Dielectric filter, dielectric duplexer and communication apparatus

摘要

There is disclosed a dielectric filter and a stripline filter comprising: a lambda /2 resonator (R1) for generating resonance of 1/2-wavelength at a predetermined frequency, having both ends open-circuited or short-circuited; and a pair of lambda /4 resonators (R2,R3) respectively for generating resonance of 1/4-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 lambda /4 resonators (R2,R3) are disposed in proximity to each of both ends from the vicinity of the center of the lambda /2 resonator (R1); a terminal (A) coupling to the lambda /2 resonator (R1) is provided as an unbalanced terminal; and terminals (B, C) coupling to the pair of lambda /4 resonators (R2,R3) is used as a balanced terminal. In the above filter, the balanced-type input/output of signals can be performed without using a balun. <IMAGE>