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The industry’s first smart Rubidium clock


Spectratime is the world’s leader in high-end rubidium and crystal based, GNSS synchronised, oscillators and timing modules. The company offers smart, high-performance, cost-effective, and high-quality products.  With a breakthrough in technology Aspen Electronics is able to offer the industry’s first smart Rubidium clock (SRO), integrating a host of complex timing and synchronisation functionality all in one low-cost, ultra-small, package.

The new patented SRO-5680(GPS/GNSS Synchronized Rubidium Oscillator) features an EMI-shielded packaging, integrating complex synchronization functionality all in one low-cost, super-small package. The SRO intelligently synchronizes, disciplines, and controls any Stratum-1 reference such as GPS/GNSS, Cesium, Hydrogen Maser, and T1/E1 at cutting-edge 1ns resolution. It is compatible to the FEI-5680 model and utilises SmarTiming+® technology to provide a host of timing features, which were previously implemented externally on a separate circuit board.
The smart SRO SynClock+® is designed with a standard Rb locked crystal oscillator using a Direct Digital Synthesizer (DDS) in its internal frequency control loop (see Fig. 1). This model allows users, or the SmarTiming+ microcontroller, to adjust and sync the SRO’s centre frequency with a cutting-edge resolution of 5E-13 per step. The SRO not only measures the relative phase of the PPS Ref, but it can also adjust its frequency to be aligned to it. Through its advanced analog ns-phase comparator, the SRO can 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 an ideal feature to sync a PPS signal from a GPS or track any other Stratum-1 references. The SRO also has a multi-vendor GPS interface to optimise the signal quality through the 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 Smart SRO SynClock+® is uniquely able to sync a PPS Ref signal with a RMS noise up to microseconds, without a control device, through the serial port.  The 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 x 101.3mm x 28.5mm. It uses a standard Rb cell size, featuring a short-term stability performance of 1E-11 at 10 sec. It is a breakthrough in technology, by providing core time, frequency, and synchronisation functionality all in one package.

Spectratime SRO-5680 large

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