Simple, Rugged Microwave Refractometer for Airborne Platforms

This document presents a proposal to fabricate arevolutionary, compact microwave refractometer system. Therefractometer will be capable of accurately (better than 01.0 ppm)sensing atmospheric refractive index gradients and turbulentfluctuations at sufficiently small scales so that it can be used tovalidate signal propagation models used/proposed to predictperformance of a variety of VHF, UHF microwave and optical communications and sensing systems. Solid state microwave and signal processing electronics will be used to activate a sensing cavity, to process its output signal and to display atmosphericrefractive index fluctuations in real time. The sensing cavity will be modified using a low cost, high stability material, such as electroplated ceramic or glaze. To minimize adverse effects of turbulence at high air speeds, the sensing cavity will beenclosed in a flow controlling aerodynamic housing. Comparative evaluation of the instrument will be done using critical components from a Thompson-Vetter laboratory standard refractometer. Calibration and field testing will be performed at the RockSprings micrometeorological/turbulence field site at Penn State University. As research progresses, we will work with the Air Force to arrange a high altitude aircraft test of the prototype unit. This will require a source of additional funding.