An Integrated Dual-Band Dual-Circularly Polarized Shared-Aperture Transmit-Array Antenna for K-/Ka-Band Applications Enabled by Polarization Twisting Elements

An integrated dual-band dual-circularly polarized (dual-CP) transmit-array (TA) antenna operating at K- and Ka-bands is proposed. Antenna-filter-antenna (AFA) based polarization twisting TA cells possessing high cross-polarized and low copolarized linearly-polarized (LP) transmission characteristics are designed. These TA cells possess highly efficient circular-polarization transmission with flipped handedness without using any 180° phase shifting lines, thus bringing about benefits such as symmetrical structures, design simplification, and more consistent circularly polarized (CP) transmission magnitudes. In addition, the dual-band dual-CP transmissive beamforming characteristics are realized by arranging K- and Ka-band cells in the same aperture and employing a hybrid phase compensation strategy. For reducing the overall device profile, right-handed CP (RHCP) and left-handed CP (LHCP) planar arrays operating at K- and Ka-bands are fabricated as feeds for the TA. A dual-band dual-CP TA antenna with independently controllable beam directions is synthesized and experimentally demonstrated. The measured 2-dB gain and axial ratio (AR) bandwidths are 11.7% and 10.2% for K-band RHCP and LHCP beams, and the two CP beams own bandwidths of about 7.5% at Ka-band. The proposed dual-band dual-CP TA antenna can be a promising candidate for satellite communications and so on.