Suppression of Spur Chirps for Fractional-N PLL-Based Heterodyne FMCW SAR
| Autor: | Michael Inggs, Mohammed Yunus Abdul Gaffar, D. Jordan |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Heterodyne
Synthetic aperture radar Masking (art) Radiation Computer science Acoustics 020206 networking & telecommunications 02 engineering and technology Condensed Matter Physics Noise floor law.invention Phase-locked loop law 0202 electrical engineering electronic engineering information engineering Chirp ComputerSystemsOrganization_SPECIAL-PURPOSEANDAPPLICATION-BASEDSYSTEMS Electrical and Electronic Engineering Radar Frequency modulation |
| Zdroj: | IEEE Transactions on Microwave Theory and Techniques. 69:409-417 |
| ISSN: | 1557-9670 0018-9480 |
| Popis: | Fractional-N phase-locked loops (PLLs) offer a low-cost solution to the precision frequency ramp requirements of frequency-modulated continuous-wave (FMCW) radar. Regrettably, however, these PLLs are known to produce undesirable spurii in their synthesized output. A subset of these spurii has recently been shown to manifest as frequency chirps, also known as spur chirps , in the deramped beat signal. These so-called spur chirps give rise to Fresnel ripples in the range domain after standard Fourier processing. Spur chirps are of particular concern for heterodyne receiver systems because the Fresnel ripples may appear at levels that far exceed the noise floor. In this article, the authors present guidelines for the avoidance of spur chirps and identify existing interference suppression techniques that are transferable to this problem. Furthermore, the authors put forward a novel technique termed range-Doppler spur masking (RDSM) that was designed specifically for the suppression of spur chirps. The developed technique was applied to both the simulated and measured synthetic aperture radar (SAR) data. Simulations reveal that RDSM significantly outperforms time-domain zeroing in terms of peak sidelobe ratio (PSLR) and other metrics. When applied to the measured data, RDSM is shown to eliminate the effects of the spur chirps in SAR imagery when masking only 0.15% of the available Doppler bins. |
| Databáze: | OpenAIRE |
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