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FM Parallel Tone Transmission System

IP.com Disclosure Number: IPCOM000076891D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Murray, JT: AUTHOR

Abstract

This is a parallel tone binary communications system for use in baseband transmission, comprising a transmitter (Fig. 1) and a receiver (Fig. 2) typically coupled over at least a voice grade telephone channel. Referring to Fig. 1, there is shown a block diagram of a frequency modulation transmitter comprising a first (2) and a second (4) manually actuable discrete frequency generator driving a frequency (product) modulator 3. The modulator combines any one of n modulating frequencies (Ai) as a first binary value with any one of m carrier frequencies (Bj) as a second binary value. The discrete modulating frequencies are chosen from the baseband frequencies, i.e., 100 Hz, 150 Hz, 200 Hz, which are below the deviation limits of the discrete carrier frequencies such as 1300 Hz, 1500 Hz, ---+/- 200 Hz.

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FM Parallel Tone Transmission System

This is a parallel tone binary communications system for use in baseband transmission, comprising a transmitter (Fig. 1) and a receiver (Fig. 2) typically coupled over at least a voice grade telephone channel. Referring to Fig. 1, there is shown a block diagram of a frequency modulation transmitter comprising a first
(2) and a second (4) manually actuable discrete frequency generator driving a frequency (product) modulator 3. The modulator combines any one of n modulating frequencies (Ai) as a first binary value with any one of m carrier frequencies (Bj) as a second binary value. The discrete modulating frequencies are chosen from the baseband frequencies, i.e., 100 Hz, 150 Hz, 200 Hz, which are below the deviation limits of the discrete carrier frequencies such as 1300 Hz, 1500 Hz, ---+/- 200 Hz. The modulator 3 may consist of any standard modulator or frequency-shift keying device. Further reference may be made to Panter, "Modulation, Noise, and Spectral Analysis," McGraw Hill Book Co., 1965, at pages 381-404 for a detailed modulator design analysis.

Referring to Fig. 2, there is shown an FM receiver adapted to detect and discriminate the parallel-tone signals from the modulator of Fig. 1. Now, the second binary value is detected by averaging the zero-axis crossings of the carrier, while the first binary value is detected as modulation on the carrier. A limiter 5 at the receiver input is employed to clip the input signal. Th...