PT626-GPS16 Disciplined OCXOs

RFX’s PT626-GPS16 disciplined OCXO delivers long-term temperature stability of ±0.001 ppb when locked to the GPS over -40°C to +70°C. Operating at a frequency of 10 MHz from a 5 V supply, this frequency standard delivers excellent phase noise performance of -168 dBc/Hz at 100 kHz.

Incorporating a 16-bit DAC for smoother holdover transition and a next-generation GPS receiver for improved sensitivity, this design provides multiple benefits for engineers wanting to replace rubidium and Caesium frequency standards.

Accurate timing signals are extremely important in the digitally networked world, enabling systems to precisely synchronize, authenticate, and verify data transfers. Equipment certification is equally important when standards are used to calibrate to international standards and reliable frequency standards are indispensable in this work.

The PT626-GPS16 can accept a variety of antennas to collect timing and positioning data from satellites that have on board Caesium clocks and is therefore as accurate as Class One timing standards when being disciplined. This is partly due to the extremely accurate internal crystal-controlled oscillators providing precise holdover stability with extremely low phase noise.

A good Caesium source is large and usually a rack mounted device whilst a good Rubidium source is smaller but still a fairly large device whereas the PT626-GPS16 has a very small footprint of just 57 mm by 38 mm and is easily incorporated as a component within a system design.

The physics packages inside of Caesium and Rubidium standards are the reason for their excellent frequency stability but are also the main cause of their relatively large size. In contrast, the main frequency-controlling element inside of the PT626-GPS16 is a very small, precision SC-cut quartz crystal which means that the overall package size is significantly more compact than Caesium or Rubidium standards.

Superficially, a Caesium frequency standard outperforms a Rubidium frequency standard which outperforms a GPS-stabilized OCXO but closer inspection of the comparative performance reinforces the reasons to specify a GPS-stabilized OCXO instead. Apart from the superior phase noise performance of the PT626-GPS16, the Allan Deviation performance is one second of close to 10-13 and close to 10-12 at several thousand seconds. By comparison, a Rubidium source will probably have an Allan Deviation of closer to 10-11 at one second. The GPS stabilization of the PT626-GPS16 will trend the OCXO towards the long-term Allan Deviation of a Caesium unit, close to 10-14, giving the user the best of all worlds.

Depending upon the application, the benefits of the PT626-GPS compared to Caesium and Rubidium standards include much smaller size, lower power consumption, significantly better phase noise performance, shorter lead times, and significantly lower cost, especially in volume.