CTLE Adaptation via Post-Cursor Error Feedback
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Solution Overview
Problem
Conventional continuous time linear equalization techniques require a time-consuming trial-and-error approach to optimize zero and pole frequency settings, which are not adaptive to time-variant channel characteristics, leading to inefficient ISI cancellation.
Innovation Solution
A receiver with CTLE control logic that generates a correction control signal based on error signals and post-cursor ISI, dynamically adjusting zero and/or pole frequencies to reduce ISI, using a digital Decision Feedback Equalizer and least-mean-square algorithm to adapt the CTLE transfer function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional trial-and-error approach is used to optimize zero and pole frequency settings, then optimal equalization performance can be achieved, but the convergence time is long and it is not adaptive to channel changes
Solution Approach 1:
The patent implements feedback mechanisms where the equalized signal is monitored and used to dynamically adjust CTLE parameters. The system continuously compares the equalized output against desired performance criteria and automatically modifies zero and pole frequency settings based on the feedback, enabling adaptive optimization without manual trial-and-error processes
Solution Approach 2:
The patent transforms the static CTLE frequency settings into dynamic parameters that can change in real-time. By making the zero and pole frequencies adjustable during operation based on channel conditions, the system adapts to time-variant characteristics without requiring lengthy convergence periods
2Power
If zero frequency is shifted to lower frequency to augment CTLE frequency response, then gain for given frequency in interested band increases, but this may not be optimal for all channel characteristics
Solution Approach 1:
The patent makes the zero and pole frequency positions dynamic rather than fixed. The system can shift these frequencies to lower values when needed to increase gain, or move them to different positions to match various channel characteristics, providing both high gain capability and adaptability through real-time parameter adjustment
3Measurement precision
If CTLE parameters are fixed to provide efficient equalization for specific channel characteristics, then equalization performance is optimized for those conditions, but the system cannot adapt to time-variant channel changes
Solution Approach 1:
The patent implements dynamic parameter adjustment where CTLE zero and pole frequencies can be modified in real-time based on detected channel conditions. This allows the system to maintain optimized equalization performance across varying channel characteristics without requiring fixed parameters
Solution Approach 2:
The system performs self-adjustment by automatically detecting channel characteristics and modifying its own CTLE parameters accordingly. This self-service capability enables the equalizer to adapt to time-variant channels without external intervention, maintaining optimal performance dynamically
Data Source
AI summary
An adaptive CTLE used in a receiver with its zero and/or pole frequencies automatically and continuously adjustable based on an error signal and post-cursors. The error signal is derived from the sliced equalized signal that is output from the CTLE. A correction control signal can be determined based on one or more delayed and sampled data (corresponding to the post-cursors) and the error signal. As controlled by the correction control signal, the CTLE zero/pole frequency setting is then adapted such that the CTLE transfer function causes the error signal to decrease while the post cursor ISI is reduced or eliminated. As a result, effective equalization can be advantageously accomplished in a consistent and fast manner.