Multi-Mode SAR ADC for Photon Counting Charge-Sharing Resolution
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Solution Overview
Problem
Photon counting X-ray systems face challenges with charge-sharing among multiple pixels due to electron cloud spread, requiring complex and power-intensive circuitry for accurate resolution, which occupies substantial area.
Innovation Solution
A multi-mode analog-to-digital converter (ADC) that operates in successive approximation and energy threshold modes, allowing for digital analysis of charge sharing, reducing power consumption and circuit area by adapting to high or low intensity areas and using anti-charge sharing logic to optimize pixel updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex circuitry is used to resolve charge-sharing among multiple pixels, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces complex analog charge-sharing resolution circuitry with a digital domain solution. Photon events are detected and processed digitally, where charge-sharing is resolved through computational algorithms rather than physical circuit components. This substitution of digital processing for analog circuitry reduces device complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces an intermediary digital processing stage between photon detection and final image formation. This intermediary layer allows for flexible, programmable charge-sharing resolution algorithms that can be adapted to different imaging conditions without requiring hardware changes, thereby reducing overall system complexity.
2Measurement precision
If complex circuitry is used to resolve charge-sharing among multiple pixels, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent replaces power-intensive analog circuitry with lower-power digital processing. By moving charge-sharing resolution to the digital domain, the system eliminates the need for high-power analog components while achieving the same measurement precision through computational methods.
Solution Approach 2:
The patent changes the operational parameters from analog domain processing to digital domain processing. This parameter change enables the use of software-based algorithms for charge-sharing resolution, which consume significantly less power than dedicated analog circuitry while maintaining or improving measurement accuracy.
3Measurement precision
If complex circuitry is used to resolve charge-sharing among multiple pixels, then measurement precision is improved, but circuit area increases
Solution Approach 1:
The patent substitutes physical circuit components with digital processing elements. By resolving charge-sharing in the digital domain, the system eliminates the need for extensive analog circuitry, thereby reducing the physical area occupied by charge-sharing resolution hardware while maintaining measurement precision.
Solution Approach 2:
The patent implements a universal digital processing platform that can handle charge-sharing resolution for all pixels through a single programmable system. This multi-functional approach replaces the need for dedicated charge-sharing circuitry at each pixel location, significantly reducing overall circuit area while maintaining precision across the entire detector array.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively counters charge-sharing in the digital domain, providing higher conversion rates and accuracy while minimizing power consumption and circuit complexity, enhancing the performance of photon counting X-ray systems.
Implementation Method 1
a photon sensor, a charge sensitive amplifier (CSA) and an ADC. The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses
Implementation Method 2
The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses
Data Source
AI summary
A photon counting system includes a photon sensor, a charge-sensitive amplifier (CSA) and an analog-to-digital converter (ADC). The CSA is configured to convert photon energy detected by the photon sensor to voltage pulses. The ADC is configured to digitize the voltage pulses generated by the CSA. The ADC includes successive approximation circuitry. The successive approximation circuitry includes an N-bit digital-to-analog converter (DAC), an N-bit successive approximation register (SAR), a plurality of N-bit registers, and a multiplexer configured to selectively route outputs of the SAR and outputs of the N-bit registers to the DAC for conversion to an analog signal.