason, range radar R₀The distance from the reflector of the q-th point to the nth subarray is denoted as r_n，

Its distance to the reference subarray is r₁'，

The envelope delay of the signal received by the nth sub-array with respect to the reference sub-array is then τ_n,1，

According to envelope delay tau of the subarray relative to a reference subarray_n,1Envelope delay tau of sum array element relative to reference array element_l,1And the distance from the target center to the radar antenna is R₀When the time is a time reference point, the echo signal of the Q-th point (Q-1, 2 … Q) of the L-th array element (L-1, 2 … L) in the N-th sub-array (N-1, 2 … N) is the echo signal of the Q-th point (Q-1, 2 … Q)Can be expressed as

Analog summation is carried out on array elements in each subarray, namely, a signal of the q point of the nth subarray is formed

3. The method of claim 1, wherein the near field spatial mesh focused beam forming comprises: in the step S5, the conjugate S of the reference signal is used₀ ^*(t) pair of signalsAfter deskew pulse compression, all signals obtained after receiving subarray pulse compression are obtainedThe method comprises the following specific steps:

delaying emission samples by tau₀(τ₀≈τ_r) With a delay error of Δ τ with respect to the reference subarray and the time reference point₀Then the reference signal S₀The expression of (t) is:

then the signal can be obtained after the deskew pulse pressure processing

4. The method of claim 1, wherein the near field spatial mesh focused beam forming comprises: in step S6, the signals received by the subarraysCarrying out aperture transition compensation to obtain a signal vector B of the q point aperture transition compensation of the N sub-arrays^qThe specific method of (t) is as follows:

since the first sub-array is set as the reference sub-array, the reference signal S₀(t) transform into:

echo signal to targetThe declivity treatment is carried out by:

at this time, the frequency value f₁＝2πμ(Δτ₀-τ_l,1)，

Phase value of

The last term of the phase value is related to the subarray channel number, and the maximum phase of the processed maximum frequency value can be used to compensate the phase term of each subarray channel, that is:

in practice 2 π μ τ_n,1(Δτ₀-τ_l,1) Very small, so choose to ignore, N childrenQ point aperture transition compensated received signal vector B of the array^q(t) is:

5. the method of claim 1, wherein the near field spatial mesh focused beam forming comprises: in step S7, the spatial mesh beam is formed by Q points focused by multiplying the compensated aperture signal of each point by the N-dimensional weighting vector, which includes the following steps:

each array element is an omnidirectional antenna, and the spatial positions of N sub-arrays are respectively (x)_n,y_n,z_n) N is equal to {1,2, …, N }, and the N sub-arrays are respectively subjected to digital weighting to form beams focused at a q point, and the coordinate of the q point is (x)_q,y_q,z_q) Then the distance d between the qth point and the nth subarray_nComprises the following steps:

the numerical weighting of the N sub-arrays is then:

where T denotes the operation of transposing,representing the numerical weighting of the nth sub-array, then for range radar R₀The beam output formed by the q-th point focus at (a) can be expressed as:

the signal B (t) compensated for by Q points is therefore [ B ═ B¹(t)…B^q(t)…B^Q(t)]And an N-dimensional weighting vector W (t) corresponding thereto, wherein W (t) W¹(t)…W^q(t)…W^Q(t)]The Q points can be respectively focused to form a space mesh wave beam to cover the whole emission space domain;

the output expression of the spatial mesh beam formed by focusing at the point Q at the time t is as follows:

y(t)＝B(t)*W(t)＝[y¹(t) y²(t)…y^q(t)…y^Q(t)]。

Technical Field

The invention belongs to the technical field of radar signal processing, mainly relates to a radar beam forming technology, and particularly relates to a near-field space network structure focusing beam forming method.

Background

With the continuous development of electronic science and technology, the electromagnetic environment becomes more complex than the past, and how to realize effective resolution, identification and monitoring on a plurality of target signals in the complex environment constitutes a severe test for modern sonar, radar and various detection systems.

