阅读说明：本技术 基于子阵正交lfm信号的mimo雷达部分相关波形设计方法 (Partial correlation waveform design method of MIMO radar based on subarray orthogonal LFM signal ) 是由 赵永波 池政刚 侯秦楠 刘宏伟 于 2020-06-18 设计创作，主要内容包括：本发明公开了一种基于子阵正交LFM信号的MIMO雷达部分相关波形设计方法,包括：建立MIMO雷达模型；其中,所述MIMO雷达模型包括若干个发射子阵；获取每个所述子阵的LFM信号波形；对每个所述子阵的LFM信号波形进行处理,得到脉冲综合结果；根据所述脉冲综合结果的旁瓣幅度构建代价函数；利用所述代价函数对每个所述子阵的LFM信号波形进行优化,得到最终的子阵LFM信号波形。本发明由于子阵结构的特殊性,不需要对发射能量覆盖图进行单独的约束,使得波形容易产生,且发射能量覆盖图匹配度较好；此外,本发明通过优化信号带宽和初始相位使得期望方向内每个角度的脉冲综合结果都具有较低的旁瓣,且主瓣不会展宽。(The invention discloses a partial correlation waveform design method of an MIMO radar based on a subarray orthogonal LFM signal, which comprises the following steps: establishing an MIMO radar model; the MIMO radar model comprises a plurality of transmitting sub-arrays; acquiring an LFM signal waveform of each sub-array; processing the LFM signal waveform of each subarray to obtain a pulse comprehensive result; constructing a cost function according to the sidelobe amplitude of the pulse synthesis result; and optimizing the LFM signal waveform of each sub-array by using the cost function to obtain the final LFM signal waveform of the sub-array. Due to the particularity of the subarray structure, independent constraint on the emission energy coverage map is not needed, so that the waveform is easy to generate, and the matching degree of the emission energy coverage map is good; in addition, the invention ensures that the pulse synthesis result of each angle in the expected direction has lower side lobe by optimizing the signal bandwidth and the initial phase, and the main lobe is not widened.)

1. A partial correlation waveform design method of a MIMO radar based on a subarray orthogonal LFM signal is characterized by comprising the following steps:

establishing an MIMO radar model; the MIMO radar model comprises a plurality of transmitting sub-arrays;

acquiring an LFM signal waveform of each sub-array;

processing the LFM signal waveform of each subarray to obtain a pulse comprehensive result;

constructing a cost function according to the sidelobe amplitude of the pulse synthesis result;

and optimizing the LFM signal waveform of each sub-array by using the cost function to obtain the final LFM signal waveform of the sub-array.

2. The method according to claim 1, wherein the sub-array orthogonal LFM signal-based MIMO radar partial correlation waveform design method is characterized in that the expression of the sub-array LFM signal waveform is:

wherein s is_kLFM signal waveform representing the kth sub-array, k being 1,2,3, …, M₁，M₁Representing the number of sub-arrays, f_kCenter frequency, mu, of waveform of LFM signal representing kth sub-array_kIndicates the chirp rate of the LFM signal waveform of the k-th sub-array, and mu_k＝B_k/T_e，T_eRepresents the pulse width of radar emission signal, and T represents 0-T_eInternal sample time, B_kThe signal bandwidth of the LFM signal waveform representing the kth sub-array,indicating the initial phase of the LFM signal waveform for the kth sub-array.

3. The method according to claim 1, wherein the processing of the LFM signal waveform of each of the sub-arrays to obtain the pulse synthesis result comprises:

obtaining LFM signal waveform matrixes of a plurality of sub-arrays according to the LFM signal waveform of each sub-array;

forming the LFM signal waveform matrix of the sub-array into a total LFM signal waveform matrix of the whole transmitting array;

and processing the total LFM signal waveform matrix to obtain a pulse comprehensive result.

4. The method according to claim 3, wherein the processing the total LFM waveform matrix to obtain the pulse synthesis result comprises:

discretely and uniformly taking P sampling angles in a range of-3 dB of an expected emission energy coverage map, and calculating a guide vector of each sampling angle;

obtaining an echo signal according to the steering vector of the sampling angle and the total LFM signal waveform matrix;

and carrying out pulse comprehensive processing on the echo signals to obtain a pulse comprehensive result.

