Dual-Band Negative Group Delay Circuit Using λ/4 Composite Right/Left-Handed Short Stubs

Abstract

In this paper, a novel design for a dual-band negative group delay circuit (NGDC) is proposed. Composite right/left- handed (CRLH) λ/4 short stubs are employed as a dual-band resonator. A CRLH λ/4 short stub is composed of a typical transmission line element as the right-handed component and a high-pass lumped element section as the left- handed component. It is possible to simultaneously obtain open impedances at two separate frequencies by the combination of distinctive phase responses of the right/left-handed components. Negative group delay (NGD) can be obtained at two frequencies by using dual-band characteristics of the CRLH stub. In order to achieve a bandwidth extension, the proposed structure consists of a two-stage dual-band NGDC with different center frequencies connected in a cascade. According to the experiment performed, with wide-band code division multiple access (WCDMA) and worldwide interoperability for microwave access (WiMAX), NGDs of —3.0±0.4 ns and —3.1±0.5 ns are obtained at 2.12 ～2.16 GHz and 3.46～3.54 GHz, respectively.