The Sapphire Whispering Gallery Mode Resonator
technology enables the design of microwave oscillators presenting
exceptional short term frequency stability. The resonator consists
in a Al2O3 monocrystal disk where the
electro-magnetical field is efficiently confined thanks to a
process analog to the optical total reflection. Due to the low
value of the sapphire dielectric losses, Q-factors as high as
200000 at the ambient temperature and better than 10 millions at
77 K is currently obtained. The sapphire resonator constitutes then
an ideal frequency reference that can be inserted in an oscillator
loop. At the Laboratoire de Physique et de Métrologie des
Oscillateurs, we implemented several sapphire resonator
oscillators operating at the ambient temperature and at 77 K. We
proposed original solutions to solve the Mayn difficulties arising
from the sapphire resonator, i.e. the large number of spurious
resonances and the large temperature sensitivity.