5. The method according to claim 4, wherein the calculation formula of the steering vector of the sampling angle is:

a(θ_p)＝[1 exp(j2πdsinθ_p/λ)…exp(j(M-1)2πdsinθ_p/λ)]^T；

wherein, a (theta)_p) Representing the sampling angle theta_pP is 1,2, …, P, and the sampling angle θ_pSatisfies theta₁＜θ₂＜…＜θ_PM represents the total number of the transmitting array elements, d represents the transmitting array element spacing, and lambda represents the wavelength of the radar transmitting signal]^TRepresenting a transpose operation.

6. The method of claim 5, wherein the expression of the pulse synthesis result is:

y(θ_p,l)＝xcorr(sr)＝xcorr(a(θ_p)^TS)；

wherein l represents-T_e～T_eThe sampling time of the inner 2L-1 point, L is 0 to T_eTotal number of sampling times in xcorr (·) denotes an autocorrelation operation, sr denotes an echo signal, and sr ═ a (θ)_p)^TS, S represents the total LFM signal waveform matrix.

7. The method of claim 6, wherein the cost function is expressed as:

wherein, B_kSignal bandwidth representation of the waveform of the LFM signal representing the kth sub-array, B_minAnd B_maxRespectively represent B_kThe upper limit value and the lower limit value of (c),

8. The method according to claim 7, wherein the optimizing the LFM signal waveform of each sub-array by using the cost function to obtain a final sub-array LFM signal waveform comprises:

respectively optimizing the signal bandwidth of the LFM signal waveform of each sub-array and the initial phase of the LFM signal waveform of each sub-array according to the cost function to obtain the optimized signal bandwidth and the optimized initial phase;

obtaining an optimized frequency modulation slope according to the optimized signal bandwidth;

and obtaining a final sub-array LFM signal waveform according to the optimized frequency modulation slope and the optimized initial phase.

9. The method according to claim 8, wherein the optimizing the bandwidth and the initial phase of the LFM signal waveform of each of the sub-arrays according to the cost function to obtain the optimized bandwidth and the optimized initial phase comprises:

will M₁B is_minAnd M₁0 s form a first column vector, and M is added₁B is_maxAnd M₁2 pi component column vectors are second column vectors;

introducing an fminimax function, taking the cost function as a function of the fminimax function, taking a signal bandwidth of an LFM signal waveform of the sub-array and an initial phase of the LFM signal waveform of the sub-array as input variables of the fminimax function, taking the first column vector as a lower input variable limit of the fminimax function, and taking the second column vector as an upper input variable limit of the fminimax function;

and calling the fminimax function to optimize the signal bandwidth of the LFM signal waveform of each sub-array and the initial phase of the LFM signal waveform of each sub-array to obtain the optimized signal bandwidth and the optimized initial phase.

10. The method of claim 9, wherein the final sub-array LFM signal waveform is expressed as:

wherein s is_k' represents the optimized LFM signal waveform of the kth sub-array, f_kDenotes the center frequency, μ 'of the LFM signal waveform of the k-th sub-matrix'_kIndicates the chirp rate, T, of the kth subarray optimization_eIndicating radar transmissionPulse width of hornIndicating the initial phase of the kth subarray optimization.

Technical Field

The invention belongs to the technical field of radars, and particularly relates to a partial correlation waveform design method of an MIMO radar based on a subarray orthogonal LFM signal.

Background

In recent years, a Multiple Input Multiple Output (MIMO) radar has attracted a wide interest and attention in the field of array signal processing as a new type of radar. The MIMO radar is divided into a distributed type and a centralized type, wherein the centralized type transceiving antenna is short in distance, each array element can transmit different waveforms, and the MIMO radar has the advantage of waveform diversity. Compared with a phased array radar, the method has higher degree of freedom, can obtain higher angular resolution, and has better parameter discrimination capability and anti-interception capability. The transmission degrees of freedom of the MIMO radar are concentrated in the MIMO radar transmission waveform. Therefore, the method has important significance for researching the waveform with higher degree of freedom, improving the system performance, increasing the system flexibility and improving the system adaptability.

