Elastic wave filter device
US9935611B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 2016 |
| Grant date | Apr 3, 2018 |
| Priority date | — |
| Expiry date | Nov 24, 2036 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H9/725
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A SAW filter device defines a filter including a high acoustic velocity member, a low acoustic velocity film, a piezoelectric film, and an IDT electrode are stacked in this order. A comb capacitive electrode electrically coupled to the filter is provided on the piezoelectric film. Where λc is a wavelength determined by an electrode finger pitch of the comb capacitive electrode, and, among modes of an elastic wave generated by the comb capacitive electrode, VC−(P+SV) is an acoustic velocity of a P+SV wave, VC−SH is an acoustic velocity of a SH wave, and VC−HO is an acoustic velocity of, out of higher-order modes of a SH wave, a higher-order mode at the lowest frequency side, VC−(P+SV)<VC−SH<VC−HO. Where fF−L is a cutoff frequency on a lower frequency side of the filter, fF−H is a cutoff frequency on a higher frequency side, and Euler angles (0°, θ, ψ) represent a propagation direction, with respect to a crystal of the piezoelectric film, of an elastic wave generated by the comb capacitive electrode, given any θ and ψ, VC−(P+SH)/λC<fF−L and VC−SH/λC>fF−H, or VC−SH/λC<fF−L and VC−HO/λC>fF−H.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.