Numerical studies for relative bandwidth of left-handed metamaterials with split-ring resonators

While an incident wave propagating through a periodic material with the dimension of its microstructure far less than the wavelength, the material can be regarded as a homogeneous medium, then its effective electromagnetic parameters in the frequency domain can be obtained by the S parameters-retrieval methods. Based on this perspective, the design of material with the desired left-handed characteristics becomes possible. Using numerical simulation techniques such as the commercial software CST Microwave Studio, we study the transmission and reflection properties of left-handed materials with arrays of split-ring resonators (S parameters). It is shown that these periodic unit cells can exhibit negative permittivity and negative permeability in some frequency spectrum with the S parameters-retrieval methods. Firstly, the LH relative bandwidth with the structural parameters such as the outer ring radius, the width of the rings, their separation, the rings´ gap and the width of the wires, is numerically analyzed respectively. Secondly, the dependences of relative bandwidth on all the parameters are contrasted for sensitivity studies. The results show that the outer ring radius R has an overwhelmingly greater effect on the relative bandwidth than other design variables (d_srr, w_srr, g, w_wire), and they will be beneficial to material design of left-handed materials.