FILTER, DUPLEXER, AND MODULE AND COMMUNICATION APPARATUS INCLUDING DUPLEXER

摘要

PROBLEM TO BE SOLVED: To provide a filter that has a high suppression degree.

SOLUTION: A duplexer (10) that has a common terminal (Ant), a transmission terminal (Tx) and a reception terminal (Rx) comprises: a transmission filter (1) connected between the common terminal (Ant) and the transmission terminal (Tx); a reception filter (2) connected between the common terminal (Ant) and the reception terminal (Rx); and a phase shift circuit (3) connected in series with the reception filter (2) between the common terminal (Ant) and the reception terminal (Rx). Part of a line extending from the phase shift circuit (3) to the common terminal (Ant) or the transmission terminal (Tx) and part of a line extending from the phase shift circuit (3) to the reception terminal (Rx) are coupled via a reactance. This can fundamentally reduce transmission signals reaching the reception circuit from the transmission filter to implement improved isolation.

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