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Case Study: Investigation of Interference into 5 GHz Weather Radars from Unlicensed National Information Infrastructure Devices, Part 3

Report ID: 
NTIA Technical Report TR-12-486
June 01, 2012
John E. Carroll, Geoffrey Sanders, Frank H. Sanders, and 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: dynamic frequency selection; electromagnetic compatibility; radar interference; radar performance degradation; RF interference; spectrum sharing technology; terminal Doppler weather radar; unlicensed national information infrastructure

The full report is available at