Patent ID: 8994472
Filing Date: 2015-03-31
Classification: H01P,H03H,H04B

Abstract:
1. An antenna duplexer comprising: an antenna terminal configured to be connected to an antenna; a first terminal configured to be connected to a first external circuit; a second terminal configured to be connected to a second external circuit; a first filter connected in series between the antenna terminal and the first terminal, the first filter having a passband in a low frequency band; and a second filter connected in series between the antenna terminal and the second terminal, the second filter having a passband in a high frequency band having a lowest frequency higher than a highest frequency of the low frequency band, the second filter including a plurality of series-arm resonators connected in series between the antenna terminal and the second terminal, and a plurality of parallel-arm resonators connected between a ground and the plurality of series-arm resonators to form a ladder-type filter together with the plurality of series-arm resonators, the plurality of parallel-arm resonators of the second filter including a first parallel-arm resonator connected at a position closest to the antenna terminal among the plurality of parallel-arm resonators, and a plurality of second parallel-arm resonators connected at positions farther from the antenna terminal than the first parallel-arm resonator, at least one second parallel-arm resonator out of the plurality of second parallel-arm resonators having a main resonance and a first auxiliary resonance, attenuation poles caused by the main resonance and the first auxiliary resonance being within the low frequency band.