A Dual-Band and Dual Circularly Polarized Wide-Angle Scanning Array Antenna With Single-Feed Elements at K-/Ka-Bands

This article presents a K/Ka-band dual circular-polarization (CP) wide-angle scanning array antenna with single-feed elements. The antenna has the properties of dual operating bands, orthogonal CPs, and wide beam coverage. The K-/Ka-band coupler is designed and employed in this antenna with ±90° phase difference excited at the same feeding port at different bands. Shorted posts are used to suppress the parasitic mode and improve the scanning performance of the antenna. Besides, the dual-band coupler is codesigned with the dual-polarized antenna to improve the axial ratio (AR) at wide scanning angles. The polarizations are left-handed circular polarization (LHCP) in K-band and right-handed circular polarization (RHCP) in Ka-band. At the boresight, the ARs are below 3 dB within the frequency bands from 17.7 to 20.2 GHz and from 28 to 30.5 GHz. At the scanning angle of ±60°, the gain drop is less than 4.5 dB in the $xo {z}$ and $yo {z}$ planes.