Research And Implementation Of Reconfigurable Microwave MEMS Low Pass Filter

Filter is one of the most critical devices in the microwave wireless communication system, which complete channel selection, image rejecting parasitic filtering and duplex in the multi-frequency, broadband wireless communication system. RF/MW MEMS filter has low insertion loss, high isolation and linearity, miniature size, and easy for integration with IC and MMIC circuits, which can fundamentality change alter the structure and characteristics of traditional RF, MW and millimeter wave devices. In the multi-standard transceiver, tunable filter can remarkably decrease the dimension of the analog front-end, choke back big signal interference and complete multi-frequency transverse.This paper is based on the theory of the RF/MW MEMS filter, and research on the design, modeling and process of the reconfigurable low pass filter. The design principle of the MEMS filter is introduced first, such as microwave transmission line and fractal self similar theory; and the MW MEMS tunable technology is researched based on the multi-contact MEMS switch, MEMS varactor, tunable inductor and the CPW transmission line. Agilent ADS, HFSS, ANSYS are used for the simulation and optimization of the circuit as well as the structure. The layout is design by L-edit, and the low pass tunable filter is fabricated on the quartz and HR silicon substrate. The state of art chip is tested and the results have been analysed. These works are presented in this thesis:1. Research on the characteristics of the CPW filtering prototype on both quartz and high resistance silicon substrate. Analyse the effect of the slow-wave transmission factor to the low pass filter unit, and the slow wave CPW transmission factor is design as 0.54.2. Analyse and research on structure model of the CPW filtering prototype, the distributed filtering unit is optimized based on the simulation of the related lumped circuit model. The ripple of the optimized filter prototype is 1 .0dB, and the out of band attenuation is about 50dB.3. Research on the appliance of the quasi fractal self similar theory on the reconfigurable filtering design. Introducing the RF/MW MEMS switches and capacitor to reconfigure the low pass filter units base on the research of CPW filtering prototype, in order to tune the cut-off frequency.4. Reach on the multi-contact switches, in order to get better isolation and insertion loss, ground the design of the MEMS band pass filter in the next step.As for the test result, the design of silicon based MW MEMS devices are reasonable, the material and process are feasible.