Characterization of Capacitor-Loaded Transmission Line for Phase Shifter Application

This paper describes a characterization of transmission line with capacitor loading which is applicable for phase shifters. The used transmission line is composed of common microstrip lines that are loaded with capacitors placed at regular intervals. A theoretical approach shows that the transmission phase on the capacitor-loaded microstrip line depends on the capacitances of the loading capacitors, thus it is beneficial for configuring a phase shifter circuit. A prototype of capacitorloaded microstrip line operating at a center frequency of 2.4 GHz has been implemented for experimental characterization. The measurement result shows that the maximum phase shift of 70o could be obtained corresponding to the transmission and return losses of less than 0.4 dB and 14 dB, respectively.