Thumbtack (Ideal) ambiguity function shape makes Costas coded signal renowned and effective in Radar pulse compression, though Linear Frequency Modulation (LFM) waveform is the utmost used in practical radar and sonar systems. The paramount drawback in LFM is the first side-lobe level at -13dB to the peak of mainlobe of the compressed waveform at the receiver side. A weighting function is desired to reduce the side-lobe with a forfeit of mismatch loss which may reduce output Signal-to-Noise-Ratio (SNR) usually by 1 to 2dB. This bitty change in SNR value can precipitate the erroneous target detection. To procure less side-lobe levels without availing weighting function, a new Non-Linear Frequency (NLFM) signal is examined. In this paper, piecewise linear frequency modulation with sweep rate defined by Costas code in each sub-pulse is developed to produce an overall novel non-linearity and their effect on side-lobes are studied. The Matlab simulation results of the proposed waveform are presented and results are compared with the normal Costas signal. Side-lobe reduction of -41.66 dB can be achieved by this proposed waveform without applying any weighting function.
Volume 11 | 08-Special Issue
Pages: 2459-2466