Research On SPDT Switch And Reconfigurable Antenna Array Based On MEMS Technology

Radio Frequency Micro-electromechanical Systems(RF-MEMS)switches are widely used in radio frequency systems because of their small size,light weight,insensitivity to acceleration,no DC loss at microwave frequencies,high isolation and low insertion loss.The pattern reconfigurable antenna can change the radiation direction of the beam by changing the current distribution on the antenna surface.In the pattern reconfigurable antenna,the frequency and polarization mode should remain stable.When pattern reconfigurable antenna is applied to antenna array,it can provide higher array gain by changing the beam direction of each element so that the beam direction of each element is concentrated in one direction.In this paper,we design a high performance single-pole double-throw(SPDT)switch and apply it to pattern reconfigurable antenna array.To solve the design problem of capacitive SPDT switch,a novel SPDT switch with double-layer electrode structure is proposed and applied to pattern reconfigurable antenna anray.The simulation and test r~esults show that the SPDT switch designed in this paper is separated fi'om each other.The accuracy of the model and design method is verified by the fact that the deviation is less than-35 dB and the insertion loss is greater than-ldB,which achieves excellent performance.The scanning angle of reconfigurable antenna arrays has a deflection of ±16 degrees?The main research results and innovations of this dissertation are as follows.Firstly,aiming at the problem of how to design a single-pole single-throw switch with unique independent electrodes,a high-performance MEMS switch with special stacked electrode structure is designed and analyzed theoretically.For the capacitive MEMS switch studied in this paper,the stacked discharge electrode structure will affect the circuit model of the original structure.It is very important to model and calculate the high performance single-pole single-throw switch with this special structure.Based on the original model,this paper presents a calculation method to solve the design problem of this kind of micro-electro-mechanical switch with independent electrode structure,which lays a foundation for the future design of SPDT.At the same time,in order to achieve the expected performance of the electromagnetic circuit in the design of the MEMS switch on the silicon-based coplanar waveguide,it is necessary to slot the coplanar waveguide near the anchorage area of the switch to form a discontinuous structure.The existence of discontinuous structure will inevitably affect the signal flowing through the signal line.In order to design the discontinuous structure accurately,the calculation of these parameters is the primary problem to be solved.By using conformal trans formation,such as power trans formation and Schwartz trans formation,combined with the first and second types of elliptic integrals,the problem of calculating parameters of discontinuous coplanar waveguides is solved.Secondly,aiming at how to make capacitive switches turn on and off with independent electrodes,a common ground structure of single-pole double-throw(SPDT)switch is designed and simulated.In order to pull down the switch beam,it is necessary to add DC driving voltage to the switch beam.Due to the restriction of the structure of copllanar waveguide,the potential of the common place will vary at this time.Additional air bridges are needed to control the formation of the common ground equipotential surface so that the switch junction can be formed.The structure is complex.Although the parallel switch with independent electrode structure can charge the electrodes without causing the problem of different potential in common place,the channel structure of the coplanar waveguide in Ka band is very narrow,which limits the size of the independent electrode,thus resulting in a smaller electrostatic force and unable to make the switch beam bend and pull down.In this method,a coplanar waveguide with common ground structure is designed.Compared with the traditional method(direct parallel connection of a single-pole single-throw(SPDT)switch on a CPW signal line),the SPDT switch designed by this method is connected together to form an equipotential surface without connecting an air bridge,and the signal line is directly connected with the switch beam.Finally,a reconfigurable antenna array with large scanning angle pattern is designed,and it is combined with SPDT switch to simulate,test and verify the experimental results.