The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 09, 1997
Filed:
Mar. 19, 1996
Hitachi Media Electronics Co., Ltd., Iwate, JP;
Abstract
Without increasing propagation loss or diffraction loss, (unlike conventional surface acoustic wave, SAW, filters which need many electrode finger pairs for constructing interdigital transducers, IDTs, to realize a steep cutoff frequency characteristic by conventional weighting or apodization that involves a high propagation loss and a high diffraction loss), there is provided a SAW filter with a very steep cutoff frequency characteristic on the low frequency side which uses three IDTs having N1, N2 and N3 electrode finger pairs, respectively. The filter is particularly applicable to a mobile radio communication device, such as a cellular radio. The relation between all the number of pairs N1+N2+N3 of the IDTs and the electromechanical coupling coefficient k.sup.2 of the piezoelectric substrate is N2<(N1+N3)<3.times.N2, and 2/k.sup.2 .gtoreq.(N1+N2+N3).gtoreq.0.8/k.sup.2.