阅读说明：本技术 Fda-mimo雷达增量距离-角度二维波束形成方法 (FDA-MIMO radar increment distance-angle two-dimensional beam forming method ) 是由 兰岚 祁佳炜 廖桂生 许京伟 朱圣棋 胡仕友 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种FDA-MIMO雷达增量距离-角度二维波束形成方法,实现对目标在每个距离门内距离的精准估计,提高目标检测性能。其实现步骤是：1)获得FDA-MIMO雷达发射阵元的发射信号；2)获得雷达接收端混频后接收阵元的接收信号；3)对发射波形进行匹配滤波,获得采样信号；4)计算雷达接收端匹配滤波后的接收信号矢量；5)根据接收信号矢量构建虚拟导向矢量,最终得到增量距离-角度二维波束形成方向图。本发明通过对FDA阵列采用MIMO技术,在接收端进行联合波束形成,实现距离、角度解耦合,产生与角度、距离同时依赖的天线方向图,在距离-角度联合域实现目标的增量距离-角度联合检测以及干扰抑制。(The invention discloses an FDA-MIMO radar increment distance-angle two-dimensional beam forming method, which can realize accurate estimation of the distance of a target in each range gate and improve the target detection performance. The method comprises the following implementation steps: 1) obtaining a transmitting signal of an FDA-MIMO radar transmitting array element; 2) obtaining a receiving signal of a receiving array element after a radar receiving end mixes frequency; 3) performing matched filtering on the transmitting waveform to obtain a sampling signal; 4) calculating a received signal vector after matching and filtering of a radar receiving end; 5) and constructing a virtual steering vector according to the received signal vector, and finally obtaining an incremental distance-angle two-dimensional beam forming directional diagram. According to the invention, the FDA array is subjected to MIMO technology, combined beam forming is carried out at a receiving end, distance and angle decoupling is realized, an antenna directional diagram which depends on the angle and the distance at the same time is generated, and the increment distance-angle combined detection and interference suppression of a target are realized in a distance-angle combined domain.)

1. An FDA-MIMO radar increment distance-angle two-dimensional beam forming method is characterized by comprising the following steps:

(1) obtaining a complex envelope s of an m-th transmitting array element transmitting signal of the FDA-MIMO radar_m(t), wherein M is 1,2, …, M represents the number of transmitting array elements;

(1a) introducing frequency step quantity delta f among all transmitting array elements of the co-location MIMO radar to obtain the signal frequency f of the m-th transmitting array element of the FDA-MIMO radar_m：

f_m＝f₀+(m-1)Δf，

Wherein f is₀The carrier frequency for the first antenna, the reference antenna;

(1b) according to the signal frequency f_mAnd the m-th transmitting array element transmitting waveform x_m(t) obtaining a complex envelope s of the Mth transmitting array element transmitting signal of the FDA-MIMO radar_m(t)：

Wherein E is the total energy of the transmitted signal, x_m(t) is a transmit waveform; j represents an imaginary number; t represents the propagation time, and 0. ltoreq. t.ltoreq.T_p，T_pIs the radar pulse width;

(2) obtaining a signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t, θ), where N is 1,2, …, N denotes the number of receiving elements;

(2a) obtaining the signal y received by the nth receiving array element and sent by the mth transmitting array element_m,n(t)：

Where β represents the complex echo power, τ_m,nRepresenting the time delay, τ, of the round-trip propagation₀Representing a common propagation delay;

(2b) obtaining the signal y received by the nth receiving array element after the receiving end mixes frequency_n(t,θ)：

Wherein θ represents an arbitrary angle; d_TIndicating the spacing of the transmitting array elements, d_RRepresenting the spacing of the receiving array elements;

(3) the signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t, theta) to obtain a sampling signal

(3a) Constructing an ith matched filter of an nth array element:

wherein denotes a conjugate operation;

(3b) constructing a public propagation time delay tau in a range gate corresponding to the incremental distance of the receiving end₀And a sampling delay t^＊Difference Δ τ of (d):

Δτ＝t^＊-τ₀，

wherein, the value range of delta tau isB represents a bandwidth;

(3c) according to the matched filter constructed in the step (3a), performing matched filtering on the signal received by the nth receiving array element to obtain the sampling time delay t^＊Output sampling signal

Wherein, after the matched filtering, the filter is further performedNew complex echo powerd is the array element spacing;

