Patent ID: 8552818
Filing Date: 2013-10-08
Classification: H03H

Abstract:
1. A tunable filter of a ladder circuit configuration, comprising: a series arm resonator provided in a series arm; a parallel arm resonator provided in a parallel arm; and a variable capacitor connected to at least one of the series arm resonator and the parallel arm resonator; wherein when a resonant frequency and an anti-resonant frequency of the series arm resonator are FrS and FaS and a resonant frequency and an anti-resonant frequency of the parallel arm resonator are FrP and FaP, FrS≦{(n−1) FrP+FaP}/n and FaP≦{(n−1) FaS+FrS}/n are satisfied where n is an integer number greater than or equal to 2 and less than or equal to 30.