Vibrations and temperature changes can impact the physical structures of timing devices, leading to clock signal drift and noise. These environmental factors often occur together and can significantly affect timing performance in aerospace applications.
Various types of devices may react differently to these factors, but the bottom line is that poor timing signals can disrupt system operation and compromise data integrity. Temperature fluctuations can alter resonant frequencies, while concurrent vibrations can induce mechanical stress. This combination ultimately degrades phase noise, increases jitter, and may result in permanent frequency drift or data errors.
Crystal-cut Selection
Designers have the option to choose between AT-cut or SC-cut crystals, each suited for different frequency ranges and offering varying levels of temperature stability. SC-cut crystals, in particular, minimize frequency deviations across wide temperature ranges, making them less susceptible to vibration-induced frequency modulation.
SC-cut crystals exhibit high Q factors and are less sensitive to temperature variations compared to AT-cut crystals. The performance of SC-cut devices remains stable over a wider temperature range, making them a more reliable choice for precision timing applications.
MEMs, BAWs, and SAWs
MEMs timing devices, including electrostatic and piezoelectric resonators, offer alternatives to traditional quartz crystals in certain scenarios. These devices are smaller and more resilient to shock and vibration, with g-sensitivity levels comparable to top-tier crystal devices.
Surface and bulk acoustic wave (SAW/BAW) devices, based on piezoelectric MEMs structures, differ in their temperature coefficient of frequency and stability under mechanical stress. BAW devices, in particular, can achieve significantly higher frequency stability compared to quartz crystals when exposed to shock and vibration.
Temperature Control Solutions
Mechanical isolation techniques can help mitigate the impact of vibration on timing devices, although complete elimination is challenging. Active designs like temperature-compensated crystal oscillators (TCXOs) and oven-controlled crystal oscillators (OCXOs) are employed to enhance temperature performance. TCXOs, for example, apply an inverse signal to counter temperature-induced errors, resulting in minimal frequency drift.
Summary
Crystal, BAW, and SAW timing devices exhibit negative temperature coefficients of frequency and are susceptible to timing errors under heavy shock and vibration. The combination of high temperature and mechanical stress can degrade signal quality, leading to frequency drift or data inaccuracies.
References
For more information on temperature and vibration testing in electronics, refer to the following sources:
- Combined Temperature and Vibration Testing for Wire Bond Interconnections in Harsh Environment Electronics
- High Temperature, Vibration & Altitude: What Aerospace Demands from Silver Plating
- MEMS vs Quartz Oscillators: Which One Suits Your Project?
- Shock & Vibration: The Hidden Enemy of Timing Accuracy in Automotive & Aerospace Systems
- Surface and Bulk Acoustic Wave Device Characterization
- Temperature and Vibration Stress Testing for Aerospace and Defense Applications
- Temperature Over Vibration: Combined Environment Compliance Testing
- The Evolution and Future of Precision Timing
- The Impact of Temperature Coefficients on SC-Cut Crystals for High-Precision Applications
- Too hot – too shaky? Thermal testing and vibration control testing come to the rescue of electronic systems
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