Phononic Comb Quartz Oscillators for Low-SWaP Frequency Stability
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Solution Overview
Problem
Current quartz oscillators face challenges in achieving low phase noise and reducing Size, Weight, and Power (SWaP) while maintaining stability, particularly in applications like radar and navigation, with existing solutions like TCXOs and OCXOs having limitations in temperature stability and g-sensitivity.
Innovation Solution
The use of a phononic frequency comb generated in a nonlinear quartz resonator, where specific teeth exhibit low drive frequency sensitivity, allowing for a high stability reference to lock a second voltage-controlled crystal oscillator (VCXO) with a Phase Locked Loop (PLL) circuit, reducing phase noise and increasing stability with minimal size and power increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Oven Controlled Crystal Oscillators (OCXOs) are used to achieve higher stability, then temperature stability is improved, but size and power consumption increase significantly
Solution Approach 1:
The patent changes the operating parameters by driving the resonator slightly off its resonant frequency into a nonlinear state to generate a phononic comb, and by selecting specific comb teeth with large slopes in the frequency vs. drive frequency relationship. This parameter change enables achieving OCXO-level stability without the need for oven control, thereby reducing size and power consumption while maintaining temperature stability.
2Reliability
If nonlinear Duffing effects are used in MEMS resonators to improve phase noise, then phase noise reduction is achieved, but frequency sensitivity to drive level increases due to operation near bifurcation point
Solution Approach 1:
The patent changes the operating parameters by driving the resonator slightly off its resonant frequency into a nonlinear state to generate a phononic comb, and by selecting specific comb teeth with large slopes in the frequency vs. drive frequency relationship. This parameter change enables achieving OCXO-level stability without the need for oven control, thereby reducing size and power consumption while maintaining temperature stability.
Solution Approach 2:
The patent uses a phononic comb as an intermediary structure generated by driving the resonator into a nonlinear state. The comb teeth act as intermediate frequency references that can be selected to have large slopes, providing frequency insensitivity to drive level variations while still benefiting from the nonlinear effects for phase noise reduction.
3Stability of the object's composition
If a phononic comb is generated by driving the resonator into a nonlinear state, then frequency insensitivity to drive amplitude is achieved, but device complexity increases
Solution Approach 1:
The patent employs a self-service approach where the nonlinear resonator automatically generates the phononic comb structure when driven slightly off resonance. The system uses itself to create the frequency references needed, eliminating the need for external frequency synthesis equipment or complex reference sources, thereby reducing overall device complexity despite utilizing nonlinear effects.
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 enhances the stability of quartz oscillators by reducing frequency instability and phase noise, achieving improved performance comparable to Oven Controlled Crystal Oscillators (OCXOs) with a more compact and power-efficient design, suitable for chip-scale applications.
Implementation Method 1
When a phononic comb is produced through modal mixing of local modes within the resonator which is driven slightly off one of its resonant frequencies
Implementation Method 2
Phononic combs form when one or more high-Q resonances are driven slightly off their resonant frequency into a nonlinear state
Implementation Method 3
the second voltage controlled oscillator is locked, in use, to a selected tooth of the comb at a frequency in which the first derivative of the drive frequency versus the frequency of the selected tooth in the comb has an absolute value greater than one, and wherein the PLL circuit controls the locking
Data Source
AI summary
A method and apparatus for enhancing the stability of an oscillator circuit by generating a comb of frequencies in a non-linear resonator member in response to a drive frequency, the oscillator circuit including a voltage controlled oscillator which is locked to a particular tooth of the comb of frequencies produced by the non-linear resonator member at a drive frequency for which the absolute value of the first derivative of the drive frequency versus said comb frequency is greater than 1, and wherein the second voltage controlled oscillator is coupled with a phase locked loop circuit which controls the locking of the second voltage controlled oscillator to said particular tooth of the comb of frequencies.