Fabrication of a non-planar helical antenna while maintaining mechanical stability and durability is always challenging. Moreover, impedance matching is an issue for helix-type antennas. To ease the fabrication challenge, the advantage of additive manufacturing is utilized. For achieving the self-matching, radiating spiral conductors in the forms of a strip and thick wire are used as two independent techniques. Consequently, a 3-turn hemispherical helical antenna (HHA) is chosen and analyzed by varying the width of the strip and the diameter of the wire. The better-performing HHA is again investigated including the effect of Poly-lactic acid (PLA) material-based supportive structure. The impacts of this extra support on antenna performance parameters are also investigated. At the initial step of fabrication, a 3-D printer is used to have the complete support structure. For ensuring the metallic part, copper strips and conductive paints are used as two different approaches. The measured data validates that both strip and wire-based HHA are self-matched. Circular polarization is obtained over wide frequency bands with axial ratio bandwidth (AR BW) of 35%. The maximum gain and beamwidths under 3-dB AR BW are 9.35 dBi and 118° respectively. The mechanically stable, low profile, and wideband circular polarization favored theuse of HHA in satellite communication.

This paper presents a novel fourth-order bandpass filter with high selectivity and out-of-band suppression based on equivalent magnetic side wall cavities (MSWCs). By loading a via hole into an MSWC to produce a zero mode as a non-resonating node and using the dual MSWC modes TEM₀₀₁ and TE₁₀₀ as resonant modes, a modified doublet with two poles and two transmission zeros (TZs) can be formed. Three types of frequency response, either quasi-elliptic or asymmetric, can be obtained and designed flexibly. The TZs can be located on both sides of the passband or both on just one side. The mechanisms for generating the TZs are analyzed, and the adjustment of the TZ positions is discussed. The proposed four-pole quasi-elliptic filter with four TZs is a cascade of two such doublets with two different types of asymmetric response. It has been fabricated and measured to validate the design. Comparison is made with some previous work on substrate integrated waveguide filters. The developed filter is free from radiation and relatively compact among high order filters with multiple adjustable TZs based on cascaded cavities of the substrate integrated waveguide type.

This letter presents a compact ultra-wideband circularly polarized (CP) crossed-dipole antenna with enhanced axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW). It consists of four modified arms which are fed by vacant-quarter phase delay rings to excite CP radiation. Four parasitic elements are utilized rotationally between the dipoles and the reflector. Not only does inducing vertical currents on the parasitic patches excite additional impedance resonance to realize an ultra-wideband operating, but also reinforced radiation is obtained to improve the ARBW and HPBW. The experimental results show that the proposed antenna realizes a -10 dB impedance bandwidth of 134.3%, and a 3 dB axial-ratio (AR) bandwidth of 115.0%, while holding a compact volume of 0.25λ_L × 0.25λ_L × 0.09λ_L (λ_L: wavelength at the lowest operating frequency). Furthermore, an HPBW and ARBW of more than 110° and 160° are realized within a broad operating band of 67.5% and 55.0%, respectively.

Moisture measurement in industrial applications, both in liquid and solid materials, presents a significant challenge. In the field of biofuels, this becomes even more critical. Among the various approaches developed for this purpose, indirect electromagnetic techniques have emerged as a valuable tool for accurately estimating moisture content. These techniques utilize the complex dielectric permittivity ε as an intermediary parameter, which is influenced by the water content in the material. As a first step toward this purpose, a 1''5/8 two-port coaxial transmission cell, developed at LNE-CETIAT, was studied to make dielectric measurements on liquids. Characterization and validation steps were requested to demonstrate the accuracy of this cell. For this purpose, an intra-laboratory comparison has been performed first at LNE-CETIAT using the 1''5/8 cell and the EpsiMu® coaxial cell - a fully validated reference tool. Then, an inter-laboratory comparison with the Fresnel Institute has been performed using a coaxial probe and another EpsiMu®cell. The measurements were carried out under identical ambient conditions, using liquid reference materials. In this work, the performance of the developed cell in the frequency band [0,1-1,1] GHz has been validated, as well as the accuracy of the three electromagnetic techniques used. The results of the experiments confirm the effectiveness of the 1''5/8 cell developed at LNE-CETIAT for measuring the dielectric properties of liquids.

