Patent ID: 9160306
Filing Date: 2015-10-13
Classification: H01Q,H03H

Abstract:
1. A duplexer, comprising: an antenna terminal; a transmission amplifier terminal; a reception amplifier terminal; a transmission filter, wherein the transmission amplifier terminal is coupled to the antenna terminal via the transmission filter, wherein the transmission filter has a passband, and wherein the transmission filter comprises at least one resonator; a reception filter coupled to the reception amplifier terminal; a band-stop filter, wherein the reception filter is coupled to the antenna terminal via the band-stop filter, wherein the band-stop filter has a stop band in the passband of the transmission filter, and wherein the band-stop filter comprises at least one same resonator as the transmission filter, wherein a resonant frequency of at least one resonator of the band-stop filter has a lower frequency so as to be below the passband of the transmission filter; wherein the transmission filter and the band-stop filter comprise ladder structures having series resonators or parallel resonators; wherein at least one series resonator of the band-stop filter is the same resonator as a parallel resonator of the transmission filter; wherein at least one parallel resonator of the band-stop filter is the same resonator as a series resonator of the transmission filter; wherein a resonant frequency of at least one series resonator of the band-stop filter differs from resonant frequencies of the remaining series resonators of the band-stop filter or a resonant frequency of at least one parallel resonator of the band-stop filter differs from resonant frequencies of the remaining parallel resonators of the band-stop filter; and wherein the resonators whose resonant frequencies differ from the other resonators have an additional mass coating that lowers the resonant frequency and which is not present, or not present to the same extent, in the other resonators; and at least one matching circuit configured to provide an open circuit for the transmission filter from the point of view of the reception filter at reception frequencies and minimize