A 3-D Wideband High-Gain Circularly Polarized Array Antenna with Low RCS Using Simplified Sequential Rotation Topology

A 3-D wideband high-gain circularly polarized array antenna with low radar cross section (RCS) is presented in this letter. Its element contains four 3-D radiation structures fed by a low-loss CP feeding structure and four polarimetric rotating-reflecting staircases (PRRSs) designed in a quasi-I shape. Radiation structure is designed as palm-leaf-shaped radiator excited by a fan-shaped line and dispersive bilayer director for bandwidth enhancement. Current inversion method is realized by mirroring fan-shaped line to enable a 180° phase change to be compensated by CP feeding structure. Then, a simplified sequential rotation topology is realized to allow CP feeding structure to reduce loss and space occupancy, further enhancing gain and AR bandwidth. By rotating PRRS 90°, current inversion method is achieved to obtain 1-bit phase quantization. Finally, 16 identical elements with unequal phase states of any two adjacent PRRSs are cascaded by a 1-to-16 power divider. The measured results exhibit that a wide −10 dB impendence bandwidth of 32.8% and a gain of 21.1 dBi at 5.8 GHz are achieved. The 3 dB gain bandwidth reaches 31.9%, while 3 dB axial ratio bandwidth is 26.7%. Moreover, the measured 10 dB RCS reduction band covers 5.1 GHz to 11.0 GHz.