March 2022 | NTIA Special Publication SP-22-560

5G In-Air Field Strength Measurements for Radar Altimeter Research

Frank H. Sanders; Kenneth Tilley; Geoffrey A. Sanders

Abstract: This brief video provides an overview of ITS's approach to taking RF measurements to provide data relevant to the topic of radio interference that might possibly occur from some U.S. 5G transmitters to band-adjacent airborne radar altimeter (radalt) receivers, which is currently of great interest to federal agencies, U.S. industry, Congress, the White House, and the general public. A key technical aspect of the problem is the amount of power that is unintentionally radiated from 5G base station transmitter antennas at high elevation angles, where aircraft fly. 5G base stations ordinarily only radiate with their intentional main antenna beams directed toward user equipment (UEs, essentially phones). NTIA’s Boulder laboratory, ITS, has begun performing measurements of the unintentional antenna radiation from 5G base stations, to quantify exactly how much power will impinge on aircraft flying near such tower locations. In this video, we briefly describe in lay terms the concern for 5G versus radalts. We go on to show how we are setting up and performing airborne 5G radiation measurements around such transmitters at the Department of Commerce’s Table Mountain field facility north of Boulder. Video sequences show viewers the putative problem, the setup for airborne measurements, and a sampling of some of the measurements themselves. The video sequences, including some data examples, allow viewers to understand qualitatively how ITS is working to solve this problem. Exactly analyzed data results are not provided; those will be provided in later NTIA Technical Reports. This video is instead an introductory overview of our approach to resolving this spectrum engineering problem.

Keywords: spectrum sharing; cellular base stations; radio interference; out-of-band (OOB) emissions; radio frequency (RF) measurement; 5G; 5G radiation; airborne radiation measurements; radar altimeter; radio altimeter

For technical information concerning this report, contact:

Frank H. Sanders
Institute for Telecommunication Sciences
(303) 497-7600

To request a reprint of this report, contact:

Lilli Segre, Publications Officer
Institute for Telecommunication Sciences
(303) 497-3572

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.

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