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:
Oct. 13, 1998
Filed:
May. 08, 1997
Northern Telecom Limited, Montreal, CA;
Abstract
A surface wave device filter comprises two 2-pole waveguide coupled double mode resonators (WCRs) electrically connected together in cascade. To permit narrowing of the filter passband for improved out-of-band rejection, e.g. for use of the filter as an intermediate frequency channel filter in a wireless communications system, while maintaining good matching for low ripple in the passband, a shunt capacitance is connected in parallel with the static capacitances of the two WCRs. The shunt capacitance is constituted by interdigital fingers provided on the same piezoelectric substrate as one or both of the WCRs, perpendicularly to the WCR fingers to avoid surface wave interference, conveniently in space otherwise used by rails of the WCRs, optionally with oppositely phased fingers to cancel surface waves generated by these fingers. A capacitance can be similarly provided on the same substrate as any other type of surface wave device.