MRI Receiver Gain Switching for Wide Dynamic Range
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Solution Overview
Problem
Magnetic resonance imaging (MRI) receivers face challenges in achieving a sufficient dynamic range for signal reception due to the limitations of 16-bit Analog-to-Digital Converters (ADCs), leading to incomplete capture of magnetic resonance signals with amplitudes beyond their theoretical range, which is also a concern in other technologies like radar and radio communication.
Innovation Solution
A receiver system that determines a gain mode based on the amplitude of the analog signal, using a group delay circuit, a controller, a gain circuit, and an amplitude-phase-processing circuit to adjust the signal power and phase, ensuring real-time gain adjustment with low costs and power consumption, thereby expanding the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 16-bit ADC is used for signal conversion, then the device complexity and power consumption are kept low, but the dynamic range is limited to 96 dB which cannot accommodate the full 117 dB range of magnetic resonance signals
Solution Approach 1:
The receiver is divided into multiple gain modes (first gain mode and second gain mode) with different amplification factors. The signal processing path is segmented into different branches based on amplitude thresholds, allowing the system to handle both weak and strong signals appropriately without requiring a single high-complexity ADC capable of the full dynamic range.
Solution Approach 2:
The receiver dynamically switches between different gain modes based on the detected signal amplitude. The system transitions from a static ADC configuration to a dynamic system where the gain can be adjusted in real-time, enabling the receiver to adapt to varying signal strengths and expand its effective dynamic range beyond the fixed 96 dB limitation of a 16-bit ADC.
2Reliability
If the gain mode is adjusted in real-time based on signal amplitude, then the dynamic range is expanded, but the response time may be insufficient due to gain switching delays
Solution Approach 1:
The system performs preliminary detection of the signal amplitude and determines the appropriate gain mode before the actual signal processing begins. This advance preparation ensures that the gain switching is completed before the signal needs to be processed, eliminating delays and ensuring real-time performance despite the gain mode transitions.
Solution Approach 2:
A delay circuit is introduced as an intermediary element between the signal input and the gain adjustment stage. This delay circuit provides the necessary time buffer for the controller to detect the signal amplitude and switch to the appropriate gain mode, ensuring that the gain adjustment is completed before the signal processing occurs, thus resolving the timing conflict.
3Reliability
If multiple ADCs with different dynamic ranges are used to cover the full signal range, then the dynamic range is expanded, but the cost and power consumption increase significantly
Solution Approach 1:
Instead of using multiple ADCs simultaneously, the system segments the signal processing into different gain modes that are activated sequentially based on signal amplitude. This allows a single ADC to handle both weak and strong signals by adjusting the gain stage, eliminating the need for multiple power-consuming ADC units while maintaining complete signal reception capability.
Solution Approach 2:
A single ADC is made multi-functional through the implementation of multiple gain modes. The same ADC can process both weak signals (when high gain is applied) and strong signals (when low gain is applied), making it a universal component that replaces what would traditionally require multiple specialized ADCs, thereby reducing both cost and power consumption.
Data Source
AI summary
Methods, devices, and apparatus for signal reception are provided. In one aspect, a receiver includes: a group delay circuit configured to perform a group delay on an original analog signal to obtain a group delayed analog signal, a controller configured to determine a gain mode according to an amplitude of the original analog signal, a gain circuit coupled to the group delay circuit and the controller and configured to adjust a power of the group delayed analog signal according to the determined gain mode to obtain an adjusted analog signal, an analog-to-digital converter coupled to the gain circuit and configured to perform an analog-to-digital conversion on the adjusted analog signal to generate a digital signal, and an amplitude-phase-processing circuit configured to adjust amplitude and phase of the digital signal according to the determined gain mode.