A Ku-band light weight circulaly polarized microstrip antenna array with very low cross-polarized radiation field

A Ku-band, planar array of circularly polarized microstrip patches with very low cross-polarized radiation field is reported here. The feed network comprises two different media located on two levels. The upper level has an integral microstrip feed network on a plastic substrate; the lower level has an inhomogeneous unbalanced strip line using a very light honeycomb substrate. Both media have a common ground and interface via short pins partially surrounded by a cylindrical grounded shield. The array offers a 150Mhz bandwith over which the cross-polarized radiation field is more than 30dB below the intended polarization. The overall efficiency is estimated at 40%.