Rate-adaptive equalizer that automatically initializes itself based on detected channel conditions, and a method

Abstract

A rate-adaptive equalizer automatically initializes its tap coefficients to values. During an initialization process, a linear search algorithm is performed that sweeps the tap coefficients through different combinations of tap coefficients while assessing information about an eye associated with an input signal received over a communications channel. When the eye information indicates that the eye is open, the current tap coefficients are selected as the initial tap coefficients to be used at the beginning of the main adaptation algorithm.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The invention relates to equalizers, and more particularly, to an adaptive equalizer that automatically initializes itself.BACKGROUND OF THE INVENTION[0002]An equalizer is an electronic device that attempts to reverse distortion incurred when a signal is transmitted through a channel. In digital communications, an equalizer promotes reduction of inter-symbol interference. Distortion occurs because a channel's frequency response is not perfectly linear. If an equalizer's transfer function is the inverse of the channel's transfer function within the frequency range of the transmitted information, the equalizer can provide a flat response. The transfer function of an equalizer is commonly defined by circuitry having a number of nodes or taps that correspond to coefficients of the transfer function. Each tap has one or more controls, such as gain and dither. Setting the gain, dither or other tap controls establishes the transfer function.[0003]In so...

AI Technical Summary

Benefits of technology

The invention provides a rate-adaptive equalizer and method that can automatically adjust the equalizer circuitry to the input signal to improve the quality of the output signal. The equalizer circuitry has clocked delay elements with variable tap coefficients that can be adjusted to change the delay provided by the equalizer. The CDR circuitry recovers a clock signal from the equalizer output signal and delivers it to the clocked delay elements. The adaptive control logic selects the tap coefficients to be applied to the taps and performs an initialization algorithm to determine which combination of tap coefficients results in the highest quality eye. The eye monitor circuitry processes the equalizer output signal to determine the eye characteristics. The technical effect of the invention is to provide a more efficient and effective equalizer that can automatically adjust to different input signals to improve the quality of the output signal.

Problems solved by technology

Distortion occurs because a channel's frequency response is not perfectly linear.

Such rate-adaptive equalizers are limited in terms of dynamic range, precision and power consumption.

CDR-based rate-adaptive equalizers, however, have limitations in terms of initializing the tap settings, i.e., the coefficients of the transfer functions of the FFE / CTLE and the DFE of the equalizer.

If the CDR is not locked, the operation of the clocked delay cells will not be optimal and will therefore lead to errors.

The equalizer, however, cannot properly perform equalization without the CDR being locked to the incoming data frequency.

This presents somewhat of a problem when it comes to initializing the tap settings.

To further complicate matters, channel conditions may change over time, which would require a change to the initial tap settings.

A customer who purchases equipment containing the equalizer may not have sufficient knowledge to correctly choose the tap settings.

Images