Narrow passband response of unbalanced CRLH transmission line structure composed of capacitively coupled dielectric resonators

This paper proposes a composite right/left-handed (CRLH) transmission line (TL) structure composed of capacitively coupled dielectric resonators (DRs), exhibiting a narrow LH passband delimited by deep and sharp-edge stopband. This selective band pass response is produced by adjusting the LC parameters of the TL so as to minimize the LH passband, which is the passband of interest in the structure, between the low-frequency stop-band due to the high-pass nature of the LH elements and the LH-to-RH branches stop band. A prototype with DRs of relative permittivity 30 operating at around 2GHz is demonstrated experimentally, in excellent agreement with FEM full-wave simulations, and a circuit model is developed to explain this LH narrow passband phenomenon and to assist in the design of future applications of this structure, such as highly-selective bandpass filters and diplexers.