In a technology collaboration with Spectratime, Aspen Electronics has created one of the industry’s first smart Rubidium clocks (SRO), integrating complex timing
and synchronisation functionality in one package.
The SRO is claimed to synchronise, disciplines, and control any Stratum-1 reference such as GPS/GNSS, Cesium, Hydrogen Maser, and T1/E1 at 1ns resolution. It is compatible with the FEI-5680 model and utilises SmarTiming+ technology to provide timing features, which were previously implemented externally on a separate circuit board.
The company advises this device is designed with a standard Rb locked crystal oscillator using a Direct Digital Synthesiser (DDS) in its internal frequency control loop. This model is claimed to allow users, of the SmarTiming+ microcontroller, to adjust and sync the SRO’s centre frequency with a resolution of 5E-13 per step. The SRO is able to measure the relative phase of the PPS Ref, but it can also adjust its frequency to be aligned to it.
This device features an advanced analogue ns-phase comparator, enabling the SRO to track a low-noise PPS Ref signal with a phase error of a few ns. Similarly, a noisy but stable signal can be tracked within a few ns. In this case, since the phase error is higher, the SRO’s frequency is finely adjusted to the frequency of the PPS Ref. The SRO’s frequency is stored in EEPROM memory. In case the PPS Ref disappears, the SRO continues to keep its frequency for many days with a phase error of less than a few µs. This is said to be an ideal feature to sync a PPS signal from a GPS or track any other Stratum-1 references.
The SRO is also said have a multi-vendor GPS interface to optimise the signal quality through its Time RAIM and Position Hold data. The SmarTiming+ ns-phase comparator is used to compute the Allan Variance of the PPS Ref signal, enabling the SRO to filter the reference signal auto-adaptively by applying an optimal time constant to the tracking loop, regardless of the quality and behaviour of the reference signal.
The company also points out that this device is able to sync a PPS Ref signal with a RMS noise up to microseconds, without a control device, through the serial port. Whilst auto-adaptive SmarTiming+ technology allows designers to have a plug-&-play solution, eliminating the need for designing an external reference locking, disciplining and control system.
The SRO-5680 measures 140mm by 101.3mm by 28.5mm. It uses a standard Rb cell size, featuring a short-term stability performance of 1E-11 at 10 sec. It provides core time, frequency, and synchronisation functionality all in one package.
Aspen Electronics
