جستجوی مقالات مرتبط با کلیدواژه "h∞" در نشریات گروه "برق"

With the increasing development of wireless technologies and the increasing demand for wide bandwidth in communication and military systems, the design of compact, efficient, and versatile antennas for ultra-wideband (UWB) applications has gained significant importance. In this paper, an innovative antenna for the frequency band of 1.3 to 10.6 GHz is designed and fabricated. This antenna is designed using a defective ground structure (DGS) and coplanar waveguide (CPW) transmission lines on a small FR4 substrate with dimensions of 26.6 × 29.3 × 1.6 mm. The proposed antenna is unidirectional with high gain, has a peak gain of 4 dBi, and the simulation results show that its VSWR value is lower than the standard value at most points of the bandwidth, which indicates the impedance matching of the antenna. The results of the antenna fabrication and simulation indicate its optimal performance in fields such as high-speed wireless communications, surveillance radars, and reconnaissance systems. Among the prominent applications of this antenna is its use in ultra-wideband jamming systems in the field of electronic warfare. The compact design, high gain, and wide bandwidth make the proposed antenna an ideal solution for advanced military and communication technologies that can effectively meet the modern needs of these fields.

In this paper, a novel wideband terahertz antenna with an imperfect ground structure and parasitic elements has been proposed. The optimized antenna geometrical parameters are obtained using an artificial neural network which employs forward feedback propagation along with the Levenberg-Marquardt optimization algorithm including 10 neurons. The objective of this design is to increase the obtained return loss bandwidth of designed antenna. This demanded objective is obtained using imperfect ground structure and parasitic elements together. The antenna structure features a substrate with a dielectric constant of 9.4 and a loss tangent of 0.00002, designed within dimensions of 100 by 100 square micrometers. The antenna configuration is derived from the neural network implemented in MATLAB program using 143 training samples. As a result, the obtained performance bandwisth is 41% more than that of ordinary terahertz microstrip antenna. Furthermore, the obtained radiation patterns are investigated over operational frequency band showing a suitable performance.

Fifth-generation (5G) wireless communication systems utilize millimeter-wave frequency bands to achieve ultra-wide bandwidth for high-data-rate transmission. To meet the system's requirements, optimal design of high-performance antenna arrays is essential. Therefore, this paper proposes the design and performance analysis of metamaterial-inspired millimeter-wave antenna arrays in single, 2x1, and 4x1 configurations. The antenna elements, operating at a center frequency of 38 GHz, are designed using Rogers 5880 as the substrate material with a dielectric constant of 2.2 and a thickness of 0.35 mm. In the simulated design of the single, 2x1, and 4x1 arrays, the return loss, bandwidth, gain, voltage standing wave ratio (VSWR), and total efficiency are -82.95 dB, -67.1 dB, -69.12 dB; 1.971 GHz, 2.278 GHz, 4.704 GHz; 7.36 dB, 9.11 dB, 11.4 dB; 1.001432, 1.0009, 1.0007; and 95.55%, 94.01%, 95.87%, respectively. Compared to previous works, considering the impact of metamaterials on the radiator and ground plane of microstrip patch antennas, improved performance is achieved. The selected type of metamaterial alters the radiation current distribution of the patch, enhancing the edge fields at the patch edges, which improves antenna radiation and reduces surface wave losses in the ground plane of the radiators. The proposed antenna arrays address the shortcomings of older designs and meet the needs of 5G communication systems.