FFT Phase Spur Detection for Mixed-Signal Sampling Alignment

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Solution Overview

Problem

High speed parallel sampling interfaces in mixed analog/digital systems suffer from data misalignment due to routing length differences, leading to spurs in the signal, which can cause unintended jumps and degrade system performance.

Innovation Solution

Detect spurs in a sampled waveform by acquiring a time domain vector, applying FFT to transform it into the frequency domain, calculating the phase response, and comparing it to a clean phase profile or deviation tolerance to identify spurs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If delay elements are added to resynchronize data, then timing alignment is improved, but device complexity increases

Engineering Contradiction:

Improvedata timing alignmentVSAvoiddelay elements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent measures and characterizes delay variations during the design phase, storing delay maps that capture routing length differences between wires. This preliminary characterization allows the system to pre-compensate for timing issues without adding complex delay elements during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces physical delay elements with a software-based solution using delay maps and lookup tables. Instead of adding hardware components to resynchronize data, the system uses pre-measured delay characteristics stored in memory to compensate for timing variations through digital processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If FFT and phase response analysis are used to detect spurs, then measurement precision is improved, but use of energy increases

Engineering Contradiction:

Improvespur detection accuracyVSAvoidcomputation energy

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the phase response information from the FFT output, ignoring magnitude information. By focusing solely on phase response and comparing it against pre-stored clean phase profiles, the system reduces computational requirements while maintaining accurate spur detection capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent pre-calculates and stores clean phase profiles during system initialization or design phase. During operation, the system only needs to perform FFT, extract phase response, and compare against stored references, significantly reducing real-time computational energy requirements while maintaining detection precision.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12523680B2Spur detection in a sampled waveform in a mixed analog/digital system using the phase of the frequency response

Publication Date: 2026.01.13 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Method, apparatus and computer program product for spur detection in a sampled waveform in a mixed analog/digital system using the phase of the frequency response comprising acquiring a sample waveform including a set of discrete uniformly spaced samples from a target system, wherein the sample waveform is a time domain vector; applying FFT transforming the time domain vector into the frequency domain; analyzing the frequency domain response including calculating the phase response; and determining whether the sample waveform has spurs including comparing the phase response to a clean phase profile including determining that the phase response having a phase profile value outside a phase deviation tolerance has one or more spurs and determining that the phase response having a phase profile value inside the phase deviation tolerance has no spurs, wherein a spur indicates unaligned data having a delayed bit flip.