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:
Jul. 07, 1987
Filed:
Oct. 11, 1985
Lynn P West, Austin, TX (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A filter suppresses energy at time varying or ensemble varying frequencies. The filter comprises multiplier sections having sets of values which are dynamically varied during the receipt of time varying or ensemble varying energy. The variation of the values of the multiplier sections provides the suppression of energy at the time varying or ensemble varying frequencies. The sets of values for the multiplier sections are chosen such that the poles of such values lie within the unit circle of the z-plane locus. The location of the poles within the unit circle guarantees that the filter remain stable even though the multipliers may be located in a feedback path. In the preferred embodiment, the dynamically varying filter is used in a dual tone multi-frequency (DTMF) receiver.