MILLIMETER-WAVE ATMOSPHERIC-TURBULENCE MEASUREMENTS - INSTRUMENTATION, SELECTED RESULTS, AND SYSTEM EFFECTS

Increasing interest in and greater usage of the millimeter-wave freque ncy bands has resulted in a need for better characterization of atmosp heric effects at these frequencies. While attenuation is recognized as the most significant effect, recent measurements of fluctuations in i ntensity and phase caused by atmospheric turbulence have shown that th ese phenomena will also degrade system performance at both millimeter- wave and microwave frequencies. This paper describes the millimeter-wa ve and meteorological instrumentation used to make these measurements and gives selected results. It is determined that phase fluctuations a s great as 1.5 radians and intensity fluctuations as large as 2.8 dB a re observed over a 1370 m path in hot, humid weather. The effects of t hese fluctuations on the performance of practical, existing microwave phased array and monopulse systems are assessed. It is determined that phase fluctuations in particular will degrade the performance of micr owave adaptive nulling arrays and monopulse trackers.