Report on NBS Dual Mixer Time Difference system (DMTD) built for time-domain measurement associated with phase 1 of GPS (Global Positioning System)

The design, construction, and testing of a Dual Mixer Time Difference (DMTD) system are reported. The precision of time difference measurement with this system was shown to be about 0.1 picosecond and the accuracy about 10 ps; similarly, the frequency stability precision was shown to be described by (signa sub y)(tau) approximately equal to 10 to the minus 13th power/tan, 0.1s tau 1000 and equal to 10 to the minus 16th power at tau equal about half a day. The request for this DMTD system was for measuring the clocks that will go on board the satellites for Phase 1 of the Global Positioning System (GPS) program. The DMTD system described is the only system that can easily meet all of the time-domain measurement requirements for this program.