Research On Polarization Reconfigurable Microstrip Antenna

In recent years, as directions of the development in the wireless communication systems are large-capacity, multi-function and ultra-wideband, the antenna which is one of the core components in the wireless communication systems gets an increasing number of attention. The reconfigurable antenna with switchable polarization is a novel antenna and receives widespread concern at home and abroad. The polarization reconfigurable antenna can choose the appropriate polarization mode according to the real-time changes in the environment. In this way, it can effectively reduce the power loss caused by the polarization mismatch, enhance the anti-jamming capability of the signal and improve the efficiency of the transmission system.In this thesis, some preliminary research has done on the polarization reconfigurable microstrip antennas. First of all, the thesis elaborates the principle and design method of the Wilkinson power divider which feeds the antenna. Then according to the design and implementation methods of the circularly polarized reconfigurable antenna, the orthogonal dual-feed circularly polarized reconfigurable microstrip patch antenna and the single-feed circularly polarized reconfigurable microstrip patch antenna with the degenerate mode separation unit which are all fed by the Wilkinson power divider are designed respectively. Finally, through the combination of the two fed modes, the antenna in the orthogonal dual-feed mode can radiate circular polarized wave, and radiate the elliptical polarized wave in the single-feed mode with the degenerate mode separation unit. It can also realize the rotation switching of both polarizations. This kind of the microstrip patch antenna, which can achieve reconfigurable axial ratio and rotation, can reduce the polarization mismatch to some extent in the depolarized environment and improve the performance of the communication systems.Subsequently a novel slot-ring coupling antenna with reconfigurable circular polarization is presented. It also uses the Wilkinson power divider to design the feed network and through loading a pair of short slots named as the degenerate mode separation unit in annular ring slot which is in the groundplane, it can radiate the circular polarized wave. This antenna can overcome the shortcoming that the microstrip patch antenna can only radiate uni-directional pattern, and radiate bi-directional pattern.The antennas are simulated by Ansoft HFSS and the prototypes of the antennas are fabricated and measured. The measured results of axial ratio and return loss coincide with the simulated results basically.