The main challenges of designing an antenna for modern wireless communication are size reduction and mutual coupling. An ultra-wideband (UWB) multiple input multiple outputs (MIMO) antennae with four elements is suggested by this paper. Each element has two ports with dual-polarized patches to reduce the result of reciprocal coupling, increase the capacity, and keep a proper size. A circular geometric shape is in front of the patch of the proposed antenna to reduce the impact of mutual coupling. The CST STUDIO 2019 program simulates the single antenna element and MIMO antenna using the four integrated elements, eight integrated ports, and an Fr-4 insulating layer in an area of (70 x 70) mm². The MIMO antenna's operating frequency, which has a band of 2.85 (3.15-6) GHz at -10 dB, is 3.67 GHz while the operating frequency of a single antenna element, which has a band of 2.8 (3.1-5.9) GHz at -10 dB and a resonance return loss of -36 dB, is 3.64 GHz. The MIMO antennas obtained a diversity gain (DG) of about 10 with a good gain of about 8 dB while the envelope correlation coefficient (ECC) was equal to or less than 0.0001.

Dynamic Inductive Wireless Power Transfer (DIWPT), used for charging and powering electric vehicles (EVs), has been presented lately as a solution for increasing the distance range of electric vehicles and reducing the utilization of heavy and bulky battery systems. In most DIWPT designs, the voltage induced by the movement of the receiving coil over a time-varying magnetic field is neglected and never quantified. In this work, a simplified phasor expression for the total induced voltage on a coil that is moving in a sinusoidal time-variant magnetic vector field is developed. If no rotation is observed in the coil, a 90˚ out of phase voltage component proportional to the speed of the coil is added to the induced voltage that would be calculated if the coil was stationary. The phase of this voltage component is delayed or advanced with respect to the stationary induced voltage, according to whether the coil is moving into or out of a region of higher magnetic flux. Then, under some assumptions on the geometry of inductive coil configurations, it is possible to estimate the minimum induction frequency for which the quasi-stationary approximation can be considered. The resulting frequency value for a representative geometry is calculated, indicating that, for automotive applications, the relative error in the induced voltage is actually negligible, except in the vicinity of the points of zero-crossing in the magnetic flux, where the absolute value of the induced voltage is low anyway.

A hexagon-shaped fractal ultra-wideband (UWB) Multiple Input Multiple Output (MIMO) antenna is proposed in this paper for S (2 GHz to 4 GHz) and C (4 GHz to 8 GHz) band applications. The proposed design consists of two microstrip fed radiating elements of dimension 82 × 44 × 1.6 mm³. One rectangular stub and four resistance loaded stubs are introduced in the ground plane to reduce the mutual coupling between the radiators. These decoupling structures reduce the notches and enhance the isolation from -5 dB to -20 dB for the entire frequency range from 2.3 to 7.4 GHz. The performance characteristics and diversity parameters are also investigated which show the values of ECC < 0.004, DG > 9.96, CCL < 0.4 and MEG < 3 dB, and it is concluded that the proposed design is a good candidate for UWB MIMO. The proposed design is fabricated and tested which shows the close agreement between the simulated and measured results.

A four-port ultra-wideband (UWB) multi-input multi-output (MIMO) Vivaldi antenna loaded with resistance and rectangular radiation patch is designed and fabricated. The compact antenna consists of an improved ground and four microstrip feeders, with an overall size of 26 mm × 52 mm × 0.8 mm. The antenna adopts the resistance loading technology to absorb the excess electromagnetic waves in the low-frequency band and broaden the low-frequency bandwidth of the antenna. The rectangular radiation patch loading technique optimizes the main radiation direction and broadens the high-frequency bandwidth of the antenna. Meanwhile, T-slots and fence-type structures are etched on the ground plane, and I-stubs are added between microstrip feeders to reduce the antenna coupling and increase the isolation degree between the antenna ports. Simulation and experiments show that the impedance bandwidth of the MIMO antenna is 3.0~12.3 GHz; the isolation degree of the whole working bandwidth is higher than 15 dB; the envelope correlation coefficient (ECC) is smaller than 0.0125; and the increased diversity gain (DG) is more significant than 9.98 dBi. The antenna has good radiation performance and stable gain, which is suitable for applying the UWB MIMO system. This antenna has a particular reference significance for the research of the MIMO Vivaldi antenna.

