MRI RF Receiver Gain Control for Single-Bit Sigma-Delta Dynamic Range
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Solution Overview
Problem
Existing radio frequency (RF) receiver systems in magnetic resonance (MR) imaging face challenges in extending their dynamic range without increasing complexity and power consumption, as multi-bit feedback DACs and higher order loop filters complicate design and consume excessive power.
Innovation Solution
A single-bit sigma delta ADC with a variable output strength feedback DAC, coupled with an automatic gain control circuit and a signal processing chain, including digital down converters and a numerical controlled oscillator, to dynamically adjust gain and frequency shift signals, thereby extending the dynamic range while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-bit feedback DAC is used to extend dynamic range, then the dynamic range of the ADC is increased, but the device complexity and power consumption increase significantly
Solution Approach 1:
The patent segments the dynamic range extension function into two parts: a single-bit sigma-delta ADC for basic conversion and a separate feedback DAC for dynamic range extension. This segmentation allows the ADC to remain simple while the DAC handles the complexity of multi-level feedback, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent introduces an intermediary feedback DAC that mediates between the single-bit ADC and the input signal. The feedback DAC converts the single-bit output into multi-level feedback signals, effectively extending the dynamic range without requiring the ADC itself to be complex. This intermediary component resolves the contradiction by externalizing the complexity from the ADC core.
2Measurement precision
If a multi-bit feedback DAC is used to extend dynamic range, then the dynamic range is increased, but power consumption increases
Solution Approach 1:
The patent segments the power consumption burden by separating the ADC core (low power single-bit operation) from the feedback DAC (which handles dynamic range extension). This segmentation allows the majority of the conversion process to consume minimal power while only the feedback path consumes additional power for dynamic range extension, resolving the contradiction between measurement precision and power consumption.
Solution Approach 2:
The patent changes the operating parameters of the feedback DAC dynamically based on the input signal characteristics. By adjusting the feedback DAC's output levels according to the actual signal range, the system achieves high dynamic range when needed while consuming less power during normal operation, resolving the contradiction between measurement precision and power consumption.
3Measurement precision
If the feedback DAC is made highly linear to compensate errors, then the dynamic range and fidelity are maintained, but the device complexity increases
Solution Approach 1:
The patent inverts the traditional approach by using a single-bit ADC with feedback instead of a multi-bit ADC without feedback. This inversion places the linearity requirements on the feedback path rather than the ADC core, allowing the main conversion process to be inherently linear while the feedback DAC handles any necessary corrections, resolving the contradiction between signal fidelity and device complexity.
Solution Approach 2:
The patent implements a feedback mechanism where the output of the single-bit ADC is fed back through a DAC to the input. This feedback loop inherently corrects for non-linearities and errors, maintaining high signal fidelity without requiring the feedback DAC to be perfectly linear. The feedback principle resolves the contradiction by using the system's own output to correct its input, reducing the linearity burden on individual components.
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AI summary
For a radio frequency (RF) receiver system (1) for providing magnetic resonance (MR) information from an examination space of a MR imaging system, a solution for increasing the dynamic range of the radio frequency (RF) receiver system (1) for a better imaging performance shall be created. A sigma delta ADC of the RF receiver system operates in single-bit mode with an automatic gain gontrol (AGC) circuit used to control the DAC feedback strength thereby extending the dynamic range of the receiver to match the MRI signal. The present invention also refers to a magnetic resonance (MR) imaging system, a method A method for extending the dynamic range of a radio frequency (RF) receiver system, a software package for a magnetic resonance (MR) imaging system, a software package for upgrading a magnetic resonance (MR) imaging system and a computer program product.