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Active and Passive Electronic Components
Volume 2012, Article ID 502465, 5 pages
Research Article

Tunable Lowpass Filter with RF MEMS Capacitance and Transmission Line

1Department of Electronics and Telecommunications, Norwegian University of Science and Technology, 7491 Trondheim, Norway
2Electronics and Nanoscale Engineering Research Division, University of Glasgow, Glasgow G12 8QQ, UK
3Institute for Micro and Nano Systems Technology, Vestfold University College, 3103 Tønsberg, Norway
4Department of Microsystems and Nanotechnology, SINTEF ICT, P.O. Box 124, Blindern, 0314 Oslo, Norway

Received 27 June 2011; Accepted 5 October 2011

Academic Editor: Jiun Wei Horng

Copyright © 2012 Shimul C. Saha et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We have presented an RF MEMS tuneable lowpass filter. Both distributed transmission lines and RF MEMS capacitances were used to replace the lumped elements. The use of RF MEMS capacitances gives the flexibility of tuning the cutoff frequency of the lowpass filter. We have designed a low-pass filter at 9–12 GHz cutoff frequency using the theory of stepped impedance transmission lines. A prototype of the filter has been fabricated using parallel plate capacitances. The variable shunt capacitances are formed by a combination of a number of parallel plate RF MEMS capacitances. The cutoff frequency is tuned from C to X band by actuating different combinations of parallel capacitive bridges. The measurement results agree well with the simulation result.