Browse Prior Art Database

Dynamic Threshold Circuit

IP.com Disclosure Number: IPCOM000077687D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Rackt, WK: AUTHOR

Abstract

The present circuit derives the dynamic average of a signal which is composed of both AC and DC components. The dynamic average thus derived will, in effect, be the DC component.

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 62% of the total text.

Page 1 of 2

Dynamic Threshold Circuit

The present circuit derives the dynamic average of a signal which is composed of both AC and DC components. The dynamic average thus derived will, in effect, be the DC component.

With signals which comprise both AC and DC components, particularly in the case where the DC component is not at a fixed level but gradually varies over the course of the signal, it is often desirable to determine the DC component in order to further determine the variation of the AC component with respect to the DC component.

An example of such a situation would be in the transmission of fingerprint information in a video system. In such a system, the video camera scans the image of a fingerprint and the same is converted into a signal for transmission. This signal includes an AC component representative of the ridges and the valleys in the topography of the fingerprint, as well as a DC component caused by gradual gradations in lighting over the surface of the fingerprint. Since it is necessary to determine the AC component with respect to the DC component, the present circuit distinguishes the two. The circuit, as shown in Fig. 2, determines the dynamic average (DC component) of the video input signal in the manner represented by the waveforms of Fig. 1. As the input signal is applied, the capacitor C1 is charged by transistor T1 and stores positive peaks. Capacitor C2 is charged by transistor T2 and stores negative peaks. Time constants are determined by the...