The field of wireless body area networks (WBAN) has seen growing interest in recent years due to applications of wearable devices, such as in healthcare. Effective on-body antenna design is necessary to provide optimal performance in real-world scenarios. This study compares several wearable antenna types, which are the monopole, patch, and e-textile antennas, to determine how human body motion affects antenna performance using a human body phantom model and human volunteers. The monopole antenna overall outperforms the patch antenna at 915 MHz and the e-textile antenna at 2.45 GHz and a Weibull distribution can be used as a probability distribution for S21 during an arm swing motion for all antenna types tested.
In phased array systems, beam pointing accuracy is one of the major issues for its great effect on radar communication. Regardless of the initial excitation error and the inherent mutual coupling between antenna elements, the anisotropy of antenna element's radiation pattern is the main reason for beam pointing error. In this paper, we propose a closed-form solution of compensating for beam pointing error with uniform linear arrays. It gives a theoretical explanation how beam pointing deviates from the desired angle when scanning angle and the number of elements vary. Then a numerical simulation validates the effectiveness of the proposed theory. Finally, an experiment with an X-band phased array verifies that the closed-form solution can be applied to practical phased array systems in the presence of mutual coupling.
A compact, two-port, oblong loop antenna producing two orthogonal waves for fifth-generation (5G) operation in the 3.4-3.6 GHz band with transmission coefficient (S12) lower than -32 dB and excellent envelope correlation coefficient (ECC) less than 0.002 is introduced for laptop antenna applications. Unlike the conventional, probe-fed, dual-polarized patch antennas, the proposed design uses the loop antenna fed by the coaxial cables and has a coplanar structure. The loop antenna is placed 1 mm above the top edge of the display, has a compact size of 30 mm × 4 mm and two feed ports spaced merely 2 mm (about 0.02-λ at 3.4 GHz) apart. Port1 is designed as a coupling feed to the loop while port2 is a direct feed in the loop, all located along the loop's central line. With this feeding arrangement, port2 is located in the current-null region when port1 is excited, whereas maximum currents of port1 excitation are located in the current nulls of port2 excitation. These properties lead to two decoupled, orthogonal radiating waves with very low ECC. Additionally, due to the oblong structure of the loop, pattern diversity is also achieved. Details of the dual-polarized loop antenna for 5G applications are presented.
Nowadays, wireless charging for electric vehicles has become popular in numerous situations by reason of safety and convenience. In this article, a composite compensation network and the corresponding charging control strategy aiming at optimizing the transmitting efficiency of the system and achieving constant current (CC) output and constant voltage (CV) output are proposed. First, the composite compensation network is analyzed by the equivalent circuit model as a reference. Second, based on the realization of CC/CV output, by analyzing the relationship between charging current/voltage and duty cycles of both DC-DC converters, the optimal duty cycles of both converters can be found. The purpose is to obtain the maximum transmission efficiency. Finally, the experimental results show good agreement with theoretical analysis, proving that the proposal can realize CC/CV charging and optimize the transmission efficiency.
In this paper, a low-profile flexible antenna using a flexible substrate is presented. The proposed antenna has concentric circle-shaped radiating elements with circular slots to achieve an ISM band. The flexible antenna having dimensions (33 mm x 18 mm x 2 mm) is designed and fabricated on a silicon rubber-based substrate, and measurements were performed to validate the simulation results. The measured and simulated results demonstrate that the antenna radiates at 2.45 GHz center frequency, with a return loss of -24.54. The operating frequency of 2.45 GHz, flexible substrate, and low SAR of 0.0658 W/Kg confirm that the proposed antenna is suitable for medical telemetry applications.
