Patent ID: 9219467
Filing Date: 2015-12-22
Classification: H03H

Abstract:
1. A duplexer comprising: a transmit filter that is connected between an antenna terminal and a transmit terminal and has a plurality of acoustic wave resonators; a receive filter that is connected between the antenna terminal and a receive terminal and has a plurality of acoustic wave resonators; and a cancel circuit that is connected in parallel with at least one of the plurality of acoustic wave resonators of the transmit filter and the plurality of acoustic wave resonators of the receive filter, wherein the cancel circuit includes an acoustic wave resonator, and further includes a first acoustic wave resonator or a first electrostatic capacitor on at least one of an input side and an output side of said acoustic wave resonator in the cancel circuit, said first acoustic wave resonator or first electrostatic capacitor being connected in series with the said acoustic wave resonator in the cancel circuit, wherein at least a part of a transmit signal leaking to the receive terminal or a receive signal leaking to the transmit terminal is cancelled by a signal passing through the cancel circuit, wherein one of the transmit filter and the receive filter having a pass band frequency lower than that of the other is a ladder type filter, and wherein an anti-resonance frequency of the first acoustic wave resonator is in a pass band of one of the transmit filter and the receive filter having a pass band frequency higher than that of the other.