(4) obtaining receiving end receiving signal vector y of FDA-MIMO radar_S：

(4a) Constructing an angle-dependent emission guide vector d (θ) and a distance-dependent emission guide vector a (Δ τ):

a(Δτ)＝[1,e^j2πΔfΔτ,…,e^{j2πΔf(M-1)Δτ}]^T，

(4b) constructing a received signal vector y of the nth receiving array element of the receiving end according to d (theta) and a (delta tau)_n：

Wherein R represents a matched filter output matrix (·)^TIndicating a transpose operation, an indication of a hadamard product;

(4c) according to the received signal vector y of the nth receiving array element of the receiving end_nObtaining the receiving signal vector y of the receiving end according to the following formula_S：

Wherein the content of the first and second substances,represents the kronecker product, b (θ) represents the angle-dependent receive steering vector;

(5) forming an FDA-MIMO radar incremental distance-angle two-dimensional beam:

(5a) according to the receiving end received signal vector y_SAnd constructing an FDA-MIMO radar virtual guide vector s (theta, delta tau):

(5b) constructing non-adaptive beamforming weight vector w (theta) of FDA-MIMO radar increment distance-angle₀,Δτ₀)：

w(θ₀,Δτ₀)＝s(θ₀,Δτ₀)，

Wherein, theta₀Representing the angle of the target, Δ τ₀Representing the time delay difference in a range gate corresponding to the target increment distance;

(5c) obtaining an FDA-MIMO radar increment distance-angle two-dimensional beam forming directional diagram function f (theta, delta tau) according to the following formula:

f(θ,Δτ)＝w(θ₀,Δτ₀)^Ts(θ,Δτ)。

2. the method of claim 1, wherein: FDA-MIMO radar emission waveform x in step (1b)_m(t), expressed as follows:

wherein the sub-pulse widthP represents the number of sub-pulses; step functionPhase encoding functionPhase code element phi_m(q)∈[0,2π]。

3. The method of claim 1, wherein: the round-trip propagation delay τ in step (2a)_m,nSpecifically, the following are shown:

4. the method of claim 1, wherein: the angle-dependent receive steering vector b (θ) in step (4c) is expressed as follows:

Technical Field

The invention belongs to the technical field of signal processing, and particularly relates to a Frequency diversity Array Multiple-Input Multiple-Output FDA-MIMO (Frequency diversity Array-Multiple-Input and Multiple-Output) radar increment distance-angle two-dimensional beam forming method which can be used for target distance parameter estimation and target detection.

Background

Frequency diversity array FDA (frequency diversity array) radar introduces a frequency step quantity far smaller than a working carrier frequency between transmitting array elements, so that each antenna signal obtains time-varying phase difference at the same time point, and a distance-angle-time three-dimensional dependent transmitting directional diagram is generated. Since the emission pattern of the FDA at a fixed time exhibits a distance-angle coupling characteristic, i.e., the distance dimension controllable degree of freedom is coupled with angle information, two-dimensional joint unambiguous estimation of the target distance and direction cannot be directly achieved. To solve this problem, a multiple-input multiple-output (MIMO) radar technology may be combined to extract distance information of a target after separating each transmitted signal at a receiving end, and obtain additional degrees of freedom in distance and azimuth dimensions, respectively.

Usually, the range of the target is estimated by the range gate size and the range gate number, however, in the FDA-MIMO radar receiving process, after the output of each filter is sampled, there is a difference between the actual delay of the target in each range cell and the sampled value. Therefore, due to the mismatch between the actual guide vector and the ideal guide vector, accurate estimation of the target distance cannot be achieved, resulting in a decrease in target detection performance. The invention provides a method for suppressing main lobe deceptive interference by using a frequency diversity array multiple-input multiple-output FDA-MIMO radar in a patent document entitled by the university of Western's electronics and technology of ' FDA-MIMO radar method for suppressing main lobe deceptive interference ' (patent authorization number: ZL 201710739763.1).

