Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Semi Synchronous Four Phase Data System

IP.com Disclosure Number: IPCOM000096696D
Original Publication Date: 1963-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Calfee, RW: AUTHOR

Abstract

This is a four phase data modulation system in which binary data can arrive from either a single source two bits at a time or from two sources operating at the same bit rate. In the transmitter: in one channel, two bits A and B are added, to provide signal (A + B) low-pass filtered, cut off at the bit period frequency fd, and then multiplied with a carrier f in a balanced modulator. In the other channel, the combination (A - B) is similarly filtered and modulated with the 90 degrees phase-shifted carrier.

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 91% of the total text.

Page 1 of 2

Semi Synchronous Four Phase Data System

This is a four phase data modulation system in which binary data can arrive from either a single source two bits at a time or from two sources operating at the same bit rate. In the transmitter: in one channel, two bits A and B are added, to provide signal (A + B) low-pass filtered, cut off at the bit period frequency fd, and then multiplied with a carrier f in a balanced modulator. In the other channel, the combination (A - B) is similarly filtered and modulated with the 90 degrees phase- shifted carrier.

Both suppressed carrier signals are then combined in an adder for transmission. Because of the A + B and A - B operation, only one of the balanced modulators provides an output at a given time to the output adder. In order to allow reconstruction of the carrier at the receiver, a weak signal, at f(d) ( 1/10sin 2 pi f(d)t) is added to one of the signals (A + B) or (A - B).

In the receiver, a pair of band pass filters pass the sum and difference frequencies f(c) +- f(d) resulting from modulation of signal f(d) with signal f(c). The signals f(c) +- f(d) are used to reconstruct the carrier. Signals (A + B) and (A - B) are recovered by demodulation in the balanced modulators which multiply one by the reconstructed carrier f(c) and the other by 90 degrees phase shifted f(c). High frequency components are then filtered out by the LPFs. The A bits are recovered by adding the two signals, while the B bits are recovered by subtract...