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Correction of Amplitude Distortion in a Television Receiver When Used for Character Display Purposes

IP.com Disclosure Number: IPCOM000083219D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Nasser, MH: AUTHOR [+2]

Abstract

A method of correcting amplitude distortion due to bandwidth limitation in a domestic TV receiver, when used for character display purposes, is described. When an "unmodified" domestic TV receiver is used for character display purposes, then to be able to respond to a given video signal made up of pulses or dots of certain width, the receiver must have a rise time at least equal to or less than the duration of the video pulse, i.e., the receiver must have adequate bandwidth to respond to the fundamental frequency of the video input pulse.

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Correction of Amplitude Distortion in a Television Receiver When Used for Character Display Purposes

A method of correcting amplitude distortion due to bandwidth limitation in a domestic TV receiver, when used for character display purposes, is described. When an "unmodified" domestic TV receiver is used for character display purposes, then to be able to respond to a given video signal made up of pulses or dots of certain width, the receiver must have a rise time at least equal to or less than the duration of the video pulse, i.e., the receiver must have adequate bandwidth to respond to the fundamental frequency of the video input pulse.

The fundamental frequency becomes progressively smaller, depending upon the number of pulses that are `merged' to form a horizontal bar or a character font. It is therefore possible, due to bandwidth limitation, to obtain unequal amplification of signals of different frequencies resulting in varying brightness on the receiver screen.

If two or more dots are displayed simultaneously as in the case of a horizontal bar, then as mentioned above, due to the bandwidth limitation of the receiver, two or more dots (which represents low-frequency white) experience less attenuation compared to a single dot (which represents fundamental high frequency). This unequal amplification of video signal results in unequal brightness when viewed on the receiver screen. A typical example where a horizontal bar appears brighter than the vertical line is readily seen, when a capital letter `T' is dis...