Design of GPS Remote Calibration System

A new design of GPS remote time and frequency calibration system is presented. Its hardware was composed with a time interval counter card, a GPS receiving modular and a controller. The counter card was manufactured with modeled number GT200 by Guide Technology, Inc. The Trimble ThunderBolt GPS disciplined clock was used as the GPS receiving modular. A personal computer with Redhat Linux operation system was utilized for the controller. The software is written by C language which controlled the GPS modular, the counter card, and data collecting. The characteristic of the counter card and GPS receiving modular were performed. A series of test were executed to valuate this system. The short baseline common clock test with hydrogen maser was studied for the system noise level. The direct phase comparison in laboratory, GPS short baseline test in laboratory, and GPS field test within 10 km between hydrogen maser and cesium clock were also experimented two methods were applied to evaluate the system performance and there were GPS all-in-view and phase difference comparison. The later one could illustrate the short-term frequency stability. The former method could demonstrate the longer term stability and time characteristic of the clock at remote site. The accuracy and stability of the experimental result of the short baseline common clock with hydrogen maser reached to a few parts of 10^-13 and the TDEV values were lower than the ITU-T G.811 requirements. The designed system with the capability could be applied for the remote time/frequency calibration and for the monitoring the performance of the primary reference clocks (PRC) of the digital telecommunication network, too.