Browse Prior Art Database

Detecting Frequency Shift Keying Information

IP.com Disclosure Number: IPCOM000075096D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Dobson, DR: AUTHOR

Abstract

The detection system shown is adapted to detect FSK (frequency-shift keying) information on a real-time basis independent of the amplitude of the input FSK signal.

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 80% of the total text.

Page 1 of 2

Detecting Frequency Shift Keying Information

The detection system shown is adapted to detect FSK (frequency-shift keying) information on a real-time basis independent of the amplitude of the input FSK signal.

Input FSK data is transmitted over line 11 to differentiators 13 and 15. The amplitude of the second derivative of the input voltage waveform signal, which is in exact phase with the input signal, is controlled by circuit 17 so that when the input signal has a frequency below a predetermined frequency W(o)(a frequency intermediate the two FSK frequencies), the magnitude of the differentiated voltage signal will be less than the magnitude of the input voltage signal at all points except zero. When the input signal exceeds predetermined frequency W(o), the magnitude of the differentiated voltage signal exceeds that of the input voltage signal. The input signal inverted by inverter 21 and the output magnitude of the differentiated voltage signal exceeds that of the input voltage signal. The input signal inverted by inverter 21 and the output of circuit 17 are magnitude compared by limiting compare circuit 19, and an output signal representative of the result of the comparison and hence of the frequency of the input signal is supplied. Logic inverters 25 and 26, NAND circuits 28 and 29 and logic AND circuit 31 are responsive to the output signals of limiting compare circuit 19 and limiter 23 to provide an output signal whose output level is indicative of the rec...