May 1976 | Other OT TM 76-218
Characteristics and Applications of a PN Channel Probe
Robert W. Hubbard
Abstract:
This report describes and illustrates the method, instrumentation and applications of a probing technique for measuring fundamental characteristics of a radio model transmission channel. The method is based upon a convolutional model of the channel, from which the time-variant impulse response can be derived from receiver processing of the probe signal in real time. The probing signal is a pseudo-random noise (PN) generated as a binary digit bit stream over a range of clock rates. The receiver of the system employs a correlation detection process for measuring two quadrature components and the power envelope of the impulse function.
The applications of the probe technique include measurement and evaluation of atmostpheric multipath and the depolarization of radio signals in transmission channels. The most significant feature is the ability to measure the dynamic changes in a transmission channel, and thus to evaluate the dynamic multiplicative effect of channel disturbances on information signals.
The appendices to the report program discuss analytic channel models and a specific measurement program using the probe. The results are equivalent to a pulse transmission of 6.7 ns in duration. The technique and the associated instrumentation have been developed by the Office of Telecommunications, Institute for Telecommunication Sciences, of the U. S. Department of Commerce.
Keywords: impulse response; digital transmission; atmospheric multipath; depolarization; pseudo-random noise (PN); analytic models; microwave measurements; multiplicative distortions
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