Due to the capabilities of modern vector network analyzers (VNAs), the usage of “True-Mode”-signals for characterizing and testing active differential devices is quite convenient. Nevertheless in cases, in which the device under test (DUT) and/or the measurement setup introduces a coupling between the required stimulus signals, current methods require some iteration time to achieve the desired phase and amplitude settings. In this paper a new approach will be introduced, which leads to an optimized testing time which can be crucial especially in industrial production test.