Use of GPS ASHTECH Z12T receivers for accurate time and frequencycomparisons

摘要

The GPS phase measurements described in this paper were obtainednusing two similar multichannel GPS ASHTECH Z12T receivers belonging tonthe Bureau International des Poids et Mesures, BIPM, and the LaboratoirenPrimaire du Temps et des Frequences, BNM-LPTF. These receivers are basednon the conventional geodetic ASHTECH Z12 unit, which has been modifiednto meet the stability requirements of time and frequency comparisons.nComparison of the two receivers operated side by side in differentnantenna configurations shows typical short-term noise of 1.1 to 3.5 ps.nLonger term variations indicate a temperature sensitivity in thenequipment, which limits the performance of the GPS phase method. One ofnthe receivers was successfully operated using a temperature-stabilizednantenna TSA from 3S Navigation, and the ASHTECH antenna, which feeds thensecond receiver, was placed in a home-built oven maintained at anconstant temperature. These precautions made it possible to reduce annumber of systematic effects. A separate study of frequency comparisonnwas carried out between two hydrogen-masers located at the BNM-LPTFn(Paris, France) and the PTB (Braunschweig, Germany) using receiversnsimilar to ASHTECH Z12T receivers. The relative frequency stabilitynobtained was about 3.3×10-15 for an average time of 15n000 s, an interesting result comparable with the outstanding performancenof new ultrastable frequency standards