Tunable evanescent-mode cavity filter

摘要

A tunable filter having an electronically tunable center frequency and dynamic bandwidth control over a large tuning range. High-Q continuously tunable evanescent-mode cavity resonators and filters using reliable RF MEMS actuators. One embodiment is a 3.4-6.2 GHz (1.8:1 tuning ratio) continuously tunable electrostatic MEMS resonator with quality factor of 460-530, with a volume of 18×30×4 mm including the actuation scheme and biasing lines. A tunable resonators is also disclosed with a 2.8:1 (5.0-1.9 GHz) tuning ratio, and Q of 300-650.

主权项

1. A tunable cavity filter with bandwidth compensation to reduce variations in bandwidth during tuning of the center frequency of the filter, comprising;
at least first and second evanescent-mode cavities each having a flexible diaphragm over a capacitive post, each said flexible diaphragm and said capacitive post separated by a respective gap; an actuator configured to vary the gap between the capacitive post of the first evanescent-mode cavity and the flexible diaphragm of the first evanescent-mode cavity and thereby vary the center frequency of said filter; a coupling iris between said at least first and second evanescent-mode cavities; and a bandwidth compensation network in parallel with said coupling iris, said bandwidth compensation network comprising:
a surface;a transmission-line section; andat least one surface mount varactor mounted on said surface.