Patent ID: 7148770

Claim:
A tunable bandpass filter comprising: a resonator having a reactance with a resonant frequency; a first electrical tuning circuit electrically coupled to the resonator and adapted to change the resonant frequency of the resonator by changing an electrical length of the resonator, wherein the first electrical tuning circuit further comprises: a capacitor having capacitance and adapted to change the electrical length of the resonator by changing the capacitance of the capacitor in response to an electric field, wherein the capacitor further comprises: a first portion of the resonator adapted to form a first plate of a first capacitor; a first portion of a ferroelectric film electrically coupled to the first portion of the resonator and having a dielectric constant with a value, related to the capacitance of the capacitor, adapted to change in response to an electric field; and a first portion of an electrically conductive element adapted to form a second plate of the first capacitor, electrically coupled to the first portion of the ferroelectric film, and disposed opposite to the first portion of the resonator.