The MIMO radar can adjust the transmitting waveform according to a specific working mode so as to reasonably distribute the transmitting energy and has higher flexibility. According to different working modes, the transmitted waveform can be divided into an orthogonal waveform, a partial correlation waveform and the like, wherein the partial correlation waveform is between the orthogonal waveform and the traditional phased array radar, the transmitted energy only covers the area to be observed, and compared with the orthogonal waveform, the energy utilization rate of the radar and the signal-to-noise ratio of an echo signal are improved, so that the target detection and parameter estimation are facilitated. LFM (Linear Frequency Modulation) signals are widely used as radar transmission waveform signals because they have a lower degree of freedom in design, have good doppler tolerance, and are easy to generate in practical applications, compared with phase-encoded signals.

Currently, the prior art proposes two methods for generating LFM waveforms: one is to realize the design of the single-beam emission energy coverage map by optimizing equal frequency intervals and initial phases with fixed difference. The method can directly obtain the transmitted waveform, the obtained partial related LFM waveform has better transmitted energy coverage map matching performance, the pulse comprehensive result has lower side lobe, but the main lobe of the pulse comprehensive result is widened greatly, and the range resolution of a radar system is seriously influenced. Secondly, the side lobe of pulse synthesis is reduced as much as possible under the condition that the error between the waveform transmitted energy coverage map and the expected transmitted energy coverage map is in a set range by adjusting the frequency interval and the initial phase of each signal. The partial correlation LFM waveform designed by the method has better transmitted energy coverage map matching performance, the main lobe of the pulse synthesis result is not widened, but the pulse synthesis result of each angle in an expected direction cannot be ensured to have lower side lobes, and the detection performance of a radar system can be influenced.

Disclosure of Invention

In order to solve the above problems in the prior art, the present invention provides a partial correlation waveform design method for MIMO radar based on orthogonal LFM signals of subarrays. The technical problem to be solved by the invention is realized by the following technical scheme:

a partial correlation waveform design method of a MIMO radar based on a subarray orthogonal LFM signal comprises the following steps:

establishing an MIMO radar model; the MIMO radar model comprises a plurality of transmitting sub-arrays;

acquiring an LFM signal waveform of each sub-array;

obtaining a pulse comprehensive result according to the LFM signal waveform of each sub-array;

constructing a cost function according to the sidelobe amplitude of the pulse synthesis result;

and optimizing each sub-array LFM signal waveform by using the cost function to obtain a final sub-array LFM signal waveform.

In an embodiment of the present invention, the expression of the LFM signal waveform of the sub-array is:

wherein s is_kLFM signal waveform representing the kth sub-array, k being 1,2,3, …, M₁，M₁Representing the number of sub-arrays, f_kCenter frequency, mu, of waveform of LFM signal representing kth sub-array_kIndicates the chirp rate of the LFM signal waveform of the k-th sub-array, and mu_k＝B_k/T_e，T_eRepresents the pulse width of radar emission signal, and T represents 0-T_eInternal sample time, B_kThe signal bandwidth of the LFM signal waveform representing the kth sub-array,indicating the initial phase of the LFM signal waveform for the kth sub-array.

In one embodiment of the present invention, obtaining a pulse synthesis result according to the LFM signal waveform of each of the sub-arrays includes:

obtaining LFM signal waveform matrixes of a plurality of sub-arrays according to the LFM signal waveform of each sub-array;

forming the LFM signal waveform matrix of the sub-array into a total LFM signal waveform matrix of the whole transmitting array;

and processing the total LFM signal waveform matrix to obtain a pulse comprehensive result.

In an embodiment of the present invention, processing the total LFM signal waveform matrix to obtain a pulse synthesis result includes:

discretely and uniformly taking P sampling angles in a range of-3 dB of an expected emission energy coverage map, and calculating a guide vector of each sampling angle;

obtaining an echo signal according to the steering vector of the sampling angle and the total LFM signal waveform matrix;

and carrying out pulse comprehensive processing on the echo signals to obtain a pulse comprehensive result.

In an embodiment of the present invention, the calculation formula of the steering vector of the sampling angle is:

a(θ_p)＝[1 exp(j2πdsinθ_p/λ)…exp(j(M-1)2πdsinθ_p/λ)]^T；

wherein, a (theta)_p) Representing the sampling angle theta_pP is 1,2, …, P, and the sampling angle θ_pSatisfies theta₁＜θ₂＜…＜θ_PM represents the total number of the transmitting array elements, d represents the transmitting array element spacing, and lambda represents the wavelength of the radar transmitting signal]^TRepresenting a transpose operation.

