Reconfigurable High-Q Evanescent Mode Micromachined Filters for Wireless Communications Front-Ends

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9979374KatehiA novel approach is proposed appropriate for the development of electronically tunable micromachined high-Q evanescent-mode filters. Small size, high-Q filters or filter banks with high isolation between the adjacent channels can be achieved by use of micromachined evanescent-mode cavities that appropriately couple to each other and to the input/output micro-strip or coplanar waveguide transmission lines. These monolithically integrated filters have the ability to electronically reconfigure their electrical performance by use of appropriate MEMS devices. The proposed approach is based on silicon (Si) micromachining and can effectively provide very high-Q and tunability by integrating evanescent mode cavities with MEMS devices in a three dimensional circuit. To allow for electronically adjusted frequency or reconfigurability of pass-band and out-band performance, the MEMS devices are placed at appropriate locations within the filter layout. These MEMS switch-like, compliant or membrane structures will be optimized to achieve as low of an activation voltage as possible and will be used for electronic tuning and control of filter performance.The proposed work will be performed in two steps: (a) development of an evanescent mode filter using micromachined cavities in S, L and X Bands, Co) use of MEMS devices for reconfiguring filter characteristics and the development of a switched diplexer. The fabrication techniques required in this approach are compatible with standard IC processing and for this reason provide very low fabrication cost and very high precision. In the proposed filter configurations, small size and high density will be achieved by vertically integrating the evanescent micromachined cavities and by incorporating an effective on-wafer Si micromachined package to house the MEMS devices and provide critical control of the coupling between the filter resonators. The developed components will be very small in size but of performance comparable to the state of the art waveguide filters in order to demonstrate excellent electrical response in addition to monolithic character, very small size, low cost and high density. As part of this effort, electronic tuning will be designed and implemented to control appropriate geometrical parameters. In addition, the tuning range of the designed filters will be studied and a filter or diplexer with the capability to switch in and out of the circuit will be investigated. The effectiveness of the MEMS devices in reconfiguring the filter characteristics will be evaluated by measuring the possible tuning range and tuning speed and evaluating the resulting Q of the filter The proposed study has as a goal to demonstrate the concept of a monolithic high-Q reconfigurable filter and investigate trade-offs in design in terms of performance, size, fabrication yield and cost. The development and demonstration of the proposed concept will be accomplished via the use of full-wave analysis tools and state of the art fabrication and measurement techniques. Success in this effort has the potential to revolutionarize communications front ends for a variety of wireless applications.****