Compensation Method Based on Phase Shift Between Pins of Crystal Resonator

Area of Science:

• Electrical Engineering
• Physics
• Metrology

Background:

• Oven-controlled crystal oscillators (OCXOs) are crucial for precise frequency generation.
• Long-term frequency drift remains a significant challenge in OCXO performance.
• External reference sources are often required to mitigate drift, adding complexity and cost.

Purpose of the Study:

• To develop a self-calibration method for improving OCXO long-term frequency stability.
• To eliminate the need for external reference sources in OCXO drift compensation.
• To establish a real-time monitoring and correction system for crystal oscillator frequency drift.

Main Methods:

• Establishing a linear equivalent mathematical model relating crystal resonator phase shift to output frequency.
• Real-time measurement of phase shift between crystal resonator pins to determine frequency drift.
• Implementing a self-calibration frequency control system based on the developed model and measurements.

Main Results:

• The OCXO drift rate was improved from 1.53 x 10^-10/day to 9.8 x 10^-12/day.
• Frequency drift settled to 5.24 x 10^-11 after three days.
• Long-term frequency stability improved from 1.16 x 10^-11/1000s and 3.24 x 10^-11/10,000s to 3.47 x 10^-12/1000s and 1.05 x 10^-11/10,000s.

Conclusions:

• The proposed self-calibration method effectively improves the long-term frequency stability of OCXOs.
• Real-time phase shift monitoring provides an accurate means to assess and correct frequency drift.
• This technique offers a viable solution for enhancing OCXO performance without external references.