The present paper proposes a novel technique to reduce the peak side lobe ratio (PSLR) in the time waveform of the synthetic aperture radar (SAR) pulse. The dependence of the instantaneous frequency on the time over the SAR pulse duration is formulated as an arbitrarily shaped piecewise linear (PWL) curve. The slopes of the linear segments of this curve are optimized to get the minimum PSLR of the received radar echo at the output of the SAR receiver. The particle swarm optimization (PSO) method is used to optimize the shape of the time-frequency curve to achieve the dual-objective of minimizing the PSLR of the received SAR echo and to realize the required pulse compression ratio (PCR). The slopes of the linear segments of the time-frequency curve are the control parameters that determine the position of each particle in the swarm. The proposed method can be considered as an optimized form of non-linear frequency modulation (NLFM) for SAR pulse compression. It is known that the conventional NLFM using second-order time-frequency curve results in a PSLR of -18 dB. The proposed method results in a PSLR of -45.6 dB and achieves a range resolution of 1.4 m. The developed PSO algorithm is shown to be computationally efficient and its iterations are fastly convergent such that a few iterations are enough to arrive at the steady state of the cost function. Finally, a SAR transceiver is proposed as a software-defined radio (SDR) in which the proposed SAR pulse compression technique is employed in the transmitter to generate the transmitted pulse and in the receiver to construct the transfer function of the matched filter (MF).
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