Design of airborne solid state digital microwave refractometer for use in the tropics

The authors describe the design considerations of an airborne solid state digital microwave refractometer and present some sample results obtained with the instrument onboard a Cessna aircraft. Such data are expected to yield fine-structure information on the radio refractive index over tropical regions and help in understanding the microphysics of the tropical troposphere and in designing radio systems in the centimetre and millimetre waves. The instrument, operating at 9.341 GHz, has a stability of 10-7 degrees C-1 and a sensitivity better than 1 N unit with a dynamic range of 0-400 N units. The results have demonstrated convincingly the utility of the technique in obtaining the vertical profile of radio refractivity, especially in a turbulent medium.