Compact Capacitively-Loaded Transmission Line with Enhanced Phase Shift Range

Capacitively-loaded transmission line realized using a common configuration has typically a narrow phase shift range, so it is unusable as a phase shifter for beamforming applications. Increasing the number of capacitors to enhance the phase shift range is usually accompanied by an increase in the transmission line section, resulting in a large circuit size. This paper presents an implementation of a mirror configuration on a capacitor-loaded microstrip line to enhance the phase shift range. The loading capacitors are located on both sides of the transmission line section, instead of being located on one side. The experimental results show that when capacitances are varied from 0.2 pF to 0.8 pF, the proposed configuration could produce a wide phase shift range of 139.48
^o
and a compact circuit size of 46.4 mm × 22.5 mm. The capacitively-loaded transmission line implemented using a mirror configuration increases the phase shift range by 55% and reduces the circuit size by 22% compared to the common configuration.