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. 12, 1977
Filed:
Dec. 01, 1975
Leonard F Shepard, Dover, DE (US);
ILC Data Device Corporation, Bohemia, NY (US);
Abstract
Method and apparatus for comparing and/or adjusting the frequency output of a frequency source, which method and apparatus is greatly simplified, and permits adjustment within a relatively short time interval and at a precision whose known difference is less than five parts in the 10.sup.12. The rubidium-controlled oscillator employed by the major networks to produce the 3.58 MHz subcarrier signal is utilized as a standard. Offsets made available at regular intervals by the National Bureau of Standards are utilized to indicate the frequency differences between the network standards and the United States Frequency Standard (USFS). The method employs two phase locked loops each having divide by N dividers to electronically perform the mathematical operations represented by the formula ##EQU1## WHEREBY THE DIVISION RATIOS FOR SATISFYING THE VALUES OF THE APPROPRIATE X, X+1, AND X-1 TERMS OF THE EQUATION ARE APPROPRIATELY ADJUSTED TO OBTAIN AN OFFSET WHICH APPROXIMATES THE PUBLISHED OFFSET WITH THE KNOWN DIFFERENCE OF LESS THAN FIVE PARTS IN 10.sup.12. The technique may be employed to adjust a local generator by offsetting its value so as to bring it into phase synchronism with a network standard or, alternatively, the network standard may be adjusted by the offset to the United States frequency standard and then compared with the local oscillator, thus removing almost all of the offset value to thereby bring the frequency of the calibrated oscillator to a value extremely close to the standard where the difference is smaller than that obtainable in any conventional method. Alternatively, the method and apparatus of the present invention permits the use of the oscillator in a standard color television receiver as a high precision frequency source for use in scientific, laboratory, industrial and other applications. Also, primary (i.e. cesium) standards may be offset by use of the electronic offset described herein arranged in multiple unit cascaded fashion.