| 摘要 |
In order to realize low impedance of input and output by introducing unbalanced balanced input/output and reduction of the number of parts, and further in order to improve the out-of-band-characteristics, a structure such that two groups of longitudinal mode resonator type SAW filter units (3IDT-LCMR) having input and output phases different by 180 degrees from each other, is proposed. Central IDT electrodes of both SAW filter units are grounded at one terminal, and are connected at the other terminals in parallel to be an unbalanced input port. Two terminals whose phases are the same among four outer IDT electrodes of both SAW filter units, are connected in parallel to be a balanced output port. The outer IDT electrodes may be connected in parallel to be an unbalanced input port, and the central IDT electrodes may be connected in parallel to be a balanced output port. In addition, the output port may be unbalanced, and the input port may be balanced.
|
