阅读说明：本技术 基于mimo雷达的频率捷变信号转发式干扰抑制方法 (Frequency agile signal forwarding type interference suppression method based on MIMO radar ) 是由 全英汇 张瑞 朱圣棋 邢孟道 于 2020-06-05 设计创作，主要内容包括：本发明提出一种基于MIMO雷达的频率捷变信号转发式干扰抑制方法,主要解决现有技术对转发式干扰抑制效果差的问题。其实现方案是：首先构建MIMO雷达发射阵元所在场景；MIMO雷达在此场景下发射频率捷变OFDM-LFM信号；MIMO雷达同时接收目标回波信号和干扰回波信号；MIMO雷达信号处理系统对目标回波信号和干扰回波信号进行求和操作得到合信号；MIMO雷达信号处理系统对合信号进行匹配滤波操作,得到匹配滤波输出结果,完成转发式干扰抑制。本发明对不同雷达体制的适应性强,降低了雷达系统发射信号转换要求,有利于提升转发式干扰抑制效果,提高了抗干扰能力,可应用于MIMO雷达目标探测与识别。(The invention provides a frequency agile signal forwarding type interference suppression method based on an MIMO radar, and mainly solves the problem that the forwarding type interference suppression effect in the prior art is poor. The implementation scheme is as follows: firstly, constructing a scene where an MIMO radar transmitting array element is located; the MIMO radar transmits frequency-agile OFDM-LFM signals in the scene; the MIMO radar receives a target echo signal and an interference echo signal simultaneously; the MIMO radar signal processing system carries out summation operation on the target echo signal and the interference echo signal to obtain a combined signal; and the MIMO radar signal processing system performs matched filtering operation on the synthetic signal to obtain a matched filtering output result and complete forwarding type interference suppression. The method has strong adaptability to different radar systems, reduces the conversion requirement of the transmitted signals of the radar system, is favorable for improving the forwarding interference suppression effect, improves the anti-interference capability, and can be applied to the target detection and identification of the MIMO radar.)

1. A frequency agile signal forwarding type interference suppression method based on MIMO radar is characterized by comprising the following steps:

(1) aiming at an MIMO radar detection scene with a target and an active deception jamming, the MIMO radar transmitting end is provided with N transmitting array elements to meet the far-field narrow-band condition, each array element is sequentially and linearly arranged, and the distance between adjacent transmitting array elements is

(2) n transmitting array elements of an MIMO radar transmitting end respectively transmit OFDM-LFM signals with agile frequencies, the N transmitting signals are mutually orthogonal, and carrier frequencies of all the transmitting signals are randomly agile among pulses;

(3) n transmitting signals are reflected by the target, transmitted through the electromagnetic wave space and received by a receiving array element of a radar receiving end to obtain echo signals of the target

(4) The jammer intercepts N transmitting signals of the MIMO radar, transmits the signals out after time delay and power amplification in sequence and receives the signals by the MIMO radar receiver to obtain an interfered echo signal J^q-1(t)；

(5) At time t, the target echo signal is processed

2. The method of claim 1, wherein the N transmit signals of the MIMO radar in (2) are respectively expressed as:

where u (t) represents a rectangular envelope, f_cIndicating the starting carrier frequency, α (Q) indicating the frequency modulation code of the Q-th pulse, Q ∈ {1,2, … Q }, Q indicating the total number of pulses, α (Q) making random agility between pulses, the value of which can be determined using randderm function, Δ f indicating the hop interval, μ indicating the modulation frequency, f_ΔIndicating a frequency increment.

3. The method of claim 1, wherein the echo signal of the target in (3)Expressed as:

where u (t) represents a rectangular envelope, f_cRepresenting the starting carrier frequency, α (Q) representing the frequency modulation code of the Q-th pulse, Q ∈ {1,2, … Q }, Q representing the total number of pulses, α (Q) being randomly agile between pulses, the values being determined using a randderm function, Δ f representing the hop interval, μ representing the modulation frequency, N ∈ {1,2, … N }, f_ΔRepresenting the frequency increment, τ_tarIndicating target to reference in the q-th pulseDelay of array elements.

