Voltage tunable microwave ferrite resonator

A novel method of implementing a tunable resonator using an applied voltage is presented. Stress is used to tune a microstrip resonator fabricated on a polycrystalline ferrite substrate. The stress was applied either mechanically with screws or electronically using piezoelectric actuators. We have demonstrated tunability of 300 MHz using screws and 50 MHz using a piezoelectric actuator at a center frequency of 2.3 GHz. Explanation of the tuning method is given and means to extend the tuning range is discussed. This method opens the possibility of compact low-power tunable filters with wide tuning range at microwave frequencies.