Novel composite right‐/left‐handed transmission lines using fractal geometry and compact microwave devices application

In this paper, novel electrically small resonant‐type composite right‐/left‐handed transmission lines (CRLH TLs) combining fractal geometry are proposed and systematically exploited. Two sets of planar CRLH cell structure are involved including the proposed one based on cascaded complementary single split ring resonator (CCSSRR) and improved one based on complementary split ring resonators (CSRRs). Fractal perturbation in these CRLH TLs is from the point of super compactness. The left‐handed (LH) electromagnetic wave propagation characteristic and miniaturization principle are investigated in depth by electrical simulation, EM simulation and finally demonstrated by effective constitutive EM parameters. To illustrate possible application, a dual‐band BPF covered satellite DMB band and WiMAX band, and a monoband branch‐line coupler covered GSM band are designed, fabricated, and measured. Consistent results between full‐wave simulation and measurement have confirmed the design concept. Measurement results indicate that the fractal perturbation is a good strategy for further miniaturization, enhanced selectivity and maintenance of good in‐band performance in both designs especially for the coupler which achieves a comparable 81% size reduction relative to its conventional counterpart.