  The phase noise and frequency stability measurements of 1 GHz, 100 MHz, and
10 MHz signals are presented which have been synthesized from microwave
cryogenic sapphire oscillators using ultra-low-vibration pulse-tube cryocooler
technology. We present the measured data using independent cryogenic
oscillators for the 100 MHz and 10 MHz synthesized signals, whereas previously
we only estimated the expected results based on residual phase noise
measurements, when only one cryogenic oscillator was available. In addition we
present the design of a 1 GHz synthesizer using a Crystek voltage controlled
oscillator phase locked to 1 GHz output derived from a cryogenic sapphire
oscillator.
