High-frequency vibration compensation of helicopter-borne THz-SAR [Correspondence]

This paper proposes a method on high-frequency vibration compensation of helicopter-borne synthetic aperture radar (SAR) in terahertz band. The SAR signal model with platform vibration is established based on the mechanism of a helicopter's vibration. Then successive Doppler keystone transform (SDKT) is used to correct the range cell migration induced by the vibration. Finally, the analytical formula of the platform vibration phase error is given as well as its compensation to achieve a focused image.

I. Introduction

Video synthetic aperture radar (ViSAR) system is regarded as a novel technology to achieve similar observation performance under the influence of climate factors as infrared systems provide in clean weather. There have been some applications of ViSAR in recent years [1]–[3]. The advantage of ViSAR system is its ability to output radar video of the observation area at a high frame rate compared with traditional SAR system in the microwave band. It is known that the most effective way for achieving a higher frame rate is to increase the radar carrier frequency [4]. In [2], coherent change detection is performed to the image sequence from an X-band ViSAR system. Its results show that the path of a walker dragging a rake is visible but unclear, and the path of a walker alone cannot be seen. In [3], the system operates at a carrier frequency of 35 GHz and produces real-time SAR video with 2 m resolution.