Optronic Focusing of Multichannel TOPS Data Processing

Abstract

Multichannel Terrain Observation by Progressive Scans (TOPS) SAR has overcomed the system-inherent limitation of conventional synthetic aperture radar (SAR). Multichannel TOPS SAR is capable of imaging a scene with high geometric resolution and wide swath. But the complexity of algorithms to process multichannel TOPS raw data has increased. Multichannel TOPS takes much more time and computer resource to focus an image than conventional SAR does. On the other hand, optical computing has the advantages of high speed, huge capacity and low power. So we tried to use optical computing, especially optical two dimensional Fourier transform, to process multichannel TOPS raw data in this paper. Due to the limitation of system devices, we just partly realized the computing on a 4-f system. In our method, the raw data was firstly compensated to a signal which could be seen as the raw data of another Stripmap system without range cell migration. In the 4-f system, the Stripmap signal is then transformed into its two dimensional frequency domain by a lens and multiplied by a filter to focus the image. We had tested our system with simulation point target signals. The result showed that the proposed method could quickly process Multichannel TOPS data with resolution loss smaller than 11%.