Omnidirectional Transponder for Narrow-band Radar Calibration

TL;DR

This paper introduces a compact, omnidirectional transponder for SAR calibration that offers high phase measurement accuracy, suitable for applications like Circular SAR despite a narrower bandwidth.

Contribution

A novel frequency-translating transponder architecture enabling omnidirectional operation with a single antenna, improving calibration accuracy for SAR systems.

Findings

Prototype validated with drone-mounted SAR

Achieves highly accurate pulse-to-pulse phase measurements

Potential for use in Circular SAR and bistatic SAR

Abstract

Conventional reference targets for Synthetic Aperture Radar (SAR) calibration, such as corner reflectors and standard transponders, are often inherently large and suffer from limited viewing angles. This paper presents a novel frequency-translating transponder architecture that circumvents these limitations, enabling a truly compact, single-antenna design capable of omnidirectional operation. While the operational bandwidth is consequently narrowed, restricting its use primarily to azimuth-direction calibrations, the design excels at providing highly accurate pulse-to-pulse phase measurements across the synthetic aperture. The transponder was prototyped and experimentally validated with a drone-mounted SAR. The results demonstrate the transponder's significant potential for applications requiring omnidirectional reference targets, such as Circular SAR (CSAR) and bistatic SAR.