Subharmonic Ring Oscillator Phase Interpolation for Wider Locking Range
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Solution Overview
Problem
Fundamental harmonic injection locked phase interpolation techniques suffer from a narrow frequency locking range and poor systematic IQ skew in generating reference In-phase (I) and Quadrature-phase (Q) signals for precise sampling of modulated signals.
Innovation Solution
A system and method utilizing a Ring Oscillator (RO) circuitry with differential delay stages in a closed loop, coupled with signal injection circuitry to apply first and second input phases, effectively locking the frequency of the output oscillator signal at half the frequency of the periodic input signal through a predetermined interpolation mapping scheme, enhancing frequency locking range and minimizing IQ skew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fundamental harmonic injection locked phase interpolation technique is used, then the number of required input phases is reduced, but the frequency locking range becomes narrow
Solution Approach 1:
The injection-locked oscillator is divided into multiple separately controllable oscillating elements (first and second oscillating elements) that can be independently injected and phased. This segmentation allows each element to contribute to the overall frequency locking range while maintaining reduced input phase requirements, thereby expanding the total locking range without increasing device complexity.
Solution Approach 2:
The patent introduces a new dimension of control by using multiple independent injection paths with different phase relationships (in-phase and quadrature-phase signals). This multi-dimensional injection approach expands the frequency locking range beyond what single-dimension fundamental harmonic injection can achieve, while still maintaining efficiency in input phase requirements.
2Device complexity
If fundamental harmonic injection locked phase interpolation technique is used, then input phase reduction is achieved, but systematic IQ skew deteriorates
Solution Approach 1:
The patent employs asymmetric injection strategies where the first and second oscillating elements receive differently phased injection signals (in-phase versus quadrature-phase). This asymmetric treatment of otherwise symmetric oscillating elements enables precise control over the generated I and Q signals, minimizing systematic IQ skew while maintaining the benefit of reduced input phase requirements.
Solution Approach 2:
The patent implements feedback mechanisms through the interconnected closed-loop structure where the second oscillating element receives injection from the first, and both are controlled by phase interpolators. This feedback architecture enables dynamic adjustment and compensation of IQ skew, achieving high measurement precision while maintaining device efficiency.
3Adaptability or versatility
If sub-harmonically locked phase interpolation is implemented, then frequency locking range is expanded, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple oscillating elements into a unified injection-locked oscillator structure where the first and second oscillating elements work together in an interconnected closed loop. This merging approach achieves expanded frequency locking range through sub-harmonic locking while avoiding the complexity of completely separate oscillator systems, as the elements share common control and injection pathways.
4Measurement precision
If sub-harmonically locked phase interpolation is implemented, then IQ skew is minimized, but device complexity increases
Solution Approach 1:
The patent designs the oscillating elements and injection circuitry to serve multiple functions simultaneously: the first and second oscillating elements both generate and are injected by oscillation signals, the phase interpolators perform both phase shifting and amplitude control, and the interconnected structure provides both frequency locking and IQ signal generation. This multi-functionality minimizes IQ skew through unified control while avoiding the complexity of separate dedicated circuits for each function.
Data Source
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AI summary
A system for generating sub-harmonically injection locked phase interpolated output signal. The system comprises ring oscillator (RO) circuitry to generate an output oscillator signal in response to a periodic input signal. The RO circuitry includes a plurality of differential delay RO stages interconnected in cascade within a closed loop, where each RO stage is configured to establish a corresponding delayed version of the output oscillator signal successively shifted in phase by a predetermined phase difference based on a predetermined interpolation mapping scheme. The system further comprises signal injection circuitry coupled to the RO circuitry to apply a first signal having a first input phase and a second signal having a second input phase to the plurality of differential delay RO stages based on the predetermined interpolation mapping scheme to lock a frequency of the output oscillator signal at one half the frequency of the periodic input signal.