Multi-Ring Frequency Divider for Unambiguous Phase Counting
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Solution Overview
Problem
Existing frequency dividers and counters used in conjunction with voltage- or current-controlled ring oscillators face ambiguity in phase measurements due to phase wrapping, especially when the sampling of the phase is much slower than the frequency of oscillation.
Innovation Solution
A circuit design for a divider or counter with improved precision, featuring multiple concentric rings where the output of each element in a first ring controls an element in a second ring, and additional rings can be coupled similarly, allowing for further frequency division and reducing ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phase sampling is performed slower than oscillation frequency in ring oscillator-based quantizers, then power consumption is reduced, but phase measurement ambiguity increases due to phase wrapping
Solution Approach 1:
The patent divides the phase measurement function into multiple independent ring oscillators, each operating at a different frequency (f, f/2, f/4, etc.). Each ring oscillator independently measures phase within its frequency range, segmenting the overall measurement task to eliminate ambiguity while maintaining low power consumption through selective operation of dividers.
Solution Approach 2:
The patent adds a frequency dimension to phase measurement by using multiple ring oscillators operating at harmonically related frequencies. This transforms a single ambiguous phase measurement problem into a multi-dimensional measurement system where the combination of measurements from different frequency oscillators uniquely determines the phase without ambiguity.
2Measurement precision
If the number of counter states is increased to eliminate phase measurement ambiguity, then measurement precision improves, but device complexity increases
Solution Approach 1:
Instead of using a single complex counter with many states, the patent segments the counting function across multiple simpler ring oscillators, each with fewer states. The overall precision is achieved through the combination of these segmented measurements rather than through a single complex device.
Solution Approach 2:
Each ring oscillator performs a partial measurement function at a specific frequency range. By combining these partial measurements from multiple oscillators operating at different frequencies, the system achieves complete phase measurement coverage without requiring any single oscillator to handle the full complexity.
Data Source
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AI summary
A circuit for a divider or counter may include a frequency divider (200) having multiple rings (210, 220, 230) for dividing an input frequency (Vin, 202) to obtain an output frequency. The first and second rings (210, 220) may include an odd-numbered plurality of elements, such as inverters, wherein each inverter of a ring is coupled to another inverter of the ring in a circular chain. An input frequency (Vin, 202) may be input to a power supply input of inverters (212A- N) of the first ring (210). The second ring inverters (222A-N) may be coupled at a power supply input to output nodes of the first ring inverters, which results in the second ring operating at a divisional rate of the first frequency given by (N-l), where N is the number of inverters in the ring. The circuits may be used in frequency dividers and counters, such as in phase-locked loops (PLLs) and analog-to- digital converters (ADCs).