Resonator Oscillator Auto-Zeroing for Low 1/f Phase Noise
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Solution Overview
Problem
Resonator-based oscillators suffer from high 1/f noise corner frequencies, leading to significant near-phase noise, which conventional technologies have not effectively mitigated.
Innovation Solution
The implementation of active offset cancellation in sustaining amplifiers, specifically through auto-zeroing and synchronous operation, reduces the 1/f noise corner frequency from approximately 5 KHz to less than 10 Hz or 1 Hz, achieving low Allan Deviation performance by synchronizing zero-crossing detection and signal amplification with resonator oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sustaining amplifiers are used in resonator-based oscillators, then the oscillator can maintain oscillation, but the 1/f noise corner frequency remains high (approximately 5 KHz), resulting in significant near-phase noise
Solution Approach 1:
The patent applies preliminary action by performing offset cancellation in advance through auto-zeroing techniques. The sustaining amplifier预先 compensates for offset errors and 1/f noise during specific phases of the oscillation cycle, thereby reducing the noise corner frequency before it significantly degrades phase noise performance. This proactive noise mitigation allows the system to achieve low phase noise without requiring complex additional circuitry.
Solution Approach 2:
The patent changes the operating parameters of the sustaining amplifier by implementing synchronous detection and auto-zeroing at specific phases of the oscillation cycle. By dynamically adjusting the amplifier's operation mode (between signal amplification and offset cancellation) and optimizing the timing of these transitions, the system reduces the effective 1/f noise corner frequency from 5 KHz to below 10 Hz, dramatically improving phase noise performance.
2Measurement precision
If active offset cancellation is implemented to reduce 1/f noise corner frequency, then near-phase noise is reduced by 20 to 30 dB, but the device complexity increases due to additional circuitry
Solution Approach 1:
The patent merges the offset cancellation function with the existing sustaining amplifier by implementing auto-zeroing techniques within the same circuit. Rather than adding a separate noise cancellation circuit, the invention combines multiple functions (signal amplification, offset cancellation, and noise reduction) into a unified sustaining amplifier structure, thereby reducing overall device complexity while achieving 20 to 30 dB near-phase noise reduction.
Solution Approach 2:
The sustaining amplifier is designed to perform multiple functions: it amplifies the resonator signal during active phases and simultaneously performs offset cancellation and noise reduction during zero-crossing phases. This multi-functional design eliminates the need for separate dedicated circuits for each function, achieving timing signal generation accuracy improvement without proportionally increasing device complexity.
3Reliability
If synchronous auto-zeroing is used to reduce 1/f noise corner frequency below 10 Hz, then Allan Deviation performance improves, but the difficulty of detecting and measuring zero-crossings increases
Solution Approach 1:
The patent employs feedback mechanisms where the output of the sustaining amplifier is fed back to detect zero-crossings, which then trigger the auto-zeroing operation. This feedback loop continuously monitors the signal and automatically adjusts the cancellation timing, making the zero-crossing detection robust and reliable. The feedback ensures that even with reduced noise margins, the system can accurately detect zero-crossings and maintain optimal Allan Deviation performance.
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.