4. The method of claim 1, wherein the interfering echo signal J in (4)^q-1(t), expressed as:

where u (t) represents a rectangular envelope, f_cRepresenting the starting carrier frequency, α (Q) representing the frequency modulation code of the Q-th pulse, Q ∈ {1,2, … Q }, Q representing the total number of pulses, α (Q) being randomly agile between pulses, the values being determined using a randderm function, Δ f representing the hop interval, μ representing the modulation frequency, N ∈ {1,2, … N }, f_ΔRepresenting the frequency increment, τ_jIndicating the time delay of the transponder interference echo signal relative to the transmit pulse.

5. The method of claim 1, wherein the sum signal s in (5)_r(t), the expression is:

6. the method of claim 1, wherein the signal s is combined in (5)_r(t) performing matched filtering operation to obtain a combined signal s_r(t) matched filtering output result s_rMF(t), achieved as follows:

(6a) involution of the signal s by_r(t) performing a matched filtering operation:

wherein, T_pRepresents the pulse repetition period, represents the transposed operation symbol;

(6b) integrating and simplifying the above formula to obtain a resultant signal s_r(t) matched filtering output result s_rMF(t)：

Wherein μ represents the modulation frequency, T_pRepresenting the pulse repetition period, τ_tarRepresenting the time delay, tau, of the target to the reference array element in the q-th pulse_jRepresenting the time delay of the transponder interference echo signal relative to the transmit pulse, and n (t) representing radar system noise.

Technical Field

The invention belongs to the technical field of radar signal processing, and particularly relates to a frequency agile signal forwarding type interference suppression method which can be applied to MIMO radar target detection and identification.

Background

The MIMO radar is a radar system of a new system which transmits orthogonal signals through a transmitting terminal antenna, and receives echo signals of all paths and performs combined processing through a receiving terminal antenna. The MIMO radar controls the transmitting signals of each transmitting unit by adopting a digital method, so that the transmitting signals of each transmitting unit are mutually orthogonal, therefore, the transmitting signals cannot be coherently superposed in space to form a narrow transmitting beam with high gain, but are incoherently superposed to form a wide transmitting beam with low gain, and the MIMO radar has great potential in the aspect of repeater interference suppression.

The frequency agility refers to the agility of the carrier frequency of a single transmitting signal in a wider range in a wider frequency band in a random or predetermined mode along with time, and has the capacity of resisting interference and low interception. Frequency agile signals are widely used in MIMO radars, similar to stepped frequency signals, except that the frequency agile signals of the MIMO radar are transmitted in parallel. In MIMO radar, each subcarrier of a frequency agile signal is transmitted over a different channel, each signal occupying a different frequency band. And at each receiving channel, a matched filter is adopted to separate echoes caused by different transmitting signals from the synthesized signal, so that convenience is provided for subsequent radar signal processing. For the frequency agile forwarding type interference suppression method of the MIMO radar, the existing research mainly includes:

the 'research on radar anti-interference technology based on waveform agility', published by Lin Hou Honghong in 2016, proposes a single-pulse radar-based forwarding type interference suppression method based on OFDM-LFM signals, but the method is only suitable for single-pulse radars and has poor adaptability to different radar systems.

In 2017, the DRFM range fault target cancellation method on slope-varying LFM chirp published by Li Wei et al uses inter-pulse frequency-modulated frequency randomly hopped chirp signals to provide a method for reconstructing an interference signal according to a false target parameter to achieve forward interference suppression, but when a radar system cannot convert a transmission waveform between pulses, the method fails.

Zhouhui is sensitive to the orthogonal waveform model of the OFDM-LFM transmitting signals, which is published in 2018, and the missile-borne MIMO radar low interception and anti-interference research provides a method for carrying out forwarding type interference suppression by utilizing the orthogonality among the OFDM-LFM signals, but the method has lower interference suppression capability when the orthogonality among the transmitting signals is poor.

Some methods in the research put forward extremely strict requirements on the transmission waveform conversion function of the radar system; some methods have poor adaptability to different radar systems; some methods have low interference suppression capability. In summary, there is no ideal frequency agile signal repeating interference suppression method in the prior art.

