Target Detection With LFMCW Radar Using Subband Technique

Low probability of intercept(LPI)radar usually adopts continuous waveform(espe-cially the linear-frequency-modulated continuous wave)with large time-bandwidth prod-uct and pulse compression techniques to make itself stealthy,which results in high range resolution performance.For applications like maritime law enforcement operations,LPI radar can resolve large targets' isolated scattering centres into different range cells on the range profile.Conventional detection strategies for point-like target are not capable for range distributed target,whose energy is dispersed along the range profile.The study on detection strategies for range distributed target in LPI scenarios is of great importance to the tactical performance of LPI radar.This thesis studies the detection of range distributed target with the help of LPI radar,which adopts linear-frequency-modulated continuous waveform.Firstly,the characteris-tics of range distributed target's echo is analysed and the model of range distributed target is formulated.On the basis above,the single-period and multi-period detection strategies for range distributed target based on subband technique are discussed,aiming at com-pensating the performance degradation caused by non-idealized primary data and range walking,respectively.The detailed work includes:(a)The echo model of range distributed target based on scattering centre theory is formulated;the expression of target's echo of sawtooth frequency-modulated continuous-wave radar with homodyne structure is derived;the formulation of binary hypotheses test for low-speed and high-speed targets are given.(b)Current range distributed target detectors use idealized primary data.To over-come this problem,an order-statistic-based subband detector for single-period distributed target detection is purposed,without the process to extract primary data.The order statis-tics theory is introduced into the design of the detector to improve the detection perfor-mance.This thesis proves that its design guarantees the bounded constant alarm false rate,and the closed form expression of false alarm probability for single-channel detector is derived.The performance assessment conducted by Monte Carlo simulations confirms the effectiveness and robustness of the proposed detector,compared with other detectors in single-pulse detection scenarios.(c)Current range distributed target detectors usually ignore the range walking of moving target.A multi-period subband joint detector is purposed to overcome this prob-lem.Range walking is suppressed by decreasing the resolution of subbands.The mod-ified expression of steering vector is derived.This thesis proves that in homogeneous Gaussian environment,the purposed detector is invariant to the scaling and rotation of steering vector and the structure of background noise.The performance assessment con-ducted by Monte Carlo simulations confirms its robustness for statical and moving tar-gets,without the performance loss caused by range walking.