Study Of Circular Polarized Antenna

Circular polarized antenna, compared to the linear polarized, attended more andmore attention in the wireless application systems. Circularly polarization is widelyused in communication systems, remote telemetry radar, electronic surveillance,electronic jamming and so on. In this paper, circular polarized antennas such asmicrostrip antenna, Quadrifilar Helix Antenna and microstrip reflectarray antenna arestudied mainly. It includes three parts：Part1: Firstly, some principles of the microstrip antenna are introduced. Thetechniques of the circularly polarization, dual-band and wideband are also presented.Secondly, a dual-band and wideband circularly polarized microstrip antenna aredesigned. The dual-band is obtained by changing the current by four L-shaped slotswhen the single-feed single-layer structure in the high-mode order. A stackedmicrostrip antenna with dual H-shaped aperture-coupled feeds for broad-band circularpolarization is proposed. A new feeding-network is used to obtain40%ofaxial-ratio(AR) bandwidth. Finally, the steps of designing wideband circularlypolarized microstrip antenna are also introduced.Part2: Some techniques of the wideband and compact quadrifilar helix antennaand its compact feeding-network are introduced. By these techniques, a compactwideband quadrifilar helix antenna with a new balun feeding-work is designed. Itmeets the design requirements well and its size is reduced in large degree.Part3: Firstly, some techniques of circularly polarized and dual-band microstripreflectarray antenna are studied. Secondly, two circularly polarized microstripreflectarray antennas are designed by these techniques: one is polarizationtransformation; the other is element rotation. A dual-band microstrip reflectarrayantenna by using frequency selective surface (FSS) is designed. The reflectarrayelement adopt cross dipole. In order to reduce the dual-frequency co-polization eachother, the normal reflect plane of the reflectarray is replaced by FSS. So the method ofdesign dual-band reflectarray is becoming simple. Finally, the methods of dual-bandcircularly polarized microstrip reflectarray are presented.