Programmable-Gain Amplifier With Super-gm Feedback for NMR Linearity

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Solution Overview

Problem

Designing integrated NMR transceiver circuits for miniaturized NMR systems poses challenges in achieving a standardized interface between components that maintain performance parameters like gain, bandwidth, noise figure, and linearity, especially at lower supply voltages, and requires efficient mixer and programmable-gain amplifier designs that are stable across process, voltage, and temperature variations.

Innovation Solution

Implementing an AC coupling network and buffer circuits with source followers, along with voltage-mode passive mixers and super-transconductance feedback loops in the programmable-gain amplifier, to decouple stages and maintain performance across varying conditions, allowing easy reconfiguration and parallel connectivity of components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If integrated NMR transceiver circuits are designed with miniaturization, then portability and signal quality are improved, but design complexity and difficulty in achieving standardized interfaces increase

Engineering Contradiction:

ImproveNMR system sizeVSAvoidinterface design complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The NMR transceiver is divided into modular functional blocks (RF front-end, mixer, PGA, ADC) that can be independently designed and then integrated. Each block has standardized interfaces that simplify the overall integration process while maintaining miniaturization benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The PGA dynamically adjusts gain parameters to optimize signal levels for the ADC across different operating conditions. This parameter control ensures that the miniaturized circuit maintains optimal performance despite size constraints that affect electrical characteristics.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If a standardized interface is implemented between receiver components, then ease of reconfiguration and manufacturing are improved, but maintaining performance parameters (gain, bandwidth, noise figure) becomes more difficult

Engineering Contradiction:

Improvereceiver reconfiguration easeVSAvoidperformance parameter stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The PGA employs feedback mechanisms to automatically adjust gain and optimize signal levels. This feedback control compensates for variations introduced by standardized interfaces, maintaining stable noise figure and gain parameters across different configurations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The receiver architecture uses dynamically adjustable parameters (gain, bandwidth) that can be reconfigured through software control. This dynamic adaptability allows the same hardware to maintain optimal performance across multiple applications while using standardized interfaces.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If voltage-mode passive mixers are used in integrated circuits, then area and power efficiency are improved, but linearity and matching performance deteriorate

Engineering Contradiction:

Improvepower consumptionVSAvoidlinearity and matching

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

Source follower buffer circuits are inserted as intermediary stages between the voltage-mode passive mixer and other receiver components. These buffers provide impedance transformation and isolation, improving linearity and matching performance without significantly increasing power consumption or area.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The design replaces traditional current-mode mixer architectures with voltage-mode passive mixers combined with buffered stages. This substitution achieves better power and area efficiency while the buffer stages compensate for the loss in linearity, effectively replacing the need for complex current-mode circuitry.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Speed

If programmable-gain amplifier is designed with open-loop architecture, then bandwidth and power efficiency are improved, but gain stability and linearity worsen

Engineering Contradiction:

ImprovebandwidthVSAvoidgain stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The PGA combines open-loop amplifier architecture with super-gm feedback loops and constant-gm biasing circuits. This composite approach maintains the wide bandwidth and power efficiency of open-loop design while adding feedback mechanisms that stabilize gain and improve linearity through the high-gm paths.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP4160241B1NMR apparatus with a programmable-gain amplifier with super-gm feedback

Publication Date: 2025.09.10 WAVEGUIDE CORP

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AI summary

A programmable gain amplifier, PGA (800) comprising an open-loop source-degenerated amplifier (802) comprising a pair of input devices (804, 806), a pair of super-gm feedback loops (812), each coupled to one of the input devices (804, 806) for boosting an effective transconductance thereof and a constant-gm bias circuit (818) for setting a bias current of devices in the open-loop source-degenerated amplifier (802). The PGA (800) may be used in an NMR apparatus (200) for processing NMR signals.