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. 27, 2001
Filed:
Apr. 30, 1998
Nortel Networks Limited, Montreal, CA;
Abstract
Supervisory audio tone (SAT) in a receive signal in a wireless communications system is detected using a discrete Fourier transform (DFT) supplied with samples of a filtered and decimated signal derived from the receive signal. The DFT can comprise M 2-input butterfly computation stages for computing an N-point DFT where N=2,. Each of the stages m from 1 to M−1 determines and stores, for each current sample at the input, at most 2,intermediate results forming only a subset of intermediate results required for computation by the next stage. Each of up to 2,other intermediate results required for computation by the next stage is produced by shifting of a respective stored intermediate result of the respective subset determined in respect of an input sample preceding the current sample by 2,samples. For example there are M=5 stages for a 32-point DFT having 18 outputs, 6 outputs for each of three SAT frequencies.