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This work proposes a spiral filter-based diplexer antenna for dual-band full-duplex 5G application in C-band. The shared radiator is formed by a cross-shape Yagi-Uda antenna. The dual-band fullduplex characteristic is obtained by applying a diplexer with two different band-stop filters (BSFs) based on a high-order rectangular spiral-shaped open-stub filter. The proposed diplexer antenna is suitable for modern 5G full-duplex communication system applications with a small frequency ratio and high isolation between two ports by applying a Wilkinson power divider. The diplexer antenna is designed, fabricated, and measured, showing good performance of channel isolations of 27 dB/23 dB and the antenna gain of 4.7 dBi/4.2 dBi at two operation bands from 3.56 GHz to 3.68 GHz and from 3.72 GHz to 3.83 GHz covering the required 100 MHz maximum bandwidth in C-band while its frequency ratio is only 1.04. [ABSTRACT FROM AUTHOR]

Many design optimization problems have problems that seek fast, efficient and reliable based solutions. In such cases, artificial intelligence-based modeling is used to solve costly and complex problems. This study is based on the modeling of a multiband helical antenna using the Latin hypercube sampling (LHS) method using a reduced data enhanced multilayer perceptron (eMLP). The proposed helical antenna is dual-band and has resonance frequencies of 2.4 GHz and 2.75 GHz. The enhanced structure of the artificial neural network (ANN) was tested using 4 different training algorithms and a maximum of 10 different MLP architectures to determine the most suitable model in a simple and quick way. Then, performance comparison with other ANN networks was made to confirm the success of the model. Considering the high cost of antenna simulations, it is clear that the proposed model will save a lot of time. In addition, thanks to the selected sampling model, a wide range of modeling can be done with minimum data. When the target and prediction data are compared, it is seen that these data overlap to a large extent. As a result of the study, it was seen that the ANN modeling and the 125 samples used, were as accurate as an electromagnetic (EM) simulator for other input parameters in a wide range selected. [ABSTRACT FROM AUTHOR]

This paper proposes a new metasurface to improve gain for dipole antenna. The antenna includes two sets of two elements (1 x 2), the integrated J shaped baluns, five metasurface cells (each metasurface cell consists of 5 periodic metallic plates printed on a thin low-cost FR4 substrate) for four antenna elements and the antenna is supplied by two T-junction power dividers. The metasurface is designed to operate as reflection surface. The antenna is designed based on RT5880 and witnesses an overall size of 140 x 37 x 35.075 mm³ (2.7λ x 0.71λ x 0.67λ at 5.8 GHz), an isolation of approximately 28 dB, a peak gain of 9.5 dBi, and a radiation efficiency of 84%. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive detailed comparative study of the three ultra-wideband and high directive antennas for the THz imaging, spectroscopy, and communication applications. Three different types of photoconductive antennas (log-spiral, Vivaldi, and bowtie antennas) are designed and simulated in the frequency range of 1 to 6 THz in the CST microwave studio (MWS). The enhanced directivity of the designed PCAs is achieved with the integration of the hemispherical silicon-based lens with the PCA gold electrode and quartz substrate of the proposed antennas. The performance of the designed PCAs is compared in terms of impedance and axial ratio bandwidths, directivity, and radiation efficiency of the proposed antennas. The reported log spiral, Vivaldi PCAs with added silicon lens exhibit the -10 dB impedance bandwidth of 6 THz, 3dB AR bandwidth of 5 THz, 6 THz, and 6 THz and peak total radiation efficiencies of 45%, 65%, and 95% respectively. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of a spiral nano-antenna dedicated to infrared energy harvesting at 28.3 THz. A comprehensive, detailed parametric study of key parameters such as the initial angle at the origin arm, width of the spiral arms, gap between the two arms, thickness of substrate, length of substrate, thickness of patch and number of turns of the nano-antenna is also presented and discussed in order to harvest maximum electric field in the gap of the spiral antenna in the frequency range of 28 - 29 THz. The maximum electric field is simulated at 28.1, 28.3, 28.5 and 28.7 THz. A variation of the electric field of the antenna for different value of incident wave angle at the resonance frequency 28.3 THz has been simulated. The main advantages of the studied structure are its ability to reach high confined electric field within its gap, its wideband behavior around the operating frequency 28.3 THz, and its insensitivity to polarization of incident electromagnetic waves. [ABSTRACT FROM AUTHOR]

In this work a novel design of an ultrawideband and highly directive Vivaldi photoconductive antenna (PCA) is reported for the first time for the THz sensing and imaging applications. The optical-to-THz conversion efficiency for the enhanced directivity of the reported PCA is enhanced by adding a hemispherical silicon-based lens with the PCA gold electrode and quartz substrate (r = 3.78, tan = 0.0001). The optimization of the antenna design parameters is performed in CST MWS for the frequency range of 1-6 THz. The design antenna has UWB -10 dB impedance and 3-dB AR bandwidths of 6 THz, maximum directivity of 10 dBi and maximum total radiation efficiency of > 40%. [ABSTRACT FROM AUTHOR]

A compact wideband coplanar waveguide (CPW) excited slot antenna with dual-circular polarization (DCP) is presented and fabricated in this paper. Two inverted-L-shaped patches are implanted in a square slot to achieve wideband DCP characteristic. The feed line is terminated on an inverted-L-shaped patch. Moreover, two rectangular slots are added on the corners of the antenna to improve the bandwidth of axial ratio (AR) and the voltage standing wave ratio (VSWR). The simulated results show that the designed antenna can generate a good impedance bandwidth of 70.4% and a 3-dB AR bandwidth of 48.6%, respectively. This antenna possesses the qualities of small size, simple structure, and good dual-circular polarization. [ABSTRACT FROM AUTHOR]

