Size-reduction and suppression of cavity-resonances in hybrid mm-wave antennas for polarimetric measurements

Size and feed structure are some of the important constraints for using antenna-elements in multi-element two-dimensional arrays, where easy planar integration with transceiver chips is essential. This applies especially when differential signaling and adaptable polarization is required. Based on a balanced-fed patch-excited cavity-backed horn antenna (hybrid antenna), feeding concepts and approaches to reduce size are discussed and evaluated in this paper. The influence of the substrate integrated cavity is analyzed and methods to overcome the restrictions are presented, together with simulated and measured results. The optimized antennas achieve a relative bandwidth of more than 17% for 10 dB return loss, a gain of more than 5 dBi as well as symmetric and homogeneous radiation patterns in amplitude and phase with low cross-polarization.