Polarization-Diversity Telemetry Receivers

Abstract

Studies at the Langley Research Center of the National Aeronautics and Space Administration have shown that certain physical properties of extraterrestrial surfaces can be determined by analysis of impact-acceleration, time-history signatures obtained by instrumented projectiles (penetrometers). This paper considers the theory and design of a polarization-diversity receiver developed to receive and combine FM/FM penetrometer telemetry data. The signals are radiated by a set of orthogonal magnetic dipoles fed in time quadrature to obtain an omnidirectional radiation pattern similar to the pattern from a conventional turnstile. A special polarization-diversity receiving system is required to reduce the effects of fading of the RF carrier resulting from random changes in the orientation of the radiating antenna system. Various combining techniques are evaluated. Finally, a maximal-ratio, postdetection, dual-channel receiver with dual conversion and subcarrier discrimination developed specifically for the application is described.