19 May 2005 Mitigation of complex target Doppler aliasing artifacts in SAR imagery using stepped-frequency waveforms
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Abstract
Traditional high resolution Synthetic Aperture Radar (SAR) systems operate by placing a narrow transmit beam on a given ground patch for an extended time period. An alternate method of achieving high resolution is to increase the beamwidth. This approach allows both high resolution and large coverage areas, but increases the Doppler spread of the clutter echoes and therefore the required Pulse Repetition Frequency (PRF). Unfortunately, the required PRF for avoiding Doppler aliasing can become impractical rather quickly. This paper begins by introducing a recently proposed technique for mitigating these Doppler aliasing artifacts using continuous transmission of Stepped-Frequency (SF) waveforms. By randomizing the subpulse frequency order on a waveform-to-waveform basis, matched filter processing has been shown to build a composite ambiguity function which places Doppler filter nulls on top of Doppler aliasing artifacts, effectively removing them from the imagery. Using Xpatch radar scattering data of a backhoe, this technique is demonstrated for the first time using a non-point scatterer target. The 2-D spatial frequency data is used to produce uncompressed target echoes of randomized SF waveforms. A Doppler mismatch is applied to simulate the return from an aliased target. By applying the appropriate filter to the SF echoes, the aliased target is eliminated, dropping the peak of the aliased energy by nearly 40 dB.
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Jonathan E. Luminati, Jonathan E. Luminati, Todd B. Hale, Todd B. Hale, Michael J. Havrilla, Michael J. Havrilla, } "Mitigation of complex target Doppler aliasing artifacts in SAR imagery using stepped-frequency waveforms", Proc. SPIE 5808, Algorithms for Synthetic Aperture Radar Imagery XII, (19 May 2005); doi: 10.1117/12.606908; https://doi.org/10.1117/12.606908
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