A compact substrate integrated folded waveguide (SIFW) H-plane horn antenna array with simultaneous omnidirectional and directional radiation characteristics for potential utilization to high-speed wireless communication is presented in this article. The realization of the proposed design has been accomplished by placing the apertures of nine exponentially tapered SIFW H-plane horns towards the circumference of a cylindrical substrate with an angular separation of 40˚ between the horns. Every horn flaring includes a column of three slots. Centre probe feed technique has been used to excite the antenna. The radiation of the field by the horn apertures and through the slots of the horns flaring, respectively, results in an omnidirectional and a directional radiation pattern at 13.8 GHz and 18.42 GHz, with the gain of 7 dBi and 10.92 dBi. The proposed antenna has performed well and is in good agreement between simulation and measurement. The dimension of the antenna is 37.3 mm (diameter) × 1 mm (height) (1.710×0.0460 at 13.8 GHz and 2.29λ0×0.061λ0 at 18.42 GHz). SIFW technology makes low profile antenna. The proposed design can be a promising option to be used as a low-profile antenna for high-speed wireless communication.
This paper presents analytical and numerical studies of electromagnetic wave propagation through an interface between a regular right-handed material (RHM) and a left-handed metamaterial (LHM). The interface is graded along the direction perpendicular to the boundary plane between the two materials, chosen to be the x-direction. The permittivity ε(ω, x) and permeability μ(ω, x) are chosen to vary according to hyperbolic tangent functions. We show that the field intensities for both TE- and TM-cases satisfy the same differential equations, and we obtain remarkably simple exact analytical solutions to Helmholtz' equations for lossy media. The obtained exact analytical results for the field intensities along the graded RHM-LHM composite are in line with the expected properties of RHM-LHM structures. Finally, we perform a numerical study of the wave propagation over an impedance-matched graded RHM-LHM interface, using the software COMSOL Multiphysics, and obtain an excellent agreement between the numerical simulations and analytical results. The results obtained in the present paper are not limited to any particular application, and are generally useful for all cases of wave propagation over impedance-matched two- and three-dimensional interfaces between RHM and LHM media. The advantage of the present method is that it can model smooth realistic material transitions, while at the same time including the abrupt transition as a limiting case. Furthermore, unlike previously existing solutions, the interface width is included as a parameter in the analytical solutions in a very simple way. This enables the use of the interface width as an additional degree of freedom in the design of practical RHM-LHM interfaces.
A pattern reconfigurable microstrip patch antenna with two parallel parasitic patches placed close to both sides of a rectangular driven patch is investigated and presented in this article. Four switchable shorting posts are used to enable the parasitic elements to act either as a reflector or director for beam reconfiguration, based on the operating state of four associated PIN diode switches. To avoid large change in the dimension of both parasitic patch and ground plane, and minimize its effect on beam steerability and return loss, two PIN diodes are placed on the top face and the other two on the slots etched on the ground plane. Radiation pattern of the proposed antenna can be reconfigured into four distinct directions in the H-plane with radiation maximum at +40˚, 0˚, -40˚ and ±45˚. With overall compact dimension of (35×55) mm2 and acceptable return loss for all reconfigurable modes around 6.2 GHz frequency, the proposed antenna is a potential candidate for Wi-Fi 6E application. The measured peak gain varies between 3.9 dBi and 5.2 dBi with an average of 4.6 dBi for all beam tilt angles. Consistency between the simulated and experimental results validates the design theory and its promising application.
In this article, a slot-antenna array with wideband and high-isolation for multiple-input multiple-output (MIMO) systems is presented that can be used in fifth-generation new radio (5G NR) communication. The MIMO antenna system is realized by loading six identical antennas (Ant1-Ant6) into an FR4 substrate to form a six-port array for a 6×6 MIMO system. Each antenna element is a slot antenna type that is composed of a T-shaped open slot and an L-shaped 50 Ω microstrip line. Each T-shaped slot is formed by inserting an I-shaped open branch in the center of the ground plane's U-shaped slot. The L-shaped microstrip line is placed on the upper surface of FR4 to enable coupling feeding in the 3.3 to 5.10 GHz frequency range to cover the 5G NR bands N77/N78/N79. The isolation is increased to more than 18.1 dB by etching the T-shaped slot between the radiation elements on the metal plate. The proposed antenna system was fabricated and tested. The experimental results indicate that the MIMO system can cover the frequency range of 3.20-5.15 GHz with a return loss of 6 dB and provides isolation greater than 16.2 dB. Additionally, a total efficiency greater than 50% and envelope correlation coefficient of less than 0.02 are obtained. The performance under hand-on scenarios is also good. Simulated and measured results indicate that the stated results are consistent. The test results indicate that the antenna satisfies the 5G communication requirements.
