阅读说明：本技术 一种基于参考信号的微弱目标双通道单脉冲测角方法 (Weak target double-channel single-pulse angle measurement method based on reference signal ) 是由 段越 沈清 崔嵬 杨子翔 刘超 李彦欣 于 2020-04-17 设计创作，主要内容包括：本发明提供一种基于参考信号的微弱目标双通道单脉冲测角方法,相比于传统三通道单脉冲测角算法,本发明将方位差通道和俯仰差通道合成一路差通道,与和通道构成双通道进行信号处理得到俯仰角和方位角的测量值；也就是说,本发明是基于通道合并的双通道单脉冲测角方法,减少了接收机通道数,从而降低了体积、质量、功耗等硬件资源,更适用于小型一体化平台；进一步地,本发明通过引入参考信号,与和、差通道信号进行匹配滤波,解决了收发分置小型一体化平台非相参工作体制下,接收信号中脉冲间存在随机相位和非相参频率差带来的测角难题,使得不同脉冲间能够进行相参积累,大大提高了微弱目标的测角性能。(The invention provides a weak target double-channel single-pulse angle measurement method based on a reference signal, compared with the traditional three-channel single-pulse angle measurement algorithm, the method synthesizes an azimuth difference channel and a pitch difference channel into a path difference channel, and forms double channels with the sum channel for signal processing to obtain the measurement values of a pitch angle and an azimuth angle; that is to say, the invention is a two-channel single-pulse angle measurement method based on channel combination, which reduces the number of channels of a receiver, thereby reducing hardware resources such as volume, quality, power consumption and the like, and being more suitable for a small-sized integrated platform; furthermore, the invention solves the angle measurement problem caused by random phase and non-coherent frequency difference between pulses in the received signal under a non-coherent working system of a transceiving split small-sized integrated platform by introducing the reference signal and performing matched filtering with the sum channel signal and the difference channel signal, so that coherent accumulation can be performed between different pulses, and the angle measurement performance of a weak target is greatly improved.)

1. A weak target double-channel single-pulse angle measurement method based on a reference signal is characterized by comprising the following steps:

s1: the receiver receives a reference signal and a plurality of echo pulses sent by a transmitter, wherein the echo pulses comprise a sum signal, a pitch difference signal and a azimuth difference signal, and then the following steps are respectively carried out on each echo pulse:

s11: the pitch difference signal is processedPhase shifting, and performing orthogonal synthesis on the pitch difference signal and the azimuth difference signal after phase shifting to obtain a synthesized difference signal;

s12: respectively preprocessing a reference signal, a sum signal and a synthesized difference signal to obtain a preprocessed reference signal, a preprocessed sum signal and a preprocessed synthesized difference signal, wherein the preprocessing comprises orthogonal down-conversion and low-pass filtering;

s13: taking the preprocessed reference signal as a matched filter, and respectively performing matched filtering on the preprocessed sum signal and the synthesized difference signal to obtain a matched filtered sum signal and a synthesized difference signal;

s2: performing inter-pulse coherent accumulation on the matched and filtered sum signal and the synthesized difference signal corresponding to each echo pulse respectively to obtain a coherent accumulated sum signal and a synthesized difference signal;

s3: judging whether the maximum peak value of the sum signal after the coherent accumulation exceeds a set threshold, if so, calculating the estimated value of the first intermediate variable theta according to the synthetic difference signal value corresponding to the position of the maximum peak value and the maximum peak value of the sum signalSpecifically, the method comprises the following steps:

wherein the content of the first and second substances,of sum signalsThe maximum peak value of the peak value is,is the modulo square of the maximum peak of the sum signal,for the resulting difference signal value corresponding to where the maximum peak of the sum signal is located,the modulo square of the composite difference signal value corresponding to the position of the maximum peak of the sum signal, μ being the difference slope of the receiver antenna;

s4: according to the maximum peak value of the sum signalWith corresponding combined difference signal valueCalculating a second intermediate variableIs estimated value ofSpecifically, the method comprises the following steps:

wherein the content of the first and second substances,is the maximum peak value of the sum signalThe real part of (a) is,is composed ofThe real part of (a) is,is the maximum peak value of the sum signalThe imaginary part of (a) is,is prepared byAn imaginary part;

s5: from an estimate of the first intermediate variableAnd an estimate of a second intermediate variableEstimate of azimuth α and pitch β are calculated:

wherein the content of the first and second substances,as an estimate of the azimuth angle α,is an estimate of pitch angle β.

