Mitigation of Side-Lobes and Improved Image Estimation for MIMO Radar Employing OVSF Codes

In a radar system, the moving target analysis needs a higher-order of degree of freedom to estimate the location, speed, direction, size, and shape of the target. The presence of high side-lobes in the matched filter response may lead to blind target detection. This paper presents a multiple-input multiple-output (MIMO) radar framework which uses orthogonal variable spreading factor (OVSF) codes as a transmit waveform to mitigate side-lobes. The side-lobes behavior is observed in terms of auto-correlation peak side-lobe levels (ACPSL) and cross-correlation peak side-lobe levels (CCPSL) values for different combinations of transmitting antennas and sequence lengths. It is observed that OVSF based radar waveforms offer ACPSL and CCPSL values of -28.18 dB and -27.86 dB for the sequence of length 1024, respectively. Further, the performance is analyzed for synthetic aperture radar (SAR) imaging using maximum likelihood estimation (MLE) and Bayesian estimation methods by calculating the peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and normalized cross-correlation (NCC) values. It is observed that OVSF codes offer better image estimation for Bayesian estimation than P4 codes.