Measurement and Deembedding Technique for the on-wafer Characterization of Multiport Devices

A useful technique is presented for on-wafer characterization of
$n$
-port devices, when measurement accesses are of unequal length and when a
$m$
-port vector network analyzer is used with
$m<n$
. The
$n-m$
unused probing ports are left unterminated to simplify the measurement setup. The elimination of parasitic reflections arising from the unterminated ports and the deembedding of access contributions are performed from three measurements on two additional test patterns only. This method is demonstrated through the characterization up to 40 GHz of an 8-port Butler matrix using a 4-port vector network analyzer.