| 摘要 |
PURPOSE: A surface acoustic filter is provided to improve the filtering frequency characteristics by forming simultaneously ladder-type and DMS(Doubled Mode coupled SAW)-type surface acoustic filters on one device. CONSTITUTION: A first surface acoustic filter(1) comprises reflectors(2) formed on an opposite place of a substrate surface at a constant distance, a plurality of IDT(Inter Digital metal Transducer) electrodes(4) formed between the reflectors(2), an input electrode(6) formed on a side of the IDT metal electrode(4), and an output electrode(8) formed on the other side of the IDT metal electrode(4). A second surface acoustic filter(11) comprises reflectors(12) formed on an opposite place of a side of the first acoustic filter(11), an IDT electrodes(14) formed between the reflectors(12), an input electrode(16) formed on a side of the IDT metal electrode(14) and connected to the output electrode(6) of the first surface acoustic filter(1), and an output electrode(18) formed on the other side of the IDT metal electrode(14). All the IDT metal electrodes(4,14) have 3000-4500Å in thickness and 4-5um in period. |
