A Ku-band Broadband Single-Ridge Waveguide Slot Antenna Array for UAV SAR Application

A Ku-band broadband waveguide wide side longitudinal slot antenna array for unmanned aerial vehicle (UAV) SAR application is designed. A single-ridge is employed to reduce the sectional size of the waveguide, and to achieve wide scanning ability. The bandwidth of the antenna is expanded by the single-ridge and subarea feeding of the slots. The active admittance of the waveguide slot is extracted based on the simulation using the HFSS software, in order to determine the size parameters of the waveguide slots. The simulation mode is built and the size parameters of the waveguide slots are modified and optimized by the aperture distribution re-deducing method. This design method has high efficiency and high veracity. An antenna array of 72 waveguide slot antenna lines is designed and manufactured. The measured results show that the relative bandwidth of VSWR smaller than 2 is 15%. The measured patterns show that the side lobe is smaller than −21.5dB, the cross polarization is better than −40dB, and the scanning angle is ±60° in azimuth direction. This waveguide slot antenna array has many advantages such as wide band, wide scanning, low side lobe and compact structure, and is suitable for UAV SAR application.