What Is G-sensitivity?

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Imagine a soldier in the field carrying a dismounted radio, a portable, rugged transmission unit used on foot for secure connectivity. Mechanical stress from vibration and shock can throw off the radio’s electronics, including its reference clock that ensures synchronization of electronic systems. High g-forces and continuous vibration can induce frequency shifts and signal noise and degrade synchronization, reducing navigation and communication reliability—critical factors for mission success and soldier safety.

G-sensitivity (or acceleration sensitivity) quantifies the vulnerability of timing devices to these forces—how sensitive they are to the acceleration caused by environmental stressors. Expressed in parts per billion per g (ppb/g), where g represents the acceleration of gravity (9.8 m/s²), it defines the change in output frequency for every g-force applied. The lower the g-sensitivity value, the more resistant a reference clock is to shock and vibration.

What Impacts G-sensitivity?

Reference clocks are oscillators that use mechanical resonators to generate a stable frequency, which serves as the timing reference for electronic systems. Their performance is governed by the physical properties of the resonator, including mass, material stiffness, and the way the device is mechanically mounted within the system. These factors determine how susceptible the clock is to environmental stress such as vibration, shock and acceleration.

Modern oscillators rely on several resonator technologies, each with distinct tradeoffs:

• Quartz crystal resonators: Fabricated from quartz crystal, this is the legacy technology for frequency stability. Quartz resonators are relatively large and high-mass, which makes them more sensitive to mechanical stress, such as shock and vibration. Under real-world conditions, this can cause frequency drift, degraded stability and excursions outside specification.
• Bulk Acoustic Wave (BAW) resonators: Based on thin-film piezoelectric materials such as aluminum nitride (AlN), BAW resonators enable higher operating frequencies and more compact form factors than quartz. BAW-based oscillators improve upon quartz by functioning at elevated frequencies and having smaller mass. However, they can still be sensitive to mechanical stress in vibration-prone environments.
• Micro-Electro-Mechanical Systems (MEMS) resonators: Fabricated from silicon using micromachining techniques, MEMS resonators are extremely low mass and well suited to scalable, solid-state integration. Their small size and robust construction provide superior resistance to vibration and shock, along with greater tolerance to mechanical stress—making them ideal for demanding applications where resilience and stability must coexist.

TCXO/OCXO Clock Comparison: MEMS vs Quartz

Note: BAW reference clocks do not currently come in a comparative TCXO or OCXO for this chart.

What Are the Benefits of Low G-sensitivity?

• Improved Signal: Reduces vibration-induced phase noise, jitter and frequency stability errors and the oscillator maintains datasheet specifications in the real-world application, resulting in cleaner signals for RF and digital communications.
• Enhanced System Reliability: By specifying a reference oscillator with low g-sensitivity, systems will maintain frequency stability even during dynamic events such as aircraft or land-vehicle vibration, sudden shifts in orientation (e.g., aircraft maneuvers) or mechanical shock.
• Better Data Integrity: Minimizes timing errors that contribute to higher bit error rates (BERs) in data links and network communications.
• Greater Positioning, Navigation and Timing (PNT) Resilience: Ensures the local clock remains precise during holdover conditions even in harsh environments when global positioning system/global navigation satellite system (GPS/GNSS) signals are disrupted or lost.

Key Applications

G-sensitivity matters in any system that experiences vibration, acceleration or motion. Here are a few key applications where low g-sensitivity is especially important:

• Aerospace and Defense: Radar, electronic warfare and tactical communication systems on rotor/turbine aircraft, ground-based wheeled/tracked vehicles and dismounted soldiers.
• Autonomous Vehicles: Drones, submersibles and robotic platforms used in defense, industrial inspection and remote exploration.
• Industrial IoT (IIoT): Factory automation systems, heavy machinery controllers and industrial sensors deployed on production floors or mobile platforms.
• 5G Infrastructure: Base stations, small cells and telecom units installed on towers, rooftops or other exposed areas subject to wind or seismic activity.

The SiTime MEMS Advantage

The most effective way to decrease g-sensitivity in an electronic system is to use a timing source engineered for it, such as a SiTime MEMS oscillator. Some SiTime advantages include:

• Mass: MEMS resonators are typically ~1000x lighter and smaller than quartz resonators. This minimal mass reduces the physical force exerted on the resonator during acceleration, enabling g-sensitivities as low as 0.004 ppb/g (SiTime Endura products).
• Integrated Architecture: The resonator and oscillator circuitry are built on a single silicon die, eliminating the weak mechanical links (e.g., epoxy, wire bonds) that often amplify g-sensitivity in quartz devices.
• Tri-Axis Stability: Advanced MEMS designs incorporate features that cancel out the effects of acceleration, minimizing frequency deviation in any direction—ideal for rugged timing solutions in aerospace and industrial environments.
• Durability: Silicon MEMS resonators are significantly more robust compared to quartz offering a tensile strength 11x greater than quartz (550 MPa vs 48 MPa for quartz). As a reference, Navy grade steel (HY-80) is 551 MPa. Silicon MEMS resonators are also 2x stiffer than quartz (130-188 GPa vs 72 GPa for quartz).

Additional measures—like vibration-damping mounts, optimized PCB placement, rigid enclosures, or phase-locked-loop (PLL) jitter cleaners—can help lower g-sensitivity, but they offer only incremental improvements. The oscillator choice itself has the greatest impact.

Want To Learn More?

Take the next step to expand your timing knowledge:

1. Explore Our Extreme Resilience Solutions: SiTime Endura™ Ruggedized Oscillators

2. Deep Dive into the Technology: Silicon MEMS Timing

3. Master the Fundamentals: Timing Essentials Learning Hub