Current-Mode Baseband Filter With Feedback Loop for Low-Distortion Paths

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Solution Overview

Problem

Existing quantum computing systems face challenges with high power consumption and distortion in signal paths, particularly in voltage mode representations, which affect coherence time and scalability of qubits.

Innovation Solution

Implementing a current-mode end-to-end signal path using a baseband filter with a feedback loop comprising an active and passive circuit branch, enabling current reuse and reducing conversions to minimize power consumption and distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If voltage mode signal path is used in quantum computing systems, then signal processing can be performed, but power consumption increases and distortion occurs

Engineering Contradiction:

Improvepower consumptionVSAvoidsignal distortion

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent replaces voltage mode signal processing with current mode signal processing throughout the signal chain. Current mode operation eliminates the need for voltage-to-current and current-to-voltage conversions, reducing power consumption and distortion. The baseband filter is implemented as a current mode filter with current inputs and current outputs, and the output stage uses a current mode amplifier, creating an end-to-end current mode signal path that avoids the harmful conversions inherent in voltage mode systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental operating parameter of the signal chain from voltage mode to current mode. This parameter change affects multiple components simultaneously: the baseband filter operates with current signals, the output stage uses current mode amplification, and the overall system achieves lower power consumption and reduced distortion by maintaining current mode operation throughout, thereby resolving the contradiction between power efficiency and signal integrity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If voltage-to-current and current-to-voltage conversions are performed in the signal path, then signal processing can be completed, but distortion products increase

Engineering Contradiction:

Improvesignal integrityVSAvoiddistortion products

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent substitutes current mode operation for voltage mode operation in the baseband filter and output stage. The baseband filter is designed with current inputs and current outputs, eliminating the need for voltage-to-current conversion at the filter input. The output stage uses a current mode amplifier that directly drives the output without requiring current-to-voltage conversion, thereby eliminating the distortion-generating conversions and preserving signal integrity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If current mode signal path is implemented, then power efficiency improves and distortion reduces, but circuit design complexity increases

Engineering Contradiction:

Improvepower efficiencyVSAvoidcircuit design

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the current mode operation across multiple functional blocks: the baseband filter and the output stage are both designed in current mode and are directly coupled together. This merging creates a unified current mode signal path that eliminates the need for interface conversions between voltage and current modes, reducing overall system complexity despite the specialized design requirements of current mode circuits.

Inventive Principle:

Principle #5Merging (Combining)

4Measurement precision

If baseband filter with feedback loop is used, then filtering performance improves, but circuit complexity increases

Engineering Contradiction:

Improvefiltering performanceVSAvoidcircuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements the baseband filter as a current mode filter with a feedback loop, where all internal signals are currents rather than voltages. The feedback mechanism uses current mode components, and the filtering is achieved through current mode integration and feedback. This current mode implementation provides the necessary filtering performance while maintaining consistency with the overall current mode architecture, avoiding additional voltage mode interfaces that would increase complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12438525B2Baseband filter for current-mode signal path

Publication Date: 2025.10.07 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

One or more systems, devices and/or methods of use provided herein relate to a baseband filter that can be used in a current-mode end-to-end signal path. The current-mode end-to-end signal path can include a digital to analog converter (DAC) operating in current-mode and an upconverting mixer, operating in current-mode and operatively coupled to the DAC. In one or more embodiments, a device used in the signal path can comprise a baseband filter that receives an input current and outputs an output current. The baseband filter can comprise a feedback loop component having an active circuit branch and a passive circuit branch coupled in a loop. A mirroring device can be coupled to the feedback loop component and can provide an output of the device. Selectively activating the mirroring device can vary gain, such as of the mirroring device.