10 GHz cryocooled sapphire oscillator with extremely low phase noise

The phase noise characterisation of two 10 GHz cryogenic sapphire oscillators exhibiting frequency stability higher than 3 x 10(-15) is reported. One of these oscillators developed for the deep space navigation ground stations of the European Space Agency, incorporates a closed cycle cryocooler as cold source. Near the carrier, the measured phase noise is limited by a flicker frequency noise: S-phi(f) = -30log(f) - 98 dBrad(2)/Hz.