Based On The Right-hand Man Of Composite Media Tunable Dual-band Coupler Design

Recently, a new type of artificial material which exhibits simultaneously negative effective permittivity and permeability over a certain frequency band has attracted a great attention. Such material, also called left-handed material (LHM), has a negative refractive index, and also has its unique electromagnetic properties such as the reversal of Snell's Law, the Doppler effect, and the Vavilov-Cerenkov effect. When LHM is combined with conventional right-handed material (RHM), some novel applications come out.This paper illustrates the principle of the design of composite right/left-handed (CRLH) and presents some novel devices utilizing CRLH on microwave. A tunable dual-broad-band branch-line coupler (BLC) utilizing CRLHtransmission lines is presented. Two A/4 segments consisting of CRLH transmission lines are added to each port to broaden the dual bands of the branch-line coupler. Numerical simulation and optimal design of the novel coupler are presented. The dual bands of the novel coupler are tunable and broad. The 1-dB bandwidth of each pass band is more than 16% of the central frequency.There are 5 chapters in this paper. The first chapter introduces NRI and CRLH. In the second chapter, the basic design principles and methods of microwave devices are discussed, including the concept of S parameter, the characteristics of transmission line and the microwave circuit CAD. The third chapter discusses the common theory and characteristic of LH and CRLH transmission lines. Chapter 4 is mainly focused on the common design theory ,ideas and methods of all kinds of microwave couplers. And in the last chapter, two novel devices are designed and the simulated and experiment results are presented.