Technical Field

The invention belongs to the technical field of radar measurement, and particularly relates to a weak target double-channel single-pulse angle measurement method based on a reference signal.

Background

For weak target angle measurement, the traditional single-pulse angle measurement technology can achieve the purpose of improving the angle measurement precision by adding an auxiliary channel and coherent accumulation.

In the text "radio Measurement Extraction in the present of sea-Surface Multipath" published by IEEE Transactions on Aero-space and Electronic Systems 39, vol.2, 550-567, A.Sinha et al, an algorithm capable of overcoming the angle Measurement error caused by the specular reflection and diffuse reflection in the Multipath effect is proposed, thereby improving the angle Measurement accuracy. In the article "Amplitude Angle monitoring for the Four-channel Hybrid polar radio System" published by IEEE Antennas and Wireless Provisioning letters, volume 16, pages 2889 and 2893, Yi Zhang et al, a method for further improving the Angle measurement precision by adding a differential channel is proposed. However, the common defects of the above algorithms are that under the condition of low signal-to-noise ratio, good angle measurement performance cannot be obtained, and meanwhile, the algorithm has high operation complexity.

On the other hand, in IEEE Transactions on Signal Processing volume 62, No. 4, No. 939-953, and "Maneuvering Target Detection radio-FractionFourier Transform-Based Long-Time Coherent Integration" published by Xiaoolong Chen et al, a new Coherent accumulation method, namely, Radon fractional domain Fourier Transform, is proposed, which can avoid the influence of distance migration in the Long-Time accumulation process of weak targets. In the publication of "Coherent Accumulation Technology for Space target amplification" published by International Symposium on photovoltaic Detection and amplification, Junhai Su et al in 2011, a method for realizing Coherent Accumulation by correcting distance walking by Keystone transformation is proposed.

However, the single pulse angle measurement technology has the problems of low angle measurement precision and incapability of realizing coherent accumulation under the condition that a non-coherent frequency difference and a random initial phase exist between received echo pulses by adopting a non-coherent working system with a transmitting and receiving split device aiming at a small integrated platform shared by a transmitting source.

Disclosure of Invention

In order to solve the problems, the invention provides a weak target two-channel single-pulse angle measurement method based on a reference signal, which combines an azimuth difference channel and a pitch difference channel into a path difference channel, can reduce the number of channels of a receiver, reduce hardware resources such as volume, quality and power consumption, and is more suitable for a small-sized integrated platform.

A weak target double-channel single-pulse angle measurement method based on a reference signal comprises the following steps:

s1: the receiver receives a reference signal and a plurality of echo pulses sent by a transmitter, wherein the echo pulses comprise a sum signal, a pitch difference signal and a azimuth difference signal, and then the following steps are respectively carried out on each echo pulse:

s11: the pitch difference signal is processedPhase shifting, and performing orthogonal synthesis on the pitch difference signal and the azimuth difference signal after phase shifting to obtain a synthesized difference signal;

s12: respectively preprocessing a reference signal, a sum signal and a synthesized difference signal to obtain a preprocessed reference signal, a preprocessed sum signal and a preprocessed synthesized difference signal, wherein the preprocessing comprises orthogonal down-conversion and low-pass filtering;

s13: taking the preprocessed reference signal as a matched filter, and respectively performing matched filtering on the preprocessed sum signal and the synthesized difference signal to obtain a matched filtered sum signal and a synthesized difference signal;

s2: performing inter-pulse coherent accumulation on the matched and filtered sum signal and the synthesized difference signal corresponding to each echo pulse respectively to obtain a coherent accumulated sum signal and a synthesized difference signal;

s3: judging whether the maximum peak value of the sum signal after the coherent integration exceeds the maximum peak valueSetting a threshold, if the sum signal exceeds the threshold, calculating the estimated value of the first intermediate variable theta according to the combined difference signal value corresponding to the position of the maximum peak value and the maximum peak value of the sum signalSpecifically, the method comprises the following steps:

