Measurement of Passive Microstrip Circuits
In order to validate the theoretical procedures, this chapter presents the results of the analysis of some microstrip test circuits physical characterization using a commercial network analyzer. The first measurement was done over a simple 25-O microstrip transmission line. The line was constructed using a substrate of polythetrafluoroetilene (Teflon) with a dielectric constant of 10.5 (DUROID® 6010, er = 10.5). The synthesis was carried out with the method of moments (MoM). The obtained dimensions were H = 0.1882 cm and L = 3.7 cm. The network analyzer was calibrated using an open-short-load (OSL) technique with a user two-port calibration for 1600 points. Theoretically, the open circuit can be constructed with a quarter-wave transmission line terminated on a short circuit which shifts by ninety electrical degrees the short circuit point on the Smith chart from 1∠180° to 1∠0°. Strictly, the use of open- and short-circuit standards for a determined technique demands a calibration by parts or segments of a defined bandwidth.