Abstract
Background/Objectives: The design of appropriate Non-Linear Frequency Modulation (NLFM) signals continues to be the focus of research in radar pulse compression theory for sidelobe reduction. This study focuses on a heuristic design and optimization algorithm to optimize the side lobe values of the NLFM signal designed using two-piece wise linear frequency modulation (LFM) functions. Methods: 1) Heuristic search identifies the optimum B1, T1, and B2, T2, which yield the lowest sidelobe value of the designed function.2) Compute all the side lobe values of the designed NLFM signal using an algorithm developed in Python scripting language. To plot a complete contour map for all the calculated side lobe values, which helps identify the associated variations in the range of side lobe values. Finally, optimize the side lobe values keeping the main lobe width and time-bandwidth (BT) product unchanged by designing a dynamic optimization algorithm. Findings: The algorithm developed considered all side lobe levels after the main lobe for optimization. The focus is mainly on the peak sidelobe ratio (PSLR) value without affecting the other parameters. The results demonstrate that the achieved side lobes exhibit their desired levels. Novelty: The method is useful in all types of hardware associated with weather radar applications to military solutions. The technique can be extended to other multistage signals consisting of piecewise linear Segments. Keywords: Contour; LFM; NLFM; optimization; PSLR
Highlights
In modern radar systems, radar waveform design based on complex signal and pulse compression is vital for better detectability and range resolution
Many studies focused on NonLinear Frequency Modulation (NLFM) waveforms as they suppress sidelobe
Whether the optimization of two-stage linear frequency modulation (LFM) yields NLFM with better peak sidelobe ratio (PSLR) values can be examined
Summary
Radar waveform design based on complex signal and pulse compression is vital for better detectability and range resolution. The autocorrelation of the designed function should have a low peak sidelobe ratio (PSLR) values and narrow main lobe width. Whether the optimization of two-stage linear frequency modulation (LFM) yields NLFM with better PSLR values can be examined. G. Jin et al,(10) used Augmented Lagrangian Genetic Algorithm (ALGA) for optimization of NLFM waveform and achieved lower sidelobes and narrow main lobe width. Jin et al,(10) used Augmented Lagrangian Genetic Algorithm (ALGA) for optimization of NLFM waveform and achieved lower sidelobes and narrow main lobe width They proposed a modified NLFM generation method based on the principle of stationary phase (POSP)(11). The NLFM waveform designed using two-piece wise LFM signals[12,13,14] is optimized to obtain a low sidelobe level under a limitation of the time-bandwidth product. This function’s best possible solution is achieved for B1=2MHz, T1=3μs, and B2=18MHz, T2=7μs with PSLR of -21.99 dB
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