Dielectric filter, dielectric duplexer, and communication apparatus

摘要

There is disclosed a dielectric filter comprising: a lambd/2 resonator for generating resonance of -wavelength at a predetermined frequency, having both ends open-circuited or short-circuited; and a pair of lambd/4 resonators respectively for generating resonance of -wavelength at a frequency substantially equal to the predetermined frequency, each having one end open-circuited and the other end short-circuited; wherein the pair of lambd/4 resonators are disposed in proximity to each of both ends from the vicinity of the center of the lambd/2 resonator; a terminal coupling to the lambd/2 resonator is provided as an unbalanced terminal; and terminals coupling to the pair of lambd/4 resonators is used as a balanced terminal. In the above filter, the balanced-type input/output of signals can be performed without using a balun