Relaxation Oscillator Flicker Noise Cancellation for Low Jitter
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Solution Overview
Problem
Wireless communication devices face challenges in reducing jitter caused by flicker noise in relaxation oscillators, which is not effectively addressed by existing solutions, particularly in mass-produced microsystems where increasing transistor size is not feasible.
Innovation Solution
A method for flicker noise cancellation in oscillators involves selectively coupling current sources to capacitors and a reference node through a controller, using a comparator to cycle the oscillator through multiple states, thereby reducing flicker noise without increasing transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of transistors is increased to reduce jitter due to flicker noise, then the jitter is reduced, but the circuit speed decreases and charge injection increases
Solution Approach 1:
The oscillator circuit is divided into multiple identical segments (first oscillator circuit and second oscillator circuit) that operate in parallel. Each segment produces an oscillation signal, and these signals are combined through differential processing to achieve flicker noise cancellation without requiring larger transistors in a single circuit.
Solution Approach 2:
The patent uses differential oscillation signals from two identical oscillator circuits to counterbalance each other's flicker noise. By subtracting one oscillation signal from the other, the common-mode flicker noise components cancel out, while the desired oscillation signals are preserved and enhanced.
2Reliability
If the size of transistors is increased to reduce jitter due to flicker noise, then the jitter is reduced, but additional capacitance is introduced
Solution Approach 1:
The oscillator circuit is divided into multiple identical segments (first oscillator circuit and second oscillator circuit) that operate in parallel. Each segment produces an oscillation signal, and these signals are combined through differential processing to achieve flicker noise cancellation without requiring larger transistors in a single circuit.
Solution Approach 2:
The patent changes the operating parameters by using differential signaling and phase shifting instead of increasing transistor dimensions. The oscillation signals are phase-shifted and differentially combined, achieving noise cancellation through parameter manipulation rather than physical size increases.
3Reliability
If a resonator-based oscillator is used to reduce jitter, then the jitter is reduced, but the size and cost increase
Solution Approach 1:
The patent replaces the mechanical resonator-based oscillation mechanism with an electronic relaxation oscillation mechanism. By using active electronic components (transistors, capacitors, resistors) in a relaxation oscillation configuration, the system achieves oscillation without requiring physical resonators, thereby reducing size while maintaining performance through differential noise cancellation.
Solution Approach 2:
The relaxation oscillator circuit is designed to perform multiple functions: generating the oscillation signal, canceling flicker noise through differential processing, and providing phase-shifting capabilities. This multi-functionality eliminates the need for separate resonator components, reducing overall circuit size.
4Area of stationary object
If relaxation oscillators are used to reduce size and cost, then the size and cost are reduced, but jitter due to flicker noise increases
Solution Approach 1:
The oscillator circuit is divided into multiple identical segments (first oscillator circuit and second oscillator circuit) that operate in parallel. Each segment produces an oscillation signal, and these signals are combined through differential processing to achieve flicker noise cancellation without requiring larger transistors in a single circuit.
Solution Approach 2:
The patent uses differential oscillation signals from two identical oscillator circuits to counterbalance each other's flicker noise. By subtracting one oscillation signal from the other, the common-mode flicker noise components cancel out, while the desired oscillation signals are preserved and enhanced.
Data Source
AI summary
An oscillator is disclosed. The oscillator includes a first capacitor. The oscillator also includes a second capacitor. The oscillator further includes a first current source. The oscillator also includes a second current source. The oscillator further includes a comparator that has a first input and a second input. The oscillator also includes a reference node. The oscillator further includes a controller that is configured to selectively couple the first current source to the first capacitor and the second current source to the reference node during a first time period.