High-gain Multi-polarization Reconfigurable Antennas

Reconfigurable antennas can be used in modern wireless communication systems.Polarization reconfigurable antennas can effectively reduce the number of antennas used in a communication system and reduce the signal loss caused by multipath fading.By frequency multiplexing,polarization reconfigurable antennas can also improve system capacity.High-gain antennas are usually valuable for satellite/wireless communications.This paper investigates high-gain polarization reconfigurable antennas.The main contributions of this work are summarized as follows:1.A high-gain horizontal/vertical polarization(HP/VP)reconfigurable antenna is proposed.The antenna makes use of the structure of the short backfire antenna(SBA)to realize the high-gain performance.The antenna configuration consists of a circular primary reflector,a square sub reflector,a ring and a feed with linear polarization reconfigurable performance.The feed is composed of two identical perpendicularly crossed slots.Four PIN diodes are used for HP/VP reconfiguration.By controlling states of four pin diodes,the HP/VP can be realized.Experimental results show that the HP/VP reconfigurable antenna has a high gain of 11 d Bi for both polarization states.The impedance bandwidth of both polarization states for |S11| less than-10 d B covers the frequency band 2.87 GHz to 3.64 GHz(23.3%),and the cross polarization of radiation patterns is less than-15 d B.2.A high-gain left-hand/right-hand circular polarization(LHCP/RHCP)reconfigurable antenna is developed.The reconfigurable antenna is still a SBA which is composed of a circular primary reflector,a square sub reflector,a ring and a feeding structure for CP reconfigurable performance.The feed is composed of two identical perpendicularly crossed slots each of which consists of three parts: a long straight slot,an arc-shaped parts etched on the end of the long straight slot and an arc-shaped slot stub at the left side of the arc-shaped slot parts.Four PIN diodes are used across the arc-shaped slots.By controlling states of PIN diodes,LHCP/RHCP reconfiguration can be realized.The antenna are fed and matched by a two-wire transmission line composed of a feeding tube and a shorting tube.Experimental results show that the LHCP/RHCP reconfigurable antenna has a high gain of 11.5 d Bi for both polarization states.The impedance bandwidth of both polarization states for |S11| less than-10 d B covers the frequency band from 1.92 GHz to 2.80 GHz(36.7%)and the axial ratio(AR)bandwidth for AR less than 3 d B covers the frequency from 2.05 GHz to 2.60 GHz(22.9%).The cross polarization level is less than-15 d B.3.Based on HP/VP and LHCP/RHCP reconfigurable antennas mentioned above,a high-gain quad-polarization reconfigurable antenna is proposed.The antenna is a SBA which is composed of a circular primary reflector,a circular sub reflector,a ring and a feed with quad-polarization reconfigurable performance.The feeding structure is still composed of two identical perpendicularly crossed slots which have arc-shaped slot parts.By selecting eight PIN diodes at the right position,the reconfigurable antenna can switch polarization states among HP,VP,LHCP,and RHCP.The antenna is fed and matched by a two-wire transmission line composed of a feeding tube and a shorting tube.Experimental results show that the quad-polarization reconfigurable antenna realizes a high gain of more than 10.5 d Bi for all the four polarization states.The impedance bandwidth of all polarization states for |S11| less than-10 d B covers the frequency band from 2.24 GHz to 2.78 GHz(22.5%)and the axial ratio bandwidth for AR less than 3 d B covers the frequency 2.24 GHz to 2.64 GHz(16.7%).The cross polarization level of radiation patterns is less than-15 d B.These high-gain multi-polarization reconfigurable antennas may find applications in satellite/wireless communciions.