Design of Circularly Polarized Synthetic Aperture Radar (CP-SAR) Onboard Unmanned Aerial Vehicle

摘要

The Faraday rotation will disturb the microwave signal during its propagation in the ionosphere, as it occurs in the current existing Linearly Polarized SAR (LP-SAR) spaceborne system. To overcome this Faraday rotation effect, a novel sensor called Circularly Polarized Synthetic Aperture Radar (CP-SAR) has been developed in Josaphat Microwave Remote Sensing Laboratory (JMRSL), Center for Environmental Remote Sensing, Chiba University. This CP-SAR sensor will be mounted onboard small satellite (μSAT CP-SAR) that will be launched in 2014 with various applications are offered, such as landcover mapping, disaster monitoring, snow cover, oceanography mapping, and etc. To test the capabilities of this sensor, initially our CP-SAR sensor will be implemented onboard Josaphat Laboratory Experimental Unmanned Aerial Vehicle (JX-1), which is operating in L-Band frequency (1.27 GHz). This paper will discusses the hardware design of CP-SAR system onboard UAV. Nowadays, parameters calculation and several single patches circularly polarized antennas fabrication has been done in our laboratory for onboard UAV. The antennas in CP-SAR system is more determined by the axial ratio (AR) characteristic of the antenna rather than the physical size of the antenna. Here, within the targeted beamwidth, the antenna should have AR<3dB.