Current-Mode Time Interpolator Circuit for Picosecond Resolution
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Solution Overview
Problem
Existing time interpolator circuits in frequency counters lack simplicity, accuracy, and cost-effectiveness for modern applications, requiring improvements to enhance measurement resolution and precision beyond digital circuit limitations.
Innovation Solution
A time interpolator circuit design featuring a current source, diode, capacitor, and logic switches for controlled charging and discharging, with a buffer amplifier and ADC for precise voltage measurement, allowing for accurate time-to-voltage conversion and digital processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitor charging circuits are used for time interpolation, then measurement resolution can be improved, but circuit complexity and cost increase
Solution Approach 1:
The patent changes the fundamental operating parameters of the interpolator by using a current-mode architecture instead of voltage-mode capacitor charging. The current source directly charges the capacitor, and the charging current magnitude encodes the time interval information, allowing high-resolution time measurement while simplifying the overall circuit structure through direct digital interface
2Measurement precision
If high-precision time interpolation is implemented, then measurement accuracy improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces complex analog voltage comparison mechanisms with a current-mode digital interface. The time interval is converted directly into a digital count by measuring the charging current of the capacitor, eliminating the need for precision voltage references, complex comparator circuits, and calibration mechanisms, thereby reducing manufacturing cost while maintaining high accuracy
3Ease of manufacture
If simple interpolator circuits are used, then manufacturing cost decreases, but measurement repeatability deteriorates
Solution Approach 1:
The patent implements a self-calibrating current source that automatically maintains constant current output despite variations in power supply voltage or temperature. The circuit uses the capacitor's own charging characteristics to generate a time-proportional current that is inherently stable and repeatable, eliminating the need for external calibration circuits or complex stabilization mechanisms
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 circuit provides high repeatability with approximately ten picosecond precision and rapid measurement readiness, suitable for integration into frequency counters and other time-measuring devices, offering a simple, inexpensive, and accurate time interpolation solution.
Implementation Method 1
The voltage across such a capacitor is: V = (1/C) ∫I dt where V is the voltage, C is the capacitance and I is the current flowing into the capacitor. If I is constant, as is the case with a good quality current source, then: V = (I/C) t. Thus, the voltage across the capacitor is directly proportional to the time during which current is allowed to flow into it.
Data Source
AI summary
A time interpolator circuit increases the accuracy of digital counting circuits.