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:
Dec. 13, 1977
Filed:
Apr. 09, 1976
Roger C Palmer, Edmonds, WA (US);
John Fluke Manufacturing Company, Inc., Mountlake Terrace, WA (US);
Abstract
A microwave input signal whose frequency is to be determined is mixed in a mixer with a local oscillator (LO) signal and the resultant difference signal is applied to a low pass filter. The frequency of the LO signal is controlled by a digital processor that samples the output of the low pass filter. Initially the LO signal is at zero. Thereafter, the frequency of the LO signal is sequentially stepped through the fundamental and, then, the harmonics of a principal oscillator signal having a fundamental frequency F.sub.R. When the difference frequency falls within the direct counting capability of a digital counter, the digital processor opens a main gate for a short period of time, and a first difference frequency (F.sub.1) count is made and stored. The frequency of the LO signal is then offset by a known amount, and a second difference frequency (F.sub.2) count is made and stored -- if this F.sub.2 count is within the direct counting capability of the digital counter. Alternatively, if this F.sub.2 count lies beyond the direct counting capability of the digital counter, the frequency of the LO signal is stepped to the next F.sub.R offset harmonic and, then, an alternate F.sub.2 count is made and stored. The relationship between F.sub.1 and F.sub.2 determines whether or not the LO signal frequency, when the counts were made, was above or below the frequency of the input signal. Subsequent to the F.sub.1 and F.sub.2 counts being made and stored, the main gate is again opened, this time for a precise period of time related to the requisite resolution required and the digital counter makes and stores a third difference frequency (F.sub.3) count. F.sub.3 is algebraically summed with the LO signal frequency produced when F.sub.3 was determined, to obtain a displayable count equal to the frequency of the input signal. A jitter generator is provided to randomly frequency modulate the LO signal to preclude phase lock between the LO signal and the input signal, when the F.sub.1 and F.sub.2 counts are being made and stored during a counting sequence.