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13 September 2004 Spectral estimation of Doppler spread vibrating targets using coherent ladar
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Abstract
Coherent laser radars observing a resolved (larger than the incident laser mode) target vibrating surface can estimate the target's piston-mode displacement motion from the target's Doppler produced frequency spectrum. We review recent work showing that a newly developed joint time-frequency transform algorithm is superior to older joint time-frequency transforms, the common short-time-Fourier transform (spectrogram) algorithm, and other elementary spectral estimation algorithms for resolving the target's spectra. In this paper we extend these approaches when the ladar is observing an unresolved (smaller than the incident laser mode) piston-mode vibrating object situated on the ground. Because the target is smaller than the laser spot, the surrounding ground produces a narrow-band constant frequency "clutter" signal at the baseband frequency. We show that a recently developed "sech-window" joint time-frequency transform is superior to other algorithms for separating the frequency modulated target piston motion signal from the narrow-band ground return. The analysis in this case includes a "signal-to-clutter ratio" (SCR) parameter variation as well as a "carrier-to-noise ratio" (CNR), or target signal strength to LO-laser noise strength, parameter variation.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Douglas G. Youmans "Spectral estimation of Doppler spread vibrating targets using coherent ladar", Proc. SPIE 5412, Laser Radar Technology and Applications IX, (13 September 2004); https://doi.org/10.1117/12.560983
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