PHASE MEASUREMENTS AND CHARACTERIZATION OF MOBILE RADIO CHANNELS

A channel phase measurement system based on stable quartz oscillators at the transmitter and at an I and Q receiver is presented, Observatio ns of the phase behavior over a 910-MHz mobile radio channel in urban and semi-urban areas are made and related to the signals physical para meters. A method to characterize channel phase variations is proposed that corresponds to taking the second difference on the phase, Standar d deviations of this phase variation measure are found to increase mor e or less linearly with distance in built-up areas, with a slope as hi gh as 10 degrees per km. Comparisons between measured and theoretical statistical distributions of the phase variations are made: while not meeting the lambda-square test criteria, quadratic error tests support ed by visual observation show that a Student's t distribution with two degrees of freedom, of the type used to describe the statistical char acteristics of random FM, offers for practical purposes a useful stati stical description of the measured phase variations.