A delay calibration system for two-way satellite time and frequency transfer

We describe a system used to calibrate delays in two-way satellite time and frequency transfer (TWSTFT) Earth stations. The calibration system is designed to measure the transmit TX(t) and receive RX(t) delays through the Earth station in real time allowing for the possibility of real-time correction of TWSTFT data. The delay calibration device is stabilized to a temperature of 45/spl plusmn/3/spl deg/ C. The measured peak-to-peak delay noise of the calibration device in loop-back operation with no common mode cancellation of delay errors is 800 ps. The time stability is on the order of 100 ps out to an averaging time of 3 days.