Research And Design For Circular Polarization Antenna

Modern wireless communication system is requested to work reliably in complex conditions,which brings a challenge for antenna design.Circular polarization(CP)wave has many unique characteristics.CP antennas can avoid polarization loss,mitigate the multipath interference,and avoid Faraday rotation effect.For these unique advantages,circular polarization antenna has been applied in various systems,such as satellite communication,RFID,and radar system.This paper illustrates the theory basis of circular polarization wave and summarizes the design techniques of CP antenna.This paper concentrates on circular polarization antenna,and designs two wide band CP antennas,a dual-band CP antenna,and a near-field focused CP antenna array.The main works accomplished are as follows:1.Two wide band CP antennas have been designed.The first CP antenna is based on V-shaped open slot technique.Tuning stub and a closed slot are applied,which increases the CP bandwidth from 23% to 70%.The second antenna is modified from planar monopole antenna.A series of improvements have been applied to obtain CP radiation.Finally,90% CP bandwidth has been achieved.2.A dual-band CP RFID reader antenna is obtained by several orthogonal slots.The two arms of the L-shaped open slot are folded to reduce antenna size.Two folded open slots with different length are arranged on a same patch to achieve dual-band CP radiation.Frequency reconfiguration is controlled by three PIN diodes.The proposed antenna can cover both entire UHF and WLAN 2.4 GHz bands.3.A circular polarization NFF antenna array with 16 elements is proposed.Both the CP and near field focus performances can be obtained simultaneously when the excitation distribution for the antenna array is properly arranged.The excitation distribution is calculated by maximum power transmission efficiency between the antenna array and the testing CP antenna.Director patch is introduced to each element to improve the focusing gain by 2.7 dB.