This paper presents a unique penta-band metamaterial absorber platform for terahertz imaging systems.The proposed fractal metamaterial absorber (FMMA) consists of fractal triangle section metasurfaces. By combining fractal resonators posing different operation skills in the same unit cell, the absorber shows multiband spectral response. The proposed unit cell structure operates at five near perfect absorption modes corresponding to the frequency bands of 1.1 THz, 3.4 THz, 4.9 THz, 5.9 THz, and 7.8 THz, respectively. Based on the fractal metamaterial absorber array, we also propose a sensing pixel design for bimaterial cantilever array sensing systems. The single pixel assembles 4x6 fractal resonator array and $$SiO_2$$
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-Al bimaterial microcantilevers. The sensing region of the FMMA pixel can bend the bimaterial cantilevers effectively at multiple modes, enhancing the imaging capacity. The effective medium theory is executed to visualize the constitute parameters during the absorption and reveal the origin of the rising modes. The absorption mechanism is also discussed based on the surface current distributions and electric field profiles. The numerical outcomes prove that the proposed fractal metamaterial unit cell is a promising candidate as an absorbing platform for THz band sensing and imaging applications. The derived iterative formula used in the fractal design procedure is explained for further investigations of microelectromechanical systems (MEMS) compatible compact absorber arrays.
5G (fifth generation) cellular system is expected to work in a wide frequency range to meet the demand for mobile services and applications. Antennas will be addressed to the future 5G applications should pose superior characteristics, such as high gain and ultralarge bandwidth response by considering atmospheric absorption/free-space path loss on planned millimeter-wave frequency range of 5G communications. Therefore, antenna design for the future 5G applications is a challenging process. In this article we present a highgain, broadband mm-Wave antenna based on a circular patch structure with a ground plane and resonator gaps. The designed antenna is analyzed using a widely used full-wave electromagnetic solver. The major antenna figure-of-merits including reflection coefficient, VSWR (voltage-standing wave ratio), antenna patterns in E-and H-planes, surface current distribution, antenna directivity and maximum gain, are obtained. The simulation results show that the gapped circular patch based design has the S11 response less than −10 dB in the frequency range of 21.6-28.8 GHz, which includes 24-28 GHz band of 5G cellular systems. Moreover, it is observed that the symmetrically located circular gaps on both top and bottom layers decrease the side lobe level under −10 dB value, and enhance the gain. We attribute the improvement in the antenna performance to the created current regions due to gaps hosting large vortex current distributions. With 10 mm × 13mm surface area, the proposed antenna demonstrates the peak gain of 9.44 dBi and the radiation efficiency of over 85%. High gain and compact size make this antenna suitable for coming 5G devices.
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