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. 20, 2009
Filed:
May. 10, 2004
Eric Barr Kushnick, Santa Clara, CA (US);
Eric Barr Kushnick, Santa Clara, CA (US);
Advantest Corporation, Ora-Gun, JP;
Abstract
The present invention is directed to the use of a DDS to generate a high purity reference signal with high frequency resolution by switching a frequency tuning word (FTW) between particular values for particular time durations to produce two or more closely spaced frequencies that appear at the DDS output as a single frequency. Given a DDS switching between Fand Fsuch that Fis present for time Tand Fis present for time T, with the total period of the repeating pattern being T=T+T, in order for the output of the DDS to produce a single high-purity frequency that is the time-weighted average of the alternating frequencies, the condition |F−F|<<π/T must be satisfied. The time-weighted average frequency Favg=(T·F+T·F)/(T+T). By an appropriate choice of Tand T, Favg can be set to any frequency between these two frequencies.