Transmit waveform design for bandwidth optimization and side lobes reduction in pulse compression radar

Abstract

In this thesis, the effectiveness of designed waveforms is checked in terms of parameters, peak side-lobe level (PSL), integrated side-lobe levels (ISL), cross-correlation side-lobes levels (CCL), time-bandwidth product (TBP), and relative main-lobe width. Three different methods are used for waveform design. In the first method, a comparative analysis of different polyphase codes is demonstrated. Using existing P4 polyphase code, a code is designed which gives significant reduction in PSL and ISL. Further, variations in PSL and ISL values are studied by applying several time-domain amplitude windows to the transmitting polyphase codes. In the second method, the 3 dB bandwidth of Legendre orthogonal polynomial (LOP) is compared. Starting with 1st order polynomial, the Auto-correlation function (ACF) performance is investigated for higher-order polynomials and the polynomial which offers wider 3 dB bandwidth with least side-lobes is chosen as the optimal waveform. In the third method, classical orthogonal polynomial cycles are modified for different order polynomials and the side-lobes behaviour is observed by the ACF response. The polynomial cycle modification depends upon the polynomial order. The modified polynomial which gives the highest PSL reduction is chosen as the proposed waveform for pulse compression technique. The modified polynomials give a significant reduction in PSL but at the loss of main-lobe width widening. Using the ambiguity function (AF), side-lobes and resolution behaviour of the designed waveforms are observed on the delay-Doppler plane. To facilitate this, two new waveforms, namely, code and Legendre sequence (L-seq) are designed. The code is produced by combining the shifted versions of code and the L-seq waveform is designed using LOP. The superiorities of the proposed waveforms are proven for PSL, ISL, and CCL parameters. newline