Low-loss bandpass RF filter using MEMS capacitance switches to achieve a one-octave tuning range and independently variable bandwidth

Abstract

We demonstrate a low insertion loss (1.5dB) tunable two-pole bandpass radio frequency filter with a tuning range of one octave (812-1752 MHz). It is also tunable in band width, with 3dB-bandwidths of 7 to 42% being achieved. The circuit used consists of two fixed high quality factor toroidal inductors mounted on a printed circuit board next to a fused-quartz substrate on which were fabricated the MEMS (Micro-Electro-Mechanical System) capacitance switches. Five arrays of MEMS elements, with a total of 34 MEMS bridges, are used on this chip. Each array is independently addressable in a four-bit scheme to permit well matched, independent tuning of the center frequency and bandwidth.