A novel and compact microstrip-line fed printed antenna for wideband circular polarization (CP) radiation is proposed. The designed antenna utilizes a crescent-shaped substrate, rotated L-shaped monopole, and defected ground structure (DGS) to achieve a wide 3-dB axial ratio (AR) bandwidth and 10-dB impedance bandwidth (ZBW) across the entire 5 GHz Wireless Local Area Network (WLAN) and Vehicle to Everything (V2X) operational bands. As the substrate of the proposed antenna is only 0.8 mm thick, it has a very low profile of 0.014λ in terms of free space wavelength (λ) at 5.5 GHz. The proposed CP antenna exhibits overlapping 10-dB ZBW and 3-dB AR bandwidth (ARBW) of 22.05% (4.80-5.99 GHz), along with broadside far-field patterns, gain greater than 2.5 dBi and efficiency above 85%throughout the desired operating band. Therefore, it is a good candidate for WLAN and V2X communication applications.

In this paper, an electrically-small microwave dipole sensor is used with machine learning algorithms to build a noninvasive continuous glucose monitoring (CGM) system. As a proof of concept, the sensor is used on aqueous (water-glucose) solutions with different glucose concentrations to check the sensitivity of the sensor. Knowledge-driven and data-driven approaches are used to extract features from the sensor's signals reflected from the aqueous glucose solution. Machine learning is used to build the regression model in order to predict the actual glucose levels. Using more than 19 regression models, the results show a good accuracy with Root Mean Square Error of 1.6 and 1.7 by Matern 5/2 Gaussian Process Regression (GPR) algorithm using the reflection coefficient's magnitude and phase.

This paper proposes a high gain array antenna operating in the Ku-band at 17.5 GHz for 5G applications. This new antenna is printed on an FR-4 substrate of thickness h = 0.8 mm and realized by changing the geometric shape of a rectangular patch, obtained by inserting an L-shaped slot to enlarge the bandwidth (1.5 GHz) and to increase the gain. To further enhance the gain, we used a 1×2 patch antenna array closely spaced and powered by a 1-to-2 Wilkinson power divider. We inserted two high-impedance surface (HIS) structures between the radiating elements and added two electromagnetic band gap (EBG) layers above the antenna. The antenna gain increases from 7.56 dB to 14.8 dB. The design and simulation have been performed by CST Microwave. A minor difference was noted between the measured and simulated data, where a slight shift was observed in the antenna's resonance frequency, which can be caused by fabrication tolerances or measurement error, uncertainty of the thickness of the FR-4 substrate, and quality of SMA connector used. The final array antenna shows a directional radiation pattern with a gain of 14.8 dB and good radiation efficiency over the operating band.

This paper derives an infinite series solution to the Laplace equation for the electric scalar potential of a stripline/microstrip transmission line. Due to the presence of a mixed Dirichlet/Neumann boundary condition, traditional solution methods involving mode orthogonality cannot be applied. Instead, three new solution methods are explored, which are collocation, minimum discrete-squared error (MDSE), and minimum mean-squared error (MMSE). Results yield excellent agreement compared to numerical simulation of capacitance per unit length. However, the Gibbs phenomenon appears to bias the outcome with a small (≈ 0.5%) under-estimation of the true result.

In this work, a planar monopole ultrawideband (UWB) antenna with continuously tunable notch band feature is presented. The designed antenna, which has a compact size of 36.6×26×1 mm³, is fabricated on a low-cost FR4 substrate and comprises a circular radiating patch with four rectangular defects, a microstrip feed line, and a partial ground plane to cover the UWB frequency band extending from 3.1 GHz to 12.5 GHz. A semi-elliptical slot is etched out from the circular patch to create the first notch band at 3.6 GHz (WiMAX) in the UWB spectrum. The second notch band is created by embedding an annular slot on the circular patch loaded with a varactor diode to continuously tune the notch frequency from 5.6 GHz to 7.7 GHz in upper WLAN and X-band. To investigate the implementation feasibility of the designed UWB antenna, a prototype is fabricated and experimentally tested.

The integrals arising in magnetic field integral equation (MFIE) can become highly singular, rendering their numerical computation extremely challenging. Here, we propose a technique by which the singular integrals of the MFIE can be accurately and efficiently evaluated. In this technique, the corresponding integrals are separated into singular and regular parts. The regular parts are computed using a very simple Fast Fourier transform, whereas the remaining singular parts are evaluated based on two three-terms recurrence relations. The accuracy of the proposed method is demonstrated by analyzing the scattering of various bodies with smooth or non-smooth geometries and comparing the results with the literature.

