Design and Implementation of a Multi-Band Active Radar Calibrator for SAR

Liang Li,Jun Hong,Feng Ming,Gukun Liu,Yu Wang

doi:10.3390/rs11111312

Abstract

Over the past decade, IECAS (Institute of Electronics, Chinese Academy of Sciences) has developed a set of L-, S-, C-, and X-band active radar calibrators that are deployed during the calibration campaigns for HJ1C synthetic aperture radar (SAR), Gaofen-3 SAR, and so on. In the near future, P-band and Ka-band spaceborne SARs will be launched. We found that it is not convenient to develop special active radar calibrators (ARCs) for a specific SAR or a specific frequency band SAR, and the acquired experience could help in the design and development of a multi-band ARC. This paper describes the design and implementation of a multi-band active radar calibrator which can operate in the L-, C-, X-, and Ka-bands. Moreover, laboratory measurements are performed to characterize the performance of the multi-band ARC, paying particular attention to the gain stability, the system transfer function, the gain flatness, and the linearity of the ARC receiver. Three such ARCs are developed, and to our knowledge, the multi-band ARC is the first of its kind in China or even in the world, and it can be used to implement the calibration campaigns of the Chinese Gaofen-3 SAR, Shenzhen-1 SAR, Luojia-2 SAR, and so on.

Highlights

Synthetic aperture radars (SARs) are an important remote sensing tool for the acquisition of quantitative information about the Earth’s environment
The active radar calibrators (ARCs) developed for Radarsat-1/2, Sentinel, ERS-1, and Gaofen-3 operate in the C-band [1,3,4,6,8], the ARCs developed for TerraSAR operate in the X-band [2], the ARCs developed for ALOS/PALSAR operate in the L-band [9], and the ARC developed for Chinese HJ1C operates in the S-band [10]
The form and performance of the antenna determine the whole structure and performance of the RAemRotCe Steonss.o2m019e, 1e1x,txenFOt.RCPoEnERsiRdEeVriInEWg the operation at a multi-band frequency of one ARC, the ant4eonfn1a5s must be able to work at a frequency range from the L-band to Ka-band

Summary

Introduction

Synthetic aperture radars (SARs) are an important remote sensing tool for the acquisition of quantitative information about the Earth’s environment. There are L-, S-, C-, and X-band spaceborne SARs in orbit. Lower P-band and higher Ka-band spaceborne SARs will be launched in the near future. External calibration should be executed, and the active radar calibrator (ARC) plays an important role in the external calibration of SAR instruments due to its adjustable radar cross section (RCS), capability of changing its internal delay, high RCS, and small size. ARCs have been developed for many famous spaceborne SARs such as Radarsat-1/2, TerraSAR, Sentinel, and Gaofen-3 [1,2,3,4,5,6,7]. Even for multi-band SAR systems, the ARCs are developed as single-band instruments.

Methods

Results

Conclusion