Key Technology Of Rf MEMS Switches Design For CPW Based On Silicon

RF MEMS technology as the key technology of the future of communications, with characteristics of lightweight, low power and low cost, could achieve more complex functions through clever design. RF MEMS switches become a hot topic in recent years due to its high isolation, low loss, small size, easy integration, excellent linearity characteristics. It becomes a trend to apply RF MEMS switches to the adjustable RF devices such as tunable filters, reconfigurable antennas, phase shifters, etc. MEMS-based RF switches and switch-based tunable RF devices have great potential applications in the field of satellite communications systems, various radar systems and new concept detection equipments.This article is for silicon-based coplanar waveguide RF MEMS switch design. The research started from needs, modeling analysis of its electromagnetic, circuit and mechanical model. Base on the research, the down state capacitance, inductance and resistance were extracted precisely. The electrical circuit model parameters carried out through the establishment of a switch circuit model. The analysis and calculation of the MEMS switch elasticity, establishment of static and dynamic analysis of static deformation and low driving voltage design methods were studied. Based on the model analysis, the analysis of the factors affecting the performance of the RF switch was studied. The switching resonant frequency was effectively reduced by the invitation for DGS on CPW. Low drive voltage switches, high isolation switches, high reliability switches and inline capacitive shunt switches were designed, simulated and tested. The effectiveness design of the switches was verified by the applying of RF MEMS switches to the analog and digital tunable filter. Two sets of flattening MEMS processing for switch design are completed. According to the switches and tunable filters testing, analyze test results, theoretical model was proved. And the technological improvements were given.The main innovations are as follows:1. A new approach for RF MEMS capacitors accurate calculationA new calculation method for MEMS switches on-state capacitance extraction was proposed through the equivalent from CPW based switches to two crossing microstrip line. The accurate extraction was proved by the comparsion of between FEM and circuit model analysis simlulation.2. Importion for DGS structures from CPW to MEMS switches designOn the basis of the electromagnetic switch model analysis, the proposed structural DGS was introduced into silicon-based CPW MEMS switch design. According to electromagnetic parameters extraction, the DGS produced additional inductance for the switch. This structure increases the design dimensions for switches design and provides a solution for the transition from high-frequency to low-frequency of the switch. Its validity verified by the design, simulation and test for the switches.3. The impact on the RF performances and frequency adjustment for switchesThe study included the influence of RF isolation and insertion loss from the geometrical property of the beam. And the switch structure optimization design was given. The resonant frequency adjustment methords was studied and proposed via the research of the program analyzes the impact of the area of the plate, the dielectric constant of the dielectric layer and the inductance of the resonant beam and DGS structures. A optimal design of switching resonant frequency was given.4. Development of a variety of high-performance MEMS switchesDepending on the different requirements for the switches, low driving voltage switches, including bending beam and double bending beam switches with a test drive voltage below30V; high isolation switches, including candy-shaped and hybrid switches, with a high isolation better than-40dB; high reliability switches, including nerve cell shaped structure and the four-way switches; stable inductance inline switches. The switches are designed to cover the Ku Ka-band. The parameters of the switches were extracted, and the test result was givn.5. Integration design of MEMS-based tunable filterBased on the design and extraction of the switch, the integrated filter design was proposed. The new low-driving voltage bending beam switch was designed in the analog and digital tunable filters. The analog tunable filter based on inverter K offered an adjustable frequency range from20.26GHz to26.15GHz. The digital filter had four frequency of19.2GHz,19.9GHz,20.5GHz,21.7GHz.6. MEMS switch planarization process designMuti gluing and dry etching process was design for the switches surface planarization. The oughness of the process is less than100A. Gold beam and aluminum beam switches were processed, tested and analysised. The influence of the resonant frequency drift for switches was verified through the analysis of the test results. Based on the failure analysis, an improvement for the process was given.Finally, a summary of the research work, gives direction for further research.