The planar physical model of ultra-broadband unidirectional waveguide based on surface magnetoplasmons (SMPs) has been derived and calculated in detail, but the coaxial physical model of ultra-broadband unidirectional waveguide based on SMPs has not been reported. Based on the gyromagnetic properties of Ferrite (taken yttrium iron garnet as an example, abbreviated as YIG), a novel ultra-broadband unidirectional coaxial waveguide is proposed in this paper. The basic model of the waveguide is a multilayer coaxial waveguide system composed of metal-layer-YIG-YIG-metal wire. The magnetization vectors of two middle YIGs are equal and opposite. Theoretical analysis and simulation results show that the waveguide supports two unidirectional transmissions, and both unidirectional bands have excellent properties of immune scattering and back reflection. The waveguide system has the characteristics of simple structure, immune scattering, and ultra-broadband unidirectional band, which is expected to be used in all-photon communication system.

In order to analyze the working status of the underwater unmanned vehicle not fully surfaced, the optimal working frequency when the whip antenna radiates the maximum power is given. The input impedance of the antenna on the water is theoretically calculated. It is regarded as the load of the underwater part of the antenna, and the total input impedance of the whip antenna is obtained. The relationship between the antenna radiated power to the external field and the input power is analyzed, and the optimal operating frequency corresponding to the maximum radiated power is determined. Using simulation experiments and actual measurements, the radiated power of the 1 m whip antenna when being immersed in seawater at 0.25 m, 0.5 m, 0.75 m is obtained, and the corresponding optimal working frequency is calculated, which are in good agreement with the theoretical deduction results. The results show that as the depth of the antenna immersed in seawater increases, the power radiated from the antenna to the external field decreases, and the optimal working frequency increases accordingly.

In this paper, a high-performance microstrip diplexer is designed and manufactured. The design is based on two pairs rectangular open-loop resonators band-pass filters and a novel zigzag junction. It operates at 3.5 GHz for fifth-generation 5G sub-6-GHz and 5 GHz for Wi-Fi communications. The proposed diplexer is considerably miniaturized with a global compact size of 30×17 mm². In addition, it presents low insertion losses less than 0.5 dB at both channels in comparison with the previous diplexers. Moreover, the isolation is higher than 20 dB, and the return loss is better than 14 dB at the bandwidths. To confirm the simulation results, the presented diplexer is manufactured and measured where a good agreement is carried out.

This paper aims to design an ultra-wideband reflectarray using True Time Delay technique that depends on compensate for the path differences of the electromagnetic waves between the feed and reflectarray surface, and reradiate them in-phase as a planar wave. The reflectarray surface is composed of numerous radiating elements. The reflecting surface is divided into several concentric annular zones; each of them has equal path delays of the electromagnetic waves. The radiating elements in each zone are implemented with two-layer square-loop type Frequency Selective Surface (FSS) structures. A TTD reflectarray with a diameter of 250 mm fed with a centered ku-band pyramidal horn antenna is studied and designed and fabricated to operate at the center frequency of 15 GHz. The proposed reflectarray provides a gain of 26.42±2 dB in the 12-18 GHz range achieving a fractional bandwidth of 40%. The simulated radiation patterns are stable with cross-polarization level below -40 dB and side-lobes level below -15 dB over the entire operating frequency range. The simulated phase efficiency is about 56% at the center frequency of 15 GHz.

For the coexistence of SUT (System Under Test) radiative emission signal and ambient interference signal, the amplitude of SUT signal will be submerged by the amplitude of interference signal, so it is difficult to accurately measure the amplitude of SUT signal. In this paper, a two-level nested array is used as the receiving array antenna, and the mixed matrix estimation method based on Blind Source Separation (BSS) is used to separate the coherent groups of the signal. Then the Sparse Reconstruction method is used for the DOA (Degree Of Arrival) estimation of each coherent group of the signal. After the DOA information of each signal is obtained, beamforming method is used to form beams of the main channel and auxiliary channel. The beam of the main channel outputs without distortion in the direction of the SUT signal and forms zero traps in the direction of the coherent signals, while the beam of the auxiliary channel forms zero traps in both the direction of the SUT signal and the direction of the coherent signal. The data received by the array are respectively multiplied by the weights of the main channel and auxiliary channel to obtain the output signals of the two channels. The output signals of the two channels are respectively fed into the Adaptive Noise Cancellation (ANC) system, and the ANC method is used to suppress the ambient interference signals and restore the SUT signal. Simulation and experiment results show that this method can accurately estimate DOA of radiation emission signals, effectively suppress ambient signals and restore the signal of SUT in field measurement of radiation emission.

