Nonlinear Frequency Modulation Signal Generator in LT-1

• Published in: IEEE geoscience and remote sensing letters Vol. 16; no. 10; pp. 1570 - 1574
• Main Authors: Jin, Guodong, Liu, Kaiyu, Deng, Yunkai, Sha, Yu, Wang, Robert, Liu, Dacheng, Wang, Wei, Long, Yajun, Zhang, Yongwei
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.10.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Compensation; Complexity theory; Error compensation; Field programmable gate arrays; Frequencies; Frequency dependence; Frequency modulation; Image resolution; Matrix decomposition; Noise levels; Nonlinear frequency modulation (NLFM) signal; Power spectral density; SAR (radar); Sidelobe reduction; Sidelobes; Signal generation; signal generator; Signal generators; Signal to noise ratio; Synthetic aperture radar; synthetic aperture radar (SAR)
• ISSN: 1545-598X; 1558-0571
• DOI: 10.1109/LGRS.2019.2905359

Generally, synthetic aperture radar (SAR) system transmits linear frequency modulation (LFM) signal to obtain the high-resolution image and weighted windowing is usually employed to suppress sidelobes. However, it will cause a 1-2-dB signal-to-noise ratio (SNR) loss. Nonlinear frequency modulation (NLFM) signal, which can construct the signal's power spectral density (PSD) to reduce sidelobes without loss of SNR, is a promising candidate. However, the real-time generation of precise NLFM signal is still a technical challenge. In this letter, a high-precision NLFM signal generator with the ability of predistortion compensation is developed, and this signal generator will be employed in LuTan-1 (LT-1, i.e., TwinSAR-L) mission which is an innovative spaceborne bistatic SAR mission and planned to launch in 2020. In addition, a two-step error compensation method is developed to compensate the system error. Finally, the ground experiment is performed to validate the designed signal generator.