Low-Profile Dual-Band Dual-Circularly-Polarized Antenna Hybridizing Folded Transmitarray and Multifeed Transmitarray

In this letter, we propose a novel low-profile dual-band dual-circularly-polarized antenna with a compact structure. The proposed shared-aperture antenna hybridizes a folded transmitarray (TA) at the K band and a multifeed TA at the Ka band. Through adopting the technique of folding and multifeed, we can reduce the height-to-diameter ratio to only 0.19. By using a dual-band receiver–transmitter structure on the TA, we achieve left-hand circular polarization at the K band and right-hand circular polarization at the Ka band simultaneously. The low-band feed using patch antenna is placed in the middle of the reflectarray aperture. The high-band feeds composed of patch arrays are placed around the low-band patch and fed by a power divider. Through the novel feed configuration and feed network, we can make the entire structure very compact and avoid feed blockage. An antenna prototype operating at the 20 GHz and 30 GHz bands is designed, fabricated and measured. The measured results show that the impedance bandwidths are 12.2% (19.3 GHz to 21.8 GHz) and 8% (28.8 GHz to 31.2 GHz), respectively. The 3 dB axial ratio bandwidths are 18.7% (18.9 GHz to 22.8 GHz) and 11.4% (28 GHz to 31.4 GHz), respectively. The proposed antenna with low profile and compact structure is well realized to offer a promising candidate for satellite communication.