Disclosure of Invention

The invention aims to provide a frequency diversity array multiple-input multiple-output FDA-MIMO radar incremental distance-angle two-dimensional beam forming method aiming at the defects of the prior art, the incremental distance is obtained by matching and filtering a receiving end of the frequency diversity array multiple-input multiple-output MIMO radar system on the basis of the frequency diversity array multiple-input multiple-output MIMO radar system, the beam forming technology related to the incremental distance is researched, the distance difference caused by the difference between the actual delay and the sampling value in each range door, namely the target incremental distance, is considered, and the capability of the method for estimating the target distance parameter and detecting the target in the distance-angle combined domain is developed. The problem that the target distance cannot be accurately estimated due to the fact that the actual guide vector is not matched with the ideal guide vector is solved, and the target detection performance of the FDA-MIMO radar is effectively improved.

The basic idea of the invention is as follows: introducing frequency intervals among all transmitting array elements of the uniformly distributed linear arrays under the background of Gaussian white noise; transmitting orthogonal waveform signals by a frequency diversity array to generate a transmission steering vector related to both distance and angle; and an adaptive beam forming technology of minimum variance distortionless response MVDR is adopted at a receiving end for echo signals, an antenna directional diagram which depends on the angle and the distance at the same time is generated, then target detection and interference suppression are carried out in a distance-angle combined domain, and finally accurate estimation of the target distance is realized.

In order to achieve the purpose, the technical scheme of the invention comprises the following steps:

(1) obtaining a complex envelope s of an m-th transmitting array element transmitting signal of the FDA-MIMO radar_m(t), wherein M is 1,2, …, M represents the number of transmitting array elements:

(1a) introducing frequency step quantity delta f among all transmitting array elements of the co-location MIMO radar to obtain the signal frequency f of the m-th transmitting array element of the FDA-MIMO radar_m：

f_m＝f₀+(m-1)Δf，

Wherein f is₀The carrier frequency for the first antenna, the reference antenna;

(1b) according to the signal frequency f_mAnd the m-th transmitting array element transmitting waveform x_m(t) obtaining a complex envelope s of the Mth transmitting array element transmitting signal of the FDA-MIMO radar_m(t)：

Wherein E is the total energy of the transmitted signal, x_m(t) is a transmit waveform; j represents an imaginary number; t represents the propagation time, and 0. ltoreq. t.ltoreq.T_p，T_pIs the radar pulse width;

(2) obtaining a signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t, θ), where N is 1,2, …, N denotes the number of receiving elements;

(2a) obtaining the signal y received by the nth receiving array element and sent by the mth transmitting array element_m,n(t)：

Where β represents the complex echo power, τ_m,nRepresenting the time delay, τ, of the round-trip propagation₀Representing a common propagation delay;

(2b) obtaining the signal y received by the nth receiving array element after the receiving end mixes frequency_n(t,θ)：

Wherein θ represents an arbitrary angle; d_TIndicating the spacing of the transmitting array elements, d_RRepresenting the spacing of the receiving array elements;

(3) the signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t,θ) Performing matched filtering to obtain a sampling signal

(3a) Constructing an ith matched filter of an nth array element:

wherein denotes a conjugate operation;

(3b) constructing a public propagation time delay tau in a range gate corresponding to the incremental distance of the receiving end₀And a sampling delay t^＊The difference of (a):

Δτ＝t^＊-τ₀，

wherein, the value range of delta tau isB represents a bandwidth;

(3c) according to the matched filter constructed in the step (3a), performing matched filtering on the signal received by the nth receiving array element to obtain the sampling time delay t^★Output sampling signal

Wherein the complex echo power updated after matched filteringd is the array element spacing;

(4) obtaining receiving end receiving signal vector y of FDA-MIMO radar_S：

(4a) Constructing an angle-dependent emission guide vector d (θ) and a distance-dependent emission guide vector a (Δ τ):

a(Δτ)＝[1,e^j2πΔfΔτ,…,e^{j2πΔf(M-1)Δτ}]^T，

(4b) constructing a received signal vector y of the nth receiving array element of the receiving end according to d (theta) and a (delta tau)_n：

Wherein R represents a matched filter output matrix (·)^TIndicating a transpose operation, an indication of a hadamard product;

(4c) according to the received signal vector y of the nth receiving array element of the receiving end_nObtaining the receiving signal vector y of the receiving end according to the following formula_S：

Wherein the content of the first and second substances,represents the kronecker product, b (θ) represents the angle-dependent receive steering vector;

(5) forming an FDA-MIMO radar incremental distance-angle two-dimensional beam:

(5a) according to the receiving end received signal vector y_SAnd constructing an FDA-MIMO radar virtual guide vector s (theta, delta tau):

