AN-003: G-Sensitivity and Vibration

Application Note AN-003 · By KCCS Engineering Team · Updated 2026 · 7 min read

What Is G-Sensitivity?

G-sensitivity (also called acceleration sensitivity, or γ) describes how much an oscillator's frequency shifts under mechanical acceleration. It is measured in parts per billion per g (ppb/g), where 1 g is Earth's gravity. A standard OCXO might have γ = 1 ppb/g. A vibration-rated version can be 0.05 ppb/g — 20× better.

When an oscillator is mounted on a moving platform — a vehicle, an aircraft, a drone, a naval vessel — vibration modulates the crystal's effective length, which modulates its resonant frequency. This creates sidebands in the output spectrum. In radar and EW systems, those sidebands can mask small targets. In inertial navigation, they directly inject position error.

How to Read the Spec

G-sensitivity is specified as a worst-case value, typically measured along three axes. The number is the maximum shift across all axes and frequencies:

Random Vibration vs Sinusoidal

A sine vibration at a single frequency produces a clean sideband. Random vibration (like road noise or rocket motor vibration) spreads the energy across a band. Random vibration is usually specified as a power spectral density (PSD), e.g., 0.1 g²/Hz from 20 Hz to 2 kHz. The resulting frequency modulation depends on both the G-sensitivity number and the vibration spectrum.

If your platform has a known vibration profile, ask the oscillator manufacturer for a predicted phase noise contribution, not just the G-sensitivity number.

When You Need Vibration-Rated Parts

You do not need KOR series for a rack-mounted lab instrument. You do need it for:

- UAV and drone-mounted timing

- Vehicle-mounted radar and EW

- Shipboard sonar and navigation

- Airborne communications and electronic warfare

- Any product that will see >0.1 g RMS of random vibration during operation

PCB Mounting Matters

Even a 0.05 ppb/g oscillator can perform poorly on a poorly designed PCB. Mounting the oscillator on a stiff section of board away from motors and fans, using stiff brackets if possible, and avoiding cantilevered SMD packages in high-vibration environments all make a measurable difference. Ask for the recommended PCB footprint in the datasheet.