SiPM Readout Circuit Using Charge Sharing Anger Logic
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Solution Overview
Problem
Current PET systems using silicon photomultipliers (SiPMs) face challenges in reducing the number of readouts while maintaining performance in detecting timing and energy information, as multiplexing approaches often degrade signal quality and increase dark noise.
Innovation Solution
The implementation of a charge-sharing Anger logic system using capacitor chains and high-pass filters, combined with two-stage summing amplifiers with weighting resistors, allows for efficient multiplexing of SiPM signals to reduce the number of readouts while preserving signal quality and maintaining pulse shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiplexing approaches are used to reduce the number of readouts in SiPM-based PET detectors, then the number of readout channels is reduced, but signal quality degrades and dark noise increases
Solution Approach 1:
The patent divides the SiPM array into multiple independent readout groups, where each group shares a common readout channel. By segmenting the array into manageable groups (e.g., 4x4 or similar configurations), the system reduces the total number of readout channels while maintaining signal integrity within each group. The segmentation allows for localized charge sharing and Anger logic processing that preserves timing and energy information quality.
Solution Approach 2:
The patent introduces charge sharing circuits and Anger logic processing as intermediary stages between the SiPM sensors and the reduced number of readout channels. These intermediaries process the signals from multiple SiPMs before they reach the final readout, enabling the system to reduce channel count while maintaining signal quality through intelligent signal processing rather than simple signal aggregation.
2Device complexity
If multiplexing approaches are used to reduce the number of readouts in SiPM-based PET detectors, then the number of readout channels is reduced, but dark noise increases
Solution Approach 1:
By segmenting the SiPM array into smaller readout groups, the patent limits the accumulation of dark noise within each group. Dark noise from individual SiPMs is processed locally through charge sharing and Anger logic before being sent to the readout channel, preventing the summation of dark noise from the entire array that would occur with full multiplexing.
Solution Approach 2:
The charge sharing and Anger logic circuits act as intermediaries that filter and process signals before they reach the readout channel. These intermediaries can distinguish between genuine signal events and dark noise based on their characteristic waveforms and timing, effectively suppressing dark noise while preserving signal quality in the reduced channel configuration.
3Measurement precision
If one-to-one coupling between SiPMs and scintillator crystals is used, then detection performance is improved, but the number of readout channels increases
Solution Approach 1:
The patent merges the readout signals from multiple SiPMs that are one-to-one coupled to scintillator crystals by implementing charge sharing and Anger logic. This merging process combines the information from multiple high-performance SiPM-crystal pairs into a reduced number of readout channels, maintaining the detection precision benefits of one-to-one coupling while reducing the overall channel count through intelligent signal combination.
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
This approach enhances timing resolution, improves signal-to-noise ratio, and allows for precise crystal identification, effectively reducing the number of readouts in PET systems without degrading performance.
Implementation Method 1
a first capacitor chain for charge-sharing Anger Logic in rows
Implementation Method 2
terminated both ends of a charge-sharing chain with (a) high-pass filters
Implementation Method 3
using weighting resistors configured in a two-stage summing amplifier configuration
Data Source
AI summary
A method and an apparatus are provided for using a capacitor chain to perform charge sharing and Anger logic to determine, for charge pulses arising from gamma-ray detection, a row position along an array of scintillation-based gamma-ray detectors. Further, high-pass filters configured at the ends of the capacitor chain perform pulse shaping to preserve timing information. To determine the column position for charge pulses, a two-stage summing amplifier configuration is used with weighting amplifiers controlling the relative gain of the second-stage amplifier with respect to respective columns in the array. Each detector element in the array is a silicon photomultiplier (e.g., Geiger-mode avalanched photodiodes biased above breakdown voltage). Position information can be generated by Anger logic on four outputs from the second-stage amplifiers. Energy and timing information can be generated as a sum of the four outputs from the second-stage amplifiers.