Browse Prior Art Database

Phase Locked Square Wave to Sine Wave Converter

IP.com Disclosure Number: IPCOM000080312D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Sensenbaugh, JD: AUTHOR

Abstract

A phase-locked square wave to sine wave converter converts a square wave by a bandpass filter to a sine wave, and phase shift between the sine and square waves is eliminated by a feedback circuit which voltage tunes the filter.

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Phase Locked Square Wave to Sine Wave Converter

A phase-locked square wave to sine wave converter converts a square wave by a bandpass filter to a sine wave, and phase shift between the sine and square waves is eliminated by a feedback circuit which voltage tunes the filter.

Square wave A applied to terminal 10 is converted to a sine wave by bandpass filter 15, which can be an active or passive bandpass filter provided it is voltage tunable. If the filter is to be an active one, there should not be an inherent 180 degrees phase shift present. Filter 15 is tuned by a signal applied by conductor 16. The sine wave is taken from the output of filter 15 on terminal
50.

The feedback signal for tuning filter 15 is developed by converting the sine wave from filter 15 to a square wave B, Fig. 2. The conversion is performed by voltage comparator 20 and the resultant square wave is in phase with the sine wave. The converted square wave B is compared with input square wave A by exclusive OR circuit 25 which detects the phase shift. Signal E0, Fig. 2, is a measure of the amount of phase shift.

Square waves A and B are also applied to permutation detector 30. Detector 30 determines if there is a positive or negative phase shift between waves A and
B. It includes AND circuits 31 and 32. AND 31 receives the A wave and the output of inverter 34 which, in turn, is connected to the output of AND 32. Similarly, AND 32 receives the B wave and the output of inverter 33 which is connec...