Browse Prior Art Database

Pulse Reflection Keyboard

IP.com Disclosure Number: IPCOM000081178D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Heath, CA: AUTHOR [+3]

Abstract

A keyboard can be constructed from a microstrip transmission line, adapted to provide discrete signals along the length thereof. The simplified construction of the keyboard lowers cost and improves reliability.

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Pulse Reflection Keyboard

A keyboard can be constructed from a microstrip transmission line, adapted to provide discrete signals along the length thereof. The simplified construction of the keyboard lowers cost and improves reliability.

Figs. 1 and 2 show a microstrip transmission line 10 incorporated into a printed-circuit board 12. The transmission line may be easily fabricated using conventional etched circuit techniques. The cyclic strip pattern provides increased pulse propagation delay between key positions along the line. More delay may also be introduced by increasing the dielectric constant between the conductive members of the line.

A pulse generator 14 incorporating a characteristic impedance 16 transmits a fast rise time pulse to the line 10. The pulse repetition rate is of the order of 1 microsecond. A portion of the pulse is bypassed into a pulse amplifier and shaper 18, for initiating the operation of a gated oscillator and counter 20. Digital output signals are provided from the element 20 which are proportional to the length of the transmission line traveled by the fast rise time pulse, before interruption by a discontinuity in the line.

Evenly spaced along the line are key positions (A, B, C, etc.), each corresponding to a specific key in the keyboard. The example shown is a six-key keyboard but any number may be installed along the line. Each key position includes a striker plate 22 adapted for up and down movement by any well known key element...