Impact of an Electromagnetic Interference on Imaging Capability of a Synthetic Aperture Radar

Sedehi, M.; Cristallini, Diego; Marini, J. W.; Lombardo, P.

doi:10.1109/aero.2007.352853

Cited by 10 publications

(4 citation statements)

References 1 publication

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“…This works well if the RFI direction is known. The SLC has been investigated in the context of SAR in [31], [32], [33]. For example in [34], a phased array is used to adapt the SLC direction every few pulses.…”

Section: Introductionmentioning

confidence: 99%

On-Ground RFI Mitigation for Spaceborne Multichannel SAR Systems Using Auxiliary Beams

Bollian

Younis

Krieger

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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Radio Frequency Interference (RFI) is becoming a major concern for future Synthetic Aperture Radar (SAR) missions due to the increased user demand for frequency occupation in a number of applications. Each occurrence of interference introduces artifacts in the radar imagery, biasing the measurements and leading to erroneous results. In addition to conventional techniques, the use of multichannel SAR for RFI mitigation has been proposed because its Digital Beamforming (DBF) capability allows for a spatial filtering of the received signals. Thereby, it becomes possible to remove RFI that arrives from a different direction than the SAR signal.Past publications on the topic presented highly flexible spatial filtering techniques. Those methods require either additional on-board processing or a substantial increase of the downlink capacity. This paper shows that by slightly reducing the flexibility of the spatial filtering, DBF can be utilized for RFI mitigation without either drawbacks: the processing is performed onground after downlinking the data and the data volume remains manageable. This is achieved with auxiliary beams. Their concept and limitations are discussed in detail in this paper and are supported with simulated RFI mitigation results. Furthermore, it is shown that the information collected with an auxiliary beam can also be used to filter the RFI signal when it is spatially non-orthogonal to the SAR signal.

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Section: Introductionmentioning

confidence: 99%

On-Ground RFI Mitigation for Spaceborne Multichannel SAR Systems Using Auxiliary Beams

Bollian

Younis

Krieger

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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“…The information that is gathered with the auxiliary antennas is coherently subtracted and the antenna pattern (AP) is nulled towards the interferer. The SLC has been investigated in the context of SAR in References [17][18][19]. In Reference [20], the phased array of the SAR is used for an interferer with known angle of arrival (AoA) or several auxiliary antennas are used to adapt the antenna pattern for interferer cancellation on a pulse by pulse basis.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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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.

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“…The effect of a wideband (WB) noise-like interference for imaging radars is to mask the scene visible in the imaged area with a high uniform noise level [1][2][3]. In order to assure the typical functionality of a Synthetic Aperture Radar (SAR) system, a strategy to suppress the undesired component of the received signal must be identified and implemented, with the requirement to be suitable for the subsequent SAR processing.…”

Section: Introductionmentioning

confidence: 99%

Integration of Frequency Domain Wideband Antenna Nulling and Wavenumber Domain Image Formation for Multi-Channel SAR

Bucciarelli

Pastina

Cristallini

et al. 2016

International Journal of Antennas and Propagation

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A Multichannel Synthetic Aperture Radar (M-SAR) exploiting an antenna nulling based Electronic Counter-Counter Measures (ECCM) technique shall be able to cancel the effects of noise-like interferences over the collected SAR data. Since SAR systems often work with wide bandwidths to provide high resolution images, ECCM technique must account for the presence of wideband interference signal. In this paper we consider a wideband antenna nulling technique based on space-frequency adaptive nulling and we propose an integration of the WB antenna nulling scheme within the focusing algorithm for M-SAR systems, thus allowing a fusion between ECCM and usual SAR processing steps. The computational cost of the integrated algorithm is compared with the cost of more traditional sequence of the wideband extension of the Side-Lobe Canceller and the focusing operation, to show the computational feasibility of the proposed integrated algorithm. The possibility to perform suboptimally the space-frequency adaptive nulling is also considered.

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Impact of an Electromagnetic Interference on Imaging Capability of a Synthetic Aperture Radar

Cited by 10 publications

References 1 publication

On-Ground RFI Mitigation for Spaceborne Multichannel SAR Systems Using Auxiliary Beams

On-Ground RFI Mitigation for Spaceborne Multichannel SAR Systems Using Auxiliary Beams

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

Integration of Frequency Domain Wideband Antenna Nulling and Wavenumber Domain Image Formation for Multi-Channel SAR

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