On the Pulse Extension Loss in Digital Beamforming SAR

Younis, Marwan; Rommel, Tobias; Bordoni, Federica; Krieger, Gerhard; Moreira, Alberto

doi:10.1109/lgrs.2015.2406815

Cited by 42 publications

(36 citation statements)

References 5 publications

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“…The dashed green boxes indicate an auxiliary spacevariant range filter to account for the case where the dispersive beams from Section 2.2 do not fully compensate the pulse extension effects in the real-time beamsteering. This causes essentially a nonuniform range spectrum for a fixed point on the ground [13]. Since the shapes of the main and ambiguous signal spectra can differ in this case, they should be compensated by an optional range variant filter.…”

Section: Processing Overviewmentioning

confidence: 99%

CEBRAS: Cross elevation beam range ambiguity suppression for high-resolution wide-swath and MIMO-SAR imaging

Krieger

Huber

Villano

et al. 2015

2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS)

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In this paper we propose a new hybrid technique to suppress range ambiguities in spaceborne SAR systems with multiple elevation beams. First, conventional scan-on-receive (SCORE) is performed in real-time onboard the satellite by employing a set of dispersive beams that maximize the collected signal energy for each transmitted pulse. The range ambiguities are then removed in a second step by a joint processing of the signals collected by the multiple elevation beams. The suggested two-stage approach has the advantage that a more robust range ambiguity suppression, which may involve advanced nulling techniques to account for local topography as well as satellite attitude and instrument phase errors, can be performed on ground without tremendously increasing the onboard processing demands or the data downlink volume.

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Section: Processing Overviewmentioning

confidence: 99%

CEBRAS: Cross elevation beam range ambiguity suppression for high-resolution wide-swath and MIMO-SAR imaging

Krieger

Huber

Villano

et al. 2015

2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS)

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“…As a consequence, target returns from multiple elevation angles are arriving at the antenna simultaneously. This instantaneous illuminated area on the ground is the pulse extent (PE) illustrated in Figure 1a, which covers the slant range distance [43]…”

Section: The Angular Extension Of Sar Signalsmentioning

confidence: 99%

“…It is evident, that the angular signal extent is especially critical in the case of an airborne system. Using a flat earth approximation (for the computation of the spaceborne scenario see Reference [43]), the angular extent is given by…”

Section: The Angular Extension Of Sar Signalsmentioning

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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“…Different approaches exist that can be used to form the image of the pipe such as back-projection algorithm [25], ω − k algorithm [3], beamforming [26], compressed sensing [27], and MUSIC-LSE [12]. However, as we are operating within the near-field region where a tiny defect needs to be detected on the reconstructed pipe image under insulation, the acquired SAR raw data need to be pre-processed and refocused before the reconstructing the pipe image.…”

Section: A Design Of Microwave Ndt Based Sar Systemmentioning

confidence: 99%

Microwave-Based SAR Technique for Pipeline Inspection Using Autofocus Range-Doppler Algorithm

2019

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In non-destructive testing and evaluation, microwave-based synthetic aperture radar (SAR) imaging have shown great potential in the detection of defects on buried objects such as pipes. However, due to pipe curvature and high standoff distance when inspecting an insulated pipe, the useful defect information used to characterise the pipe image is lost as a result of low signal-to-noise ratio (SNR) resulting in a blurred and unfocused image. In this paper, we proposed a robust microwave-based SAR imaging using autofocus range-Doppler algorithm (RDA) for the inspection of an insulated pipe. Singular value decomposition (SVD) is used to mitigate the effect of the insulation layer by removing dominant singular values that characterise the insulation layer, and the autofocus RDA is designed to refocus the SAR image using RDA residual refocusing. SNR, improvement factor (IF) and squared error (SE) are used to evaluate the qualitative image information of the defect on the pipe. Experimental results showed the efficacy of the method in detecting defects on an insulated pipe, in particular, a significant reduction in the noise content of the image compared to the known SAR Omega-k algorithm. It was found that the autofocus RDA gave higher values of SNR and IF (3 dB and 6 dB) compared to the Omega-k algorithm (-1 dB and 2 dB) respectively.

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On the Pulse Extension Loss in Digital Beamforming SAR

Cited by 42 publications

References 5 publications

CEBRAS: Cross elevation beam range ambiguity suppression for high-resolution wide-swath and MIMO-SAR imaging

CEBRAS: Cross elevation beam range ambiguity suppression for high-resolution wide-swath and MIMO-SAR imaging

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

Microwave-Based SAR Technique for Pipeline Inspection Using Autofocus Range-Doppler Algorithm

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