In an embodiment of the present invention, the expression of the pulse integration result is:

y(θ_p,l)＝xcorr(sr)＝xcorr(a(θ_p)^TS)；

wherein l represents-T_e～T_eThe sampling time of the inner 2L-1 point, L is 0 to T_eTotal number of sampling times in xcorr (·) denotes an autocorrelation operation, sr denotes an echo signal, and sr ═ a (θ)_p)^TS, S represents the total LFM signal waveform matrix.

In an embodiment of the present invention, the expression of the cost function is:

wherein, B_kSignal bandwidth representation of the waveform of the LFM signal representing the kth sub-array, B_minAnd B_maxRespectively represent B_kThe upper limit value and the lower limit value of (c),

the initial phase of the LFM signal waveform representing the kth sub-array,M₁indicating the number of sub-arrays.

In an embodiment of the present invention, optimizing the LFM signal waveform of each sub-array by using the cost function to obtain a final LFM signal waveform of the sub-array includes:

respectively optimizing the signal bandwidth of the LFM signal waveform of each sub-array and the initial phase of the LFM signal waveform of each sub-array according to the cost function to obtain the optimized signal bandwidth and the optimized initial phase;

obtaining an optimized frequency modulation slope according to the optimized signal bandwidth;

and obtaining a final sub-array LFM signal waveform according to the optimized frequency modulation slope and the optimized initial phase.

In an embodiment of the present invention, optimizing the signal bandwidth of the LFM signal waveform of each of the sub-arrays and the initial phase of the LFM signal waveform of each of the sub-arrays according to the cost function respectively to obtain an optimized signal bandwidth and an optimized initial phase includes:

will M₁B is_minAnd M₁0 s form a first column vector, and M is added₁B is_maxAnd M₁2 pi component column vectors are second column vectors;

introducing an fminimax function, taking the cost function as a function of the fminimax function, taking a signal bandwidth of an LFM signal waveform of the sub-array and an initial phase of the LFM signal waveform of the sub-array as input variables of the fminimax function, taking the first column vector as a lower input variable limit of the fminimax function, and taking the second column vector as an upper input variable limit of the fminimax function;

and calling the fminimax function to optimize the signal bandwidth of the LFM signal waveform of each sub-array and the initial phase of the LFM signal waveform of each sub-array to obtain the optimized signal bandwidth and the optimized initial phase.

In an embodiment of the present invention, the expression of the final sub-array LFM signal waveform is:

wherein s is_k' represents the optimized LFM signal waveform of the kth sub-array, f_kDenotes the center frequency, μ 'of the LFM signal waveform of the k-th sub-matrix'_kIndicates the chirp rate, T, of the kth subarray optimization_eRepresents the pulse width of the radar transmission signal,indicating the initial phase of the kth subarray optimization.

The invention has the beneficial effects that:

1. the partial correlation waveform design method of the MIMO radar adopts the subarray structure, and due to the particularity of the subarray structure, independent constraint on the emission energy coverage map is not needed, so that the waveform is easy to generate, and the matching degree of the emission energy coverage map is good;

2. the related waveform design method of the MIMO radar part enables the comprehensive result of the pulse of each angle in the expected direction to have lower side lobes and the main lobe not to be widened by optimizing the signal bandwidth.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Drawings

Fig. 1 is a schematic diagram of a partial correlation waveform design method of a MIMO radar based on orthogonal LFM signals of a sub-array according to an embodiment of the present invention;

FIG. 2 is a comparison graph of waveform emission energy coverage of a prior art method and a method of the present invention under simulation conditions;

FIG. 3 is a comparison graph of waveforms of the prior art method and the proposed method under simulation conditions for a-5 clock integration according to the present invention;

FIG. 4 is a comparison graph of waveforms of the prior art method and the proposed method under simulation conditions, which are integrated at 0 degrees according to the present invention;

FIG. 5 is a comparison graph of waveforms of the prior art method and the proposed method under simulation conditions, which are integrated at 5 degrees;

FIG. 6 is a comparison graph of waveform emission energy coverage of the prior art method and the proposed method under the second simulation condition provided by the embodiment of the present invention;

FIG. 7 is a comparison graph of waveforms of the prior art method and the method of the present invention under the second simulation condition, which are integrated at 20 degrees.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.