(5b) constructing non-adaptive beamforming weight vector w (theta) of FDA-MIMO radar increment distance-angle₀,Δτ₀)：

w(θ₀,Δτ₀)＝s(θ₀,Δτ₀)，

Wherein, theta₀Representing the angle of the target, Δ τ₀Representing the time delay difference in a range gate corresponding to the target increment distance;

(5c) obtaining an FDA-MIMO radar increment distance-angle two-dimensional beam forming directional diagram function f (theta, delta tau) according to the following formula:

f(θ,Δτ)＝w(θ₀,Δτ₀)^Ts(θ,Δτ)。

compared with the prior art, the invention has the following advantages:

firstly, the invention defines the difference value of the common propagation delay and the sampling delay in a range gate corresponding to the incremental distance of the receiving end, thereby realizing the accurate estimation of the distance of the target in each range gate, overcoming the problem caused by the mismatching of the actual guide vector and the ideal guide vector, and effectively improving the FDA-MIMO target detection performance.

Secondly, the FDA array is subjected to combined beam forming at the receiving end by adopting a multi-input multi-output MIMO radar technology, so that the receiving end extracts the distance information of the target after separating each transmitting signal, thereby respectively obtaining the additional freedom degrees of the distance and the direction dimension, generating the response of decoupling with the distance and the angle, solving the problem that the transmitting directional diagram of the FDA at a fixed time presents distance-angle coupling, and realizing the target increment distance-angle combined detection; compared with a common array one-dimensional beam forming mode, the controllable degree of freedom of incremental distance-angle two-dimensional beam forming is higher.

Drawings

FIG. 1 is a flow chart of an implementation of the present invention;

FIG. 2 is a schematic diagram of a process of the FDA-MIMO radar receiving end in the present invention;

FIG. 3 is a schematic diagram of a difference between a common propagation delay in a range gate and a sampling delay corresponding to an incremental distance of an FDA-MIMO radar receiving end in the present invention;

fig. 4 is a simulation diagram of FDA-MIMO radar incremental distance-angle two-dimensional beamforming in the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments.

Referring to the attached figure 1, the specific implementation steps of the invention are as follows:

step 1, obtaining complex envelope s of Mth transmitting array element transmitting signal of FDA-MIMO radar_m(t), wherein M is 1,2, …, M represents the number of transmitting array elements;

(1.1) introducing a frequency step quantity delta f among all transmitting array elements of the co-location MIMO radar to obtain a signal frequency f of the mth transmitting array element of the FDA-MIMO radar_m：

f_m＝f₀+(m-1)Δf，

Wherein f is₀The carrier frequency for the first antenna, the reference antenna;

(1.2) each transmitting array element sends a phase coding pulse consisting of P sub-pulses to obtain a transmitting waveform x of the m array element of the FDA-MIMO radar_m(t)：

Wherein the sub-pulse widthP represents the number of sub-pulses; step functionPhase encoding functionPhase code element phi_m(q)∈[0,2π]J denotes an imaginary number, T_pIs the radar pulse width;

(1.3) according to the signal frequency f_mAnd the m-th transmitting array element transmitting waveform x_m(t) obtaining a complex envelope s of the Mth transmitting array element transmitting signal of the FDA-MIMO radar_m(t)：

Wherein E is the total energy of the transmitted signal; t represents the propagation time, and 0. ltoreq. t.ltoreq.T_p，T_pIs the radar pulse width;

step 2, obtaining a signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t, θ), where N is 1,2, …, N denotes the number of receiving elements;

(2.1) at θ for an angle₀A distance of R₀To construct a time delay tau of the round trip propagation_m,nSpecifically, the following are shown:

(2.2) according to the round trip propagation delay tau in the step (2.1)_m,nConstructing the signal y received by the nth receiving array element and sent by the mth transmitting array element_m,n(t)：

Wherein β represents the complex echo power, which takes into account the transmission amplitude, phase, target reflectivity and channel propagation effects; tau is_m,nRepresenting the time delay, τ, of the round-trip propagation₀Representing a common propagation delay;

(2.3) acquiring the signal y received by the nth receiving array element after the receiving end mixes the frequency according to the following formula_n(t,θ)：

Wherein θ represents an arbitrary angle; d_TIndicating the spacing of the transmitting array elements, d_RRepresenting the spacing of the receiving array elements; the signal is obtained as shown in fig. 2.

