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A high doppler tolerance and low side-lobe NLFM waveform optimization method for SAR application.

Kai Yao1,2, Chang Liu3,4

  • 1Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, 100094, China. yaokai20@mails.ucas.ac.cn.

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|November 14, 2025
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Summary

This study enhances Non-linear Frequency Modulation (NLFM) waveforms for Synthetic Aperture Radar (SAR) imaging. The optimized NLFM waveform improves Doppler tolerance while maintaining low side-lobes, enabling advanced SAR applications.

Keywords:
Doppler toleranceMulti-objective optimizationNon-linear frequency modulationSynthetic aperture radar

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Area of Science:

  • Radar systems engineering
  • Signal processing for remote sensing
  • Synthetic Aperture Radar (SAR) imaging

Background:

  • Non-linear Frequency Modulation (NLFM) waveforms offer reduced side-lobes in SAR without compromising SNR or requiring windowing.
  • Increasing complexity in SAR operational scenarios necessitates improved radar waveform performance.
  • A key limitation of NLFM waveforms is their restricted Doppler tolerance, hindering broader SAR applications.

Purpose of the Study:

  • To address the Doppler tolerance limitation of NLFM waveforms.
  • To propose a multi-objective optimization approach for enhancing NLFM waveform performance.
  • To improve the suitability of NLFM waveforms for diverse and advanced SAR imaging tasks.

Main Methods:

  • Utilized a Non-linear Frequency Modulation (NLFM) waveform model based on Fourier series.
  • Employed a multi-objective optimization strategy using the NSGA-II algorithm.
  • Applied Pareto optimal theory to fine-tune waveform parameters and manage design criteria conflicts.

Main Results:

  • The optimized NLFM waveform successfully maintained low side-lobe levels.
  • Significant improvements in Doppler performance were achieved with the optimized waveform.
  • Simulation results validated the effectiveness of the proposed NLFM waveform enhancement.

Conclusions:

  • The proposed multi-objective optimization approach effectively enhances NLFM waveforms for SAR.
  • The improved Doppler tolerance makes the optimized NLFM waveform suitable for advanced SAR imaging.
  • This advancement supports the development of more versatile and high-performance SAR systems.