Resolution Synthetic Aperture Radar Systems Research Articles

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

Channel error correction for wideband sar—A joint multiple subpulses processing method

A novel method, referred to as joint multiple subpulses processing, is developed to calibrate the nonideal transfer function of radio frequency front-end and I/Q imbalance in quadrature modulate/ demodulate systems simultaneously, which frequently occur in wideband Synthetic Aperture Radar (SAR) systems. Based on the time-frequency relation of the chirp signal and the analyses of the channel errors in wideband SAR, joint multiple subpulses processing method is adopted to separate the image frequency component due to the I/Q channel error. Then, the complete description of the channel error is acquired for building the correction function, which is used to correct the radar raw echo in frequency domain. The validity and capability of this method are demonstrated by the experiments of the channel error correction on the high resolution SAR system with the effective bandwidth of 500 MHz.

Precise Topography- and Aperture-Dependent Motion Compensation for Airborne SAR

Efficient synthetic aperture radar (SAR) processing algorithms are unable to exactly implement the aperture- and topography-dependent motion compensation due to the superposition of the synthetic apertures of several targets having different motion errors and potentially different topographic heights. Thus, during motion compensation, a reference level is assumed, resulting in residual phase errors that impact the focusing, geometric fidelity, and phase accuracy of the processed SAR images. This letter proposes a new short fast Fourier transform-based postprocessing methodology capable of efficient and precise compensation of these topography- and aperture-dependent residual phase errors. In addition to wide beamwidth (very high resolution) SAR systems, airborne repeat-pass interferometry especially benefits from this approach, as motion compensation can be significantly improved, especially in areas with high topographic changes. Repeat-pass interferometric data of the E-SAR system of the German Aerospace Center (DLR) are used to demonstrate the performance of the proposed approach.

System Choice for Data Processing, Analysis and Applications in Defence

The design of a suitable system for image data processing, analysis and applications in Defence is governed by users' requirements during peace time and prehostility/hostility period. The users need timely information and image products for decision-making. The product specifications in terms of their scale, geometrical accuracy, information content, and turnaround time among other things are crucial for the design of systems. The systems are not complete without efficient software for information extraction and analysis and for aiding decision-making process. Usually, the base data is from high resolution remote sensing systems, both airborne and spaceborne, and also from conventional sources, like topomap and other intelligence gathering mechanisms. The database thus evolved is basic and vital for a decision support system. The sensors providing input to the database creation could be airborne high resolution camera systems, high resolution synthetic aperture radar systems and thermal imaging systems operating from a stand-off range of 50 to 100 km, or from high resolution spaceborne panchromatic optical and synthetic aperture radar imagery. High resolution stereo data from airborne and spaceborne sensors are also increasingly needed for image interpretation and analysis. The digital elevation data is another important information, derived from either existing topographic maps or high resolution space stereo imagery. The system also should cater to a large information archival/retrieval system and data dissimination system for the users spread far and wide. This may call for to and fro traffic between central operational system and units spread over different locations, preferably, through high speed satellite communication channels. Finally, the total system should have reliability, data security, adequate redundancy, user-friendliness and be efficient enough to provide timely information transfer for the decision makers. This paper discusses the various application requirements, data sources, software and packages for interpretation, approach to analysis, database needs and hardware systems.