| 摘要 |
PROBLEM TO BE SOLVED: To manufacture the filter with a sharp and wide band, which is demanded by a vehicle and a portable telephone set by using the change in resonance characteristics, generated by varying the film thickness of electrode thin films in plural surface acoustic wave resonators formed on the same piezoelectric substrate. SOLUTION: Four surface acoustic wave resonators, constituted of electrodes 3-8 and one gap capacitor constituted of electrodes 9 and 19, are provided on a piezoelectric board 1, that can transmit a surface acoustic wave so as to form the composite filter. The electrode 4 is electrically connected to an electrode pattern 10 by bonding wire 11, and matching inductances 23-26 and sound- absorbing materials 31-36 are provided. In such a case, the electrode film thickness h1 and h2 of the electrodes 3-5 and that of the electrodes 6-8 on the board 1 are set to be 900Åand 2700Å, and a filter characteristics is composited by using the difference of the resonance characteristics, which are generated by the difference in film thickness. Thus, a filter of the sharp and wide frequency characteristics, which is requested in digital movable communication, can be obtained.
|
