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:
Feb. 05, 1991
Filed:
Jul. 05, 1990
Richard Stepp, Munich, DE;
Siemens Aktiengesellschaft, Berlin and Munich, DE;
Abstract
A method and circuit arrangement identifies the presence or absence of known frequencies in an input signal composed of a plurality of frequencies, whereby a frequency generator controlled by a reference frequency generates four switch signals having frequencies dependent upon the frequency to be identified and having a phase difference of 90.degree. and respectively one switch signal is mixed with the input signal in a respective mixer. The respective mixer products of two mixers are additively combined and are filtered through a respective filter for filtering AC components out, and the DC voltage component contained in the respective mixer product given the presence of the known frequency is evaluated with respect to the amplitude.