The short term part of its spectrum is mainly related to the possibility of multiplying a signal source up to the millimeter region. The SSB phase noise and the Allan Variance are the physical quantities usually measured, with different techniques, to represent the two spectral regions of phase stability, with a crossover around one second. Here we propose a new data acquisition system, essentially dedicated to the measurement of the Allan Variance, which is built around two programs, written in the LabView environment. The RF configuration is the same of the one used for phase noise measurements, so it turns out to be very convenient to characterize the wide range of LO frequencies, expected in ALMA, both at long and short term.
All information is recorded on disk and, optionally, hard copied on paper at each batch end.
A second program, called TSAcal, makes a very accurate calibration of the transfer function of the mixer, used as a phase detector.