What is a GPSDO? GPS-Disciplined Oscillators Explained

A GPSDO (GPS-disciplined oscillator, also called a GNSS-disciplined oscillator) combines a high-quality crystal oscillator, typically an OCXO, with a GPS receiver. The extremely accurate timing signal from GPS satellites is used to continuously correct the oscillator's frequency.

How a GPSDO works

The crystal oscillator provides excellent short-term stability, while the GPS signal provides an independent, highly accurate long-term reference. A control loop compares the two and makes small ongoing adjustments, giving you the best of both: the smooth, low-noise short-term performance of a good OCXO, and the drift-free long-term accuracy of GPS timing.

Why not just use GPS directly?

GPS signals can momentarily drop out, for example indoors, in urban canyons, or due to interference. A GPSDO's internal oscillator provides holdover: it keeps running accurately on its own for a period after GPS is lost, before gradually drifting. A good OCXO-based GPSDO can hold accurate timing for hours during a GPS outage. Read more in What is holdover in timing systems?

Typical applications

• Telecom network synchronisation
• Broadcast timing
• Test and measurement labs requiring traceable frequency references
• Any system needing long-term accuracy without the cost of an atomic standard

GPSDO or rubidium?

If you need longer holdover, or the unit must work without a satellite signal, a rubidium standard may be the better choice. See the comparison in GPSDO vs rubidium frequency standard, or read about rubidium frequency standards in our product category.

GPS-disciplined timing solutions from Vikronix

Vikronix supplies GPS-disciplined oscillators (GPSDO) and frequency references for applications across Scandinavia and Europe, with local support from Malmö. Browse our GPS disciplined OCXO range within our frequency standards, or get in touch to discuss your timing requirements.