Multi-frequency And Broadband Circularly Polarized Antenna Research And Design

Antennas, as one of the most important part of many electronic products, have been considerably developed in recent decades, for the increasing demands and stricter standards for the service. Circularly polarized antennas have obtained a broad and in-depth application in many fields, such as space communications, positioning and navigation, remote sensing and radar technology, because of its incomparable advantages of high receiving efficiency and Interference suppression ability of rain and fog to linearly polarized antenna. In this paper, we have done much in-depth studies about the realization of circularization of an antenna and the technologies of realizing multi-band and broadband operation. On basis of this, a tri-band antenna and two broadband circularly polarized antenna have been designed.Then, an important parameter -antenna phase center is carefully studied for it is requested in the project. We have developed a Matlab program to help the determination of antenna phase center, and the calculation of the phase center stability, which can be used to guide the design of the antenna conveniently. On basis of that, a tri-band circularly polarized microstrip antenna with laminated structure and multi fed geometry has been developed, as well as a planar self-complementary Archimedean spiral antenna and its balun. In simulation, the latter antenna shows a good circular polarization performance, and it can meet the phase center specifications. After manufacture and measurement, the results agrees with the simulation, the antenna has a bandwidth of 350MHz-3GHz (S11<-10dB), which can cover all the required working frequency. Within the every specific work frequency, the phase center of the antenna is very stable in the main beam of±65°,the gain is above -4dB,。In general, this antenna design basically meets the targets.This article also raises another antenna which is a novel broadband single-feed planar antenna with broadband circular polarization. The antenna consists of a square ground with a cross shaped branch at its corner and a modified PIFA structure. By introducing a protruding cross at the ground, wideband circular polarization is generated, and the modified PIFA structure gives the antenna a broadband impedance bandwidth characteristic. The antenna has a very compact structure with a dimension of 94mm×94mm for the substrate. The prototype has been designed, built and found to have an impedance bandwidth of 46.67% (1.02 GHz-1.72 GHz) and a 3dB AR bandwidth of 660MHz(1.02 GHz-1.72 GHz), which is suitable for handheld terminal application of multi-mode satellite navigation.