This paper presents a triple band proximity fed 2x1 array antenna with defected ground plane. The proposed antenna configuration is composed of two radiating elements, and both radiating elements are made of a pattern similar to the first iteration level David fractal geometry. The proposed David fractal 2x1 array antenna is designed and simulated on an FR-4 substrate of thickness 1.6 mm and dielectric constant 4.3 by using the CST Microwave Studio simulation tool. In order to improve the radiation characteristics of the antenna an H-shaped defect is etched in the ground plane. The antenna is fabricated and tested. The experimental data show good agreements with simulation results. The fabricated triple band fractal 2x1 array antenna resonates at 2.527 GHz, 3.329 GHz and 3.742 GHz having bandwidths of 303 MHz, 99 MHz, and 102 MHz, respectively. The proposed fractal array antenna can be used in mobile applications such as Wi-Fi, WLAN, Bluetooth and Wi-Max.
This article presents a new Butler matrix made on stacked Printed Circuit Boards (PCBs). The matrix is based on Substrate Integrated Waveguides (SIW) and microstrip lines. Transitions using through metallic vias are designed and optimized for the crossover sections of the matrix. The other components of the circuit are as follows: 3-dB SIW directional coupler, 45° phase-shifter, and SIW dual-slot linear antenna array. Different sections of the matrix were simulated, fabricated, and tested. Using the full structure with radiating elements, we obtained good numerical and experimental results in terms of radiations patterns for the different beam directions, impedance matching, and isolation between the input ports.
In this paper, a dual-model based adaptive sampling method is proposed for the fast calculation of broadband electromagnetic scattering. The difference between the rational function model (RFM) and cubic-spline (CS) based polynomial model issued to generate new frequency samples adaptively. Then, the cubic Hermite interpolation is used to approximate the final broadband RCS curve. The radar cross section (RCS) at each frequency sample is computed by the method of moment (MoM) which is accelerated by the adaptive cross approximation (ACA). Numerical results demonstrate that the proposed method is able to obtain the broadband RCS curve with high accuracy and reduce the computation time significantly. Compared with the method of moment and adaptive cross approximation method, the adaptive algorithm improves the computational efficiency by 77.13% in the sphere case, 83.79% in the rail model and nearly 90.72% in the missile example. In addition, the method proposed in this paper has the characteristics of nonuniform sampling and strong applicability and flexibility, which is able to combine other matrix compressed methods to effectively solve problems in electromagnetic field.
In this communication, a compact Dielectric Resonator (DR) based multiple-input-multiple-output (MIMO) antenna is presented for wideband applications. The antenna consists of two modified kite-shaped monopoles where four DRs have been placed on the patch. Corners of four DRs have been etched to implement the orthogonal phase, which leads to circular polarization characteristics. Implementation of DRs also helps in bandwidth enhancement purpose. Two L-shaped parasitic strips along with a Y-shaped stub have been used in the ground plane so as to obtain high isolation, which leads to a decrease of mutual coupling between the antenna elements. The proposed antenna achieves a wide impedance bandwidth of 7.1-22 GHz (106%) along with low mutual coupling of less than -15 dB within the entire frequency range as well as circular polarization characteristics, which covers the frequency range (-3 dB) of 7.1-7.9 GHz (10.6%). Thus the antenna can be considered as a potential candidate for modern wireless communication systems.
