Frequency counting apparatus and method
US4786861A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 1, 1987 |
| Grant date | Nov 22, 1988 |
| Priority date | — |
| Expiry date | Sep 1, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R23/10
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A device and method for measuring the frequency of an input signal by measuring the number of cycles of the input signal that occur in a sample interval between successive sampling times t.sub.n. An integer counter determines an estimated integer number of input signal cycles, and fraction counters determine fractional counts by counting cycles of a clock signal during time intervals between a first measurement time before the sampling time and a second measurement time after the sampling time. A correction circuit refines the fractional counts by determining the phase relationships between the clock and input signals at each measurement time. The correction circuit includes a constant current source, a capacitor, a first switch connected between the constant current source and a reference potential, a second switch connected between the constant current source and the capacitor, and a control circuit for the switches. The control circuit disconnects the current source from the reference potential at each measurement time, and disconnects the current source from the capacitor upon the next occurance of a periodic characteristic of the clock signal that occurs after the measurement …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.