As is well known, image coregistration, interferometric phase noise suppression, and phase unwrapping are three key processing procedures of syntheticapertureradar interferometry (InSAR). The three procedures are ca...
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As is well known, image coregistration, interferometric phase noise suppression, and phase unwrapping are three key processing procedures of syntheticapertureradar interferometry (InSAR). The three procedures are cascaded in the conventional processing flow of InSAR. Unlike the conventional processing flow, in this paper we propose a joint processing idea to carry out image coregistration, interferometric phase noise filtering, and phase unwrapping simultaneously based on subspace projection for multibaseline InSAR systems. The joint processing method can perform the fine coregistration of all SAR images implicitly by extracting the correlation information in the neighboring pixel sets, suppress the phase noise by utilizing the orthogonality of the signal subspace and the corresponding noise subspace, and optimally estimate the unwrapped interferometric phases (or the terrain heights) by combining the pixel coherence and the baseline diversity of a multibaseline InSAR system. Simulated results are presented to verify the effectiveness of the joint processing method.
In this letter, we present a subaperture-based processing scheme for syntheticapertureradar (SAR) imaging using frequency-modulated continuous-wave (FMCW) radar transmission. An efficient two-stage azimuth subapertu...
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In this letter, we present a subaperture-based processing scheme for syntheticapertureradar (SAR) imaging using frequency-modulated continuous-wave (FMCW) radar transmission. An efficient two-stage azimuth subapertureprocessing scheme is proposed for high-resolution SAR image generation. A new bulk range-cell-migration-correction technique is proposed. The algorithms are validated with point target simulations at the X-band and also using real data samples at the C-band. The results show that subaperture-based processing can be used to image extended ground scenes without mosaicing.
Seventeen interpreters ranked sets of computer-generated radarimagery to assess the value of post-correlation processing on the interpretability of SAR (syntheticapertureradar) imagery. The post-correlation process...
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Seventeen interpreters ranked sets of computer-generated radarimagery to assess the value of post-correlation processing on the interpretability of SAR (syntheticapertureradar) imagery. The post-correlation processing evaluated amounts to a nonlinear mapping of the signal exiting a digital correlator and allows full use of signal bandwidth for improving the spatial resolution or for noise reduction. The results indicate that it is reasonable to hypothesize an optimal SAR presentation format for specific appliations even though this study was too limited to be specific.
syntheticapertureradar (SAR) imagery requires image reproduction through the successive signal processing of received data before browsing images and extracting information. The received signal data records of ALOS-...
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syntheticapertureradar (SAR) imagery requires image reproduction through the successive signal processing of received data before browsing images and extracting information. The received signal data records of ALOS-2/PALSAR-2 are stored in the onboard mission data storage and transmitted to the ground. To compensate for storage usage and transmission data capacity through the mission data communication network, the operation duty of PALSAR-2 is limited. This balance strongly relies on network availability. The observation operations of current spaceborne SAR systems are rigorously planned by simulating the mission data balance, given conflicting user demands. This problem should be solved so that we need not compromise the operations and potential of next-generation spaceborne SAR systems. One of the solutions is to compress the SAR data through onboard image reproduction and information extraction from the reproduced images. This is also beneficial for fast delivery of information products and event-driven observations by constellation. The Emergence Studio (Sohatsu kobo in Japanese) of the Japan Aerospace Exploration Agency has been developing evaluation models of the imageprocessing system with the field-programmable gate array for onboard SAR image reproduction. The first model called the "Fast L1 Processor (FLIP)" can reproduce a 10-m resolution, single-look complex image (level 1.1) from ALOS/PALSAR raw signal data (level 1.0). FLIP processing speed at 200 MHz results in processing about five times faster than CPU-based computing at 3.7 GHz, corresponding to 50% real-time processing capability for ALOS/PALSAR. The FLIP'S image is almost identical to the image reproduced by 32-bit simulation in MATLAB. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
Quantitative expressions are required of the response of a syntheticapertureradar (SAR) to both point and distributed scatterers for purposes such as calibration and polarimetry. image gains depend on the viewing ge...
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Quantitative expressions are required of the response of a syntheticapertureradar (SAR) to both point and distributed scatterers for purposes such as calibration and polarimetry. image gains depend on the viewing geometry. Unlike the "flat Earth" case which often is assumed to apply, in an orbital geometry. imagesignal-to-noise ratio is dependent on footprint velocity, but the mean clutter-to-noise ratio for distributed scatterers is dependent on spacecraft velocity. When imagery of a distributed scene observed by an orbital SAR is to be calibrated by comparison to the impulse response of a reference point scatterer, for example, the velocity ratio enters the expression for peak power, but does not enter when an integral is used over the impulse response. The velocity ratio effect is about -0.5 dB for typical systems, and thus is significant when compared to modern SAR calibration goals. The paper also looks at the processing gain resulting from overlapping image pixels in azimuth through the sampling of the pulse repetition frequency. The general approach uses end-to-end SAR impulse response rather than approximate extrapolation of the "standard radar equation" to the imaging mode.
