Composite right/left-handed transmission line based on complementary single-split ring resonator pair and compact power dividers application using fractal geometry

A new resonant-type composite right/left-handed transmission line (CRLH TL) is proposed based on the combination of a complementary single-split ring resonator pair (CSSRRP) etched on the ground plane and a series gap embedded in the conductor strip of a microstrip line. The CSSRRP, which is composed of two identical complementary single-split ring resonators (CSSRR) with face-to-face splits, demonstrates negative permittivity. An equivalent circuit model is presented and studied in depth through the Bloch theory and finally validated by the simulated full-wave S-parameters. The balanced condition for novel CRLH TL is also derived. Moreover, the negative refractive index and backward wave propagation are confirmed by the effective constitutive parameters. It is proved that the zero-degree phase-shift CRLH TL exhibits a significantly lower resonant frequency by constructing the CSSRRP as Koch curves of different iteration order (K-CSSRRP). To demonstrate the applicability, two compact prototype device examples are provided, these being a three-way fork power divider and a four-way series power divider. The three-way divider achieves a 74.2% size reduction and displays comparable performance relative to its conventional counterpart, whereas the four-way divider obtains a 56% bandwidth enhancement and a 48% size reduction in comparison with a conventional one using a one-wavelength meandered transmission line.