A compact (25×28×1.57 mm³) and wide-band multimode frequency tunable antenna with defected ground structure (FRDGS) for 4G and 5G conformal portable devices and multi-band wireless systems is presented in this article. In a previous study, frequency reconfigurable antenna designs only used the method of adding slots on the patch or ground. In this study, a combination of multiple slots, partial ground, and defective ground structure techniques were utilised to attain the advantages of compactness, wide impedance bandwidth, and steady radiation pattern. Multiple slots on the top layer of the substrate and F-shaped slot etched at the bottom makes the proposed antenna. Two PIN diodes are inserted in the F-shaped slot for frequency reconfiguration, allowing the antenna to switch between different resonances. Ansys high frequency structure simulator 15.0v is used to simulate the antenna parameters. This antenna performance is demonstrated using measured and simulated data. The simulated and measured results clearly show that the proposed antenna can switch between six dissimilar resonant frequency bands via various modes of operation across the frequency spectrum from 2.3 to 8.9 GHz. The antenna works in a variety of commercial bands, such as WLAN/Bluetooth (2.4-2.5 GHz), LTE/4G (2.3-2.7 GHz), S-band (2-4 GHz), Radio Navigation (2.7-2.9 GHz), and 5G/sub-6 (3.3-4.9 GHz), according to simulations and experiments. The proposed design features narrowband, wideband, and ultra-wideband properties with a consistent radiation pattern, adequate gain (1.6 to 5.8 dB), and high radiation efficiency (86 to 94%) in a small package. Furthermore, the performance comparison of the proposed antenna with that of the state-of-the-art antennas in terms of compactness, frequency reconfigurability, number of operating bands, and impedance bandwidth demonstrates the novelty of the proposed antenna and its potential application in multiple wireless applications.

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.

A novel compact dual-band bandpass filter with wide stopband using stub-loaded stepped-impedance resonators is presented in this paper. The characteristics of the dual-mode resonator are investigated by using even/odd mode analysis. The center frequencies and bandwidths of the two passbands can be controlled by adjusting the geometric dimensions of the stub-loaded stepped-impedance resonators. Moreover, the filter has been implemented with five transmission zeros to improve the selectivity. A prototype of a dual-band bandpass filter centered at 3 and 4.35 GHz has been designed and fabricated. The measured bandwidths are 8.3 and 4.6%, and the corresponding insertion losses are 1.7 and 1.6 dB, respectively. A compact dual-band bandpass filter with sharp roll-off rate of 113.3/56.7/56.7/170 dB/GHz, wide stopband of 5.3 GHz, and isolation between two passbands of 25 dB is achieved. The measured results are in good agreement with the simulated ones.

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.

This research article proposes a Defected Star-Shaped Microstrip Antenna (DSSMSA) for wideband applications. A designed monopole antenna has a defected star-shaped tuning stub with a defected ground structure energised with a microstrip feed line. An appropriate tuning of resonating modes wideband frequency effect has been achieved by optimising the dimensions of the tuning stub and the dimensions of the defected ground and its notch. Surface current distribution plays a vital role in optimising the antenna geometry and developing mathematical resonating frequencies equations. The simulated and experimental results show that the DSSMSA radiates under the frequency band from 1.6638 GHz to 6.652 GHz with measured fractional bandwidth of 119.9692% for |S₁₁| < -10 dB. Optimised DSSMSA resonates at frequencies 2.05 GHz, 3.382 GHz, and 5.494 GHz. As the geometry of DSSMSA is symmetrical, the symmetric far-field pattern has been found in the far-field.

In this paper, a textile based fractal monopole antenna is proposed with a defected ground structure for wearable application. The proposed antenna is designed on Flannel fabric with a thickness of 1 mm, which translates to 0.03λ at 10 GHz. The total dimensions of proposed antenna is 60 x 40 x 1 mm. The measured fractional bandwidth of the antenna is 110.1%. The proposed flannel based conductive ink antenna is characterized, and the results for washable fabric are illustrated. Both simulated and measured results are presented. The concept of application of low cost conductive ink on flannel fabric is demonstrated using conventional screen printing method. The antenna is characterized for commercial wash ability; the measurement results are invariant with the machine wash of the flannel fabric indicating robustness of the proposed method of fabrication of the antenna element.

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.