Nested LC-Tank PLL Layout for Wide Tuning and Low Phase Noise
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Solution Overview
Problem
Existing phase-locked loop (PLL) designs face challenges in achieving a wide tuning range and low phase noise while minimizing physical area, as LC-tank oscillators are limited in tuning range and ring oscillators do not meet noise requirements, and previous solutions either increase size or introduce unacceptable noise.
Innovation Solution
A nested LC-tank oscillator design with two oscillators of differing radii, where one is disposed within the other, utilizing a digital phase-locked loop (DPLL) architecture to minimize area and achieve a full octave of tuning range with low phase noise, by activating one oscillator and tuning the other to produce beneficial effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two or more LC-tank oscillators are used to achieve wide tuning range, then the tuning range is improved, but the physical area is dramatically increased
Solution Approach 1:
The patent applies nesting by placing one LC-tank oscillator inside another, with the second oscillator's inductor positioned within the circumference of the first oscillator's inductor. This nested configuration allows both oscillators to occupy overlapping spatial regions, dramatically reducing the total physical area compared to side-by-side placement while maintaining the ability to achieve wide tuning range through oscillator switching.
2Adaptability or versatility
If switched inductors are used to improve tuning range, then the tuning range is improved, but the phase noise increases to unacceptable levels
Solution Approach 1:
The patent employs dynamic switching between multiple LC-tank oscillators, where each oscillator is tuned to different frequency ranges. A detector circuit dynamically determines which oscillator is appropriate for the desired frequency, and switches selectively activate the appropriate oscillator. This dynamic approach achieves wide tuning range without using switched inductors within a single oscillator, thereby avoiding the phase noise problems associated with inductor switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a compact, wide-tuning-range synthesizer with low phase noise, effectively addressing the limitations of previous designs by reducing physical area and enhancing frequency range without increasing noise levels.
Implementation Method 1
a first LC-tank oscillator and a second LC-tank oscillator, the second oscillator having an inductor that is smaller in circumference than the inductor of the first LC-tank oscillator
Data Source
AI summary
A design for an oscillator, and a PLL incorporating such an oscillator, which takes up little physical area but maintains a large tuning range and low phase noise. Two LC-tanks are nested and switched. Through tuning the inactive tank, the range of the active tank may be increased and finer tuning becomes possible.