Study of microstrip antennas on double negative metamaterials

Pao Yue-kong Library Electronic Theses Database

Study of microstrip antennas on double negative metamaterials

 

Author: Zhu, Yaxuan
Title: Study of microstrip antennas on double negative metamaterials
Degree: M.Phil.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Microstrip antennas
Metamaterials
Negative refractive index
Department: Dept. of Electronic and Information Engineering
Pages: xii, 112 leaves : ill. (some col.) ; 31 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2343015
URI: http://theses.lib.polyu.edu.hk/handle/200/5713
Abstract: The work of this thesis consists of two parts. Rectangular patch microstrip antennas printed on homogeneous Double Negative (DNG) metamaterials substrates are investigated in part one. In the second part, loading DNG metamaterials at the edges of rectangular patch microstrip antennas is considered to enhance their impedance bandwidth. Throughout the thesis, Drude model is used to simulate the dispersion of DNG metamaterials and all the patch antennas are simulated using the finite-difference time-domain method. As the refractive index of the metamaterials increases monotonically from negative infinity to positive one, the rectangular microstrip patch antenna structure considered in part one supports resonant modes in negative refractive index region, at zero refractive index and in positive refractive index region. The first resonant mode in the positive refractive index region f(₁) (For simplicity, f(₁) is used to denote this mode as well as its resonant frequency throughout this thesis), the first resonant mode in the negative refractive index region f(-₁) and the resonant mode f(₀) at the zero refractive index are investigated. The resonant frequencies of f(₁) mode and f(-₁) mode are calculated using cavity model. The field distribution of f(₁) mode is very similar with that of TM₁₀ mode of a rectangular microstrip antenna printed on a dielectric substrate. The refractive index at the resonant frequency of this mode lies between zero and positive one. The antenna size of this mode is larger than half free space wavelength. On the other hand, the f(-₁) mode is very similar to a microstrip antenna printed on a substrate with a high dielectric constant. Therefore, the antenna size is smaller than half free space wavelength but its bandwidth is very narrow. The f(₀) mode, also termed zero-order mode, resonates when the refractive index of the DNG metamaterials is zero. The resonant condition of this mode is independent from the size of the antenna patch. As there is a surface wave mode lies between f(₀) and f(-₁) , different kind of the surface wave modes, which supported by the DNG substrate, are also investigated in part one. In the second part, the f(₀) mode resonance is applied to enhance the bandwidth of rectangular patch antenna. Slabs of DNG metamaterial are loaded to the radiating edges of a rectangular patch microstrip antenna, which was printed on another DNG metamaterial or dielectric substrate. At the resonance frequency, either the f(₁) mode, f(-₁) mode or TM₁₀ mode is excited under the microstrip antenna while the f(₀) mode is excited inside the loaded DNG metamaterial. Using this structure, 9.65% of -10dB bandwidth is achieved for bandwidth enhanced f(-₁) mode.

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