Browse Prior Art Database

Phase Modulated System

IP.com Disclosure Number: IPCOM000096554D
Original Publication Date: 1963-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Hopner, E: AUTHOR [+3]

Abstract

This system extracts a reference signal from a distorted phase modulated carrier signal. The distortion is in the form of a spectrum shift a introduced during transmission.

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Phase Modulated System

This system extracts a reference signal from a distorted phase modulated carrier signal. The distortion is in the form of a spectrum shift a introduced during transmission.

Prior to transmission, a carrier frequency f(c) is modulated with a binary signal N. The difference frequency f(c) -N is added to two pilot frequencies f(p1) and f(p2) forming a composite signal. The relationship of the two pilot frequencies with respect to the carrier frequency f(c) is chosen so that f(c) = 2f(p1) -f(p2), where f(p2) is greater than f(p1) and f(p1) is greater than f(c).

The composite signal is transmitted over the channel and applied to the receiver shown at terminal 1. A spectrum shift a is introduced during transmission. Filters (F) 2, 3, and 4 separate the component frequencies in the received signal at their respective outputs. The output F4 is applied to the frequency multiplier 5 which multiplies the applied frequency by a factor of 2. The outputs of F3 and multiplier 5 are modulated in Modulator (M) 6. F7 extracts the difference frequency resulting from the modulation in M6 which is employed as the reference signal. This reference frequency can be expressed as 2 (f(p1) +
a) - (f(p2) + a) = 2f(p1) -f(p2) + a = f(c) + a. The outputs of F2 and F7 are applied to M8. F9 extracts the binary signal N which is the difference between the signals modulated in M8.

In a system using a carrier frequency of 2400 cps, f(p1) could be 2700 cps and f 2 could be 30...