| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a dual mode piezoelectric filter having a filter characteristic with low loss and a smooth passband. <P>SOLUTION: A dual mode piezoelectric filter includes a piezoelectric material layer 1 composed of a piezoelectric thin film of a high-cut type formed on a substrate, a first electrode 2 and a second electrode 3 formed on one of major surfaces of the piezoelectric material layer with a gap formed between, a third electrode 4 formed on the other major surface of the piezoelectric material layer opposite to the first electrode, the second electrode, and the gap, and an interelectrode mass load element 5 formed in the gap or at a position opposite to the gap on the surface of the piezoelectric material layer. Relationships (ρ1×h1)≤(ρa×ha) and (ρ2×h2)≤(ρa×ha) are satisfied, where h1 is the thickness and ρ1 is the density of the first electrode, h2 is the thickness and ρ2 is the density of the second electrode, and ha is the thickness and ρa is the density of the interelectrode mass load element. <P>COPYRIGHT: (C)2008,JPO&INPIT |
