Waveguide slotted antenna array with broadband, dual-polarization and low cross-polarization for X-band SAR applications

A broadband dual-polarization slotted waveguide planar antenna array for X-band SAR application is presented. The vertical polarization (VP) is realized with a ridged-waveguide longitudinal slot linear antenna array, while the horizontal polarization (HP) is realized with an untilted narrow-wall slot linear array. The basic part of the array is a subarray comprising an HP and a VP slotted waveguide single-polarization linear array. Each single-polarization linear array with 16 uniformly radiating elements is divided into four groups and fed by a 4-way waveguide power divider to broaden the bandwidth. The ridged slotted waveguide linear array for the VP is fed by a novel waveguide power divider which adapts to the compact width of the radiating guide. An untitled narrow-wall slot waveguide (half height) linear array excited by shaped irises for the HP, which can achieve very low cross polarization, is used. The benefits of this dual-polarization waveguide array, particularly when compared to microstrip arrays, are very low loss and good cross-polarization suppression. A panel of 16×16 dual-polarized waveguide slotted antenna array is designed, fabricated and measured. The measured results show a good agreement with the calculated ones, verifying the design. With the active transmit/receive module used, an active phased array antennas consisting of several hundreds of dual polarized subarrays can be carried out.