International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Quartz crystal is an important electronic element in the field of communication systems, computer
systems, etc. It is important to precisely measure the frequency of quartz crystal unit for
manufacturing. The Pi-network transmission system recommended by International Electrotechnical
Commission (IEC) is generally acknowledged as a measurement technique. However it needs a
precise frequency source. The frequency source must be calibrated within a regular period in the
process of manufacturing. Frequency counters, time internal counters, phase comparisons, which are
the most common frequency calibrations, are introduced in the paper. Nowadays GPS has also
become the primary system for frequency calibration. GPS receivers provide 1 PPS (Pulse Per
Second) with accuracy < 100 nanoseconds to UTC under normal conditions. Motorola UT Oncore
timing GPS with time accuracy < 50ns (1 sigma) uses time RAIM algorithm to ensure the validity
and reliability of measurements. The comparison between the precise 1PPS and local reference is
implemented. And the phase differences are logged and read by computer. According to the values,
the frequency output of DDS is coordinated. In order to reduce the phase ambiguity, local reference
is divided before comparison. The calibration can be implemented at any time by GPS. Block
diagrams of calibration are presented in this paper.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/605599 |
| Date | 10 1900 |
| Creators | Jun, Yang, Qishan, Zhang, Jinpei, Wu |
| Contributors | Beihang University |
| Publisher | International Foundation for Telemetering |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Proceedings |
| Rights | Copyright © International Foundation for Telemetering |
| Relation | http://www.telemetry.org/ |
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