| 摘要 |
PURPOSE:To reduce spurious radiation by constituting an input electrode with a normal interdigital electrode and constituting an output electrode with an interdigital electrode applied with crossing width weighting so as to eliminate unbalance of direct waves. CONSTITUTION:Since the output electrode 24 is subjected to crossing width weight, the area of the electrode is large. Thus, a capacitance with a shield electrode at the back face is large. A direct wave output Vs01 extracted from a bus bar 32 placed between an input electrode 23 and the output electrode 24 is a voltage division of the level of the direct wave from the electrode 23 to the 24 through a capacitance Cs1 between both the electrodes and a capacitance C01 between the bus bar 32 and the 2nd shield electrode at the back face. This is similar as to a bus bar 33. In this case, the relation of the capacitances is Cs1<<C01 and since the C01 is nearly 5 times the capacitance of the normal output electrode in using a PZT substrate, the direct wave output is decreased to nearly 1/5. Since the direct wave amount propagated to the bus bars 32 and 33 is reduced largely, the amount of unbalance of the propagated direct wave is reduced largely. |
