Surface acoustic wave filter

摘要

A surface acoustic wave filter unit having three interdigital transducers arranged along the surface acoustic wave propagation direction is disposed on a piezoelectric substrate. An unbalanced signal terminal and balanced signal terminals are provided for the surface acoustic wave filter unit. At least one of the three interdigital transducers is out of phase relative to the other interdigital transducers. Reflectors are arranged so as to sandwich the three interdigital transducers therebetween. The reflectors are grounded. Thus, a surface acoustic wave filter having a balance-to-unbalance conversion function and having high balance between the balanced signal terminals is achieved.