Echo Cancellation Filter for Time-of-Flight ADC Baseline Perturbations

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Solution Overview

Problem

In Time of Flight mass spectrometry, small impedance mismatches in signal lines cause reflections and parasitic capacitance effects, leading to unwanted perturbations and artefacts in mass spectra, particularly at high ion flux, which existing finite impulse response (FIR) filters do not adequately address by reducing baseline distortions in digitized signals.

Innovation Solution

Applying a finite impulse response (FIR) filter or echo cancellation filter to digitized signals from ion detectors, with filter coefficients set to match and reduce baseline perturbations, echoes, and ringing effects, thereby producing a second digitized signal with minimized distortions, which can then be processed to improve mass spectral data quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If signal lines with impedance mismatches are used to transmit ion detector signals, then the signal can be transmitted to the ADC, but reflections and baseline perturbations occur that degrade mass spectral quality

Engineering Contradiction:

Improvesignal transmissionVSAvoidbaseline perturbations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by measuring and characterizing the impulse response of the signal line before actual ion detection. This pre-characterization allows the system to prepare correction filters that compensate for known impedance mismatches and reflections, eliminating baseline perturbations before they affect mass spectral quality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses copying by creating a digital model (impulse response) of the signal line's electrical characteristics. This copy is then used to generate correction filters that replicate the inverse of the signal line's distortions, allowing digital cancellation of reflections and baseline perturbations without modifying the physical signal line

Inventive Principle:

Principle #26Copying

2Ease of manufacture

If standard FIR filters are applied to digitized signals, then some signal processing is achieved, but baseline perturbations and ringing effects are not adequately reduced

Engineering Contradiction:

Improvesignal processingVSAvoidmass spectral data quality

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting FIR filter coefficients based on the measured impulse response of the signal line. Instead of using fixed standard filter parameters, the system tailors the filter characteristics to match the specific electrical properties of its signal path, optimizing baseline correction for its particular conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback by using the measured impulse response from the signal line to continuously optimize the FIR filter coefficients. The system measures the actual signal line characteristics and uses this information to adjust the filter parameters, creating a closed-loop system that adapts to the specific electrical environment

Inventive Principle:

Principle #23Feedback

3Productivity

If high ion flux is detected, then more mass spectral data is obtained, but artefacts from reflections and baseline perturbations increase

Engineering Contradiction:

Improveion detection rateVSAvoidspectral artefacts

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of reflections into a benefit by measuring the impulse response caused by impedance mismatches and using this information to create correction filters. The same physical phenomenon that causes artefacts at high ion flux is characterized and then used to generate the solution that eliminates those artefacts

Inventive Principle:

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

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The approach significantly reduces baseline perturbations and artefacts in mass spectra, enhancing the accuracy and clarity of mass spectral data without altering the shape or width of ion peaks, particularly effective at high ion flux conditions.

Implementation Method 1

echo cancellation filter to the first digitised signal in order to reduce the effect of baseline perturbations, echoes or ringing effects

Methodology Applied

Scientific EffectEcho cancellation: Echo

Implementation Method 2

applying a finite impulse response ('FIR') filter or an echo cancellation filter to the first digitised signal

Methodology Applied

Scientific EffectFinite impulse response filtering: Filter (electronic)

Data Source

PatentUS10825671B2Echo cancellation for time of flight analogue to digital converter

Publication Date: 2020.11.03 MICROMASS UK LTD

AI summary

A method of mass spectrometry is disclosed comprising digitising a signal output from a detector to provide a first digitised signal. A finite impulse response (“FIR”) filter, a digital filter or an echo cancellation filter is applied to the first digitised signal in order to reduce the effect of baseline perturbations, echoes or ringing effects. Alternatively, an analogue signal output from a detector is passed to one or more first power splitters or dividers, wherein one or more first transmission lines are attached to one or more ports of one more said first power splitters or dividers in order to reduce the effect of baseline perturbations, echoes or ringing effects.