Study On Accelerating Target Detection And Tracking

Improved detection and tracking performance of maneuvering targets in the modern radar system is a forefront and urgent task within the radar domain. Under the background of missile defense, time-frquency representations is applied to accelerating target dedetcion, and acceleration is measured directly from echo signals, then the acceleration measurements is introduced in target tracking.1) Detection performance, estimation accuracy, and resolution is analyzed when LFM signals is processed by the fractional Fourier transform(FRFT). The FRFT of a finite duration LFM signal is derived, and the coordinates of its amplifude peak in fractional Fourier domain are determined, then the relation between the coordinates and the unknown parameters of a LFM signal are given. so the FRFT is appropriate to process LFM signals of unknown parameters. From the point of view of output Signal-to-Noise Ratio(SNR), detection preformance of an unknown parameter LFM signal based on FRFT is analyzed, and in the condition of high SNR only lower 3dB to the output SNR of matched filter of ideal situation (i.e. parameters of LFM signal are known). From the point of view of parameter measurement accuracy, the expressions for root mean square of estimation error of LFM signal parameters are derived by a first order perturbation analysis approach. Results show that the method is optimal in the sense of estimation accuracy. From the point of view of resolution, the frequency resolution, the frequency rate resolution and the united frequency and frewuency rate resolution. Results show that the method is optimal in the sense of resolution. So the FRFT is effective to process LFM signals of unknown parameters.2) Detection performance of an accelerating target based on Wigner-Hough transform is analyzed. The relations between the output amplitude of the two most widely applied dicrete forms of FRFT and acceleration, pulse number are analyzed, results show that there is not an ideal discrete form which possesses properties of continuous FRFT though the discrete forms exit a lot. Because the identical relation between of the square of magnitude of FRFT and Wigner-Hough transform, Wigner-Hough transform is adopted to accelerating targets detection and parameter measurement. For single threshold and double detection thresholds cases, detection performance of LFM signals based on Wigner-Hough transform is analyzed in theory, and expressions for PF and PD, as a function of the number of accessible Hough space accumulator cells and detection threshold, is derived, which provide a basis for setting radar detection threshholds. Finally comparison of detection performance of based on Fourier transform and based on Wigner-Hough transform is made, and comparison of detection performance of different Swerling fluctuating targets is also made, which provide a reference to estimate the radar operating range for a fluctuating target.3) The algorithm of parameters estimation of an accelerating target based on Wigner-Hough transform is proposed. The algorithm of estimating radical acceleration based on Wigner-Hough transform is studied, and estimation flow is provided. The impact of observation interval on radial acceleration resolution is analyzed. Simulation is carried out and results verify its efficiency.4) The tracking filter design and tracking performance evaluation is studied when acceleration measurements are incorporated into the tracking filter. According to the non-recursive solution for the discrete Riccati equation, a closed-form steady-state solution is derived for a three-state Kalman filter which estimates the range, range rate and range acceleration when range, range rate and range acceleration are measured, and a new normalization of the steady-state covariance is introduced. Constant gain filter design is studied according to the steady-state solution, and ultimate performance is given by numerical analysis when measurements accuricies tend to infinitely high. Tracking a target in clutter is taken to a situation with measurement origin uncertainty, and the tracking performance is analyzed when velocity measuremrents, and furthermore acceleration measurements are incorporated into the tracking filter. Results show that whether in clutter or not, lower steady state tracking errors and earlier attainment of steady state accuricies are the direct consequence when acceleration measurements are incorporated into the tracking filter.The results of this thesis are beneficial not only to improve detection and tracking performance of the missile defense radar for maneuvering reentry warhead, but also to study penetration technologies and penetration effectiveness evaluation.