SDH/SONET
Rakon has a strong
track record in providing timing devices conforming to SDH/SONET
Stratum requirements, including devices approved by chipset vendors Semtech
and Zarlink.
Mobile
basestations
Mobile
communications
applications require extremely accurate synchronization of the signal
frequency throughout the network. Without absolute frequency stability
typically within ±0.05 ppm at all points, cut-outs and
failed
calls will occur. To minimize frequency discrepancies, each timing
device within the network is locked to an external reference source,
e.g. GPS in the case of CDMA. This imposes two key requirements on each
timing device: it must be able to synchronize adequately to the
reference clock over its entire lifetime of ten years or more, and it
must be able to hold its frequency stable for a period of 24 hours or
more in the event of loss of the external reference signal.
While
high-stability rubidium clocks are usually specified to meet the strict
timing requirements of mobile basestations, they are significantly
bulkier and more costly than quartz-based devices. However, our CFPO-SC1
range of self-calibrating, oven controlled quartz crystal oscillators
(OCXOs) can in many aspects outperform traditional rubidium clocks.
The
self-calibrating CFPO-SC1
OCXO compensates for crystal ageing effects that normally require
re-calibration of an oscillator after it has been installed in the
customer's system. Because of this, it can offer free-run frequency
stability to within ±0.016 ppm over a 15-year lifetime, even
without an external reference. With short-term stability of
±0.00015 ppm and a power requirement after warm-up of less
than
3.0 W, the CFPO-SC1 is more than adequate for use in mobile
basestations yet comes in a standard six-pin hermetically sealed metal
package measuring just 67 x 60 x 40 mm and costs less than
rubidium-based alternatives. Standard output frequencies include 4.096,
5.0, 8.192, 10.0 and 10.24 MHz.
Less tightly
specified but even more competitively priced than the CFPO-SC1, the CFPO-DO3
is a single-oven OCXO that surpasses the performance of double-oven
devices but in a significantly smaller package. Through precise
optimization of the thermal design, complementary adaptation of the
components, and highly controlled in-house manufacturing, we have
achieved free-run holdover stability of around ±0.0002 ppm
over
24 hours in the event of reference clock failure, and an overall
lifetime stability of ±0.06 ppm within a 51.0 x 41.0 x 19.0
mm
package. This is suitable for certain mobile basestation applications.
Both the CFPO-SC1
and CFPO-DO3 have excellent phase noise characteristics.
Related links:
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