The range-Doppler algorithm and the chirp-scaling algorithm (CSA) process syntheticapertureradar (SAR) data with approximations to ideal SAR processing. These approximations are invalid for data from systems with wi...
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The range-Doppler algorithm and the chirp-scaling algorithm (CSA) process syntheticapertureradar (SAR) data with approximations to ideal SAR processing. These approximations are invalid for data from systems with wide beamwidths, large bandwidths, and/or low center frequencies. While simple and efficient, these frequency-domain methods are thus limited by the SAR parameters. This paper explores these limits and proposes a generalized chirp-scaling approach for extending the utility of frequency-domain processing. We demonstrate how different order approximations of the SAR signal in the 2-D frequency domain affect image focusing for varying SAR parameters. From these results, a guideline is set forth, which suggests the required order of approximation terms for proper focusing. A proposed generalized frequency-domain processing approach is derived. This method is an efficient arbitrary-order CSA that processes the data using the appropriate number of approximation terms. The new method is demonstrated using simulated data.
A new method for processing multichannel syntheticapertureradar (SAR) data to achieve desirable image characteristics is presented. The method is optimal because it is derived by minimizing a mean-square-error cost ...
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A new method for processing multichannel syntheticapertureradar (SAR) data to achieve desirable image characteristics is presented. The method is optimal because it is derived by minimizing a mean-square-error cost function and generalizes current methods for high-resolution wide-swath SAR signal processing. The proposed method is easily implementable, can support a wide range in the pulse repetition frequency (PRF), including cases with highly nonuniform spatial sampling, and is robust against PRFs where current projection techniques fail, cases where the PRF is ideally suited to clutter suppression. Point spread functions for the proposed algorithms are presented, and the theory and simulations are further corroborated by results using multichannel SAR data measured by radarSAT-2. We demonstrate that, if radarSAT-2 were able to illuminate a 250-km swath (300 km ground range), then, conceptually, the new method would be able to process the highly nonuniformly sampled data to provide an extremely wide mode at approximately 5-m azimuth resolution.
In this letter, we propose a compressive sensing approach for syntheticapertureradar (SAR) imaging of sparse scenes with 1-bit-quantized data. Within the framework of maximum a posteriori estimation, we formulate th...
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In this letter, we propose a compressive sensing approach for syntheticapertureradar (SAR) imaging of sparse scenes with 1-bit-quantized data. Within the framework of maximum a posteriori estimation, we formulate the SAR image reconstruction problem as a sparse optimization problem and then solve it using a first-order primal-dual algorithm. The processing results of both simulated and real radar data show that our approach can eliminate the ghost target caused by 1-bit quantization in high signal-to-noise ratio situations and suppress the noisy background very well.
syntheticapertures sample the signal of wide aperture sensors with either arrays of static or single moving smaller aperture sensors whose individual signals are computationally combined to increase the resolution, d...
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syntheticapertures sample the signal of wide aperture sensors with either arrays of static or single moving smaller aperture sensors whose individual signals are computationally combined to increase the resolution, depth-of-field, frame rate, contrast, and signal-to-noise ratio. This principle has been used for radar, telescopes, microscopes, sonar, ultrasound, laser, and optical imaging. With airborne optical sectioning (AOS), we apply camera drones for syntheticaperture imaging to uncover the ruins of a 19th century fortification system that is concealed by dense forest and shrubs. Compared to alternative airborne scanning technologies (such as LiDAR), AOS is cheaper, delivers surface color information, achieves higher sampling resolutions, and (in contrast to photogrammetry) does not suffer from inaccurate correspondence matches and long processing times.
This paper addresses signal reconstruction for future multiple-input multiple-output syntheticapertureradars (SARs) equipped with a multichannel antenna to enable wide-area high-resolution imaging. To image large sw...
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This paper addresses signal reconstruction for future multiple-input multiple-output syntheticapertureradars (SARs) equipped with a multichannel antenna to enable wide-area high-resolution imaging. To image large swaths without range ambiguities, these high-resolution wide-swath (HRWS) SAR systems use a low pulse repetition frequency (PRF). Such a PRF, however, causes the radar echoes received by each channel to be strongly aliased. By introducing new techniques, this paper extends the theory of multichannel signal processing for reconstructing the SAR signal from the aliased signals. The reconstruction performances of the proposed processing methods in terms of signal-to-noise ratio, resolution, point target ambiguity ratio, peak-to-sidelobe ratio, and signal-to-ambiguity-plus-noise ratio are investigated according to the PRF and compared with each other for an exemplary HRWS SAR system.
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