CAD of left-handed transmission line bandpass filters

Owing to the negative and nonlinear nature of phase constant (beta) versus frequency, left-handed transmission lines (LH-TLs) can present higher values of beta as compared to right-handed ones. As such, left-handed (LH) structures are promising in terms of size minimization of microwave circuits. In this paper, a simulation study leading to computer aided design (CAD) of LH-TL bandpass filters is presented. Motivated by a recent work, in which, a bandpass filter is realized by coupling several LH units, we propose a new structure consisting of a single unit with composite right/left-handed (CRLH) characteristics. The structure offers several advantages over traditional filters, e. g., compact dimensions and low loss. A new CAD algorithm for automated filter design, which can be valuable to designers, is demonstrated through an example.