Browse Prior Art Database

Touch Key Circuit with Reduced RF Radiation

IP.com Disclosure Number: IPCOM000082896D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Taub, DM: AUTHOR

Abstract

A touch-key circuit which relies on conduction of RF current to ground through the body of an operator may generate undesirable RF radiation. This circuit supplies RF voltages to a two-element touch key and when touched causes current flow only in the operator's finger tip, thus reducing RF radiation.

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 100% of the total text.

Page 1 of 2

Touch Key Circuit with Reduced RF Radiation

A touch-key circuit which relies on conduction of RF current to ground through the body of an operator may generate undesirable RF radiation. This circuit supplies RF voltages to a two-element touch key and when touched causes current flow only in the operator's finger tip, thus reducing RF radiation.

The drawing shows a touch key consisting of two interleaved elements arranged so that the operator will always touch both elements. A two-phase RF generator supplies 180 Degrees out-of-phase voltages to the two elements via detector circuits, which each generate a DC signal when the key is touched. These DC signals are taken to an analog add circuit to provide a DC output indicating operation of the touch key.

As the admittances to ground due to touching may not be exactly equal, the circuit is balanced by a feedback path. The DC signals are taken to a differential amplifier whose output controls the RF generator, causing it to increase one of its outputs and decrease the other in such a sense as to make the detector outputs equal, and thus the RF currents through the key elements equal.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]