Chriss A. Hammerschmidt, Robert T. Johnk, Savio Tran, and Mike Chang

Abstract:

Channel sounders are used to measure channel characteristics for radio systems. There are several types of channel sounders used today: continuous-wave (CW), direct pulse, frequency domain using a vector network analyzer (VNA), correlation-based, and swept-time delay cross-correlator. Each of these has unique advantages and disadvantages. CW systems have a larger dynamic range than other systems with a signal that can propagate farther into the environment. As the audio sampling rates allow smaller file sizes than other systems, data collection can be continuous and last for several hours.

This article discusses a CW-channel sounder system, which has been used to make numerous propagation loss measurements in various cities in the United States of America. Such propagation measurements should be accurate, reproducible, and free of artifacts or biases. This article shows how to set up the measurement, how to validate and verify that the system is making reliable measurements, and, finally, shows results from some of the measurement campaigns, i.e., repeatability measurements, clutter loss measurements (where clutter loss is defined as the excess loss from free-space transmission loss), and reciprocity measurements.

ITS has used the technique shown here to validate other measurement systems so that the measurements are consistent. This protocol does not address electromagnetic interference or electromagnetic compatibility issues that can appear when multiple pieces of equipment are placed near one another.

Keywords: calibration; radio frequency (RF) measurement; continuous wave (CW); propagation measurement best practices; channel-sounding measurement system

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

For questions or information on this or any other NTIA scientific publication, contact the ITS Publications Office at ITSinfo@ntia.gov or 303-497-3572.

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