In array signal processing, it is generally assumed that the distance between the source and the sensor array is infinity, in which case the signals received by the array can be treated as plane waves, and the difference between the signals received by the sensors of the array only has the problem of phase difference, thereby greatly reducing the complexity of the beam forming problem. However, when the source is located in the near field of the array, the signals radiated by the source received by each array element are spherical waves, so that the array beam design needs to be designed differently according to the relative position of the target in the array, and the far field assumption at this time is no longer applicable to some extent. The near-field wave beam designed by the spherical wave model can effectively separate two signals which are positioned in the same direction and at different distances at the same time, which cannot be realized by adopting a far-field wave beam technology; it is still a challenge how to use such beams to achieve proper focusing of multiple targets in near field space.

Compared with a narrow-band signal, the broadband signal has richer target information and is more advantageous in the aspects of target detection, parameter estimation, target extraction and the like, but when the phased array radar uses the broadband signal and the instantaneous bandwidth is larger, the normal focusing on a required target can be influenced by the large-aperture antenna due to the aperture transit time difference.

Disclosure of Invention

Aiming at the problems in the background art and aiming at the detection and resolution of multiple targets, the invention aims to provide a near-field spatial mesh structure focused beam forming method.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a near-field spatial mesh focused beam forming method, comprising the steps of:

step S1, determining parameters of a radar antenna system, wherein the radar system comprises 1 transmitting array element and M receiving array elements, the transmitting array element is a directional antenna, a directional diagram of the M array elements is an isotropic omnidirectional antenna, and a radar transmitting signal is a linear frequency modulation signal with the wavelength of lambda;

step S2, dividing M receiving array elements into N sub-arrays, each sub-array is composed of L array elements, the first sub-array is set as a reference sub-array, the first array element of the reference sub-array is set as a reference array element, and the distance from the target center to the reference array element is set as R₀Dividing Q points at equal intervals in an airspace covered by the transmitted wave beam at the distance to form a mesh structure, wherein each point reflects signals transmitted by the radar, the signals reflected by each point are linear frequency modulation broadband signals with the wavelength of lambda, and the signals reflected by each point have different time delays;

step S3, obtaining an echo signal of the qth point (Q-1 … Q) of the ith array element (L-1 … L) in the nth sub-array (N-1 … N) according to the delay of each sub-array relative to the reference sub-array and the delay of each array element relative to the reference array elementThen analog summation is carried out on the array elements of each subarray to form echo signals of the q point of the nth subarray

Step S4, setting the distance from the target center to the radar antenna reference array element as R₀Time is a time reference point, and the time delay of the emission sample is set to be tau₀(τ₀≈τ_r) With a delay error of Δ τ with respect to the reference subarray and the time reference point₀To obtain a reference signal S₀(t)；

Step S5, theAnd a reference signal S₀Conjugation of (t) S₀ ^*(t) performing deskew pulse compression processing to obtain echo signals after all receiving subarray pulse compression

Step S6, echo signal received by the subarrayCarrying out aperture transition compensation to obtain a q point aperture transition compensated signal vector B of N sub-arrays^q(t)，

Step S7, according to the aperture transition compensated signal B obtained in step S6^q(t) mixing B^q(t) and the N-dimensional weight vector of the q-th pointMultiplying, i.e. focusing to form a beam at Q points, and obtaining Q point compensated signals and corresponding N-dimensional weighting vector W (t) respectively, wherein W (t) is [ W ═ W¹(t)…W^q(t)…W^Q(t)]And then the Q points are respectively focused to form a spatial mesh beam covering the whole transmitting airspace.

The invention has the beneficial effects that:

the method reduces aperture transit time difference by dividing array elements in the radar into sub-arrays, compensates the aperture transit time difference, focuses to form a space mesh-shaped wave beam to cover a target, does not need to scan, improves the processing of a target range profile, and is suitable for detecting the actual position of the target by the radar under a broadband signal in a near-field environment.

Drawings

FIG. 1 is a flow chart of the present invention.

Fig. 2 is a radar linear array time delay compensation geometric model.

Fig. 3 is a block diagram of a spatial mesh focused beamforming implementation of the present invention.

Detailed Description

The invention is further described with reference to the drawings and the detailed description, and the method provided by the invention is suitable for the phased array radar using chirp signals as transmitting signals.

