Accurate on-wafer measurement of orthogonal four-port networks using the thru-reflection-unequal-line (TRuL) calibration method

For on-wafer four-port measurement, if probing arms are set at east-west and north-south sides, it is inevitable to utilize orthogonal CPW thrus during the calibration process, and then one might get erroneous measurement results due to undesired modes of orthogonal CPW thrus when using SOLT calibration. We will show that the measured scattering parameters of a multilayer 180° hybrid using the multiport thru-reflection-unequal-line (TRuL) calibration method will be more stable than using SOLT method. In addition, the required number of touchdown is greatly reduced when using the TRuL calibration method.