PET Sensor Network Clock Synchronization With Picosecond Feedback
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Solution Overview
Problem
Current sensor systems for applications like PET, LiDAR, and FLIM face challenges in achieving picosecond-level time synchronization accuracy due to manufacturing variations, temperature, and power supply mismatches, which hinder the precise measurement of photon time-of-flight and spatial resolution.
Innovation Solution
A sensor network architecture utilizing a daisy-chained configuration with custom integrated circuits and a physical layer protocol for picosecond time digitization, including a Phase-Locked Loop (PLL) and Time Digitization Units (TDUs), allows for chip-to-chip synchronization and compensation for variations, ensuring accurate time synchronization across multiple sensor modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive synchronization approach is used with matched-length traces and identical clock buffers, then device complexity is reduced, but measurement precision deteriorates due to manufacturing variations, temperature, and power supply mismatches causing time skew
Solution Approach 1:
Instead of passively distributing identical clock signals and hoping for matching arrival times, the invention actively measures the actual arrival time differences at each sensor chip and uses feedback to compensate for these differences. The system inverts the approach by measuring skew rather than assuming it away, enabling picosecond-level synchronization accuracy despite manufacturing variations and environmental conditions.
2Productivity
If more sensor chips are added to improve system sensitivity and measurement throughput, then productivity increases, but maintaining synchronization accuracy becomes more difficult due to accumulated trace mismatches and chip variations
Solution Approach 1:
The invention implements feedback by having each sensor chip measure the actual arrival time of the reference clock signal and report this information back to the system. This feedback mechanism allows the system to compensate for accumulated trace mismatches and chip-to-chip variations, maintaining picosecond synchronization accuracy even as the number of sensor chips increases to improve measurement throughput.
3Measurement precision
If active synchronization strategy is implemented to adjust for trace mismatch and chip variations, then measurement precision improves, but device complexity increases due to additional circuitry and calibration requirements
Solution Approach 1:
The invention applies self-service by enabling each sensor chip to autonomously measure its own clock signal arrival time and generate correction data. This distributed self-measurement approach reduces the need for complex external calibration equipment and centralized control, achieving picosecond synchronization accuracy with manageable system complexity.
Data Source
AI summary
A sensor network, which includes a sensor controller serially coupled to a plurality of sensor modules, is configured to program the sensor modules so as to transfer measurement data to the sensor controller and to synchronize the sensor modules to picosecond accuracy via on-chip or on-module custom circuits and a physical layer protocol. The sensor network has applications for use in PET, LiDAR or FLIM applications. Synchronization, within picosecond accuracy, is achieved through use of a picosecond time digitization circuit. Specifically, the picosecond time digitization circuit is used to measure on-chip delays with high accuracy and precision. The delay measurements are directly comparable between separate chips even with voltage and temperature variations between chips.