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Self Adjustable Waveform Squaring Circuit

IP.com Disclosure Number: IPCOM000079370D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Roth, O: AUTHOR [+4]

Abstract

The circuit shown can be used to dynamically adjust the symmetry of a squared cyclic waveform, Wherein the average DC level of the waveform slowly varies. In particular, the apparatus is used to adjust the symmetry of an optical tachometer signal whose average DC level varies, due to the variations in the strength of the radiation used with the optical tachometer.

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Self Adjustable Waveform Squaring Circuit

The circuit shown can be used to dynamically adjust the symmetry of a squared cyclic waveform, Wherein the average DC level of the waveform slowly varies. In particular, the apparatus is used to adjust the symmetry of an optical tachometer signal whose average DC level varies, due to the variations in the strength of the radiation used with the optical tachometer.

The radiant energy reflected off of the tachometer is detected by a phototransistor 10. The signal on the phototransistor 10 is passed to the Schmitt trigger 12 via transistors 14, which converts current from transistor 10 to a voltage to be applied to Schmitt trigger 12. The cyclic waveform applied to the Schmitt trigger 12 may be sinusoidal or a clipped sinusoid, depending upon the strength of the radiant energy striking phototransistor 10. Resistors 16 may be dynamically gated by gates 18, as hereinafter described, to control the DC level of the cyclic signal applied to the input of the Schmitt trigger 12, to compensate for changes in average DC level of the signal from phototransistor 10.

The Schmitt trigger operates to shape the input waveform applied to it into a square wave, ideally having a 50-50 symmetry. The output of the Schmitt trigger is the squared signal that may be used by other circuits, such as servo loops in the case of a tachometer signal being produced by the Schmitt trigger.

The output of the Schmitt trigger is also passed through the low-pass filter 20, which detects the average DC level of the square waveform. This DC level of the square waveform is a measure of the symmetry of the wave...