Band-pass filter having multilayered coil structures

Abstract

A band-pass filter comprising a shielded housing having a first and a second chamber. First and second quarter-wave resonators are disposed in the first and second chambers, respectively, for coupling with input energy and delivering output energy. First and second parallel-circuit resonators are disposed in the first and second chambers, respectively, to provide interstage coupling between resonators in the respective chambers. Each of the resonators comprises a multilayered coil structure on a finned bobbin juxtaposed on a common insulative substrate so that its coil portions are separately wound on adjacent fins of the bobbin. Each of the quarter-wave resonators has one end being short-circuited by coupling with the housing and the other end being open-circuited. Each of the parallel-circuit resonators includes a capacitor to form a parallel resonance circuit and has one end coupled to one end of the other parallel-circuit resonator at a point outside of the housing. First and second auxiliary coils are inductively coupled respectively with the parallel-circuit resonators, one end of each auxiliary coil being connected to the housing and the other ends of the auxiliary coils being coupled together to an external circuit.