In order to determine various operational parameters of a power amplifier (for example, a complex load impedance or a complex forward and return power or a reflection factor or a voltage standing wave ratio) on a connecting line between an output of the power amplifier and a complex load, complex analog forward and return voltages on the connecting line are determined by an analog coupling device. These analog voltages are digitized and converted down into a baseband by one or more digital down-converters. From these digital values corresponding in absolute value and phase to the complex forward and return voltages and present in the baseband, desired operational parameters may then be calculated by a computer.