26 January 2023

Improved GPS disciplined OCXO from RFX that competes with Atomic Standards

PT626-GPS16 disciplined OCXO

RFX Group have launched a new, completely redesigned version of its PT626-GPS16 disciplined OCXO. Incorporating a multitude of changes including a 16-bit DAC designed for smoother holdover transition and a new GPS receiver for improved sensitivity, this next generation design provides multiple benefits for engineers wanting to replace rubidium and caesium frequency standards.

Accurate timing signals are extremely important in the digital networked world, enabling systems to precisely synchronise, 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 new PT626-GPS16 can accept a variety of antennas to collect timing and positioning data from satellites which 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 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 the GPS Stabilised OCXO but closer inspection of the comparative performance reinforces the reasons to specify a GPS stabilised OCXO instead. The PT626-GPS16 delivers excellent low phase noise of -168 dBc/Hz at 100kHz which is significantly better than Caesium and Rubidium standards. In addition, the Allan Deviation performance of the PT626-GPS16 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 stabilisation 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-GPS16 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. For further information, visit www.rfx.co.uk/products/ocxos.

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