Design and realisation of a 100MHz synthesis chain from an X-band reference signal

LPMO has undertaken the building of a cryogenic sapphire oscillator with the support of th french Space and Metrolgy agencies (CNES and BNM). The aim of this project is to provide a reference oscillator presenting short frequency stability better than 5.10-14 in order to fulfill reference tests requirements for spacial and metrological applications. The cryogenic oscillator can operate on different frequencies ranging from 8 to 13GHz depending on the sapphire resonator mode chosen as reference. The exact output signal frequency is not ‘a priori' known with a great accuracy due to the large relative uncertainties (of the order of 10-4) affecting the resonator frequencies theoritical determination. Then a special synthesis chain has to be designed in order to transfert the cryogenic oscillator performances to a reference signal whose frequency is fully compatible with most of Time and Frequency instrumentation. In this paper, we present the design, realization and preliminary tests of a synthesis chain generating a 100MHz signal from an X-band reference. The performances of the two realyzed prototypes will enable to transfert better than 5.10-14 short term frequency stability