Storage Cell Ring TDC With Loop Counting for Picosecond Timing
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Solution Overview
Problem
The performance of time-to-digital converters (TDCs) is limited by the resolution of analog-to-digital converters (ADCs) and the complexity of digital circuits, which restricts the accuracy, speed, and resolution of time measurements in electronic systems.
Innovation Solution
A bidirectional storage cell ring (BDSCR) is employed, oscillating in both clockwise and counterclockwise directions in response to phase errors, with a loop counter and analog quantifier working together to generate a high-resolution time measurement by concatenating less-significant and more-significant bits, reducing the complexity of the ADC required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard ADC is used for time-to-digital conversion, then the device complexity is reduced, but the measurement precision and resolution are limited
Solution Approach 1:
The patent divides the time measurement process into multiple segments by using a storage cell ring with multiple storage cells (e.g., 8 cells). Each storage cell contributes a portion of the time measurement, allowing the total time to be measured with higher resolution than a single ADC could achieve. The time interval is segmented into discrete storage cell traversal events, with each cell providing a time segment that is later summed to get the total time measurement.
Solution Approach 2:
The patent transitions from a single-dimensional ADC conversion to a multi-dimensional measurement approach by combining digital counting (loop counter) with analog voltage measurement (capacitor voltage). The storage cell ring adds a spatial dimension to the measurement by using the position of the oscillating signal around the ring to encode time information, while the capacitor voltage provides an additional analog dimension for fine resolution measurement.
2Measurement precision
If the ADC resolution is increased to improve time measurement precision, then the measurement precision improves, but the device complexity and power consumption increase
Solution Approach 1:
The power consumption burden is segmented and distributed across multiple storage cells rather than concentrated in a single high-resolution ADC. Each storage cell performs simple operations (voltage integration and threshold comparison) that consume minimal power, while collectively achieving high time measurement resolution that would require a much more power-hungry ADC.
Solution Approach 2:
The patent replaces the mechanical/electronic complexity of a high-resolution ADC with a different mechanism based on time-domain oscillation and voltage integration. Instead of using a complex ADC to directly convert time to digital, the system uses the natural oscillation of the storage cell ring and integrates voltage over time intervals, substituting a simpler physical mechanism for the complex electronic conversion process.
3Measurement precision
If a high-resolution ADC is used to achieve picosecond-level measurements, then the measurement precision improves, but the speed of conversion decreases
Solution Approach 1:
The storage cell ring operates as a periodic oscillator, with the signal circulating around the ring in regular cycles. This periodic action allows the system to naturally sample and measure time intervals at high speed, as each oscillation cycle provides a fresh measurement opportunity. The regular oscillation enables continuous high-speed time measurements without the conversion bottlenecks associated with high-resolution ADCs.
Solution Approach 2:
The storage cell ring performs preliminary time measurement through its oscillation and storage cell traversal before the final digital value is generated. The ring oscillator preemptively encodes the time interval information in its oscillation pattern and capacitor voltages, allowing the subsequent digital readout to simply decode pre-computed information rather than performing complex real-time conversion, thus enabling high speed.
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 resolution of time measurements beyond what is achievable with standard ADCs, allowing for precise time-to-digital conversions with reduced ADC complexity and increased speed, enabling measurements at the picosecond level.
Implementation Method 1
Each storage cell includes a respective capacitor for generating a respective integrated voltage responsive to a respective duration a respective storage cell is selected
Data Source
AI summary
In described examples, a storage cell ring includes circularly coupled storage cells. Each storage cell includes a respective capacitor for generating a respective integrated voltage responsive to a respective duration a respective storage cell is selected, a respective thresholding converter for generating a respective thresholded signal for indicating whether the respective integrated voltage has crossed a threshold, and respective selection circuitry configured to generate a respective select signal responsive to select signals generated by a respective adjacent storage cells. The ring is coupled to an analog quantifier for generating a conversion value responsive to the generated respective integrated voltage and a respective select signal. The ring is coupled to a loop counter for generating a loop count value responsive to changes of values of at least some of the respective thresholded signals. The conversion value and the loop count value can comprise a time measurement.