Design Of Left-handed Materials And Their Applications In Ultra-wideband System

Left-handed materials (LHMs) have great application prospects because of itsextraordinary electromagnetic properties. It has attracted more and more attention andbecome one of research hot spots in the current international physics andelectromagnetic field since the first left-handed material in microwave band wasmanufactured in2001.The current design methods of LHMs can be classified into two categoriesmainly. One is the improved and derived structures based on Smith model which isnamed as resonant-type LHMs in this paper. The other is planar compositedright/left-handed transmission line (CRLH TL) and its simplified models which isnamed as transmission-line-type LHMs in this paper.The principle of the realization methods of two kinds of LHMs is analyzed and avariety of LHMs are proposed based on two basic methods in this paper. For the firstLHMs type, a novel resonant-type LHMs unit cell is proposed. The model issimulated and the corresponding transmission characteristics are obtained. The relatedeffective electromagnetic parameters are calculated by the Smith parameter retrievalmethod. Furthermore, the U-band LHMs based on double-layered split ring resonator(SRR) structure are demonstrated by tuning the dimensions parameters of SRR,according to the design of LHMs mainly concentrated in the microwave regionproblem. For the second LHMs type, a compact and good performance bandpass filterapplied in UWB system is obtained based on CRLH TL theory. Because the5.25GHzwireless local area network technology is widely used in wireless communicationfield, an ultra-wideband single notched-band bandpass filter with good performancesis developed by consisting of a CRLH TL unit cell and an embedded open-circuitedstub in order to overcome the interference problems between ultra-wideband andwireless local area network.