Patent ID: 7865319

Claim:
A method to accurately measure the loading impedance of measurement systems using a test fixture, said method comprising the steps of: (a) providing a test fixture having at least one transmission line, each said at least one transmission line having a port at two ends, said test fixture having a plurality of transmission line legs, each transmission line leg extending between a mid-point reference plane of said at least one transmission line and a port; (b) measuring characteristics of an unloaded test fixture to obtain scattering parameters of said test fixture, said scattering parameters arranged in at least one test fixture scattering matrix; and (c) calculating scattering parameters of each transmission line leg of said test fixture, said step of calculating scattering parameters of each transmission line leg of said test fixture comprising the steps of: (i) determining a line impedance of each said transmission line; (ii) normalizing said at least one test fixture scattering matrix of said unloaded test fixture to the line impedance of each said transmission line to obtain at least one renormalized test fixture scattering matrix of said unloaded test fixture; (iii) determining at least one input reflection coefficient of a pair of split matrices for each said transmission line using said at least one renormalized test fixture scattering matrix, said at least one input reflection coefficient being parameters of said pair of split matrices, said pair of split matrices having a plurality of parameters; (iv) solving for remaining parameters of said plurality of parameters of said pair of split matrices using said at least one renormalized test fixture scattering matrix and said at least one input reflection coefficients; and (v) normalizing said pair of split matrices to 50Î©; (d) measuring said test fixture loaded with a measurement system to produce a combined measurement of said test fixture and said measurement system; and (e) removing test fixture effects defined by said scattering parameters of each transmission line leg of said test fixture from said combined measurement by a de-embedding calculation to obtain measurement system effects of said measurement system alone.