Frequency Ratio Measurement Using Delta-Sigma Phase Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing frequency ratio measurement devices require a switching mechanism to adjust the division ratio of frequency dividers, which complicates the process of accurately measuring the frequency ratio between input and reference signals.
Innovation Solution
A frequency ratio measurement device that uses a counter, time-to-digital converter, combiner, subtractor, quantizer, and feedback sections to generate a delta-sigma modulated signal directly representing the frequency ratio, eliminating the need for a switching mechanism by combining count values and phase differences, and feeding back quantized values to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a switching mechanism is used to adjust the division ratio of frequency dividers, then frequency ratio measurement can be achieved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the switching mechanism from the frequency ratio measurement system. Instead of using a frequency divider with switchable division ratios, the invention uses a fixed division ratio frequency divider combined with a counter that accumulates phase errors over multiple cycles. This extraction of the switching mechanism eliminates its complexity while preserving the ability to measure frequency ratios through the counter's accumulation function.
Solution Approach 2:
The patent replaces the mechanical switching mechanism with a digital counting system. Instead of physically switching division ratios, the system uses a counter to accumulate phase differences over N cycles of the reference signal. This substitution transforms a mechanical switching problem into a digital accumulation problem, eliminating wear, contact resistance, and switching time issues while maintaining measurement accuracy.
2Measurement precision
If feedback control with division ratio switching is implemented, then phase error can be reduced to zero, but the measurement process becomes more complex
Solution Approach 1:
The patent extracts the switching function from the feedback control loop. Instead of switching division ratios to achieve phase error reduction, the system uses a fixed division ratio and relies on the counter to accumulate phase errors. The feedback is then applied to adjust the VCO frequency directly, eliminating the need for switching mechanisms in the feedback path while maintaining phase error reduction capability.
Solution Approach 2:
The patent changes the control parameter from division ratio to VCO frequency. Instead of adjusting the division ratio N to achieve phase lock, the system maintains a fixed division ratio and adjusts the VCO frequency through feedback based on the accumulated phase error count. This parameter change simplifies the feedback control mechanism by removing the switching element while preserving the ability to reduce phase errors.
3Measurement precision
If multiple quantizer sections are used to process quantization errors, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent merges the function of multiple quantizer sections into a single quantizer followed by a counter. Instead of using multiple quantizer stages to process and reduce quantization errors, the system uses one quantizer to convert the phase error to a digital value, then uses a counter to accumulate these values over N cycles. This merging reduces device complexity while maintaining the ability to process quantization errors through statistical accumulation.
Data Source
AI summary
A frequency ratio measurement device includes a counter section configured to count a time event of a first signal and output a count value obtained by multiplying the time event by k0, a time to digital converter section configured to output a time digital value corresponding to a phase difference between the first signal and a second signal, a combiner section configured to output a combined value of the count value and the time digital value, a subtractor section configured to output a difference value between a first value based on the combined value and a second value, a quantizer section configured to compare a third value based on the difference value with a predetermined threshold to thereby output a quantized value obtained by quantizing the third value, and a feedback section configured to output, based on a time event of the second signal, the second value based on the quantized value. The frequency ratio measurement device outputs, based on the quantized value, a delta-sigma modulated signal corresponding to a frequency ratio of the first signal and the second signal.