Step 3, the signal y received by the nth receiving array element after frequency mixing of the FDA-MIMO radar receiving end_n(t, theta) to obtain a sampling signal

(3.1) constructing the ith matched filter of the nth array element:

wherein denotes a conjugate operation;

(3.2) construction of ambiguity function χ of FDA-MIMO Radar_l,m(t₁,f₁)：

Wherein, t₁＝t-τ₀，f₁＝Δf(m-l)；

(3.3) with reference to FIG. 3, a common propagation delay τ in a range gate corresponding to the receiver incremental distance is constructed₀And a sampling delay t^＊Difference Δ τ of (d):

Δτ＝t^＊-τ₀，

wherein, the value range of delta tau isB represents a bandwidth;

(3.4) constructing a sampling time delay t by the difference value delta tau between the fuzzy function constructed in the step (3.2) and the public propagation time delay constructed in the step (3.3)^★Corresponding matched filter output matrix R:

wherein R is_l,mIs the (l, m) th element of the matched filter output matrix R;

(3.5) constructing according to the step (3.4)The established matched filtering output matrix R obtains the nth array element to match the mth transmitting waveform and then carries out sampling time delay t^★The output signal, namely the signal received by the nth receiving array element is matched and filtered according to the constructed matched filter to obtain the sampling time delay t^★Output sampling signal

Wherein, beta₁Representing the complex echo power updated after matched filtering,

step 4, obtaining receiving end receiving signal vector y of FDA-MIMO radar_S：

(4.1) constructing an angle-dependent emission steering vector d (θ):

(4.2) construction of a distance-dependent emission guide vector a (Δ τ):

a(Δτ)＝[1,e^j2πΔfΔτ,…,e^{j2πΔf(M-1)Δτ}]^T，

(4.3) constructing a received signal vector y of the nth receiving array element of the receiving end according to d (theta) and a (delta tau)_n：

Wherein R represents a matched filter output matrix (·)^TIndicating a transpose operation, an indication of a hadamard product;

(4.4) constructing an angle-dependent receive steering vector b (θ) as follows:

(4.5) receiving signal vector y according to nth receiving array element of receiving end_nObtaining the receiving signal vector y of the receiving end according to the following formula_S：

Wherein the content of the first and second substances,represents the kronecker product, b (θ) represents the angle-dependent receive steering vector;

step 5, forming FDA-MIMO radar increment distance-angle two-dimensional wave beams:

(5.1) receiving the signal vector y from the receiving end_SAnd constructing an FDA-MIMO radar virtual guide vector s (theta, delta tau):

(5.2) constructing a non-adaptive beamforming weight vector w (theta) of FDA-MIMO radar increment distance-angle₀,Δτ₀)：

w(θ₀,Δτ₀)＝s(θ₀,Δτ₀)，

Wherein, theta₀Representing the angle of the target, Δ τ₀Representing the time delay difference in a range gate corresponding to the target increment distance;

(5.3) obtaining an FDA-MIMO radar incremental distance-angle two-dimensional beam forming directional diagram function f (theta, delta tau) according to the following formula:

f(θ,Δτ)＝w(θ₀,Δτ₀)^Ts(θ,Δτ)。

the effect of the present invention is further explained by combining the simulation experiment as follows:

1. simulation conditions are as follows:

the simulation experiment of the invention is carried out under the hardware environment of Intel (R) core (TM) i5-8300H CPU @2.3GHz and the software environment of Matlab2019 a;

simulation parameters of the FDA-MIMO radar system are set, and are shown in the table 1:

TABLE 1 FDA-MIMO Radar System simulation parameters

2. Simulation content and result analysis:

under the simulation parameters in table 1, the beam forming directional diagram of the FDA-MIMO radar related to the incremental distance is simulated by using the technique of the present invention, and the simulation result is shown in fig. 4.

The simulation result shows that the frequency diversity array multiple-input multiple-output FDA-MIMO radar adopts the MIMO technology, can obtain separated transmitting signals and has extra distance dimensional freedom. The beamforming pattern of the FDA-MIMO radar has the property of angular decoupling from distance, illustrating that the beamforming pattern of the present invention is not only a function of angle, but also distance dependent.

The simulation analysis proves the correctness and the effectiveness of the method provided by the invention.

The invention has not been described in detail in part of the common general knowledge of those skilled in the art.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.