| Natural materials usually are right-hand material with positive effective permittivity and permeability. However, artificial materials, the well-known left-hand materials, could have opposite characteristics. Left-hand(CRLH) material, which is a merging topic and has been widely investigated, have such different characteristics as a negative refractive index, backwards propagation and so on. This paper analyzed the effective circuit model of transmission line, based on it, constructed a composed right/left-hand transmission line, and designed a electrically tunable phase shifter, as well as a electrically tunable circularly polarized leaky wave antenna. In this way, this paper also presents some applications of CRLH transmission line in transmission and radiation. Specific work includes:Firstly, basic characteristics of left-hand materials and recent applications of left-hand materials and CRLH transmission line in antennas and microwave components are introduced, including detailed analysis on their principle and realization.Secondly, elemental mechanism of transmission line is analyzed from the view of effective circuit model. A design of electrically tunable phase shifter is proposed by introducing diodes and other lumped components to common right-hand transmission line to construct a continuously tunable unit cell of a phase shifter. The permittivity and permeability of this unit cell, deduced from its S-parameter, avers a left-hand characteristics. Bias networks optimized by full wave simulator, adding to five cascaded unit cells, eventually form a phase shifter with tuning range of 360 degree, which is verified by experiments and tests.Finally, working mechanism of leak wave antenna and traditional circularly polarized antenna are investigated and combined to give a design of a circularly polarized leak wave antenna with slotting and cutaway. The axial ratio keeps less than 6d B in its scanning range from negative to positive 30 degree. |
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