The significance of radiation efficiencies when using S-parameters to calculate the received signal correlation from two antennas

The correlation coefficient between signals received by two antennas can be calculated from port S-parameters. Antenna radiation efficiencies must, however, also be considered. They result in an uncertainty in the calculated received signal correlation, if the correlation between the losses is unknown, which is often the case. Relations are presented for the effect antenna efficiencies have on the calculated correlation.