Investigating the semi-rigid cable of a jig to improve the S-parameter method

摘要

Recently, the S-parameter method using a vector network analyzer was proposed whereby the differential input impedance of a balanced-fed antenna was obtained. To improve its measurement accuracy, the dependence on diameter of the semi-rigid cable used for the measurement jig is obtained from results of calculations using the FDTD method. Three jigs made from semi-rigid cables of differing diameter are fabricated; when coupled to a dipole antenna, the input impedances are measured as well as calculated using the S-parameter method. The impedances are also compared with those obtained from theories of King. Results from the S-parameter method indicate that using thinner-diameter coaxial cable produced very accurate measurements.