Disclosure of Invention

The invention aims to provide a frequency agile signal forwarding type interference suppression method based on an MIMO radar to overcome the defects of the prior art, so as to improve the suppression capability of the MIMO radar to forwarding type interference.

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

(1) aiming at an MIMO radar detection scene with a target and an active deception jamming, the MIMO radar transmitting end is provided with N transmitting array elements to meet the far-field narrow-band condition, each array element is sequentially and linearly arranged, and the distance between adjacent transmitting array elements is

And the first array element is taken as a reference array element, wherein N is more than or equal to 2, and lambda represents the wavelength;

(2) n transmitting array elements of an MIMO radar transmitting end respectively transmit OFDM-LFM signals with agile frequencies, the N transmitting signals are mutually orthogonal, and carrier frequencies of all the transmitting signals are randomly agile among pulses;

(3) n transmitting signals are reflected by the target, transmitted through the electromagnetic wave space and received by a receiving array element of a radar receiving end to obtain echo signals of the target

(4) The jammer intercepts N transmitting signals of the MIMO radar, transmits the signals out after time delay and power amplification in sequence and receives the signals by the MIMO radar receiver to obtain an interfered echo signal J^q-1(t)；

(5) At time t, the target echo signal is processedAnd interference echo signal J^q-1(t) performing a summation operation to obtain a combined signal s of the two echo signals_r(t) the signal processing system at the receiving end of the MIMO radar processes the combined signal s_r(t) performing matched filtering operation to obtain a combined signal s_r(t) matched filtering output result s_rMFAnd (t) completing the forwarding type interference suppression of the frequency agile signal.

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

first, the transmit signal conversion requirements for the radar system are reduced. In the prior art, a single-pulse radar-based forwarding type interference suppression method is well researched, when a radar system cannot convert transmitting signals among pulses, the method fails, and the MIMO radar-based frequency agile signal forwarding type interference suppression method has the advantages that the transmitting signals can be adjusted in a self-adaptive mode according to the radar system, the requirement on the transmission signal conversion of the radar system is lowered, and the forwarding type interference suppression is favorably realized.

Second, the suppression of the turnaround interference is improved. In the prior art, the orthogonality among the transmitting signals is mainly utilized for carrying out forwarding type interference suppression, but the interference suppression capability is low when the orthogonality among the transmitting signals is poor. The invention carries out random agility among pulses through the carrier frequency of the transmitting signal, and simultaneously improves the inhibition capability of the forwarding interference by combining the orthogonal characteristic among the transmitting signals.

Thirdly, the adaptability is strong. The prior art mainly carries out forwarding type interference suppression based on a radar platform with a single system, but the method has low adaptability to different radar systems, and the method can be applied to radars with different systems through flexible waveform conversion operation.

Drawings

Fig. 1 is a flow diagram of a forward interference mitigation implementation of the present invention;

fig. 2 is a graph of simulation results for range spoofing interference suppression using the present invention.

Detailed description of the preferred embodiments

Embodiments and effects of the present invention are described in detail below with reference to the accompanying drawings.

Referring to fig. 1, the implementation steps of the invention are as follows:

step 1: and constructing a scene where the MIMO radar transmitting array elements are located.

Aiming at an MIMO radar detection scene with a target and an active deception jamming, the MIMO radar transmitting end is provided with N transmitting array elements to meet the far-field narrow-band condition, each array element is sequentially and linearly arranged, and the distance between adjacent transmitting array elements is

And the first array element is taken as a reference array element, wherein N is more than or equal to 2, and lambda represents the wavelength.

Step 2: and transmitting the OFDM-LFM signal with the agility frequency.

N transmitting array elements of the MIMO radar transmitting end respectively transmit OFDM-LFM signals with agile frequencies, the N transmitting signals are mutually orthogonal, and carrier frequencies of all the transmitting signals are randomly agile among pulses.

