AC-Coupled Video Link SAG Compensation via Adaptive Filtering

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Solution Overview

Problem

AC-coupled video transmission systems suffer from the signal amplitude gain (SAG) effect, which causes degradation of low-frequency components in video signals due to the high-pass filtering action of coupling capacitors, leading to costly and spatially prohibitive solutions for mitigating this issue.

Innovation Solution

An adaptive filtering method is employed to compensate for the SAG effect by applying a filter with a transfer function dependent on transmission parameters, adjusting these parameters based on predefined content extracted from the received signal, allowing for improved compensation of SAG effects due to PVT variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If AC-coupled transmission is used to transmit video signals, then signal transmission capability is improved, but SAG effect degrades low-frequency components

Engineering Contradiction:

Improvesignal transmission capabilityVSAvoidSAG effect

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the receiver detects SAG effect in the transmitted video signal, calculates compensation parameters, and sends feedback to the transmitter. The transmitter then adjusts its transmission parameters based on this feedback to compensate for the SAG effect, creating a closed-loop system that continuously optimizes signal quality.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes transmission parameters dynamically to compensate for SAG effect. Specifically, it adjusts the DC offset level and gain parameters of the video signal at the transmitter based on feedback from the receiver, thereby modifying the signal characteristics to counteract the low-frequency attenuation caused by AC coupling.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If larger coupling capacitors are used to reduce SAG effect, then SAG compensation is improved, but device area and cost increase

Engineering Contradiction:

ImproveSAG effect compensationVSAvoiddevice area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent replaces the passive physical solution of using large coupling capacitors with an active signal processing approach. Instead of relying on the physical properties of large capacitors to reduce SAG effect, the system uses digital signal processing and adaptive parameter adjustment to compensate for the effect, thereby eliminating the need for large physical components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the transmission signal parameters (DC offset, gain) dynamically to compensate for SAG effect, replacing the need for large physical capacitors. This parameter-based compensation approach achieves SAG mitigation without requiring additional physical space for large coupling components.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If DC-coupled transmission is used instead of AC-coupled, then SAG effect is eliminated, but cost and spatial requirements increase

Engineering Contradiction:

ImproveSAG effect eliminationVSAvoidcost and spatial requirements

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses feedback from the receiver to the transmitter to detect and compensate for SAG effect, enabling AC-coupled transmission to achieve performance comparable to DC-coupling without the associated cost and space penalties. The feedback loop allows the system to adaptively optimize transmission parameters.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent substitutes the physical DC-coupling architecture with AC-coupling combined with signal processing compensation. Instead of using DC-coupled transmission paths that require larger components and higher cost, the system uses AC-coupling with active SAG compensation through parameter adjustment and feedback control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10855951B2Methods and devices for compensating sag effect

Publication Date: 2020.12.01 ANALOG DEVICES GLOBAL UNLTD

AI summary

Disclosed herein are systems and methods for performing SAG effect compensation on a video signal received over an AC-coupled video link. In one aspect, a method for performing SAF effect compensation includes applying a filter to the received video signal to generate a corrected video signal, where a transfer function of the filter is dependent on a transmission parameter that is based on a plurality of parameters of the AC-coupled link. The method further includes extracting predefined content from the corrected video signal, and adjusting the transmission parameter based on a comparison of the extracted predefined content with certain expected content, so that adjusted transmission parameter can be used for one or more subsequent applications of the filter, thereby realizing an adaptive filter.