Improved GPS disciplined OCXO competes with atomic standards

RFX Group has released a fully redesigned version of its PT626-GPS16 disciplined OCXO. Incorporating many changes, including a 16-bit DAC developed for smoother holdover transition and a new GPS receiver for enhanced sensitivity, this next-generation design offers multiple benefits for engineers wishing to replace rubidium and caesium frequency standards.

Accurate timing signals are very important in the digital networked world, allowing systems to exactly synchronise, authenticate and verify data transfers. Equipment certification is just as important when standards are calibrated to international standards, and reliable frequency standards are indispensable in this work.

The new version can accept various antennas to collect timing and positioning data from satellites with onboard Caesium clocks and is, therefore, as accurate as class one timing standards when being disciplined. This is partly due to the very accurate internal crystal-controlled oscillators supplying precise holdover stability with remarkably low phase noise.

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

The device provides excellent low phase noise of -168dBc/Hz at 100kHz, particularly better than Caesium and Rubidium standards. Also, the Allan Deviation performance of the device is one second of close to 10-13 and close to 10-12 at several thousand seconds. By comparison, a Rubidium source will likley have an Allan Deviation of closer to 10-11 at one second. The GPS stabilisation of the device 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 device compared to Caesium and Rubidium standards include far smaller size, lower power consumption, notably better phase noise performance, shorter lead times and substantially lower cost, particularly in volume.