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