Article: The effect of high stability reference oscillators on system phase noise.(TUTORIAL)

Highly accurate microwave systems derive their frequency stability from lower frequency reference oscillators, crystals or atomic standards. The resulting phase noise is, ideally, the lower frequency reference oscillator noise multiplied by 20 log N, where N is the frequency multiplication factor. In microwave systems, this factor can be very significant and mandates the use of a very low noise reference (for example, a Ku-band system will typically have a 12 GHz final local oscillator signal derived from a 10 MHz reference, increasing the reference phase noise by 20 log [12000 MHz/10 MHz] = 61.6 dB). The use of phase-locked loop multipliers can mitigate some of this ...