Wavefront curvature correction for radar imaging in a degraded visual environment

Colin D. Kelly; Traian V. Dogaru; Brian R. Phelan; Kelly D. Sherbondy; Ram M. Narayanan

doi:10.1117/12.2560300

4 May 2020 Wavefront curvature correction for radar imaging in a degraded visual environment

Colin D. Kelly, Traian V. Dogaru, Brian R. Phelan, Kelly D. Sherbondy, Ram M. Narayanan

Author Affiliations +

Proceedings Volume 11408, Radar Sensor Technology XXIV; 114080U (2020) https://doi.org/10.1117/12.2560300
Event: SPIE Defense + Commercial Sensing, 2020, Online Only

Abstract

One of the primary challenges in helicopter flight is landing in a degraded visual environment (DVE). In a DVE, the situational awareness of the pilot is inhibited by natural phenomena such as rain, snow, fog, etc., or aircraft induced phenomena such as brownout or whiteout. Typically, the pilot is assisted by feedback from a lidar system, but if the particles are dense enough, the lidar is unable to provide useful information about the terrain and other obstacles. Nonetheless, radar can be used to create useful imagery of the surrounding area, albeit at a reduced resolution, as it has the ability to penetrate precipitation, dust, and other obscurants. In this paper, a forward-looking synthetic aperture radar (FLSAR) concept, which can form three-dimensional (3-D) imagery from a 1-D array, is proposed. A frequency domain imaging algorithm, the polar format algorithm (PFA), is investigated for its applicability to the FLSAR geometry. We show that a wavefront curvature correction (WCC) procedure is required to compensate for the far-field approximation made in the PFA which is not valid at the frequencies and operational ranges under consideration. A filter transfer function for WCC for the FLSAR geometry is derived. Finally, the effectiveness of the derived filter transfer function is demonstrated in simulated 2-D imagery.

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Colin D. Kelly, Traian V. Dogaru, Brian R. Phelan, Kelly D. Sherbondy, and Ram M. Narayanan "Wavefront curvature correction for radar imaging in a degraded visual environment", Proc. SPIE 11408, Radar Sensor Technology XXIV, 114080U (4 May 2020); https://doi.org/10.1117/12.2560300

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KEYWORDS

Radar

Wavefronts

3D image processing

Driver's vision enhancers

Visualization

Fourier transforms

Antennas

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