Switchable Filter Precharging for Minimal Signal Transients

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Solution Overview

Problem

Existing switchable filters generate detrimental transients when coupled into a signal path, which can disrupt the fine tuning of sensitive devices such as quantum computers, requiring slow and complex tuning processes.

Innovation Solution

A switchable capacitor assembly with a voltage follower and a second switch to short-circuit the resistor, allowing the filter to be coupled in and out without generating transients, using a second switch to minimize voltage differences and reduce transient generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a switchable filter is coupled into a signal path, then signal filtering is achieved, but detrimental transients are generated that disrupt fine tuning of sensitive devices

Engineering Contradiction:
Improvesignal filtering performanceVSAvoidtransient generation
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-charging the capacitor through the voltage follower before the filter is switched into the signal path. This ensures the capacitor is already at the correct voltage potential, preventing transient generation when the filter is engaged. The method prepares the system in advance to avoid the harmful effect of transients.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The voltage follower acts as an intermediary between the signal path and the capacitor. It buffers the voltage and provides a controlled charging path through the resistor, isolating the capacitor from direct switching transients. This intermediary component enables smooth voltage transfer without generating detrimental transients.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If tuning of sensitive devices is performed slowly to avoid transients, then device stability is maintained, but tuning time increases significantly

Engineering Contradiction:
Improvedevice stabilityVSAvoidtuning time
Core Design Contradiction:
Stability of the object's compositionVSLoss of time

Solution Approach 1:

By pre-charging the capacitor before switching the filter into the signal path, the system eliminates the need for slow tuning. The capacitor is prepared in advance at the correct voltage, allowing immediate engagement of the filter without causing transients. This resolves the time-stability trade-off by preparing the system beforehand.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The voltage follower provides voltage feedback from the signal path to the capacitor through the resistor. This feedback mechanism ensures the capacitor voltage tracks the signal path voltage, maintaining stability while enabling fast switching. The feedback loop automatically adjusts the capacitor charge state to match the desired operating condition.

Inventive Principle:
Principle #23Feedback

3Ease of operation

If a capacitor is directly switched into a signal path, then filter switching is simple, but voltage differences cause transient generation

Engineering Contradiction:
Improvefilter switching simplicityVSAvoidvoltage difference transients
Core Design Contradiction:
Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The voltage follower serves as an intermediary that mediates the voltage transfer between the signal path and the capacitor. It provides galvanic isolation while maintaining voltage tracking, eliminating direct voltage differences that would cause transients. This intermediary approach maintains switching simplicity while preventing harmful voltage mismatches.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters by introducing a high-input-impedance voltage follower that tracks the signal path voltage. This parameter change ensures the capacitor charges to the correct voltage through the resistor without creating significant voltage drops or transients, maintaining both simplicity and transient-free operation.

Inventive Principle:
Principle #35Parameter changes

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

Enables faster and more precise tuning of sensitive devices by minimizing transients, allowing swift signal variation and reducing the time required for optimization.

Implementation Method 1

A voltage follower is provided having an input operationally connected to the first terminal and an output operationally connected to the first resistor. The voltage follower may determine or detect the voltage on the first terminal and may output, on an output, a voltage corresponding more or less to that voltage.

Methodology Applied
Scientific EffectVoltage follower operation:

Implementation Method 2

The assembly further comprises a second switch configured to short circuit the first resistor. Short circuiting a resistor means providing an alternative electric path around the resistor, where the alternative electric path has a resistance lower than that of the first resistor.

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP4352876B1A method of precharging a switchable filter
Publication Date: 2026.02.18 QDEVIL APS
  • EP4352876B1 patent drawingFigure 1~3

AI summary

A switching or switchable filter configured to switch in and out a filter with a minimal transient, the filter comprising a capacitor charged via a voltage follower. A resistor between the capacitor and the voltage follower may be short-circuited.