Adaptive equalizer with improved distortion analysis
AssigneeXerox Corporation
InventorJohn Brian Evans
Life of this patent
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Abstract
A receiving terminal for a switched analog data communications system is equipped with an adaptive equalizer which is adjusted on a single pass in response to a series of test pulses transmitted during a predetermined equalizer adjustment period.
Claims4
A method for analyzing the phase distortion characteristics of a limited bandwidth transmission channel, said method comprising the steps of
- obtaining a baseband response of said channel to a seris of test pulses,
- rectifying said response,
- tracking peak values of said rectified response to generate a first current proportional to said peak values,
- tracking ripple components of said rectified response to generate a second current proportional to said ripple components,
- differentially combining said first and second currents in accordance with predetermined weighting factors to obtain a weighted difference current, and
- integrating said difference current to obtain a weighted peak-to-average rectified ripple measurement for said channel.
A method for judging the relative performance of a plurality of delay networks, which have different phase versus frequency characteristics, in compensating for any phase distortion caused by a limited bandwidth transmission channel, said method comprising the step of
- transmitting a series of test pulses through said transmission channel,
- sequentially routing said test pulses through successive ones of said delay networks to obtain the combined response of said transmission channel and each of said delay networks to said test pulses during successive test cycles,
- rectifying said response,
- tracking peak values of said rectified response to provide a first current of one polarity proportional to said peak values,
- tracking ripple components of said rectified response to provide a second current of opposite polarity proportional to said ripple components,
- algebraically combining said first and second currents in accordance with a predetermined weighting to provide a weighted difference current,
- cyclically integrating said weighted different current to provide separate weighted peak-to-average rectified ripple difference measurements for each of said delay networks,
- storing the largest of the weighted peak-to-average rectified ripple difference measurements obtained during earlier test cycles as a dynamic reference, and
- comparing the weighted peak-to-average rectified ripple difference measurements obtained during subsequent test cycles against said reference.
Dependencies are inferred from the claim text.