The theoretical method to design negative refractive index metamaterials by single negative permittivity metamaterials is
presented. By designing the electric and magnetic response metamaterials separately, the complexity of the design work
can be simplified a lot. For the magnetic response metamaterials, the metallic post structure is adopted. Varying the
height of the post, the response wavelength can be adjusted linearly. For electric metamaterials, wire-mesh structure is
adopted. The effective material parameters, including refractive index, impedance, permittivity and permeability are
given. Such a structure has negative refractive index during a broad frequency band and easy to design.