A reflection based and thru-less de-embedding technique for impedance and absolute power flow measurements suitable for on-wafer large-signal characterization of microwave transistors is proposed. The developed system was tested for both 50 X and non-50 X terminated passive and active devices and the results obtained are compared with those obtained with commercial instruments. V C 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE 20: 306-312, 2010.