Surface acoustic wave filter

摘要

A surface acoustic wave filter includes an antenna terminal, an antenna, a transmitting filter, a branching line and a receiving filter. The antenna is coupled to the antenna terminal. The transmitting filter is coupled to the antenna terminal. The transmitting filter receives an electrical power. The branching line is coupled to the antenna terminal. The branching line has a first length that is longer than lambda/4 length so that the electrical power received by the transmitting filter when the antenna terminal is opened is smaller than when the antenna terminal is terminated, wherein lambda is a wave length of a center frequency of transmitted and received bands of the surface acoustic wave filter. The receiving filter is coupled to the branching line.