John E. Carroll; Geoffrey A. Sanders; Frank H. Sanders; Robert L. Sole

Abstract: In early 2009, the Federal Aviation Administration (FAA) became aware of interference to Terminal Doppler Weather Radars (TDWRs) that operate in the 5600–5650 MHz band and provide measurements of gust fronts, windshear, microbursts, and other weather hazards for improved safety of operations in and around airports. National Telecommunications and Information Administration (NTIA) engineers, with assistance from FAA engineers, determined the interference to be caused by some unlicensed national information infrastructure (U-NII) dynamic frequency selection (DFS) devices operating in the same frequency band as TDWR systems. These devices use DFS technology that is supposed to detect the presence of nearby co-channel radars and change operating frequencies to prevent interference to those radars. This report, the third of a three-part series, describes some U-NII emission spectra and introduces an additional set of TDWR test waveforms that the Federal Communications Commission (FCC) may use during DFS U-NII device testing. This report also explores the distances and geometries at which interference to TDWRs from U-NII devices is likely to occur.

Keywords: electromagnetic compatibility (EMC); radar interference; RF interference; radar performance degradation; unlicensed national information infrastructure (U-NII); spectrum sharing technology; terminal Doppler weather radar (TDWR); dynamic frequency selection (DFS)

For technical information concerning this report, contact:

John E. Carroll
Institute for Telecommunication Sciences
(303) 497-3367

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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