Study And Simulation On The Realization Of Left-Handed Material Structures

In 1968, Veselago investigated a material with negative permittivity and permeability (left-handed materials) theoretically, and obtained novel results of negative refraction and reversed Doppler shift. At microwave frequency, J. B. Pendry realized such materials using periodic structures consisting of an array of split-ring resonators (SRRs) that exhibit a negative permeability, and an array of metallic printed lines (or rods) that exhibit a negative permittivity. The experiment verifying the negative index of refraction was first proposed by D. R. Smith in 2000. Since then plenty of papers studying the left-handed materials (LHM) are reported.Several shortcomings of SRR suggested by Pendry resist the practice of LHM. The composite structure of SRR and wires has the disadvantages of high loss and narrow frequency band. On the other hand, the size of SRR cell is relatively large compared to the wavelength, which is about 0.1 wavelength in free space.In this thesis, many new structures are reported to widen the bandwidth of negative permeability. A method is summarized from the papers to design the magnetic resonator with the wide bandwidth.We searched a few new structures to reduce the resonant frequencies using the same-size unit cell as the traditional SRR. One of the structures is selected as the double spiral resonator (DSR), which is set up by two opposite spirals. DSR and wires together constitute the composite of LHM. Electromagnetic simulations and theoretical analysis are given to show the efficiency and better performance of such LHM. The purpose of this thesis is to reduce the resonant frequency significantly.Anther structure, named single spiral resonator (SSR), has the lower resonant frequency than DSR. But the capacitance is smaller and the resistance is larger. The simulation shows that the resonance of SSR is weaker than DSR.It is time consuming to compute finite periodic structure made of LHM. An efficient method, named as the modified Sub-Entire Domain (SED) Basis Function Method, is also proposed to accelerate the calculation of the array with finite periodic structure, for example, SRR array. The modified SED method is based on MoM and SED basis function. Through simplifying the test function, the computational efficiency has been improved significantly.