Abstract

Future spaceborne synthetic aperture radar (SAR) missions require complete and frequent coverage of the earth with a high resolution. Terrain Observation by Progressive Scans (TOPS) is a novel wide swath mode but has impaired azimuth resolution. In this paper, an innovative extended TOPS mode named Alamouti Space-time Coding multiple-input multiple-output TOPS (ASTC-MIMO-TOPS) mode combined with digital beam-forming (DBF) in elevation and multi-aperture SAR signal reconstruction in azimuth is proposed. This innovative mode achieves wide-swath coverage with a high geometric resolution and also overcomes major drawbacks in conventional MIMO SAR systems. The data processing scheme of this imaging scheme is presented in detail. The designed system example of the proposed ASTC-MIMO-TOPS mode, which has the imaging capacity of a 400 km wide swath with an azimuth resolution of 3 m, is given. Its system performance analysis results and simulated imaging results on point targets demonstrate the potential of the proposed novel spaceborne SAR mode for high-resolution wide-swath (HRWS) imaging.

Highlights

  • Traditional single channel synthetic aperture radar (SAR) systems suffer from the contradiction between swath width and azimuth resolution: generally no system can have both wide swath coverage and high resolution [1,2]

  • Multiple-input multiple-output (MIMO) SAR [9,10,11,12,13,14] is the further extension of the displaced phase center multiple azimuth beam (DPCMAB) technique, in which additional transmitters with different waveform diversities can generate more effective azimuth spatial samples to extend the unambiguous swath width or/and improve the obtained azimuth resolution

  • Space-time Coding multiple-input multiple-output (ASTC-MIMO) Terrain Observation by Progressive Scans (TOPS) mode combined with digital beam-forming (DBF) in elevation is proposed

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Summary

Introduction

Traditional single channel synthetic aperture radar (SAR) systems suffer from the contradiction between swath width and azimuth resolution: generally no system can have both wide swath coverage and high resolution [1,2]. Multiple-input multiple-output (MIMO) SAR [9,10,11,12,13,14] is the further extension of the DPCMAB technique, in which additional transmitters with different waveform diversities can generate more effective azimuth spatial samples to extend the unambiguous swath width or/and improve the obtained azimuth resolution. Space-time Coding multiple-input multiple-output (ASTC-MIMO) TOPS mode combined with digital beam-forming (DBF) in elevation is proposed. In this imaging scheme, the TOPS mode is used to obtain the wide swath coverage, while the ASTC-MIMO technique is used to obtain more gains including array and waveform diversity gains to reduce the desired PRF requirement and the receive antenna length.

Recent Proposed SAR Modes for HRWS Imaging
ASTC-MIMO-TOPS
Signal Processing
DBF on Receive for Each Sub-Array in Elevation
Spatial Processing in Elevation
ASTC Decoding
Azimuth Signal Reconstruction
Monostatic TOPS SAR Imaging
System Example
Performance Analysis
Imaging Simulation
Conclusions
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