N transmitting signals of the MIMO radar are respectively expressed as:

where u (t) represents a rectangular envelope, f_cDenotes the initial carrier frequency,. DELTA.f denotes the hop interval,. mu.denotes the tuning frequency,. f_ΔThe frequency increment is represented, Q represents a pulse number, Q ∈ {1,2, …, Q }, Q represents the total number of pulses, α represents a frequency modulation code, and the value α (Q) is determined by using a randderm function, namely α (Q) ═ randderm (Q, Q).

And step 3: receiving a target echo signal

N transmitting signals are reflected by the target, transmitted through the electromagnetic wave space and received by a receiving array element of a radar receiving end to obtain echo signals of the targetExpressed as:

where u (t) represents a rectangular envelope, f_cDenotes the starting carrier frequency,. DELTA.f denotes the hop interval,. mu.denotes the tuning frequency, N ∈ {1,2, …, N }, f_ΔRepresenting the frequency increment, τ_tarThe delay from the target to the reference array element in the qth pulse is shown, Q is the pulse number, Q ∈ {1,2, …, Q }, Q is the total number of pulses, α is the frequency modulation code, and the value of α (Q) is determined using a randderm function, i.e., α (Q) ═ randderm (Q, Q).

And 4, step 4: receiving an interference echo signal J^q-1(t)。

The jammer intercepts N transmitting signals of the MIMO radar, transmits the signals out after time delay and power amplification in sequence and receives the signals by the MIMO radar receiver to obtain an interfered echo signal J^q-1(t), expressed as:

where u (t) represents a rectangular envelope, f_cDenotes the starting carrier frequency,. DELTA.f denotes the hop interval,. mu.denotes the tuning frequency, N ∈ {1,2, …, N }, f_ΔRepresenting the frequency increment, τ_jQ represents the pulse number, Q ∈ {1,2, …, Q }, Q represents the total number of pulses, α represents the frequency modulation code, and the selection of α (Q) value is determined by using randderm function, namely α (Q) is randderm (Q, Q).

And 5: to the target echo signal

And interference echo signal J^q-1(t) summing.

At time t, the target echo signal is processedAnd interference echo signal J^q-1(t) performing a summation operation to obtain a combined signal s of the two echo signals_r(t), the expression is:

step 6: involution signal s_r(t) performing matched filtering to obtain a matched filtering result s_rMF(t)。

6.1) Signal processing System at MIMO Radar receiver end to combine Signal s by the following equation_r(t) performing a matched filtering operation:

wherein, T_pRepresents the pulse repetition period, represents the transposed operation symbol;

6.2) integrating and simplifying the above formula to obtain a resultant signal s_r(t) matched filtering output result s_rMF(t), the expression is:

wherein μ represents the modulation frequency, T_pRepresenting the pulse repetition period, τ_tarRepresenting the time delay, τ, of the target to the reference array element_jRepresenting the time delay of the transponder interference echo signal relative to the target, and n (t) representing the radar system noise.

The effect of the present invention will be further explained by simulation experiments.

Simulation parameter

The simulation parameters are shown in table 1:

TABLE 1 simulation parameters of the present invention

Second, simulation content

Under the simulation parameters, the suppression of the range-deception jamming is simulated by adopting the frequency-agile signal jamming suppression method based on the MIMO radar, and the specific parameters are used in practical application, so that the target can be correctly detected and identified, the range-deception jamming is successfully suppressed, and the result is shown in figure 2. The x-coordinate in fig. 2 represents the distance value and the y-coordinate represents the amplitude value.

As can be seen from FIG. 2, the target has a matched filtering peak at a distance of 4000m, the amplitude is 0dB, and the target distance simulation result is the real target distance R₀And (5) the consistency is achieved. Due to the mismatch of the interference with the matched filter, the interference cannot be correctly matched to the filtered output, the interference is suppressed and the target is correctly detected.

The simulation experiment verifies the correctness, effectiveness and reliability of the method.

In summary, the frequency agile signal forwarding interference suppression method based on the MIMO radar provided by the invention. The technical problem that target signals of the MIMO radar are easily interfered is solved.

The foregoing description is only an example of the present invention and is not intended to limit the present invention, and it will be apparent to those skilled in the art that various modifications and variations in form and detail can be made without departing from the principle and structure of the invention, but these modifications and variations are within the scope of the invention as defined in the appended claims.