Duplexer having transmit and receive sections mounted on a single substrate

摘要

A duplexer usable for both transmission and reception in a mobile communication apparatus such as a car phone has both its transmission section and reception section mounted on a single substrate. The transmission section is connected between an input terminal and an antenna terminal and includes an isolator and either a circuit having only inductors and capacitors or a trap circuit having a dielectric resonator and an inductor and a II-type low-pass filter having an inductor and capacitors. The reception section is comprised of a filter using dielectric resonators.