Feed-Forward Equalizer Transmitter for Distortion and Common-Mode Stability
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Solution Overview
Problem
High-speed serial link circuits experience signal distortion and common mode voltage fluctuations due to coefficient errors in feed forward equalizers, leading to decreased linearity and additional burden on receivers.
Innovation Solution
A transmitter comprising a feed forward equalizer with a delay unit, transition detection filter, and common mode balancing information to maintain a constant common mode voltage, using a pair of signals to adjust the driver slice of the voltage driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coefficient error robust feed forward equalizer is used to reduce signal distortion, then robustness against coefficient errors is improved, but common mode voltage stability deteriorates
Solution Approach 1:
The patent segments the feed forward equalizer into multiple independent driver slices (first driver slice, second driver slice, etc.), each handling specific signal components. This segmentation allows independent control of common mode voltage for each slice, enabling stable common mode voltage maintenance while preserving coefficient error robustness through the transition detection filter structure.
Solution Approach 2:
The patent dynamically adjusts the common mode voltage parameter by controlling the switching states of transistor pairs in each driver slice. When coefficient errors occur, the common mode voltage control unit modifies the voltage parameter to compensate, maintaining stability despite signal transitions. This parameter adjustment resolves the contradiction between robustness and stability.
2Reliability
If transition detection filter is applied to reduce signal distortion, then coefficient error robustness is improved, but linearity of CTLE deteriorates
Solution Approach 1:
The patent introduces a common mode voltage control unit as an intermediary between the transition detection filter and the CTLE. This intermediary compensates for the non-linearity introduced by the transition detection filter by dynamically adjusting common mode voltage, thereby maintaining CTLE linearity while preserving the coefficient error robustness benefits of the transition detection filter.
3Stability of the object's composition
If multiple driver slices are used to maintain common mode voltage, then common mode voltage stability is improved, but device complexity increases
Solution Approach 1:
The patent merges the common mode voltage control functionality into the existing driver slice structure by using transistor pairs within each slice. Rather than adding separate control circuits, the common mode control is integrated into the differential driver architecture, reducing overall device complexity while maintaining stable common mode voltage through coordinated transistor switching.
Data Source
AI summary
A transmitter comprising a feed forward equalizer according to an embodiment of present invention comprises a delay unit receiving an input signal and generating at least one delay signal, a transition detection filter generating an input data information based on the input signal and the at least one delay signal, a transition information for the input signal and the at least one delay signal, and a common mode balancing information for the transition information and a voltage driver outputting a differential transmission signal based on the input data information, the transition information, and the common mode balancing information.