As shown in fig. 1, a method for forming a focused beam of a near-field spatial mesh structure includes the following steps:

step S1, determining parameters of a radar antenna system, wherein the radar system comprises 1 transmitting array element and M receiving array elements, the transmitting array element is a directional antenna, a directional diagram of the M array elements is an isotropic omnidirectional antenna, and a radar transmitting signal is a linear frequency modulation signal S (t) with the wavelength of lambda;

the emission signal S (t) of the radar is:

whereinf₀Is the carrier frequency, mu is the chirp rate, T_pRepresents the pulse width;

step S2, dividing M receiving array elements into N sub-arrays, each sub-array is composed of L array elements, the first sub-array is set as a reference sub-array, the first array element of the reference sub-array is set as a reference array element, and the distance from the target center to the reference array element is set as R₀The space covered by the transmitting beam at the distance is divided into Q equally-spaced partsThe points form a mesh structure, each point reflects signals transmitted by the radar, the signals reflected by each point are linear frequency modulation broadband signals with the wavelength of lambda, and the signals reflected by each point have different time delays;

step S3, obtaining an echo signal of the qth point (Q-1 … Q) of the ith array element (L-1 … L) in the nth sub-array (N-1 … N) according to the delay of each sub-array relative to the reference sub-array and the delay of each array element relative to the reference array elementThen analog summation is carried out on the array elements of each subarray to form echo signals of the q point of the nth subarray

Echo signal of q point of nth sub-arrayThe method is obtained by the following specific method:

establishing a space rectangular coordinate system by taking a first array element of a first subarray as a reference point, wherein the space position of the ith array element is (x)_l,y_l,z_l) L is equal to {1,2, …, M }, and the spatial positions of the N sub-arrays are (x) respectively_n,y_n,z_n) N is equal to {1,2, …, N }, and the spatial position of the reference subarray is (x)_a,y_b,z_c)；

Because the distance of the target relative to the radar antenna reference array element is R₀Then its delay isThe airspace azimuth angle corresponding to the q-th point is assumed to be theta_qAngle of pitch isThe coordinates of the q-th point are

Range radar R₀The distance from the reflector of the q-th point to the l-th array element is recorded as r_l,

Its distance to the reference array element is denoted as r₁，

The relative envelope delay of the signal received at the 1 st array element with respect to the reference array element is τ_l,1，Wherein c is the speed of light;

for the same reason, range radar R₀The distance from the reflector of the q-th point to the nth subarray is denoted as r_n，

Its distance to the reference subarray is r₁'，

The envelope delay of the signal received by the nth sub-array with respect to the reference sub-array is then τ_n,1，

According to envelope delay tau of the subarray relative to a reference subarray_n,1Envelope delay tau of sum array element relative to reference array element_l,1And the distance from the target center to the radar antenna is R₀The time is a reference point of time,then, the echo signal of the Q-th point (Q-1, 2 … Q) of the L-th array element (L-1, 2 … L) in the N-th sub-array (N-1, 2 … N) is equal to 1,2 8932LCan be expressed as

Analog summation is carried out on array elements in each subarray, namely, a signal of the q point of the nth subarray is formed

Step S4, setting the distance from the target center to the radar antenna reference array element as R₀Time is a time reference point, and the time delay of the emission sample is set to be tau₀(τ₀≈τ_r) With a delay error of Δ τ with respect to the reference subarray and the time reference point₀Is provided with S₀(t) is a reference signal, then

Step S5, theAnd a reference signal S₀Conjugation of (t) S₀ ^*(t) performing deskew pulse compression processing to obtain echo signals after all receiving subarray pulse compression

In the step S5, the conjugate S of the reference signal is used₀ ^*(t) pair of signalsAfter deskew pulse compression, all signals obtained after receiving subarray pulse compression are obtainedAs shown in the following formula:

step S6, echo signal received by nth sub-arrayCarrying out aperture transition compensation to obtain a q point aperture transition compensated signal vector B of N sub-arrays^q(t)，

