| With the development of mobile communications and wireless systems,reconfigurable antennas have become a hot topic of study because they can be reconfigurable in terms of frequency,beam pointing,and antenna polarization.Frequency reconfigurable and pattern reconfigurable antennas can be better applied in complex electromagnetic environments and can effectively reduce electromagnetic interference and channel interference.What's more,they have the advantages of improving the reliability and security of the system,and energy conservation.In the selection of antenna type,the ceramic dielectric antenna is chosed in this paper as it has the advantages of low cost,short processing cycle,miniaturization,high efficiency and light weight Compared with the traditional antenna,it is more competitive.Whether for frequency-reconfigurable antennas or pattern-reconfigurable antennas,the main reconfigurable technologies contains changing the size,shape or dielectric constant of the dielectric,using mechanically movable components,loading the electrical switches or components,loading frequency selection surface and etc.In this dissertation,a frequency reconfigurable dielectric resonant antenna is designed,and then a pattern-reconfigurable dielectric resonant antenna and a wideband mechanically adjustable phase shifter are designed.Firstly,a frequency reconfigurable antenna with an adjustable frequency ranging from 4.14 GHz to 8.65 GHz is designed.The structure of overall antenna is a U-shaped monopole antenna with a rectangular ceramic dielectric loaded.A PIN diode acts as a switch loaded on the left of the U-shaped monopole and a DC bias circuit is designed around it.When the PIN diode is turned on or off,the antenna exhibits different resonant frequencies,which are 4.14GHz-6.19 GHz and 6.9GHz-8.65 GHz,respectively.By switching the two states of the PIN diode,the antenna can achieve frequency reconfigurable performance.Secondly,a reconfigurable circularly polarized dielectric resonant antenna with pattern-reconfigurable is proposed,which operates at 2.4 GHz.The antenna has the function of zero-spot scanning.Making the maximum radiation direction to the receiving point and the zero-radiation point to the interference source,which can effectively reduce the electromagnetic interference.The antenna consists of two major components,an omnidirectional circularly polarized dielectric resonant antenna and an directional circularly polarized circular patch antenna.When changing the phase difference between the two antenna feed ports,the antenna can achieve reconfigurable patterns.Finally,a adjustable phase shifter based on microstrip structure is designed.The phase shifter is designed to be suitable for the reconfigurable antenna designed in the previous chapter.It works at 2.4GHz.Since the pattern reconfigurable antenna has three input ports,the phase shifter is designed to have three output ports.It is composed of two major parts,an adjustable phase shifter with a circular arc microstrip line and a 90° phase shifter.one output port of the arc microstrip phase shifter is connected to the input port of the 90° bridge phase shifter,forming a three outputs adjustable phase shifter.Finally,the phase shifter and the antenna are connected by a coaxial line. |
