What are metamaterials | basics of metamaterial antenna
This page covers metamaterials characteristics or features, metamaterials process and metamaterials applications such as antenna, sensor, absorber etc.
The materials which have properties not found in the nature such as negative index of refraction (n) are known as metamaterials. The term is made of "meta" and "material". Here "meta" is grrek word which refers to something beyond or advanced. They are man made materials. In other words, they are composite materials which have material properties not commonly found in ordinary materials.
Metamaterials can be characterized based on Maxwell equations. Following figure depicts classification of materials based on ε and μ.
The metamaterials are categorized into two main types viz. resonant metamaterials (viz. left handed metamaterials, refractive index less than one) and nonresonant metamaterials (viz. anisotropic metamaterials, hyperbolic metamaterials).
Metamaterials characteristics or properties
As shown there are four quadrants.
• First Quadrant: ε>0, μ>0, they are right handed materials commonly found. They are known as forward propagating waves.
• Second and fourth quadrants: ε<0, μ>0, describes electric plasmas which support evanescent waves.
• Third quadrant: ε<0, μ<0, this quadrant represents metamaterials. They are also known as left handed material or double negative material.
Metamaterials process of realization
Following should be considered in the process of metamaterials realization.
➨The material with negative "n" is very difficult to be found in the nature. It can be generated or manufactured by forming array of metal split rings & rods (i.e. short parallel wires).
➨The split ring resonators produce permeability μ which is negative while rods produce permittivity ε which is also negative.
➨The metallic rings and rods dimensions must be smaller compare to one wavelength, but it should be larger compare to an atomic dimension in order to achieve negative index of refraction.
➨It is possible to obtain imaging beyond diffraction limit of λ/2 as set by Abbe. The sub-wavelength imaging is very difficult to obtain in regular materials. This is due to the fact that evanescent waves decay exponentially with distance, which makes them effectively non-existent at image plane.
Following are the applications of metamaterials.
• Metamaterial can be used in the design of antenna. It helps in cell phone antenna design with five times smaller size with wider bandwidth (700MHz-2.7GHz).
• Metamaterial as absorber
• Metamaterial as superlens
• Metamaterial as cloaks
• Metamaterial as sensor
• Metamaterial as phase compensator