Frequency Stability Degradation in Quartz and MEMS Oscillators.

The operating frequency of a resonant oscillator is determined by the coupled behavior of the resonator, sustaining electronics, package, power supply, mounting conditions, and operating environment. Frequency stability is critical in sensor systems, where oscillators provide references for sampling, synchronization, phase-sensitive measurements, sensor fusion, and distributed sensing. This review examines how these factors affect the short- and long-term stability of quartz oscillators (XOs, TCXOs, and OCXOs) and microelectromechanical systems (MEMS) oscillators. Organized by physical cause rather than device type, the review covers temperature, including gradients and hysteresis, aging, acceleration, vibration, shock, pressure, humidity, power-supply and load variations, electric and magnetic fields, electromagnetic interference, and ionizing radiation. For each factor, the dominant degradation mechanisms and compensation methods are compared across both technologies. The comparison indicates that OCXOs retain an advantage in low-noise timekeeping over long averaging times, whereas advanced MEMS oscillators can approach quartz performance in selected operating regimes while offering smaller size, monolithic integration, and, in ruggedized products, 0.01 ppb/g acceleration sensitivity and 20,000 g shock ratings. In the literature reviewed, appropriate measurement methods exist but are applied inconsistently across technologies. Oscillator selection should therefore be based on a comprehensive error budget covering all relevant environmental and system-level factors.