In step S6, the signals received by the subarraysCarrying out aperture transition compensation to obtain a signal vector B of the q point aperture transition compensation of the N sub-arrays^qThe specific method of (t) is as follows:

the subarray received signal obtained in step S5Taking the data of the reference subarray as the reference data, and multiplying the data of the remaining subarrays by the conjugate of the reference data, taking subarray 2 as an example, the result is as follows:

wherein the frequency value f is 2 pi mu (tau)_1,1-τ_2,1)；

Phase value

From the above formula, it can be seen that the aperture transit is mainly caused by the time delay of the subarray relative to the reference subarray, and the aperture transit compensation can be completed as long as the compensation of the time delay is completed;

since the first sub-array is set as the reference sub-array, the reference signal S₀(t) transform into:

echo signal to targetThe declivity treatment is carried out by:

at this time, the frequency value f₁＝2πμ(Δτ₀-τ_l,1) Phase value ofThe frequency value after the deskew processing is irrelevant to the channel number of the subarray, and the frequency offset is effectively compensated;

the last term of the phase value being related to the subarray channel number, the phase term of each subarray channel being compensated by the maximum phase of the processed maximum frequency value, i.e. the phase of each subarray channel is compensated by the maximum phase of the processed maximum frequency value

In practice 2 π μ τ_n,1(Δτ₀-τ_l,1) It is small, the loss of the system is negligible,

thus, the q point aperture transition compensated received signal vector B for the N sub-arrays^q(t) is:

step S7, according to the aperture transition compensated signal B obtained in step S4^q(t) mixing B^q(t) and the N-dimensional weight vector of the q-th pointMultiplying, i.e. focusing to form a beam at Q points, and obtaining Q point compensated signals and corresponding N-dimensional weighting vector W (t) respectively, wherein W (t) is [ W ═ W¹(t)…W^q(t)…W^Q(t)]^TFocusing at Q points to form a space mesh wave beam covering the whole emission space domain;

in step S7, the spatial mesh beam is formed by Q points focused by multiplying the compensated aperture signal of each point by the N-dimensional weighting vector, which includes the following steps:

each array element is an omnidirectional antenna, and the spatial positions of N sub-arrays are respectively (x)_n,y_n,z_n) N is equal to {1,2, …, N }, and the N sub-arrays are respectively subjected to digital weighting to form beams focused at a q point, and the coordinate of the q point is (x)_q,y_q,z_q) Then the distance d between the qth point and the nth subarray_nComprises the following steps:

the numerical weighting of the N sub-arrays is then:

where T denotes the operation of transposing,representing the numerical weighting of the nth sub-array, then for range radar R₀The beam output formed by the q-th point focus at (a) can be expressed as:

the signal B (t) compensated for by Q points is therefore [ B ═ B¹(t)…B^q(t)…B^Q(t)]And an N-dimensional weighting vector W (t) corresponding thereto, wherein W (t) W¹(t)…W^q(t)…W^Q(t)]The Q points can be respectively focused to form a space mesh wave beam to cover the whole emission space domain;

the output expression of the spatial mesh beam formed by focusing at the point Q at the time t is as follows:

y(t)＝B(t)*W(t)＝[y¹(t)y²(t)…y^q(t)…y^Q(t)]

the principle of the invention is as follows:

fig. 2 is a geometric model of radar linear array time delay compensation, in which a first array element is used as a reference array element, and corresponding compensation is performed according to the time delay of a signal received by each array element relative to the reference array element to obtain the output of a focused beam;

fig. 3 is the spatial mesh focused beam forming of the present invention: firstly, a radar array surface receives a target echo signal to obtain a plurality of paths of echo signals, time delay control is carried out according to a transmitting signal to obtain a reference signal, the reference signal and the echo signal are subjected to deskew processing, each path of signal is converted through a high-speed analog-to-digital conversion device, and the analog signal is converted into a digital signal; the method comprises the steps of completing low-pass filtering, orthogonal down-conversion, sampling rate reduction and the like in a digital domain, then adding delay difference into echo signals for compensation, completing multi-channel receiving delay processing, then performing inter-channel phase compensation to complete aperture transition compensation, and then applying a weight to each subarray for focusing to form a plurality of space mesh beams to cover a plurality of targets.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention; thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

The present invention is not described in detail in the prior art.