The Design Of Metamaterial For Polarization Manipulating And Its Application In Antennas

As the improvement of modern communication technology, the requirement ofcircularly polarized antenna with high gain and multi-polarization character has beenmore and more urgent in satellite communication and inside communication domain.However, traditional circularly polarized antennas, like microstrip antennas, helixantennas et al. can not satisfy this requirement for their low gain and single polarizationstate characters. Metamaterial，which expands rapidly in recent years can greatlymanipulate the polarization states of the incident electromagnetic waves, provides a newapproach to design circularly polarized antennas with high performance. In thisdissertation, we focus on the polarization conversion of metamaterial and designbiaisotropic and chiral metamaterials. Circularly polarized antennas with high gain andmulti-polarization are constructed by integrating the designed metamaterials withtraditional microstrip antenna and horn antennas. The main work of the dissertationincludes:1. The traditional polarizers (λ/4wave plate) are mostly very thick and hard tointegrate. In order to solve this problem, we designed a metamaterial realizes thepolarization conversion in17%relative bandwidth, and has the thickness of less thanone twentieth based on the anistropic structure. In order to improve the performance ofchiral metamaterials, which has the problem of few working frequency bands and highloss, we provide new theory and method to achieve circular splitting based on planarspiral chiral structure. The designed chiral metamaterials with the minimum loss of only0.6dB, and can convert the incident linearly polarized wave into different circularlypolarized waves at different resonances，which increases the working bands of the chiralmetamaterial.2. To satisfy the requirement of multi-polarization in modern communicationsystems, we propose a new method to construct polarization reconfigurablemetamaterial by loading diodes in the unit cells. And two new kinds of metamaterial aredesigned with the transmittarray and chiral structure, which switch the polarizationstates of the outgoing wave between linear polarization and circular polarization.Therefore, this tunable metamaterial greatly broaden the polarization manipulationcharacter of the metamaterial. 3. In order to increase the gain of the antennas, the anisotropic metamaterial isintegrated with a microstrip antenna to convert its radiated field into circularly polarizedfield, and greatly increase its gain level by4dBi. Besides, a dual-band dual-polarizationKu band circularly polarized antenna was constructed by integrating the chiralmetamaterial with a traditional horn antenna, which satisfies the requirement of theoperating bands and polarization states of satellite antennas in up-link and down-link.