Differential Wander Current Sensing for SerDes Baseline Correction

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Solution Overview

Problem

Serializer/Deserializer (SerDes) architecture experiences baseline wander issues due to improper design, leading to complexity, low efficiency, and additional data processing, necessitating a novel approach for effective baseline wander correction without introducing side effects.

Innovation Solution

An apparatus employing differential wander current sensing, comprising multiple filters and a correction circuit with amplifiers and resistors, generates differential signals and compensates for baseline wander by sensing differential wander current, thereby stabilizing common mode voltage and improving power supply rejection ratio and skew calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If filters are used in the SerDes receiver front-end circuit to filter unwanted low frequency signals, then filtering performance is improved, but baseline wander effect is introduced

Engineering Contradiction:

Improveunwanted low frequency signalsVSAvoidbaseline wander effect

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful baseline wander effect into a useful signal by sensing the wander current that flows through the feedback resistor. This wander current contains information about the baseline shift, which is then used to generate a compensation signal that cancels out the baseline wander, transforming a harmful artifact into a beneficial correction mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a feedback mechanism where the sensed wander current is fed back through a compensation circuit that generates a correction signal. This feedback loop continuously monitors the baseline wander and actively compensates for it, maintaining stable operating conditions despite the presence of filtering components

Inventive Principle:

Principle #23Feedback

2Object-generated harmful factors

If conventional baseline wander correction methods are applied, then baseline wander is reduced, but circuit complexity and additional data processing are introduced

Engineering Contradiction:

Improvebaseline wander effectVSAvoidcircuit architecture complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent introduces a wander current sensing path as an intermediary mechanism that indirectly measures baseline wander through current sensing rather than direct voltage measurement. This intermediary approach simplifies the correction circuitry by using current mirrors and transconductance amplifiers instead of complex digital processing units

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex digital baseline wander correction algorithms with an analog circuit implementation using current mirrors, transconductance amplifiers, and feedback resistors. This mechanical/electrical substitution eliminates the need for additional data processing while achieving effective baseline wander compensation through purely analog means

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-generated harmful factors

If conventional baseline wander correction is used, then baseline wander is addressed, but compensation time delay increases

Engineering Contradiction:

Improvebaseline wander effectVSAvoidcompensation time delay

Core Design Contradiction:

Object-generated harmful factorsVSLoss of time

Solution Approach 1:

The patent performs preliminary action by continuously sensing the wander current and maintaining readiness to compensate for baseline wander. The feedback circuit is always active and prepared to immediately counteract baseline shifts as they occur, rather than waiting for detection and processing delays

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by implementing a continuously active feedback loop that constantly monitors and compensates for baseline wander. The wander current sensing path operates without interruption, and the compensation signal is continuously generated and applied, eliminating gaps in correction that would cause time delays

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS11381222B2Apparatus for performing baseline wander correction with aid of differential wander current sensing

Publication Date: 2022.07.05 FARADAY TECH CORP

AI summary

An apparatus for performing baseline wander correction (BLWC) with the aid of differential wander current sensing includes filters and a correction circuit. The filters are positioned in a front-end circuit of a receiver and coupled to a set of input terminals of the receiver, and filter a set of input signals on the set of input terminals to generate a set of differential signals on a set of secondary terminals, for further usage by the receiver. The correction circuit is positioned in the frontend circuit and electrically connected to the set of input terminals and the set of secondary terminals, and performs BLWC on the set of differential signals according to the set of input signals. In the correction circuit, amplifiers and resistors form a differential wander current sensor to sense differential wander current, and a set of current mirrors generate corresponding baseline wander compensation current to perform BLWC.