Browse Prior Art Database

Reference Locked Variable Frequency Generator

IP.com Disclosure Number: IPCOM000086364D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Cole, TG: AUTHOR [+2]

Abstract

The reference-locked generator described locks the frequency of a voltage-controlled oscillator (VCO) to N times the frequency of reference pulses, where N is in the range of 10 to 2,000. A counter counts pulses from the oscillator and every Nth pulse is compared to a reference pulse, to provide adjustment to correct the frequency and phase of the oscillator. Logic blocks in the circuit provide fast pull-in.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 85% of the total text.

Page 1 of 2

Reference Locked Variable Frequency Generator

The reference-locked generator described locks the frequency of a voltage- controlled oscillator (VCO) to N times the frequency of reference pulses, where N is in the range of 10 to 2,000. A counter counts pulses from the oscillator and every Nth pulse is compared to a reference pulse, to provide adjustment to correct the frequency and phase of the oscillator. Logic blocks in the circuit provide fast pull-in.

Operations of the circuit shown in Fig. 1 will be described with reference to Fig. 2. With the VCO running at the correct frequency the short reference pulse sets the Counter latch, the Go-faster latch and resets the Go-slower latch. The VCO output decrements the number N in the counter to zero, generating a zero signal which sets the zero signal latch and the Go-slower latch. The first VCO pulse resets the Go-faster latch. Under correct frequency conditions, the pulse outputs from the Go-slower and Go-faster latches are equal in length to give constant charge on a voltage control storage capacitor in the VCO.

When the VCO is running too fast, the Go-slower latch output is set for a longer period than the Go-faster latch. Hence charge is removed from the storage capacitor to reduce the VCO frequency.

When the VCO is running too slowly, the Go-slow latch remains reset and the Go-faster latch output adds charge to the storage capacitor to increase the VCO frequency.

Gate G1 prevents random or "long setting" setting...