| 摘要 |
<p>The present invention provides a surface acoustic wave filter (20A) having an unbalance-to-unbalance conversion function and an impedance conversion function. This surface acoustic wave filter includes a piezoelectric substrate (21), a first surface acoustic wave filter (22) that is made up of input (24) and output (25, 26) interdigital transducers (IDTs), and a second surface acoustic wave filter (23) that is also made up of input (27) and output (28, 29) IDTs. The phase difference between the first surface acoustic wave filter (22) and the second surface acoustic wave filter (23) is approximately 180 DEG . The input IDT (24) of the first surface acoustic wave filter (22) is connected to the input IDT (27) of the second surface acoustic wave filter (23) by a connecting wire (32), and a terminal (34) extending from this connecting wire (32) serves as an unbalanced terminal. An output terminal (35A) extends from the output IDTs (25, 26) of the first surface acoustic wave filter (22) that are not connected to the second surface acoustic wave filter (23), and another output terminal (35B) extends from the output IDTs (28, 29) of the second surface acoustic wave filter (23) that are not connected to the first surface acoustic wave filter (22). These output terminals (35A, 35B) constitute a balanced terminal (35). <IMAGE></p> |
