Filter device and duplexer including compensation circuit

摘要

A filter device includes a single terminal and first and second balanced terminals. A balanced filter is connected between the single terminal and the first and second balanced terminals. The filter device includes a compensation circuit including at least one of a first compensation circuit portion connected between the single terminal and the first balanced terminal and a second compensation circuit portion connected between the single terminal and the second balanced terminal. The compensation circuit includes a resonant circuit that increases attenuation in a specified frequency band within a stop band of the balanced filter, compared with a case in which the compensation circuit is not connected.

主权项

1. A filter device comprising:
a single terminal; first and second balanced terminals; a balanced filter connected between the single terminal and the first and second balanced terminals; a compensation circuit including at least one of a first compensation circuit portion connected between the single terminal and the first balanced terminal and a second compensation circuit portion connected between the single terminal and the second balanced terminal; wherein the compensation circuit includes a resonant circuit configured to increase attenuation in a frequency band within a stop band of the balanced filter; and the resonant circuit is configured such that a signal propagating through a first signal path from the single terminal to the first balanced terminal and a signal propagating through a second signal path from the single terminal to the second balanced terminal have a same amplitude and phase in a portion of the frequency band.