An experimental mm-wave receiver system for measuring phase noise due to atmospheric turbulence

The ultimate limitation of phase coherence in one-way communication systems is due to the irreducible propagation phase noise impressed upon a carrier wave due to scattering by atmospheric turbulence. The paper describes an experimental receiver designed to measure that phase noise using, initially, a satellite down link path and the 40 GHz propagation beacon of ITALSAT. Particular features of the system include: extremely low phase noise of the microwave first boal oscillator, complex demodulation (I & Q) without carrier phase acquisition (i.e. "on the fly") and menu driven interface electronics and data handling by a laptop acting as data logger and controller/house keeper of the system. The main design parameters are presented and include the various theoretical and experimental Lc(f) (dBc/Hz).