Cascaded Oscillator Auto-Zeroing for Low Near Phase Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional resonator-based oscillators suffer from high 1/f noise corner frequencies, leading to significant near phase noise, which limits their performance and accuracy.
Innovation Solution
The implementation of active mitigation or canceling of time-varying offsets within a sustaining amplifier, specifically through auto-zeroing techniques, reduces the 1/f noise corner frequency from approximately 5 KHz to less than 10 Hz, and in some cases, to less than 1 or 2 Hz, thereby reducing near phase noise by 20 to 30 dB or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional resonator-based oscillators are used, then the device structure is simple, but the 1/f noise corner frequency is high leading to significant near phase noise
Solution Approach 1:
The oscillator is divided into multiple independent resonators (first resonator and second resonator) operating at different frequencies. Each resonator handles a specific frequency range, with the first resonator (e.g., 20 MHz) addressing lower frequency noise and the second resonator (e.g., 38 MHz) addressing higher frequency noise. This segmentation allows each resonator to be optimized for its specific frequency range, reducing the overall 1/f noise corner frequency without requiring a single complex resonator structure.
Solution Approach 2:
The patent implements a nested oscillator architecture where a second resonator is effectively nested within the overall oscillator system that already contains the first resonator. The second resonator operates at a higher frequency and is integrated into the existing oscillator framework, creating a multi-level nested structure. This nesting allows the system to benefit from both resonators simultaneously, achieving low 1/f noise corner frequency while maintaining a structured, organized design rather than a chaotic complex one.
2Reliability
If a single high-frequency resonator is used, then the phase noise at high frequencies is reduced, but the 1/f noise corner frequency remains high
Solution Approach 1:
The frequency spectrum is segmented into different ranges handled by separate resonators. The first resonator operates at a lower frequency (e.g., 20 MHz) and the second resonator operates at a higher frequency (e.g., 38 MHz). This segmentation allows the system to achieve a low 1/f noise corner frequency by combining the benefits of multiple frequency ranges, rather than relying on a single high-frequency resonator that would leave the low-frequency noise performance unchanged.
3Reliability
If multiple resonators are cascaded, then the 1/f noise corner frequency is reduced, but the device complexity increases
Solution Approach 1:
The second resonator is nested within the oscillator system that already contains the first resonator, creating a hierarchical structure. The nested configuration allows both resonators to function simultaneously with coordinated interaction, where the second resonator's higher frequency operation complements the first resonator's lower frequency operation. This nesting reduces the effective complexity compared to a fully parallel cascaded structure, as the nested resonators share common circuit elements and control mechanisms.
Data Source
AI summary
An oscillator includes a resonator, sustaining circuit and detector circuit. The sustaining circuit receives a sense signal indicative of mechanically resonant motion of the resonator generates an amplified output signal in response. The detector circuit asserts, at a predetermined phase of the amplified output signal, one or more control signals that enable an offset-reducing operation with respect to the sustaining amplifier circuit.