wherein the content of the first and second substances,is the maximum peak value of the sum signal,is the modulo square of the maximum peak of the sum signal,for the resulting difference signal value corresponding to where the maximum peak of the sum signal is located,the modulo square of the composite difference signal value corresponding to the position of the maximum peak of the sum signal, μ being the difference slope of the receiver antenna;

s4: according to the maximum peak value of the sum signalWith corresponding combined difference signal valueCalculating a second intermediate variableIs estimated value ofSpecifically, the method comprises the following steps:

wherein the content of the first and second substances,is the maximum peak value of the sum signalThe real part of (a) is,is composed ofThe real part of (a) is,is the maximum peak value of the sum signalThe imaginary part of (a) is,is prepared byAn imaginary part;

s5: from an estimate of the first intermediate variableAnd an estimate of a second intermediate variableEstimate of azimuth α and pitch β are calculated:

wherein the content of the first and second substances,as an estimate of the azimuth angle α,is an estimate of pitch angle β.

Has the advantages that:

the invention provides a weak target double-channel single-pulse angle measurement method based on a reference signal, compared with the traditional three-channel single-pulse angle measurement algorithm, the method synthesizes an azimuth difference channel and a pitch difference channel into a path difference channel, and forms double channels with the sum channel for signal processing to obtain the measurement values of a pitch angle and an azimuth angle; that is to say, the invention is a two-channel single-pulse angle measurement method based on channel combination, which reduces the number of channels of a receiver, thereby reducing hardware resources such as volume, quality, power consumption and the like, and being more suitable for a small-sized integrated platform;

furthermore, the invention solves the angle measurement problem caused by random phase and non-coherent frequency difference between pulses in the received signal under a non-coherent working system of a transceiving split small-sized integrated platform by introducing the reference signal and performing matched filtering with the sum channel signal and the difference channel signal, so that coherent accumulation can be performed between different pulses, and the angle measurement performance of a weak target is greatly improved.

Drawings

Fig. 1 is a flowchart of a weak target two-channel single-pulse angle measurement method based on a reference signal according to the present invention.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

Fig. 1 is a flowchart of a weak target two-channel single-pulse angle measurement method based on a reference signal according to the present invention. The following takes a single-frequency signal modulated by pulses as an example to explain the invention in detail, and specifically includes the following steps:

s1: the receiver receives a reference signal and a plurality of echo pulses transmitted by the transmitter, wherein the echo pulses comprise a sum signal U_ΣPitching difference signal U_βAnd azimuth difference signal U_αThen, steps S11 to S13 are performed for each echo pulse, respectively, and further, the sum signal U_ΣAzimuth difference signal U_αPitching difference signal U_βAnd the reference signal may be expressed as:

where A is the received signal amplitude, A_rFor reference signal amplitude, ω is the angular frequency of the received signal, ω_rFor the transmit signal angular frequency, τ is the target echo delay, φ_0kRepresents the initial phase of the k-th pulse, andφ_0kα and β are azimuth and elevation angles, respectively, mu is the antenna difference slope,is represented by T_pIs a pulse width rectangular pulse.

The steps S11-S13 are as follows:

s11: the pitch difference signal is processedShifting the phase and communicating the shifted pitch differenceOrthogonal synthesis is carried out on the signal and the azimuth difference signal to obtain a synthesis difference signal U_Δ；

In the formula (I), the compound is shown in the specification,from the above formula, the azimuth α and the pitch β information of the target are contained in the single-path composite difference signal U_ΔIn amplitude and phase, and thus, can be applied to U_ΔSignal processing is performed to estimate azimuth α and pitch β information.

S12: respectively preprocessing a reference signal, a sum signal and a synthesized difference signal to obtain a preprocessed reference signal, a preprocessed sum signal and a preprocessed synthesized difference signal, wherein the preprocessing comprises orthogonal down-conversion and low-pass filtering;

specifically, the reference signal, the sum signal and the synthesized difference signal are respectively subjected to quadrature down-conversion and low-pass filtering, for simplification, I, Q two paths of the sum signal, the difference signal and the reference signal can be synthesized into a complex signal form, and then the result after preprocessing the reference signal, the sum signal and the difference signal corresponding to the kth echo pulse can be represented as:

wherein, ω is_dRepresenting the Doppler angular frequency of the target, Δ ω representing the non-coherent frequency difference between the transmitting source and the receiving device, n_r(t) reference signal channel observation noise, n_∑(t) is the sum signal path observation noise, n_Δ(t) observed noise for the difference signal path。

