Surface acoustic wave resonator

摘要

A surface acoustic wave filter includes an antenna terminal, a transmitting filter and a variable branching line both of which are coupled to the antenna terminal and a receiving filter coupled to the variable branching line. The transmitting filter has a first end series-arm SAW resonator, a second end series-arm SAW resonator, a middle series-arm SAW resonator coupled between the first and second end series-arm SAW resonators and parallel-arm SAW resonators. Each of the first and second end series-arm SAW resonator has a first resonance frequency. The middle series-arm SAW resonator has a second resonance frequency that is higher than the first resonance frequency.