Parallel ADC and DAC Paths for Spur Cancellation

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Solution Overview

Problem

Analog to digital and digital to analog converter circuits introduce spurs, or unwanted signals, that degrade signal quality and reduce the spurious-free dynamic range, as existing technologies fail to effectively mitigate these spurs during conversion processes.

Innovation Solution

The use of parallel conversion components, such as ADCs or DACs, where one pathway is inverted or phase-shifted by 180 degrees relative to the other, and the outputs are combined to subtract or cancel out spurs, thereby reducing or eliminating them in the converted signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional single-pathway ADC or DAC circuits are used, then the device complexity is low, but spurs are introduced that degrade signal quality and reduce spurious-free dynamic range

Engineering Contradiction:

Improvesignal qualityVSAvoidconversion circuit structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The conversion process is divided into multiple parallel pathways (first and second ADCs/DACs) that process the signal independently. Each pathway processes a portion of the input signal, and their outputs are combined to produce the final converted signal with reduced spurs

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

One of the parallel pathways (specifically the second ADC or DAC) has its output inverted or phase-shifted by 180 degrees relative to the other pathway. This inversion causes spurs to cancel out when the outputs are combined, while the desired signal components add constructively

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If parallel conversion components with inversion are used, then spurs are reduced or eliminated, but the device complexity increases

Engineering Contradiction:

Improvespurious-free dynamic rangeVSAvoidparallel conversion pathways

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Multiple parallel conversion pathways are merged by combining their outputs through addition. The first and second converted signals are summed to produce the final output, achieving spur cancellation while maintaining signal integrity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The inversion or phase-shifting of one pathway transforms the harmful effect of spurs into a beneficial cancellation mechanism. By inverting the second pathway's output, spurs from both pathways destructively interfere and cancel each other, converting the potential harm of duplicated conversion circuits into a benefit for spur reduction

Inventive Principle:

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

Data Source

PatentUS11909411B2Reducing spurs in analog to digital and digital to analog conversions

Publication Date: 2024.02.20 VIAVI SOLUTIONS INC(US)

AI summary

Embodiments disclosed herein may reduce or even eliminate spurs introduced into the signals during analog to digital or digital to analog conversions. The spurs may be introduced by components such as clocks of the converter circuits. In an analog to digital conversion, the input signal may be split into two parts: the first portion passing through a first analog to digital converter (ADC) and an inverted second portion passing through a second ADC. A digital subtractor may subtract the output of the second ADC from the output of the first ADC converter thereby reducing the spurs. In digital to analog conversion, a digital input is passed through a first digital to analog converter (DAC) and an inverted digital input is passed through a second DAC. The output of the second DAC is inverted and combined with the output of the first DAC to reduce the spurs.