Research And Design Of Broadband Circular Polarizer And Microstrip Reflectarray Antenna Based On FSS

The Circularly polarized waves(CPWs) are of great importance for the efficient operation of modern radar and satellite communication systems. On one hand, circular polarization provides better performance to overcome unwanted multipath reflections, on the other hand, circularly polarized waves offer superior signal propagation characteristics over linearly polarized waves. Because the microwave device mostly produces linear polarized wave, how to realize CPWs is a hot research topic. Circular polarizer based on FSS, which has compact structure and easy to load other linear polarized antenna, has many technological advantages and wide application.With the development of high frequency radar system and long-distance communication, the high gain antenna becomes necessary. Parabolic antenna or phased array antenna is traditional method. The parabolic antenna is heavy and large. Although the phased array radar can achieve a wide scanning angle, it has high cost and large loss. Therefore the FSS microstrip reflectarray antenna based on FSS with low profile, light weight, and pattern reconfigurable and other advantages, has a potential application prospect in engineering.Thus, A broadband circular polarizer and microstrip reflectarray based on FSS operating in X-band is designed in this paper by summarizing the latest application of FSS. The content of this paper is as follows:1. A compact broadband circular polarizer based on double-layer FSSs is proposed. The unit cell of FSS consists of S-shaped semi-circle metal strip and two circular metal patch. By optimizing variable parameters of the array element, a simulated operation bandwidth of axial ratio lower than 3d B is achieved over 2GHz,from 9GHz to 11.5GHz, while the amplitude of transmission coefficient is higher than 0.8.The polarizer unit cell is also less sensitive to the range of oblique incidence angles. To confirm the proposed design, a circular polarizer prototype with 20×20 elements is fabricated and measured. The results show that good axial ratio performance can be achieved, the measured axial ratio of the transmission wave is lower than 3d B in the band from 9 to 11.5GHz,while the amplitude of transmission coefficient is higher than 0.78,The measured results agree well with the simulated results.2. A circular polarization discriminator based on FSS operating in X-Band is presented. It consists of cascaded circular polarizer-linear polarizer-circular polarizer divided by air gaps. The proposed structure allows the transmission of LHCPW while reflecting RHCPW. A prototype of discriminator has been simulated, fabricated and measured. The transmission coefficient could be higher than-2.5d B for incident LHCPW between 9.2GHz and 11.2GHz, meanwhile lower than-20 d B for an incident RHCPW. So the proposed structure achieves good polarization selective function.3. A microstrip reflectarray antenna based on FSS is designed. The reflect array lantern type unit with double ring resonator structure achieves the desired phase shift through the dimensional changes. A miscrostrip reflectarray antenna in X-band is established with the unit cell. The feed of the proposed array antenna uses a standard conical horn antenna and an antipodal tapered slot antenna. The results of simulation and measurement show the proposed micro-strip reflect array operating in X-band not only increase the gain of the feed but also focus the feed beam.In this paper, The circular polarization and microstrip reflect array based on the FSS unit were simulated by Floquet port of HFSS, the actual test showed that the solution was more accurate and simple simulation.