الفهرس 
Millimeter Wave Antennas for 5G ApplicationOnly 14 pages are availabe for public view
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Abstract
Epsilon Near Zero (ENZ) materials are special cases of metamaterials which are characterized by very small relative permittivity approaching zero value. Materials with epsilon near zero (ENZ) may be directly found in nature. A well-known example is an electron gas where the conduction current created by the drift of free electric charges may effectively interact with radiation as continuous medium having ε near zero. Artificial ENZ materials can be fabricated at a desired frequency as metamaterials by embedding suitable inclusions in a host medium.
ENZ materials are characterized by low-wave-number which provides a relatively small phase variation over a physically long distance in these media. When these materials are interfaced with materials with larger wave number, they present a region of space with almost uniform phase distribution. This property can be used to develop artificial lens structure which convert the non-planar equiphase wavefront of low directive antenna to a planar equiphase wavefornt providing the possibility for directive radiation toward the broadside to a planar interface.
ENZ materials can also be used to squeeze and tunnel electromagnetic energy through narrow subwavelength waveguide channels. This property can be used to enhance the efficiency of some waveguide devices and also to reduce the reflection coefficient at a waveguide junction or bend. On the other hand, this tunneling effect is characterized by narrow bandwidth which is affected by any slight change in material properties inside the sub-wavelength waveguide channel. This property is found to be quite useful for measuring electric permittivity of dielectric materials in microwave range.
This research is focused on investigating the feasibility of using ENZ metamaterial structures to improve the performance of antennas operating at millimeter wave and microwave frequencies. The metamaterial design process is challenging because they are primarily composed of resonant particles. Hence, their response is frequency dependent due to the dispersive behavior of their effective medium properties. However, one can take advantage of this situation by exploiting these strange properties while finding other antenna applications for such metamaterial designs.
This research investigates several antenna applications of artificial magnetic materials(AMMs). The initial work is devoted to optimize and design an ENZ metamaterial unit cells to operate in the required band for a specific application (5G and microwave imaging system). Then these ENZ unit cells are embedded with antenna structure to enhance the antennas gain without increasing their size. This research show how these low refractive index materials can be used to enhance the performance of ultra wide band antennas by simulation program and fabrication method.