Multi-Phase Digital Sampling for Precise Frequency Comparison
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Solution Overview
Problem
Existing signal sampling methods, whether analog or digital, face challenges in precision due to timing limitations and non-linear output issues when comparing input and reference signals, failing to accurately determine frequency relationships.
Innovation Solution
A method and circuit that utilize internal timing signals derived from a reference signal to sample an input signal at multiple times within a period, correlating these samples with previous period values to derive the relationship between input and reference signal frequencies, employing a level detection circuit, time alignment circuit, and correlator to achieve precise frequency comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog components are used to compare input and reference signals, then both magnitude and sign of the difference can be obtained, but the precision is reduced due to inherent timing limitations and non-standard response/delay times
Solution Approach 1:
The patent replaces analog comparison mechanisms with a digital sampling and correlation system. Instead of using analog components to directly compare signals, the system samples both input and reference signals at multiple phases and uses digital correlation to determine frequency relationships, thereby eliminating analog timing limitations
Solution Approach 2:
The patent divides the reference signal period into multiple phases (e.g., 8 phases) and samples both signals at each phase point. This segmentation allows the system to capture timing relationships more accurately by distributing samples across multiple time points rather than relying on a single analog comparison point
2Reliability
If digital logic components are used for frequency comparison, then timing precision is improved, but the output becomes non-linear and does not indicate how much higher or lower the input frequency is
Solution Approach 1:
The patent uses correlation between sampled signals to create a feedback mechanism that provides linear output. The correlation process compares the phase relationships of input and reference signals across multiple samples, generating an output that linearly indicates the frequency difference magnitude and direction
Solution Approach 2:
The patent transitions from single-point digital logic comparison to multi-dimensional sampling across multiple phases. By sampling at 8 different phase points and analyzing the correlation across these dimensions, the system achieves both timing precision and linear frequency relationship indication
Data Source
AI summary
A method and apparatus for determining a relationship between an input signal frequency and a reference signal frequency is envisioned. The system derives a plurality of internal reference signals from the reference signal. The internal reference signals are provided to a level detection circuit which in turn samples the input signal a number of times within a period of time. Values associated with these samples are stored, as is one value of a sample from a previous period. The stored samples are correlated, and a relationship between the input signal frequency and the reference signal frequency is derived.