Multi-State Circularly Polarized Antenna Based on the Polarization Conversion Metasurface With Gain Enhancement

In this paper, a multi-state circularly polarized antenna with gain enhancement is proposed based on the polarization conversion metasurface(PCM). The antenna is composed of a simple monopole antenna and a modified PCM coating which is made up of a series of arrow-shaped elements distributed partly on the back of the substrate. The dimension of the antenna is 42 × 43 mm. And Genetic Algorithm (GA) is adopted to obtain the best performance of the PCM. The coating is used as a reflector, compared with the radiating wave, the amplitude of the reflected wave is equal and the phase is 90° difference. Therefore, circularly polarized antenna is obtained with a low profile. By rotating the orientation of the element, the antenna changes from LHCP to RHCP which means the antenna can work in multi-state. In addition, the gain of the antenna is improved. Both of the simulated and measured results have verified the design. The simulated and measured results show that the operating band of the proposed CP radiation is 10.2 to 10.9 GHz. And the gain is improved for 1 dB in average with the peak being 2 dB at 10.9 GHz.