Recently, ingestible capsule endoscopy has been developed to ease the dosimetry process in the stomach and tract. In this application, a helical antenna is used because its shape is suitable for a capsule. The electric performance of a coil antenna can be analyzed by the normal-mode helical antenna (NMHA) concept. Previously, the design equations for NMHA have already been developed in free space application. Application of NMHA in the human body is innovative. Antenna design equations and electrical performance should be clarified. Presently, only self-resonant structure equations are clarified. In this paper, fundamental electric performances such as the input resistance, bandwidth and radiation characteristics are clarified through electromagnetic simulations and experiments. As for a human body tissue, the muscle is selected and a muscle phantom is used for measurements. It is made clear, that the input resistance and the bandwidth are increased by the increase of the human body conductivity, while the antenna gains are decreased. [ABSTRACT FROM AUTHOR]

A modified octree grouping scheme of the multilevel fast multipole algorithm (MLFMA) is proposed to analyze the electromagnetic (EM) scattering from the electrically large target, which is illuminated by a spiral parabolic antenna. The spiral parabolic antenna is used to generate the electromagnetic vortex of a specific mode number by adjusting the height of split. The proposed method builds two octree groups and decouples the interaction between the antenna and the target, so as to save the computational resource and improve the computational efficiency. Using this scheme, the numerical example with double metal spheres illuminated by the electromagnetic vortex reveals some special phenomena due to the spiral phase distribution, while the example with a scaled-down airplane at long operating range demonstrates that the electromagnetic vortex tends to be plane wave locally with the increase of propagation distance. [ABSTRACT FROM AUTHOR]

We use a genetic algorithm to minimize the relative sidelobe level (RSLL) of a dual polarized concentric ring array. The optimization variables are the placement of uniformly weight spiral antennas in an aperture with a small area. We optimized a cost function with isotropic sources instated of spiral elements to make the cost function reasonable to evaluate. We developed approaches to calculate a faster cost function and reduce the number of function calls in the optimization. We then calculated the array with an approximation of the element pattern to evaluate its performances. [ABSTRACT FROM AUTHOR]

In this paper, a new configuration of broad band circularly polarized (CP) array antenna is presented by a modified feeding network The proposed feed network includes two hybrid 90-degree branch line coupler and a 180-degree rat-race coupler. The feed network of array provides sequential rotation condition for consisting of four L-shaped microstrip lines which coupling through four ring-shaped slots. Each element of array is printed on two layer of substrate which connected together with a ring aperture. Employing wideband CP elements and feeding network structure causes the creation of innovation at CP array. The 3dB axial-ratio bandwidth of the array extends to approximately 650 MHz with impedance bandwidths of 24.7% for C-band applications and a relative high gain of about 10.2 dBic. The performance of the antenna has been approved by comparing between measurement and simulation results. [ABSTRACT FROM AUTHOR]

An experimental study of coupling compensation for AOA estimation using compact low profile antenna arrays with element separations of a quarter wavelength has been conducted. Two circular arrays of low profile miniaturised logarithmic spiral antennas deployed on a circular metal plate were used for data acquisition. Using the MUSIC direction-finding algorithm, the AOA estimation errors in receiving mode were observed before and after compensation: the errors were significantly decreased by coupling compensation. [ABSTRACT FROM AUTHOR]

A novel compact spiral antenna with planar feed structure is presented. The proposed antenna is a two-arm Archimedean spiral antenna, which has similar properties of wideband and circular polarization to traditional one. A remarkable improvement of the proposed antenna is the completely planar feed structure. The whole antenna is compact, its spiral diameter is only 23.2mm and the balun is also small. It has an impedance bandwidth of 67% from 4.5GHz to 9GHz and a 4-dB axial-ratio bandwidth of 46.67% ranging from 4.6 GHz to 7.4 GHz. It can be widely used in wideband planar antenna array and other low profile applications. [ABSTRACT FROM AUTHOR]

Sinuous antennas, like spiral antennas, have wideband characteristics, such as constant beam width and low axial ratio over a broad range of frequencies, and thus they are suitable for communicating in transmitting and receiving over bands of frequencies that may encompass multiple channels. In the presence of the back cavity, the performance of the sinuous antenna is affected. The purpose of this paper is to study the affects of the back cavity, and use these findings to build an optimized lossy cavity to improve the performance of the sinuous antenna. The performance of the antenna with and without the back cavity is compared to the antenna with the optimized loaded cavity. [ABSTRACT FROM AUTHOR]

Recently, for Radio Frequency (RF) signal identification on air vehicles, it has become critical to not only be able to detect the direction and angle of arrival of signals, but to also properly identify the polarization of such signals. For decades, cavity-backed dual-spiral antennas were heavily used for this purpose. However, that required the placement of both right-hand and left-hand elements to perform this function. Due to limited space and other issues, an alternative type of broadband antenna had to be identified. The Cavity-Backed Dual-Sinuous (CBDS) antenna makes an excellent replacement for this function. With its elements rotated 45° about its center, each element exhibits slant linear performance. Such an antenna, paired with proper connections and detection hardware, allows the detector to determine the polarization of arriving RF signals. A CBDS antenna was developed in the WIPL-D CEM code. Its RHCP and LHCP performance was studied over a broad range of frequencies. Results did prove that CBDS antennas have excellent broadband performance and polarization extraction. [ABSTRACT FROM AUTHOR]