In this manuscript, the realization of penta-band notches with the aid of an ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna for diverse wireless applications is demonstrated. A single port UWB antenna is utilized to construct the proposed MIMO antenna, which comprises an altered patch loaded with three U-shape slots and an inverse U-shape slot on the feed line followed by a C-shape stub adjacent to the feed line. These slots and C-shape stub are liable to generate five notches at 3.4 GHz (3.16-3.67 GHz), 4 GHz (3.88-4.10 GHz), 4.6 GHz (4.56-4.75 GHz), 5.7 GHz (5.65-5.92 GHz), and 7.8 GHz (7.39-8.12 GHz), respectively. These notches depreciate interference from WiMAX, C-band, WLAN and X-band (satellite communication) frequencies. Alternatively, the reported antenna can also be utilized as a proximity radar (8-12 GHz) in X-band. The proposed antenna engraved on a Rogers RT/Duroid 5880 substrate having an overall size of 80 × 80 × 1.6 mm3 or 0.8λ0 × 0.8λ0 × 0.016λ0 (λ0 is the free-space wavelength at lowest frequency 3 GHz). Simulation and experimentation have been performed to corroborate the performance of the reported antenna. Results emphasize that the proposed MIMO antenna operates from 3 GHz to 14 GHz with measured peak gain 4.8 dBi, radiation efficiency above 82% and isolation less than -20 dB. Except at notches, the computed envelope correlation coefficient (ECC) is less than 0.03; diversity gain (DG) is approximately 10; total active reflection coefficient (TARC) is less than -10 dB; channel capacity loss (CCL) is less than 0.35 bps/Hz. These characteristics qualify it as a multifunctional antenna for wireless applications, lowering the antenna count needed in compact wireless devices.
In this paper, the inversion method of mesospheric neutral wind is studied based on mid-latitude AgileDARN HF radar. Firstly, the meteor target observation method is carried out using 7.5 km range resolution and 2 s integration time. Then, the method of extracting the meteor echo from the data according to the doppler characteristics of the meteoris studied. Finally, the meridional and zonal components of mesospheric neutral wind are obtained by singular value decomposition method based on doppler velocity of meteor echo. The data analysis shows that the meteor echo has the highest incidence in the morning of local time and the lowest incidence in the evening of local time. The semi-diurnal characteristics of tidal waves can be seen from the meridional and zonal components of mesospheric neutral wind. Aiming at the ambiguity of elevation angle measured by AgileDARN HF radar, a method is proposed to reduce the ambiguity of elevation angle, and the wind field profile of mesospheric neutral wind along altitude is obtained, which lays a foundation for the subsequent study of gravity wave, tidal wave and planetary wave based on mesospheric wind field.
This research introduces a novel design of a metamaterial absorber having the range in terahertz, capable of sensing changes in the refractive index of the encircling medium. The layout includes adjoining rectangular patches in the form of a plus symbol along with four circular patch resonators (CPRs) on the pinnacle of a Gallium Arsenide (GaAs) substrate. The proposed design comes up with three consecutive absorption peaks, with an absorptivity of 99.0%, 99.75%, and 98.0% at three different resonant frequencies of 2.36 THz, 2.675 THz, and 2.97 THz, respectively, and a Full Width Half Maximum (FWHM) of 0.08, 0.04 and 0.05. This structure's quality factor (Q-factor) at the three resonant frequencies is 29.5, 66.8 and 59.4 together with 6.75, 17.5 and 30 as figure of merit (FoM), respectively. The proposed design offers a sensitivity of 0.54 THz/RIU, 0.7 THz/RIU, and 1.5 THz/RIU in those three absorption bands. To support the selection of design parameters, parametric assessment was done. The designed sensor can find its applications in terahertz sensing.
Complex reservoirs such as fresh-water formations and water-flooded reservoirs developed by water injection have complex electrical characteristics owing to the influence of formation water salinity. It is difficult to accurately evaluate and identify the fluid in such complex reservoirs by using the conventional resistivity method. However, the water salinity of the formation has a reduced effect on its dielectric constant; therefore, dielectric logging technology can be used to effectively identify fresh-water formation and evaluate the water-flooding level of the water-flooded layer. The accuracy of the formation response inversion charts of dielectric logging instruments is important for accurately evaluating fluids in complex reservoirs when these instruments are used. This study proposes a full-wave simulation method based on Maxwell's equations and the engineering parameters value of the dielectric logging instrument. The formation response conversion charts of the dielectric logging instrumentare accurately calculated and can be used in practical logging; the simulation results are compared with those obtained using an equivalent magnetic dipole model; Based on the accurate simulation of the formation response of the dielectric logging instrument, a high-frequency dielectric logging instrumentis developed, and it is applied to the fresh-water formation and water-flooded layer in the Nanyang and Ordos Basins.