This paper analyzes the influence of the Rayleigh fading channel on the performance of a single-frequency continuous-wave (CW) signal-based I/Q regeneration in five-port junction-based direct receivers. This method uses a single-frequency CW signal to estimate the I/Q regeneration parameters. Simulation results show that the eye diagram, error vector magnitude, and bit error rate performances of five-port junction-based direct receivers using a single-frequency CW signal-based I/Q regeneration are almost the same as those of conventional coherent demodulators, even in fading channels.