Using of Spirent GPS/Galileo HW Simulator for Timing Receiver Calibration

Kurzfassung

Time transfer between atomic clocks is usually carried out using the well known GNSS Common View / All in View technique. This technique is based on time receivers measuring the time differences between the connected atomic clock and the GNSS satellite clocks. These obtained results can be used for time scale generation such as UTC or TAI. In order to produce a very accurate time scale from all provided time differences measured with different GNSS time receivers the accurate calibration of them is essential. In the last years two main methods for time receiver calibration were proposed. One is to compare the obtained time differences relative to a calibrated receiver. Following the second method one performs an absolute calibration of time receivers using a GPS HW simulator. In this paper the absolute calibration of time receivers with a Spirent GPS/Galileo HW simulator is analyzed and described in detail. The primary step is to calibrate the simulator itself. In this context the most important facts and values which have to be measured are explained. After the calibration of the simulator the receiver is fed with satellite signals generated by the simulator belonging to a standard GPS satellite constellation to determine the absolute offset of the receiver (internal delay) compared to the simulator output. To improve these calibration results supplementary specific satellite constellations are used. Additionally the precision of a combined GPS/Galileo receiver for frequency transfer is investigated and determined. The combined GPS/Galileo frequency transfer is finally compared to the GPS stand alone solution.