Compact Dual Circularly Polarized Phased Array Antenna with Improved Beam-Scanning Performance by Loading a Shorted Conductive Layer

In this communication, a Ku-band dual circularly polarized (CP) phased array antenna with improved beam-scanning performance is proposed. The antenna element is mainly composed of a hybrid coupler-fed ring patch, a stacked parasitic patch, a metallic cavity, and a shorted conductive layer. The hybrid coupler with ±90 degrees outputs is modified for compactness and used to excite the left-handed CP (LHCP) and the right-handed CP (RHCP) radiation in the same band. Additionally, a shorted conductive plane is loaded on the top layer to suppress the surface wave, leading to an improved wide-angle beam-scanning performance. The active impedance match and axial ratio (AR) under different scanning angles are analyzed to verify the effectiveness of the design step-by-step. As a proof-of-concept, a 1 × 8 dual CP phased array is developed with every two adjacent elements are rotated by 90° and compensated with phase delay lines. Such a layout can maintain the AR less than 3 dB when the main beam is scanned to over 60 degrees. The phased array is prototyped and measured, demonstrating an overlapped impedance/AR bandwidth from 11.5 to 13.5 GHz for both orthogonal CPs. The main beam can be steered up to ±65 degrees with the scanning loss less than 2 dB and the AR below 3 dB for both CPs.