Measurement Method of Amplitude Ratios and Phase Differences Based on Power Detection Among Multiple Ports

A method of measuring the amplitude ratios and phase differences among the same RF output signals from multiple ports at the same frequency is proposed. A power-combining module is used to couple multiple signals vectorially from the ports. In the proposed method, the amplitude ratios among the RF signals from multiple ports are calculated using the output power of the module to which only one port is connected, and using the S-parameters of the module itself. However, the phase differences among multiple ports cannot be simply represented by the differences between the output power of the module and the ideally combined power, because the impedances of all ports except measuring ports should be perfectly matched. The proposed method uses a parameter that compensates for the impedance mismatches generated at the other ports to achieve precise measurement of the phase differences among multiple ports. The measurement results using the passive component with three ports reveal that the mean errors of the proposed method are 1.26% and 2.15° in the amplitude and phase, respectively, when compared with measurements using the vector network analyzer. The standard deviations of the errors show 1.68% and 1.67° in the amplitude and phase, respectively.