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

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Solution Overview

Problem

Quantum computing systems face challenges with high power consumption and distortion in signal paths, particularly in cryogenic environments, due to the use of voltage mode representations, which limit scalability and coherence time of qubits.

Innovation Solution

Implementing a current-mode end-to-end signal path with a baseband filter that includes a feedback loop with both active and passive circuit branches, allowing for current reuse and reduced distortion by minimizing voltage-to-current and current-to-voltage conversions, and enabling cascaded filtering solutions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If voltage mode representations are used in signal paths, then conventional signal processing can be achieved, but power consumption increases and distortion occurs

Engineering Contradiction:

Improvepower consumptionVSAvoiddistortion

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

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, thereby reducing power consumption and minimizing distortion products generated by these conversion stages. The entire signal path from DAC to output is implemented in current mode, substituting the conventional voltage mode architecture.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental operating parameter of the signal path from voltage mode to current mode. This parameter change affects multiple stages including the baseband filter, mixer, and output stage, enabling current reuse and reducing the number of conversion stages required, which directly reduces power consumption and distortion.

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If voltage-to-current and current-to-voltage conversions are performed in the signal path, then signal processing functions can be implemented, but additional distortion products are introduced

Engineering Contradiction:

Improvedistortion productsVSAvoidsignal path conversions

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent substitutes current mode operation for voltage mode operation in all signal processing stages. By implementing the baseband filter, mixer, and output stage in current mode, the system eliminates multiple voltage-to-current and current-to-voltage conversion stages that would otherwise generate distortion products. The current mode architecture maintains full signal processing functionality without requiring these harmful conversions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

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

Engineering Contradiction:

Improvepower efficiencyVSAvoidcircuit design

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent implements feedback mechanisms in the current mode baseband filter to stabilize operation and simplify design. The feedback loop compensates for variations in current mode parameters and ensures stable filtering performance. This feedback approach helps manage the increased design complexity by providing automatic stabilization and performance optimization.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces intermediate current mode stages that facilitate smooth signal transitions between different functional blocks. These intermediate stages act as mediators, ensuring proper impedance matching and signal level translation in current mode, which simplifies the overall circuit design while maintaining power efficiency and low distortion characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Loss of energy

If conventional baseband filter design is used, then filtering function is provided, but current reuse is limited and power consumption is high

Engineering Contradiction:

Improvecurrent reuseVSAvoidpower consumption

Core Design Contradiction:

Loss of energyVSPower

Solution Approach 1:

The patent merges the baseband filter design with the subsequent mixer stage in a unified current mode architecture. This merging enables current reuse by allowing the output current of the filter to directly drive the mixer without requiring separate voltage mode stages. The integrated design shares current paths between stages, reducing total power consumption while maintaining filtering functionality.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11736091B2Baseband filter for current-mode signal path

Publication Date: 2023.08.22 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.