Tunable periodic slow-wave transmission line

A tunable slow-wave (SW) transmission line (TL) is proposed in this research. Periodic grooves are etched on a double-sided parallel-strip line (DSPSL) which is symmetrical about the substrate to obtain a slow wave characteristic. All nails between the grooves are modified to load varactors so that the dispersion curve of the transmission line can be tailored at will. Furthermore, these varactors also contribute to the alteration of the cutoff frequency of the proposed SW TL. Due to the controllable propagation constant and the adjustable cutoff frequency, the tunable periodic transmission line provides various potentials in the field of antenna design and microwave circuits.