A Novel Real-Time Echo Separation Processing Architecture for Space–Time Waveform-Encoding SAR Based on Elevation Digital Beamforming

Jinsong Qiu,Xiangrui Meng,Zhimin Zhang,Yuhao Wen,Shuo Han,Zhen Chen,Wei Wang,Huaitao Fan

doi:10.3390/rs14010213

Abstract

Space–time waveform-encoding (STWE) SAR can receive echoes from multiple sub-swaths simultaneously with a single receive window. The echoes overlap each other in the time domain. To separate the echoes from different directions, traditional schemes adapt single-null steering techniques for digital receive beam patterns. However, the problems of spaceborne DBF-SAR, in practice, such as null extension loss, terrain undulation, elevation angle of arrival extension, and spaceborne antenna beam control, make the conventional scheme unable to effectively separate the echoes from different sub-swaths, which overlap each other in the time domain.A novel multi-null constrained echo separation scheme is proposed to overcome the shortcomings of the conventional scheme. The proposed algorithm can flexibly adjust the width of the notch to track the time-varying pulse extension angle with less resource consumption. Moreover, the hardware implementation details of the corresponding real-time processing architecture are discussed. The two-dimensional simulation results indicate that the proposed scheme can effectively improve the performance of echo separation. The effectiveness of the proposed method is verified by raw data processing instance of an X-band 16-channel DBF-SAR airborne system.

Highlights

High-resolution wide swath (HRWS) imaging is a “development goal” for the generation of spaceborne synthetic aperture radar (SAR) [1,2,3]
The experiments were conducted using an X-band digital beamforming (DBF)-SAR system with 16 channels in the elevation to verify the effectiveness of the proposed scheme and real-time processing architecture
The raw data were collected by an experimental airborne SAR system, which was made by the Aerospace Information Research Institute, Chinese Academy of Sciences (AIRCAS)

Summary

Introduction

High-resolution wide swath (HRWS) imaging is a “development goal” for the generation of spaceborne synthetic aperture radar (SAR) [1,2,3]. Owing to the inherent restrictions of the minimum SAR antenna area constraint, the traditional single-channel SAR cannot achieve a high-resolution image and wide swath simultaneously [4]. The mosaic mode does not fully meet the demand of next-generation spaceborne SAR for HRWS imaging. To overcome the minimum SAR antenna area constraint, the digital beamforming (DBF). An equivalent wide (but low-gain) beam pattern is applied to cover the wide swath. An equivalent high gain and sharp digital receive beam pattern is formed along the varying direction of the received echo in real-time

Results

Discussion

Conclusion