Phase-Interpolated Clock Circuit for Tunable Frequency Matching
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Solution Overview
Problem
There is a need for tunable reference frequencies in clock synthesis systems while maintaining low implementation costs, as variable frequency crystal oscillators are expensive and fixed frequency oscillators lack tunability.
Innovation Solution
A circuit that includes a phase interpolator and a phase controller, which generates an output clock signal by interpolating between two reference phases, allowing for frequency tuning using a fixed-frequency crystal oscillator, thereby matching the output frequency to an input frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable frequency crystal oscillator is used, then tunable reference frequencies are achieved, but implementation cost increases
Solution Approach 1:
The oscillator system is segmented into a fixed-frequency crystal oscillator and a separate frequency tuning mechanism (phase interpolator and phase controller). The crystal oscillator provides stable base frequencies while the phase interpolator segments the phase domain into multiple discrete phases that can be combined to achieve frequency multiplication and tuning, resolving the contradiction between stability and tunability.
Solution Approach 2:
A phase interpolator is introduced as an intermediary component between the fixed-frequency crystal oscillator and the output clock signal. The phase interpolator receives multiple phases from the crystal oscillator and generates interpolated phases through digital signal processing, enabling frequency tuning without requiring a variable frequency crystal oscillator, thus maintaining low cost while achieving adaptability.
2Ease of manufacture
If a fixed frequency crystal oscillator is used, then implementation cost is reduced, but frequency tunability is lost
Solution Approach 1:
The system introduces dynamic control through a phase controller that adjusts the variable control value in real-time. This dynamic adjustment of the control value changes the phase rotation rate, enabling the output frequency to be tuned to match different input frequencies while using a fixed-frequency crystal oscillator, thus achieving adaptability without sacrificing cost-effectiveness.
Solution Approach 2:
The invention changes the control parameter from crystal oscillator frequency to phase rotation rate. By keeping the crystal oscillator frequency fixed and instead varying the phase rotation rate through the phase controller, the system achieves frequency tunability through parameter transformation, resolving the contradiction between fixed frequency and tunability.
3Ease of manufacture
If phase interpolation is used for frequency tuning, then cost is reduced, but phase control complexity increases
Solution Approach 1:
The invention replaces complex analog phase control mechanisms with digital signal processing in the phase interpolator. The phase interpolator uses digital logic to generate interpolated phases from multiple crystal oscillator phases, and the phase controller uses digital control values to adjust the phase rotation rate, substituting mechanical/analog complexity with simpler digital control while maintaining cost-effectiveness.
Data Source
AI summary
A circuit generates an output clock signal synchronized to an input clock signal. The circuit includes a reference clock port, a phase interpolator, and a phase controller. The reference clock port receives a reference clock signal. The phase interpolator generates the output clock signal that, as a function of a variable control value, is an interpolation between two reference phases. The reference phases are generated from the reference clock signal and have a reference frequency. The phase controller generates the variable control value providing a phase rotation rate. An output frequency of the output clock signal equals a sum of the reference frequency and the phase rotation rate. The output frequency matches an input frequency of the input clock signal.