We present a combination of split ring resonators for THz absorption applications. This combination creates a fractal organization with an ultra-wideband characteristic between 45.5 and 56.7 THz. During the design process, a very thin ZnSe substrate with a thickness of 0.6 μm was used, and copper resonators were placed on the substrate layer. The back layer was also covered with a very thin layer of copper to prevent the transmission of electromagnetic waves. The proposed design exhibits a wideband absorption characteristic with peak resonance points at 46.36, 47.57, 48.98, 50.39, 52.97, 54.62, and 56.1 THz. Furthermore, the electric field distributions at these peak resonances were obtained to further explore the absorption characteristics. The absorption response was also analyzed for both transverse electric and transverse magnetic modes to demonstrate mode stabilization in the absorption performance. Finally, polarization and angle of incidence variations were studied, and polarization independence was achieved. This design is a promising candidate for THz imaging and stealth applications due to its wideband performance.
A C-shaped split ring resonator-based metamaterial (MTM) structure placed on a patch antenna is proposed. An artificial neural network (ANN) is applied to design and determine dimensions of an MTM structure that is similar to those used in wireless communication systems, such as Wi-Fi and WiMax, as well as in military vehicles and space stations. The proposed microstrip antenna interacts with the MTM-based structures to improve the reflection coefficient (S11) and quality factor. The design of the proposed structure is optimized for this purpose in accordance with the ANN studies in the related literature. Both simulation and experimental studies show that ANN calculated MTM antennas improved the quality factor, which is calculated as 230 at 5.18 GHz. The simulated S11 is verified by experiment to show the integrity of the proposed work.
We present a system that displays an image of any metal structure in a scene by the use of microwave radiation from a cavity resonator in a 10-GHz frequency band. An 80 mm × 80 mm mushroom-like electromagnetic band gap (EBG) structure was arranged, designed, analyzed, and integrated with an X band monopole antenna and the designed EBG monopole antenna has ∼2-GHz bandwidth. Meanwhile, a cubic cavity resonator is constructed and an EBG grounded monopole antenna is located on one wall of the cavity resonator to create a narrow band radiation. The formed narrow band radiation from the cavity resonator reaches to the metal structure located in the scene. Backscattered radiation collected by a 8 to 12 GHz waveguide receiver that is located near the cavity to scan the whole scene and sweep the waveguide throughout the resonator plane performs to gather various transmission values from a scene. These various transmissions from the cavity resonator antenna to the waveguide receiver were used for imaging. In addition, tunability of the designed EBG structure is studied and presented. The designed structure has advantages such as easy design and fabrication, high accuracy performance, and compatibility to the other frequency regimes. In addition, the designed EBG plane is based on RLC circuit theory, which enables us to understand the antenna performance and EBG structure. This system can be integrated with various areas, such as medical imaging, military applications, weapon detections, security imaging purposes, stealth technology, and other appropriate applications.
Our paper presents the design, fabrication, and characterization of metamaterial absorber-based microwave imaging detector that is operating in industrial, scientific, and medical (ISM) band. The results reveal that the structure has almost perfect absorption at 2.39 GHz in the simulation and 2.51 GHz in the experimental measurement. For energy-harvesting applications, Schottky diodes have been used and 11.8-mV dc voltage across a Schottky diode has been observed with 84.2% dc conversion efficiency in harvesting application. To show the different incident angle imaging, MATS-1000 antenna training kit is used, and different imaging pictures are given, which are obtained by MATLAB with the help of a microcontroller card. Both experimental and simulation study results verify that the microwave detector generates accurate images with negligible distortions. The innovative side of this study when it is compared with similar studies can be sorted as having more dc obtained voltage, incident angle characterization, and operation frequency. Simulated and measurement results show that the proposed structure can effectively be used in the imaging at ISM frequency band, which is the most common frequency band in wireless appliances.
In a lossy media, anisotropic chiral metamaterial (MTM) structures with normal incidence asymmetric transmission of linearly polarized electromagnetic (EM) waves are investigated and analyzed in both microwave and terahertz frequency regimes. The proposed lossy structures are used to perform dynamic polarization rotation and consist of square-shaped resonators with gaps on both sides of dielectric substrates with a certain degree of rotation. Asymmetric transmission of a linearly polarized EM wave through the chiral MTMs is realized by experimental and numerical studies. The dynamic structures are adjustable via various parameters to be tuned for any desired frequency regimes. From the obtained results, the suggested structure can be used to design new polarization control devices for desired frequency regimes.
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