Browse Prior Art Database

Forward Correction of Data Induced Noise in a Communication Channel

IP.com Disclosure Number: IPCOM000117888D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31

Publishing Venue

IBM

Related People

Authors:
Camp Jr, WO Coyne, PT Farabaugh, MJ Gruzka, MP [+details]

Abstract

It is a problem with direct frequency modulation of an oscillator whose frequency is being held constant by a Phase Locked Loop (PLL), that the PLL will remove the modulation components that fall within the loop bandwidth. For the case of modulation that is a data signal, this distortion will cause an increase in Bit Error Rate (BER). The underlying effect of this combination of modulation type and an oscillator that is part of a PLL, is the addition of a signal that is simply the integration over time of the unbalance in the input data signal. The integration time constant is set by the loop bandwidth of the PLL. The unbalance in the input signal is the deviation from 1.0 of the weighted ratio of plus symbols to negative symbols. (Weighting allows for multivalued symbols.)