Design of high resolution radar waveforms for target detection

Abstract

This thesis presents the design strategies of frequency coded waveforms for High-Resolution Radar (HRR) applications which can improve the probability of detection and resolution of closely spaced targets in multitarget as well as in multiuser environments. Investigations have been carried out using different Discrete Frequency Coded Waveform (DFCW) sequences, implementing - Optimization Criteria, Algebraic Construction Methods, novel Modified Pushing Sequence (MPS) Technique involving Lee Code Words and Linear Congruence (LC) Codes, for obtaining excellent autocorrelation characteristics as well as desired cross-correlation features. A classic adaptive waveform design that combines the advantageous features of Linear Frequency Modulation (LFM) and Linear Congruence Modified Pushing Sequence (LC-MPS) for modern HRR applications is also suggested.In optimization approach, a New Hybrid Algorithm (HA) is used to obtain impulse like autocorrelation function and thumbtack like Ambiguity Function (AF) of DFCW sets, which could be employed in a multi radar environment. The HA combines the desirable features of Threshold Accepting (TA) Algorithm and Hamming Scan (HS) Algorithm is proposed and used for the optimization of DFCW sets. The optimized DFCW sequence sets exhibit near ideal thumbtack AF and desirable cross-correlation properties, which may be used in multiple target environments as well as in multiuser/netted radar systems. Frequency coded sequence sets of different lengths N, varying from 25 to 300 have been optimized. Each sequence length N consists of three random waveforms in a set (L = 3). Use of optimized sequences resulted in an improved sidelobe level suppression near mainlobe (as much as 8.1 dB for N = 25 to 3.5 dB for N = 300), which is much better than the results obtained in the literature {the sidelobe level being approximately L/N as obtained from the use of Simulated Annealing (SA) Algorithm approach}.