New Pattern Reconfigurable Antennas

Due to the advantages of small size,versatility,improved system reliability and security,reconfigurable antennas have attracted great attention.Pattern reconfigurable antennas can change the shape of radiation pattern or the direction of radiation to meet the requirements for different environments of communications.The omnidirectional antenna and the directional antenna have completely different radiation patterns.An omnidirectional/directional pattern reconfigurable antenna can realize the two types of radiation patterns and change each other in real time according to the environment to improve the efficiency of the system.It is also important to expand the beam coverage and to enhance the bandwidth of the reconfigurable antennas.Therefore,it is valuable to study omnidirectional/directional pattern reconfigurable antennas and wideband multi-beam reconfigurable antennas.For practical applications,this paper investigates several new type of pattern reconfigurable antennas,including two omnidirectional/directional pattern reconfigurable antennas and a wideband multi-beam reconfigurable antenna.The main contributions of this work are summarized as follows.1.An omnidirectional/directional pattern reconfigurable antenna is proposed.The antenna is composed of two layers of upper and lower layers.The upper and lower layers are connected by metal pillars.The upper layer is a radiating unit composed of an inner circle and an outer ring.Two PIN diodes are loaded on the slot between the inner circle and the outer ring.The lower layer is composed of a floor and a matching circuit.The floor is etched on the back of the dielectric substrate,and the matching circuit is etched on the front of the dielectric substrate.The omnidirectional radiation pattern is improved with the help of the matching circuit.The third PIN diode is loaded on the matching circuit.By switching the states of the three PIN diodes,omnidirectional/directional radiation patterns and/or two perpendicular polarizations are achieved.Experimental results show that the antenna can achieve three working modes with a bandwidth of 2.34-2.6 GHz for| S11 | <-10 d B.2.In order to enhance the bandwidth of the omnidirectional/directional pattern reconfigurable antenna,a broadband omnidirectional/directional pattern reconfigurable antenna is proposed.The radiating unit of the antenna is composed of an inner circle and a concentric outer ring.In order to enhance the bandwidth of the omnidirectional radiation mode,two short metal pillars are introduced between the inner circle and the outer ring.The short metal pillars and the inner circle are connected by PIN diodes.Due to the introduction of two metal shorting posts,the antenna size of the monopole mode is reduced.At the same time,the coupling feed is used to expand its bandwidth.By controlling the on-off state of the PIN diodes,the antenna can achieve both omnidirectional pattern and directional pattern.Experimental results show that the antenna can achieve omnidirectional/ directional pattern reconfigurability using three PIN diodes with a wide bandwidth of 24%(3.3-4.21 GHz).3.A wideband multi-beam pattern reconfigurable antenna is proposed.The antenna consists of a radiating unit,a feeding unit and a reflecting plate.The radiating unit is composed of a pair of dumbbell-shaped dipoles placed orthogonally.The feeding unit is composed of four baluns,and each balun is loaded with a PIN diode switch.Through the DC bias circuit to control the PIN diodes switch on the feeding unit,the antenna can realize six states of reconfigurable patterns in three dimensions.Simulated results show that the impedance bandwidth of the antenna is 27.6%,(3.21-4.24 GHz)and the average gain of the antenna in the six states is 7.5 d Bi.The proposed omnidirectional/directional pattern reconfigurable antennas and the multibeam reconfigurable antenna may find wide applications in wireless communications.