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Proceedings Paper

Phase-wrapping ambiguity in along-track interferometry
Author(s): Ross Deming; Roman Ilin; Matthew Best
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Paper Abstract

In a previous SPIE paper we described several variations of along-track interferometry (ATI), which can be used for moving target detection and geo-location in clutter. ATI produces a phase map in range/Doppler coordinates by combining radar data from several receive channels separated fore-and-aft (along-track) on the sensor platform. In principle, the radial velocity of a moving target can be estimated from the ATI phase of the pixels in the target signature footprint. Once the radial velocity is known, the target azimuth follows directly. Unfortunately, the ATI phase is wrapped, i.e., it repeats in the interval [-π, π], and therefore the mapping from ATI phase to target azimuth is non-unique. In fact, depending on the radar system parameters, each detected target can map to several equally-likely azimuth values. In the present paper we discuss a signal processing method for resolving the phase wrapping ambiguity, in which the radar bandwidth is split into a high and low sub-band in software, and an ATI phase map is generated for each. By subtracting these two phase maps we can generate a coarse, but unambiguous, radial velocity estimate. This coarse estimate is then combined with the fine, but ambiguous estimate to pinpoint the target radial velocity, and therefore its azimuth. Since the coarse estimate is quite sensitive to noise, a rudimentary tracker is used to help smooth out the phase errors. The method is demonstrated on Gotcha 2006 Challenge data.

Paper Details

Date Published: 23 May 2013
PDF: 13 pages
Proc. SPIE 8746, Algorithms for Synthetic Aperture Radar Imagery XX, 87460E (23 May 2013); doi: 10.1117/12.2015231
Show Author Affiliations
Ross Deming, Solid State Scientific Corp. (United States)
Roman Ilin, Air Force Research Lab. (United States)
Matthew Best, Air Force Life Cycle Management Ctr. (United States)

Published in SPIE Proceedings Vol. 8746:
Algorithms for Synthetic Aperture Radar Imagery XX
Edmund Zelnio; Frederick D. Garber, Editor(s)

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