Low-elevation-angle direction-of-arrival estimation method based on time reversal

Abstract

The invention discloses a low-elevation-angle direction-of-arrival estimation method based on time reversal. The method comprises the steps of determining an antenna array A which comprises M array elements, transmitting a forward detecting signal by the antenna array A, transmitting the forward detecting signal to the antenna array A after target scattering, obtaining a forward echo time domain signal Yn(t) which is transmitted back after target scattering by an n-th array element in the antenna array A, calculating a time reversal receiving signal yn(t) of the n-th array element in the antenna array and furthermore calculating a covariance matrix RY(omegaq) of the time reversal frequency domain receiving signal at a sampling frequency point omegaq of the n-th array element in the antenna array A; performing bandwidth focusing on the RY(omegaq), successively calculating a focused covariance matrix RY(omega0) of the n-th array element at the bandwidth focusing frequency omega0 and a focused smoothing matrix {RY(omega0)}SS of the n-the array element at the bandwidth focusing frequency omega0, calculating a spatial spectrum function S(theta) of the n-th array element in the antenna array A, and furthermore calculating H maximal values of the spatial spectrum function S(theta) of the n-th array element in the antenna array A, wherein the angle which corresponds with each maximal value is the direction-of-arrival.

Description

technical field [0001] The invention belongs to the technical field of signal processing, and in particular relates to a method for estimating the direction of arrival at low elevation angles based on time inversion, which is suitable for estimating the direction of arrival of coherent targets at low elevation angles, thereby realizing target positioning and tracking. Background technique [0002] The DOA estimation of the direction of arrival is an important research direction in radar and sonar signal processing. The low-elevation DOA estimation problem in low-altitude target detection has always been a research hotspot in the field of DOA estimation; because under the condition of low elevation angle, complex terrain will produce A large number of multipath signals and the aliasing of multipath signals and direct wave signals make it difficult to extract target information and estimate DOA. At home and abroad, the existing DOA estimation models that use the direct wave as...

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Problems solved by technology

[0002] The DOA estimation of the direction of arrival is an important research direction in radar and sonar signal processing. The low-elevation DOA estimation problem in low-altitude target detection has always been a research hotspot in the field of DOA estimation; because under the condition of low elevation angle, complex terrain will produce A large number of multipath signals, multipath signals and direct wave signals are mixed together, making target information extraction and DOA estimation difficult

[0004] (1) Maximum likelihood method based on accurate signal model: This method uses prior information such as antenna height, target height, distance between target and radar, earth curvature, atmospheric refraction, etc., fully considers the influence of multipath signals, and establishes an accurate multipath signal reflection model to reduce the number of parameters to be estimated and improve the accuracy of parameter estimation; due to the complexity of the actual situation, the reflection angle and reflection coefficient are often not accurate or even obtainable, so this method has poor adaptability to the environment. This greatly limits the application of this method

[0005] (2) Equivalent DOA estimation model method based on terrain matching: Specifically, this method first explores the terrain confidence, and then establishes the corresponding terrain information table; before the measurement, the line performs terrain matching operation, and establishes the corresponding The equivalent DOA estimation model for DOA estimation; Chen Boxiao and Zhu Wei discussed in detail in "Altitude measurement based on terrain matching in VHF array radar" published in Circuits System Signal Process, Volume 32, Issue 2, Page 647–662, 2013 Terrain matching algorithm, and applied this method to the field of meter-wave radar altimetry; however, this method has a defect, that is, in the actual radar target detection process, the terrain information is very complicated and not completely known, so the complete matching of the terrain cannot be guaranteed , which limits the application of this method in complex environments

[0006] (3) DOA estimation method based on the comprehensive modeling of the reflected signal of the direct wave signal: this algorithm comprehensively models the reflected signal of the direct wave signal, and synthesizes the steering vectors of the two to obtain the DOA estimation model, and then performs DOA estimation; The accuracy of the method model is closely related to the accuracy of the incident angle and reflection angle; in complex terrain, the multipath information is very complicated, and it is usually impossible to accurately know the reflected signal information, which will inevitably lead to a certain degree of model mismatch, and then the estimation of DOA Performance has an impact

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