The Research Of Differential Pattern Reconfigurable Antennas

With the diversification of modern wireless communication systems,antennas as their core components are required to undergo changes and updates accordingly to adapt to the development trend of science and technology.Pattern reconfigurable antennas can satisfy the application demands of antenna radiation pattern in various fields,by dynamically changing the shape or the main beam direction of radiation pattern.Differential antennas can be directly connected to the RF front-end products,which is beneficial to system high integration,system transmission efficiency improvement.And they have the advantages of low noise,high suppression ratio etc.That makes they a wide range of application.Therefore,the research on differential pattern reconfigurable antenna has far-reaching exploration.The work of this thesis mainly focuses on the follows:1.A two-beam differential pattern reconfigurable antenna is designed.The radiating element of the antenna is composed of a pair of dipoles with a “bow”-shaped slots;two PIN diode switches are loaded on the proper position of parasitic elements.The antenna is excited by differential signal through a short microstrip line.By controlling the on/off states of PIN diode switches using DC bias circuit,two modes of pattern reconfigurability can be realized.The experimental results show that the proposed antenna can obtain an impedance matching bandwidth of 13.7%,ranging from 3.25-3.73 GHz.The antenna average gain is about 5.6 dBi with the radiation efficiency of 62%.The structure of the proposed antenna is simple and symmetrical with stable radiation performance.2.A four-beam adjustable differential pattern antenna is presented.A method of combining four dipoles on the same dielectric plate and realizing the reconfigurable pattern is studied.There are two pairs of differential ports to excite the corresponding two dual-dipole elements.By switching the excitation differential ports and controlling the working states of PIN diodes,based on the theory of Yagi-Uda antenna,four directions of main beam can be achieved in horizontal plane(xoy).The experimental results show that the antenna has an impedance bandwidth of 8.98% operating from 3.25-3.58 GHz,and an average gain about 5.4 dBi.The antenna is low cost and easy to fabricate.3.A six-beam tunable differential pattern reconfigurable antenna is proposed.The proposed antenna is composed of radiator elements,resonating elements,Yagi parasitic elements,“ten”-shaped feeding structure and a reflector.By switching the excitation differential ports and controlling the on/off states of PIN diodes on the Yagi parasitic elements,six different beams are obtained.The proposed antenna operates from 3-3.75 GHz with impedance bandwidth of 20.8%,with an average gain about 7.6 dBi and a radiation efficiency of 81%.The antenna has a moderate profile height,good orientation,high gain,high radiation efficiency.These researches enrich the theory and design method of the differential pattern reconfigurable antenna,and provide technical support for future practical applications.