A Low-RCS Circular Polarization High-Gain Antenna Based on Metasurfaces

A novel frequency selective absorber (FSA) with high in-band transmission and out-of-band absorption response is proposed in this article. Then, we apply it to a high-gain, low radar cross section (RCS) circularly polarized (CP) antenna. The proposed composite frequency selective absorber consists of a single resistive absorbing layer (RAL) and a bandpass metasurface (MS) layer with an air gap of approximately 1/4 λ0(λ0is the wavelength at the central frequency.) between them. The bandpass metasurface is composed of five metal layers etched on four dielectric substrates, featuring a compact structure. By adjusting the metal dimensions of the bandpass MS unit cell, the phase response of the unit can be regulated to compensate for the optical path difference from the feed source, thereby achieving the beam convergence function. To realize a circularly polarized response antenna, a reflective linear-to-circular polarization MS cell is also designed. The final designed high-gain circularly polarized antenna is of a folded type. The simulated and measured max gain of the antenna is 22.4 dBic and 21.8 dBic, respectively. The 3 dB circular polarized axis ratio (AR) bandwidth is 9.26%. Meanwhile, the antenna obtains obvious RCS reduction for dual-polarized impact wave at both low lower and higher frequencies out of the operating band.