NTIA Technical Memorandum TM-05-430

Comparison of Radar Spectra on Varying Azimuths Relative to the Base of the Antenna Rotary Joint

August 2005

Frank H. Sanders, Bradley J. Ramsey

Abstract: This technical memorandum describes the results of radiated measurements of the emission spectrum of a maritime radar at varying azimuths relative to the base of the radar transmitter antenna rotary joint. The measurements were performed to address the question of whether the emission spectrum of such a radar might vary as a function of the pointing azimuth of the radar antenna as it rotates due to variation in the joint’s voltage standing wave ratio (VSWR) with azimuth. If such variation were to occur, then the radiated spectrum would need to be characterized as a function of azimuth. The measurement results indicate that the emission spectrum of this radar does not vary as a function of transmitter antenna azimuth. It is concluded that this issue is probably not a concern for radar emission measurements in general, and that the radiated spectrum measurement procedures described in NTIA Report TR-05-420 are adequate.

Keywords: radar emission measurement techniques; radar rotary joint voltage standing wave ratio (VSWR); radar spectrum engineering criteria

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