Frequency Measurement Circuit Using Time-Difference Compensation
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Solution Overview
Problem
Existing frequency measurement apparatuses face limitations in precision due to the dependence of gate time on the period of the rectangular wave signal, resulting in lower measurement accuracy for shorter signal periods.
Innovation Solution
A frequency measurement circuit that includes an oscillation circuit generating a reference clock, counters for both the reference and measurement target clock signals, a time-to-digital conversion circuit for generating time difference data, and a calculation circuit to calculate the frequency using the count data and time differences, allowing for improved precision independent of the measurement target clock signal's period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency counter counts the period of the rectangular wave signal with the base clock, then the gate time for frequency measurement is determined, but the measurement precision deteriorates for shorter signal periods
Solution Approach 1:
The patent introduces a time-to-digital conversion circuit as an intermediary component that measures the time difference between the start/end timing of the gate time signal and the start/end timing of the measurement target clock signal. This intermediary measurement of time differences (tp1 and tp2) allows the system to compensate for timing variations and achieve precise frequency measurement independent of the signal period, thereby resolving the contradiction between measurement precision and adaptability to different signal periods
Solution Approach 2:
The patent changes the measurement parameter from direct period measurement to time difference measurement. By measuring the time differences tp1 and tp2 between gate signal edges and clock signal edges, and using these time differences in the frequency calculation formula Fm=Nm/(T0×Nt+tp2−tp1), the system achieves frequency measurement precision that is independent of the measurement target clock signal's period, thus resolving the technical contradiction
2Measurement precision
If delay elements are used to improve frequency measurement resolution, then measurement resolution improves, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical delay element-based time measurement system with a digital time-to-digital conversion system. Instead of using multiple delay elements to create time steps for measurement, the invention uses a digital circuit that directly measures time differences between clock edges and gate signal edges, converting time measurements into digital values through counter operations. This substitution reduces circuit complexity while maintaining or improving measurement precision
Data Source
AI summary
A frequency measurement circuit includes a first counter that counts a pulse number of a reference clock signal and generates first count data, a second counter that counts a pulse number of a measurement target clock signal and generates second count data, a time-to-digital conversion circuit that generates first time difference data indicating a time difference between a first timing at which the first counter starts counting of the pulse number and a second timing at which the second counter starts counting of the pulse number, and second time difference data indicating a time difference between a third timing at which the first counter ends counting of the pulse number and a fourth timing at which the second counter ends counting of the pulse number, and a calculation circuit that performs calculation based on the second count data, the first time difference data, and the second time difference data and generates frequency data indicating a frequency of the measurement target clock signal.