A Coaxially Located K/Ka-Band Shared Aperture Dual Circularly Polarized Phased Array Antenna

This letter presents a compact dual-band, dual-circularly polarized shared-aperture phased array antenna for K/Ka-band satellite applications. The K- and Ka-band antennas are stacked coaxially with the low-band antenna placed above the high band. Such a design can eliminate the difficulty of accommodating two phased arrays within the same aperture. To enable the radiation of the Ka-band antenna, a crossed slot is slit on the radiator of the K-band antenna without affecting the operation of the K band. In addition, a quarter-wavelength filtering stub is introduced on the feed of low-band antenna to improve the cross-band isolation. As a proof-of-concept, a 2 × 8 linear array is designed and excited by sequentially rotated feeding networks for improving the axial ratio (AR) performance. The measured results agree reasonably well with the simulations, showing an overlapped bandwidth from 19.6 GHz to 21.2 GHz for the K-band operation and a bandwidth from 28.4 GHz to 30 GHz for the Ka-band operation. The phased array can realize ±60° and ±35° scanning range in the low and high bands with an average scan loss of around 3 dB.