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Article

Adaptive Antenna Pattern Notching of Interference in Synthetic Aperture Radar Data Using Digital Beamforming

1
NASA Goddard Space Flight, Greenbelt, MD 20771, USA
2
Universities Space Research Association, Columbia, MD 21046, USA
3
Microwaves and Radar Institute, German Aerospace Center (DLR), 82234 Weßling, Germany
4
Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(11), 1346; https://0-doi-org.brum.beds.ac.uk/10.3390/rs11111346
Received: 3 April 2019 / Revised: 21 May 2019 / Accepted: 24 May 2019 / Published: 4 June 2019
(This article belongs to the Special Issue Radio Frequency Interference (RFI) in Microwave Remote Sensing)
Radio Frequency Interference (RFI) is a growing problem in Synthetic Aperture Radar (SAR) systems as scientific motivations push the radars to lower frequencies and as more wireless services share the frequency spectrum. New, advanced SAR instruments, such as NASA’s EcoSAR, DBSAR and DLR’s Tandem-L mission, employ a multichannel architecture capable of Digital Beamforming (DBF). Radars with DBF are capable of notching the antenna pattern in specific directions, which can be utilized to suppress RFI on board or in post-processing. A well-researched beamformer for this purpose is the Minimum Variance Distortionless Response (MVDR) Beamformer. However, the number of interferers that can be removed through notching is limited by the number of receive channels. It is therefore essential to adaptively change the antenna pattern notching throughout the image in time and frequency for the best results with a given number of receive channels. In this paper, we present several methods to achieve this notching by making use of the spatial SAR signal distribution in range time, range frequency, azimuth time and azimuth Doppler that is inherent to the SAR imaging geometry. Because this distribution is time-variable and yet predictable, it can be used to improve the angle of arrival estimation of the RFI and the adaptive notching. The presented methods can be applied to a Digital Beamforming (DBF) SAR signal with multiple channels in elevation and/or in azimuth. Simulations show that the proposed methods increase the ability to notch out-of-swath interference from multiple directions and lessen the impact on in-swath interference. The improvement of the interferometric coherence for a single-pass interferogram acquired by NASA’s EcoSAR system (capable of DBF in elevation) is demonstrated. The removal of periodic RFI artifacts is achieved. View Full-Text
Keywords: Synthetic Aperture Radar; interference; RFI; digital beamforming; beamformer Synthetic Aperture Radar; interference; RFI; digital beamforming; beamformer
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MDPI and ACS Style

Bollian, T.; Osmanoglu, B.; Rincon, R.; Lee, S.-K.; Fatoyinbo, T. Adaptive Antenna Pattern Notching of Interference in Synthetic Aperture Radar Data Using Digital Beamforming. Remote Sens. 2019, 11, 1346. https://0-doi-org.brum.beds.ac.uk/10.3390/rs11111346

AMA Style

Bollian T, Osmanoglu B, Rincon R, Lee S-K, Fatoyinbo T. Adaptive Antenna Pattern Notching of Interference in Synthetic Aperture Radar Data Using Digital Beamforming. Remote Sensing. 2019; 11(11):1346. https://0-doi-org.brum.beds.ac.uk/10.3390/rs11111346

Chicago/Turabian Style

Bollian, Tobias, Batuhan Osmanoglu, Rafael Rincon, Seung-Kuk Lee, and Temilola Fatoyinbo. 2019. "Adaptive Antenna Pattern Notching of Interference in Synthetic Aperture Radar Data Using Digital Beamforming" Remote Sensing 11, no. 11: 1346. https://0-doi-org.brum.beds.ac.uk/10.3390/rs11111346

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