Research Of Circularly Polarized Dielectric Resonator Antenna For WLAN Applications

At present,Wireless local area network(WLAN)has been widely used in public places with a large flow,centralized offices,schools and other regions for its merits such as high-speed date transfer,mobile office and easy installation.Antenna as the core of access equipment,its capacity has a significant impact on the performance of communication network WLAN.Circularly polarized antenna has a much higher efficiency in the transmission and reception of signals than the linear polarization antenna,and polarization reconfigurable antenna can improve the immunity of the system to the interference signal and the spectrum utilization and the capacity of the communication system,so it is being used in a variety of wireless transmissions.For the time being,WLAN access devices usually use omnidirectional antennas for considering the requirements of the signal coverage area,but in the short-distance local area network communication,the unidirectional antenna is adopted for considering the requirements of transmission and reception signal angle,the signal coverage distance and the signal security.The mian focus of this paper is to design two types of circularly polarized dielectric resonator antennas(DRA)used for wireless and local networks(WLAN).The main researches are summrized as follows: 1.A wide-beam circularly polarized unidirectional dielectric resonator antenna with high front-to-back ratio is studied.The CP unidirectional patterns are obtained by combining an equivalent magnetic dipole and electric dipole which using the complementary antenna concept.The influences of the phase difference between magnetic dipole and electric dipole,the modified ground,the shape of DRA on 3-dB AR beamwidth and front-to-back ratios(FTBRs)are investigated.The back radiation even disappears,giving a good unidirectional antenna when the phase difference between magnetic dipole and electric dipole is 180°.To make the ground plane current more directional along the x-and y-directions,the copper of the four ground plane corners is removed,which have an significant improvement to axial ratio.2.An omnidirectional circularly polarized dielectric resonator antenna with low cross-polarized radiation is studied.Rotated L-shaped slots are fabricated in the ground plane,the circular patch on the bottom layer plays as planer choke,The influences of L-shaped slots on AR and the size of planer choke on cross-polarized radiation are investigated.Then,a polarization reconfigurable dielectric resonator antenna is studied.It is demonstrated that by introducing a reconfigurable arc-shaped slot in a circular patch antenna,the polarization of the radiation of the antenna,operating either left hand circularly polarization or right hand circularly polarization,can be switched effectively.By changing the voltage connected to dc biasing line,the polarization reconfigurable characteristic is realized by controlling the states of the two switching diodes mounted over a concentric circular slot incorporated on the patch,so as to vary the orientation of the arc-shaped slot shift from clockwise to anti-clockwise.