Highly Versatile Coplanar Waveguide Line With Electronically Reconfigurable Bandwidth and Propagation Characteristics

Abstract

This paper describes a coplanar waveguide coupled to two split-ring resonators that, in turn, are loaded with two different reactive elements. By these means, balanced composite right/left-handed-like (CRLH-like) and also dual balanced CRLH-like (D-CRLH-like) responses can be obtained with the same structure showing opposite propagation characteristics. This behavior is achieved by simply varying one of the reactive elements, i.e., the capacitive or inductive load. The physical behavior of these transmission lines has been successfully explained by means of a single equivalent circuit. Besides, the proposed transmission lines have an extended bandwidth due to the balanced nature of the structure. The bandwidth of these lines can be electronically controlled using varactor diodes reverse-biased by an external dc voltage. Thus, a reconfigurable cell with CRLH-like and D-CRLH-like propagation has been designed and manufactured. The simulated and measured results show fractional bandwidths from 0% (no transmission) to 9.3% for simulations and from 0% (no transmission) to 8.7% for measurements. Undoubtedly, these new proposed transmission lines will be useful for designing reconfigurable devices that can be used in future communication systems such as radar, wireless applications, global positioning systems, or radio-frequency identification systems, among others.