The Significance of Composite Right/Left-Handed (CRLH) Transmission-Line Theory and Reactive Loading in the Design of Small Antennas

Abstract

In discussions of small antenna designs based on the composite right/left-handed (CRLH) transmission-line model, the concept of left-handedness and resonant-mode order number are common. These properties are attributed to establishing the antenna's performance properties. The resonances of these small antennas are assigned order numbers that may be negative, zero, or positive. In many of these discussions, it is not made clear as to why CRLH transmissionline theory and the associated resonance-mode order number are significant in the design of the small antenna. Several questions not fully addressed in the discussions of these antennas include: 1) How does the CRLH design approach differ from conventional small antenna design approaches? 2) What significance is there in assigning a resonance-mode order number? 3) How does the resonance-mode order number being negative, zero, or positive affect the performance properties of the antenna? In this paper, we discuss the general design of small antennas, specifically with the focus of understanding how and whether or not the CRLH design approach differs from conventional design approaches. We illustrate that the resonance-mode order number is not significant in the design of the small antenna, nor is it significant in establishing the small antenna's performance properties. Furthermore, we show that the CRLH design approach is just one of several possible reactive-loading topologies for impedance matching, and that the fundamental radiating structure itself is most significant in establishing the matching frequency with a CRLH or left-handed design.