A study on jig using microstrip line for the S-parameter method

Recently, the S-parameter method using a vector network analyzer and a measurement jig instead of a balun was proposed whereby the differential input impedance of a balanced-fed antenna were obtained. As no balun is used, measuring impedance over a wide frequency bandwidth is now possible. To improve the measurement accuracy of the S-parameter method, the dependence on direction of SMA connectors of the measurement jig is obtained from the results of calculations using the FDTD method. Two types of jigs installed the connectors vertically or horizontally are modeled, and the input impedance of the dipole antenna is calculated using the S-parameter method. The input impedances are compared with those obtained from the available theories by King. Results from the S-parameter method roughly agree with the available theories by King, and the influence of direction of the connector is relatively small.