Broadband Phase Shifter Based On Composite Right/Left-handed (CRLH) Transmission Lines

Metamaterials(MTMs), defined as "a composite or structured ma-terial that exhibits properties not found in naturally occurring materials or compounds", really constitute a new field of science and engineering.Left-handed(LH) media was predicted by Veselago in 1967,which is at the origin of all research on LH MTMs. The first experimental demonstration of a left-handed (LH) structure emerged in 2000.Some scientists adopted an engineering approach to realize the MTMs, based on a generalized transmission line (TL) theory, Which is so-called Composite Right/Left-handed(CRLH) Transmission Line.This paper presents electromagnetic MTMs and the foundations of CRLH structures. Their applications in the general framework of CRLH TL MTMs are also presented.The CRLH transmission line has the ability to synthesize an arbi-trary phase response, it provide an approach to realize the phase-adjusting circuit. The slope of the phase-response curve of a CRLH TL can be the same as that of a conventional TL along with a stable phase increment, such as 90°, over a wideband frequencies.In this paper, we use CRLH approach to realize the 90°roadband phase shifter. It consists of a Wilkinson power divider and two phase adjusting TLs, namely a CRLH TL and a conventional TL. The Wilkin-son power divider equally separates the input power into two output ports, and also provides good isolation between them. The conventional TLs and CRLH TLs are connected to two output ports of the divider as a phase adjusting circuit to achieve broadband phase shift. Hence, it provides a balanced amplitude with 90°phase difference and good isola- tion between two output ports. As the name describes, CRLH consist of left-handed (LH) transmission line and right-handed (RH) transmission line. In this design, the LH TL part is cascaded by two T-type networks. Then, the power divider, the TLs and the lumped elements for the CRLH TLs are co-simulated together in ADS software.Compared with conventional RH transmission line phase shifter, the CRLH phase shifter is compact, occupying only a fraction of the area. In addition, the bandwidth of it is much wider.The artificial LH network part in the CRLH TL is realized by 0603(1.6mmx0.8mm) surface-mount-technology (SMT) chip inductors and capacitors. However, there are limited discrete available values of inductance/capacitance of SMT chip components. Therefore, the values of inductance or capacitance in the fabricated circuit are slightly differ-ent from the design values. In practice, the parasitic effects of soldering and vias have to be taken into account in the CRLH case. It will signif-icantly affect the phase shift performance。Generally speaking, my work is to analyze, design, simulate, im-plement and measure a broadband phase shifter using CRLH method.Besides, a compact feeding network for a wideband circularly po-larized multi-mode Global Navigation Satellite System (GNSS) antenna is presented. Fur feed method for the antenna is adopted to suppress the higher modes and increase the 3dB axial ratio(AR) bandwidth. A broadband phase shifter with 0°,90°,180°,270°phase difference using CRLH transmission line structure combined with novel schiffman phase shifter is made in this article.