Coil-Less Overtone Crystal Oscillator With RC Fundamental Suppression
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Solution Overview
Problem
Existing overtone crystal oscillators require expensive inverted-mesa crystals and inductor-capacitor circuits to achieve high frequencies, which increase costs and complexity, and are not compatible with modern CMOS processes, limiting their integration and sideband noise performance.
Innovation Solution
A coil-less overtone crystal oscillator design using a crystal with a fundamental resonant frequency and an RC network with multiple inverting amplifiers to suppress fundamental oscillations and enable oscillation at higher overtone frequencies, integrated onto a CMOS chip without the need for external inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an inductor-capacitor (LC) circuit is used to suppress the fundamental frequency of the overtone crystal, then oscillation at higher harmonic frequency is achieved, but manufacturing cost and device complexity increase due to the inductor component
Solution Approach 1:
The patent removes the inductor component from the traditional LC circuit configuration. By extracting the inductor element, the design eliminates the associated manufacturing costs, PCB space requirements, and potential coupling issues while maintaining the fundamental frequency suppression function through alternative circuit topologies using only resistors and capacitors.
Solution Approach 2:
The patent replaces the traditional inductor-based frequency suppression mechanism with an active circuit implementation using operational amplifiers, resistors, and capacitors. This substitution eliminates the need for magnetic components and their associated parasitic effects, achieving the same frequency selection function through electronic circuitry.
2Speed
If an inductor-capacitor (LC) circuit is used to suppress the fundamental frequency, then oscillation at overtone frequency is enabled, but manufacturing cost increases due to the inductor component
Solution Approach 1:
The patent removes the inductor component from the traditional LC circuit configuration. By extracting the inductor element, the design eliminates the associated manufacturing costs, PCB space requirements, and potential coupling issues while maintaining the fundamental frequency suppression function through alternative circuit topologies using only resistors and capacitors.
Solution Approach 2:
The patent replaces expensive inductor components with inexpensive resistor and capacitor elements that can be easily manufactured and integrated into standard PCB designs. This substitution significantly reduces component costs while achieving the same functional outcome of fundamental frequency suppression and overtone oscillation.
3Speed
If an inductor is used in the overtone crystal oscillator circuit, then fundamental frequency suppression is achieved, but PCB space or integrated circuit area increases
Solution Approach 1:
The patent removes the inductor component from the traditional LC circuit configuration. By extracting the inductor element, the design eliminates the associated manufacturing costs, PCB space requirements, and potential coupling issues while maintaining the fundamental frequency suppression function through alternative circuit topologies using only resistors and capacitors.
4Speed
If an inductor is used in the overtone crystal oscillator circuit, then fundamental frequency suppression is achieved, but undesired coupling to or from nearby circuitry is enabled
Solution Approach 1:
The patent removes the inductor component from the traditional LC circuit configuration. By extracting the inductor element, the design eliminates the associated manufacturing costs, PCB space requirements, and potential coupling issues while maintaining the fundamental frequency suppression function through alternative circuit topologies using only resistors and capacitors.
Solution Approach 2:
The patent replaces the traditional inductor-based frequency suppression mechanism with an active circuit implementation using operational amplifiers, resistors, and capacitors. This substitution eliminates the need for magnetic components and their associated parasitic effects, achieving the same frequency selection function through electronic circuitry.
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 solution allows for high-frequency oscillation without the need for expensive inductors, reducing manufacturing costs and enabling integration in standard CMOS processes, while maintaining low sideband noise performance and supporting wider modulation bandwidths in communication systems.
Implementation Method 1
A coil-less overtone crystal oscillator includes a crystal having a fundamental resonance frequency and an overtone resonance frequency. Multiple amplifiers and an RC network are coupled together. The multiple amplifiers and the RC network are collectively configured to suppress oscillation of the crystal at the fundamental resonance frequency and to enable oscillation at an overtone resonance frequency of the crystal.
Data Source
AI summary
An overtone crystal oscillator including a crystal, multiple amplifiers and an RC network. The crystal has a fundamental resonance frequency and at least one overtone resonance frequency. The amplifiers are coupled in series between terminals of the crystal and the RC network is coupled to the amplifiers. The amplifiers and the RC network are collectively configured to suppress oscillation of the crystal at the fundamental resonance frequency and to enable oscillation at an overtone resonance frequency of the crystal. The amplifiers and the RC network may be configured to cause a phase shift between the fundamental resonance frequency and the overtone resonance frequency. The overtone resonance frequency may be any odd harmonic of the fundamental frequency, such as a third overtone of the crystal. The overtone crystal oscillator may be integrated with CMOS processes and does not require an inductor to suppress the fundamental mode of oscillation.