Phase Interpolator Input Mapping for Nonlinear Output Correction

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Solution Overview

Problem

Phase interpolators introduce distortion in their output due to nonlinear behavior, which existing technologies have not effectively mitigated.

Innovation Solution

A pre-distorter is used to convert input values into replacement values that compensate for the nonlinearity of the phase interpolator, reducing distortion by adjusting the input signal to the phase interpolator before processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a phase interpolator is used to generate interpolated output signals, then signal phase flexibility is improved, but output signal linearity deteriorates due to nonlinearity

Engineering Contradiction:

Improvesignal phase flexibilityVSAvoidoutput signal linearity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by using a pre-distorter to modify the input signal before it reaches the phase interpolator. The pre-distorter applies inverse nonlinearity compensation to the input values, so that when the phase interpolator processes these pre-distorted values, the output becomes more linear. This anticipates and counteracts the nonlinearity effect before it occurs in the main signal path.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful nonlinearity of the phase interpolator into a benefit by characterizing its nonlinearity behavior and using that knowledge to create compensation values. The nonlinearity is measured and stored as lookup table values, then applied in reverse to cancel out the distortion, effectively turning the defect into a correctable characteristic.

Inventive Principle:

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

2Manufacturing precision

If replacement values are stored in a converter to compensate for nonlinearity, then output signal linearity is improved, but device complexity increases

Engineering Contradiction:

Improveoutput signal linearityVSAvoidconverter structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary component - the pre-distorter with lookup tables - that mediates between the input signal and the phase interpolator. This intermediary stores pre-calculated compensation values and applies them to correct the nonlinearity, acting as a buffer that simplifies the overall system architecture while improving linearity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses copying by creating a model of the phase interpolator's nonlinearity behavior through measurement and storing it as lookup table values. Instead of directly modifying the phase interpolator hardware, a digital copy of its characteristics is created and used to generate compensation values, simplifying the correction mechanism.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS8913688B1Pre-distortion for a phase interpolator with nonlinearity

Publication Date: 2014.12.16 XILINX INC

AI summary

An embodiment of an apparatus for nonlinearity compensation is disclosed. For an embodiment, a pre-distorter is coupled to receive a first signal. The pre-distorter is configured to convert first values of the first signal into second values for a second signal. The pre-distorter includes a converter for converting the first values to the second values. A phase interpolator is coupled to receive the second signal. The second values are associated with nonlinearity of the phase interpolator. The phase interpolator is configured to provide an interpolated output from the second signal. The second signal is adjusted for the nonlinearity of the phase interpolator by use of the second values.