S13: taking the preprocessed reference signal as a matched filter, and respectively performing matched filtering on the preprocessed sum signal and the synthesized difference signal to obtain a matched filtered sum signal and a synthesized difference signal;

specifically, the preprocessed reference signal corresponding to the kth echo pulse is used as a matched filter to perform matched filtering on the preprocessed sum signal and the preprocessed composite difference signal, so that the influence of non-coherent frequency and initial phase change can be eliminated. The matched filtering process can be expressed in the form of time domain convolution, and the processing result is as follows:

wherein the content of the first and second substances,represents convolution operation, represents conjugate transpose; it should be noted that since the reference signal does not contain doppler frequency information, the doppler frequency is not eliminated from the sum and difference signals.

S2: performing inter-pulse coherent accumulation on the matched and filtered sum signal and the synthesized difference signal corresponding to each echo pulse respectively to obtain a coherent accumulated sum signal and a synthesized difference signal;

after matching and filtering, the sum and difference signals are subjected to pulse coherent accumulation to improve the signal-to-noise ratio, so that the angle measurement precision is improved; coherent accumulation may be achieved by Fourier transform (FFT), which may be denoted as

Wherein the content of the first and second substances,for the sum signal after the coherent integration,is the synthesized difference signal after coherent accumulation.

S3: judging whether the maximum peak value of the sum signal after the coherent accumulation exceeds a set threshold, if so, calculating the estimated value of the first intermediate variable theta according to the synthetic difference signal value corresponding to the position of the maximum peak value and the maximum peak value of the sum signalSpecifically, the method comprises the following steps:

wherein the content of the first and second substances,is the maximum peak value of the sum signal,is the modulo square of the maximum peak of the sum signal,for the resulting difference signal value corresponding to where the maximum peak of the sum signal is located,the modulo square of the composite difference signal value corresponding to the position of the maximum peak of the sum signal, μ being the difference slope of the receiver antenna;

specifically, the maximum value is selected from the accumulated sum signals, and echo time delay information and doppler shift information corresponding to the target are obtained, which are expressed as:

if K echo pulses are received and K frequency points are obtained by performing FFT (coherent accumulation) on the K echo pulses, then^k _mThe frequency point where the maximum peak value is located is referred to; echo time delay t at maximum peak_mCan be converted into distance information of a target, and a Doppler frequency point k_mIt represents the doppler frequency resulting from the motion of the object. Different from the traditional three-channel single-pulse angle measurement method, because the Doppler resolution is limited (related to the number of accumulated pulses), in order to eliminate the phase estimation error caused by the Doppler frequency shift measurement residual error, the sum signal and the difference signal can be used for eliminating the Doppler frequency information:

wherein G is the total gain of matched filtering and coherent accumulation,andthe processed I, Q two-path noise signal is obtained.

Expression (13) for obtaining the estimated value of θ from the coherent-accumulated sum signal selected by expression (14) and the resultant difference signal corresponding to the maximum peak value and the position thereof.

S4: according to the maximum peak value of the sum signalWith corresponding combined difference signal valueCalculating a second intermediate variableIs estimated value ofSpecifically, from equations (15) and (16), derived I, Q signals with doppler information removed can be obtainedIs estimated value ofExpression (c):

wherein the content of the first and second substances,is the maximum peak value of the sum signalThe real part of (a) is,is composed ofThe real part of (a) is,is the maximum peak value of the sum signalThe imaginary part of (a) is,is prepared byAn imaginary part;

s5: from an estimate of the first intermediate variableAnd an estimate of a second intermediate variableEstimate of azimuth α and pitch β are calculated:

wherein the content of the first and second substances,as an estimate of the azimuth angle α,is an estimate of pitch angle β.

Therefore, the invention aims to provide a dual-channel angle measuring method which can be applied to the conditions that the frequency between a transmitting source and receiving equipment is not coherent and the initial phase between receiving pulses is inconsistent; the method comprises four stages of quadrature synthesis of difference signals, quadrature down-conversion and low-pass filtering, matching filtering based on reference signals and coherent accumulation.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it will be understood by those skilled in the art that various changes and modifications may be made herein without departing from the spirit and scope of the invention as defined in the appended claims.