Super-compact multilayered left-handed transmission line and diplexer application

A novel super-compact multilayered (ML) composite-right/left-handed (CRLH) transmission line (TL) is proposed. This ML architecture consists of the periodic repetition of pairs of U-shaped parallel plates connected to a ground enclosure by meander lines. The parallel plates provide the left-handed (LH) series capacitance, and the meander lines provide the LH shunt inductance, while the right-handed parasitic series inductance and shunt capacitance are generated by the metallic connections in the direction of propagation and by the voltage gradient from the TL to the ground enclosure, respectively. In contrast to previously reported planar LH or CRLH TLs, the ML TL has its direction of propagation along the vertical direction, perpendicular to the plane of the substrates. This presents the distinct advantage that large electrical length can be achieved over an extremely short TL length and small transverse footprint. The LH-range characteristics of the multilayer CRLH TL are analyzed by the finite-element method and finite-difference time-domain (FDTD) full-wave simulations. In addition, the CRLH equivalent-circuit model is applied to gain simple insight into the behavior of the structure. Finally, the theoretical results are confirmed by experiments using the initial prototype with the very small length (thickness) of 0.016λ_g and footprint of 0.06λ_g×0.08λ_g (λ_g=λ₀/√ε_r=235 mm at the center of the LH band, 0.4 GHz). The proposed miniaturized ML line can find applications in bandpass filters, delay lines, and numerous phase-advance components. As an example of application, a 1-GHz/2-GHz diplexer, composed of two ML CRLH TLs, is demonstrated. The ML CRLH TL proposed here presents a great potential for the development of novel microwave components taking profit of new multilayer technologies such as low-temperature co-fired ceramic technology.