Polarization combining scheme for radio direction finding with multipath

For NASA's Mars sample return (MSR) program, there is a strong need to enhance the received signal strength for the radio direction finding (RDF) application. We consider the possibility of linearly combining the outputs from two orthogonal, polarized antennas to prevent polarization loss. The problem is complicated due to the dynamics of the beacon transmitter. In particular, it is assumed that the transmitter is rotating and that it radiates a linearly polarized wave. Initial results are based on the assumption of perpendicular incidence. It is also extended for arbitrary incidence, in which case there are gain and phase differences between the orthogonally polarized antenna pair outputs. An innovative algorithm for polarization combining is proposed and performance data in a multipath environment are presented with simulation results. The SNR improvement using this algorithm translates into a more favorable channel condition for the overall RDF system design.