Study On Circular Polarization Microstrip Antenna Array In S Band

Nowadays,the information times that people live around is undergoing great changes. Furtherly, the arrival of 4G mobile communications promotes its developments with the wireless communication technology updating every day. As one of the most important parts of them,the antenna also gets a rapid development. During the past decades, the traditional antennas have been playing a stable role and serving the wireless communication system. Recently, because of the special requirements of the antenna applying platform, the traditional single linearly polarized antenna has been unable to meet the actual requirements, while circularly polarized antenna have drawn more and more people's attention. Currently, the investigations of the microstrip antennas are mainly about high gain circular polarization antenna, high gain circular polarization antenna, dual circular polarization microstrip antenna, broadband circular polarization antenna and so on. This dissertation makes a reserch on the analysis design of a high-gain circularly polarized microstrip antenna array and a dual circular polarized microstrip antenna array, major works are summarized in the following aspects: 1. This paper has designed a circularly polarized microstrip antenna element. The element has two microstrip lines which are used to feed in two ortho-H-slots, they can encourage two linear polarization electric field component with equal amplitude and 90 deg phase difference, so that we can achieve circularly polarized waves. And then,a two-element antenna array is designed and fabricated.Measured results agree well with the simulation, and the gain of the antenna in the band is more than 10 dBic. 2. A 2x2 antenna array is designed by using the above described antenna element.Every element is rotated with 90 deg phase shift in order to achieve good cross-polarization level. According to the feeding positions and phases of the elements, a sequential-phase feeding network is designed. The measured results agree well with simulation, indicating the feasibility of the microstrip antenna array.3. Finally this paper adopted the feed combination between coupled feed slot and coplanar microstrip line with the benefits of separating two feed feed layer from each other. Then a 3dB directional coupler is designed, it is not only used to connect the upper and lower feed network, but also changes the phase of the port, finally it turned dual linear polarization into dual circular polarization. In order to reduce the antenna sidelobes, antenna elements differ in magnitude.The simulation results show that the antenna has a low side-lobe level and both good left-handed circular polarization and right-handed circular polarization properties at all the three frequencies.At last, this paper summarizes the work proposed to make further research and improvement.