On the Measurement of Atmospheric Multipath and Doppler Spread by Passive Means

摘要

The literature contains several procedures for the measurement of multipath and Doppler spread characteristics of a linear time-varying filter. These procedures imply processing which has access to the input waveform. For satellite communications applications, there is interest in determining the multipath and Doppler spread introduced by the atmosphere at microwave frequencies. A method is proposed in this report which permits determination of these properties without the need for launching a satellite to be used as a signal scatterer or generator. The sun or the moon is used as a source of power. An autocorrelation technique is shown to yield an estimate of the channel multipath; a dual procedure is shown to yield an estimate of Doppler spread. The effect of the receiver's front-end noise and filter is considered. Various unanswered questions are raised. (Author)