Multiport method for the measurement of the scattering parameters of N-ports

The multiport method for the precise measurement of the scattering parameters of N-port devices with a two-port vector network analyzer (VNA) is presented. The scattering parameters of an N port cannot be measured directly with a two-port VNA if N>2. Only the scattering parameters of all two-port combinations of the device-under-test (DUT) are measurable. Thereby, the measured two-port scattering parameters strongly depend on the external terminations of the DUTs ports, which are not connected to the VNA during the measurements. In order to eliminate the influences of these external possibly reflective terminations, an error correction has to be performed. In comparison to known correction methods, the multiport method has some advantages. Firstly, the external terminations can be chosen arbitrarily, i.e., short and open circuits are realizable as long as the topology of the DUT allows it. Secondly, the terminations, except for one, can be unknown, leading to a reduction of the inconsistency problem caused by erroneous data of the external terminations, which is also known from the calibration of VNAs with completely known calibration standards. The good performance of the multiport method is shown by measured results.