SiPM Microcell Interconnects Using Impedance Matching Networks
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Solution Overview
Problem
Radiation detection devices employing silicon photomultipliers (SiPM) face challenges in achieving good timing resolution due to pulse shape distortions caused by transmission line reflections and impedance mismatches, leading to variations in pulse propagation across microcells within the array.
Innovation Solution
The implementation of impedance matching networks in the circuit traces connecting microcells in SiPM arrays helps reduce reflection and impedance mismatch issues, preserving timing information and improving pulse shape by using transmission lines such as slot, microstrip, or stripline with proper matching networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trace length is extended to equalize pulse propagation across microcells, then timing resolution is improved, but parasitics increase and signal pulse shape degrades
Solution Approach 1:
The patent transforms the interconnect structure from traditional metal traces to transmission line structures (microstrip, stripline, or coplanar waveguide) with controlled impedance parameters. This allows the interconnect to function as a proper transmission medium, controlling signal propagation characteristics and reducing parasitic effects while maintaining timing resolution.
Solution Approach 2:
The patent introduces impedance matching networks as intermediary components between microcells and readout circuits. These matching networks act as buffers that transform impedance levels, reducing reflections and parasitic interactions while preserving signal integrity and timing information.
2Device complexity
If traditional metal traces are used to interconnect microcells, then device complexity is reduced, but transmission line reflections and impedance mismatches cause pulse shape distortion
Solution Approach 1:
The patent replaces traditional metal trace interconnects with transmission line structures that have controlled electromagnetic field distributions. This substitution transforms the interconnect from a simple conductive path to a controlled electromagnetic transmission medium, reducing reflections and impedance mismatches while maintaining manufacturing feasibility.
3Area of stationary object
If microcells are positioned at different locations in the array, then area coverage is improved, but transit time variation degrades pulse characteristics
Solution Approach 1:
The patent implements local impedance matching networks at or near each microcell position. These local matching structures compensate for position-dependent variations in transit time and signal characteristics, allowing microcells to be distributed across large areas while maintaining uniform pulse characteristics from all positions.
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 the timing resolution of photon events by minimizing signal distortions and maintaining the integrity of pulse shapes, particularly in analog SiPM devices, leading to improved performance across the SiPM array.
Implementation Method 1
transmission line (e.g., slot line, microstrip, stripline, etc.) circuit traces with proper matching network(s) are fabricated in the photomultiplier array to interconnect the microcells
Implementation Method 2
Proper matching and termination eliminates the reflection, improves the pulse shape in analog SiPM
Implementation Method 3
circuit traces with proper matching network(s) are fabricated in the photomultiplier array to interconnect the microcells
Data Source
AI summary
A silicon photomultiplier array including a plurality of microcells arranged in rows and columns. A plurality of circuit traces connecting microcell output ports to the array pixel output port, with one or more impedance matching networks connected to at least one of the circuit traces. The impedance matching networks can be connected between each row circuit trace and the pixel output port. Impedance matching networks can be located between junctions of adjacent microcell output ports and row circuit traces.