In order to solve the problem of the influence of magnetic saturation and voltage source inverter (VSI) nonlinear factors on the parameter identification of permanent magnet synchronous wind generator (PMSWG), a variable neighborhood search-adaptive genetic algorithm (VNS-AGA) based on magnetic saturation and VSI compensation is proposed in this paper. Considering the existence of magnetic saturation, a mathematical model of PMSWG considering magnetic saturation is established. The least square method is used to identify the inductance of dq axis. The influence of VSI nonlinear factors on the system is regarded as a disturbance voltage, which is used as an electrical parameter; the parameters of PMSWG are identified simultaneously; and voltage compensation is carried out. After the accurate distortion voltage compensation mathematical model and fitness function are established, GA and adaptive algorithm are combined to increase the diversity of the population. Then variable neighborhood search (VNS) strategy is introduced to search the optimal region. Experimental results show that the proposed method is more accurate and convergent after considering magnetic saturation and on-line identification and compensation of disturbance voltage.

This paper proposes a coplanar L-strip feeding technique to excite the dominant transverse electric (TE) mode in a rectangular microstrip patch antenna. To excite the TE mode, the patch and ground layers are composed of artificial magnetic conductor (AMC) unit cells, and the L-strip is fashioned so that it is coplanar with the AMC patch layer. Two TE-mode microstrip patch antennas are full-wave analyzed and fabricated, one in which the AMC patch is centered with respect to the ground plane and one in which the AMC patch is shifted laterally with respect to the ground plane to improve radiation pattern symmetry. Results from the fabricated antennas are discussed and compared to the simulations. The proposed antennas successfully excite the dominant TE₁₀ mode while having at least 11% impedance bandwidth, 8 dBi gain, and stable broadside radiation patterns.

This paper presents an in-depth review of the performance improvement of antennas using metasurface. Metasurface is a periodic arrangement of perfect electric conductors (PECs) on a metal-backed dielectric substrate that do not exist in nature and are able to manipulate the behavior of electromagnetic (EM) waves incident on it. The manipulations of EM waves improve the performances in terms of impedance bandwidth, gain, size, specific absorption rate (SAR), radar-cross-section (RCS), and polarization conversions. Consequently, numerous recent works on metasurface-inspired antenna design and their theoretical perspectives on performance enhancements are discussed. By adopting the discussed theories, novel metasurfaces are developed and proposed that analyze impedance-bandwidth enhancement, gain enhancement and SAR reduction. For designing the metasurfaces, initially a conventional rectangular unit cell (CRUC) is theoretically developed using transmission line model at 2.45 GHz. Following that, the CRUC-based metasurface is incorporated with a monopole antenna, which enhanced the impedance-bandwidth from 140 MHz to 320 MHz and the gain from 2.5 dB to 7.4 dB. On the body, the presence of the metasurface retains all the performances as free space, with a reduced 1 g SAR of 0.034 and 10 g SAR of 0.024 W/Kg.

The paper proposes a antenna design that can serve as a comprehensive solution for covering 4G/5G cellular bands 850-1000 MHz, 1900 MHz, 2100-2700 MHz, 3300-4900 MHz, Global Navigation Satellite System (GNSS-L1) Band 1.56 GHz-1.61 GHz, V2X 5.850-5.925 GHz band which are appropriate for use in automobile applications. The proposed antenna is designed with respective polarization for cellular and GNSS applications, where the cellular antenna is linearly polarized, and the GNSS antenna is circularly polarized by chamfering the square patch. FR4 substrate material is used to construct the Long Term Evolution/4G (LTE) antenna. The optimization of the antennas ensures minimal coupling between them. The cellular antenna is designed using a hexagonal base with a modified ground plane to achieve the required cellular bands using a monopole (fractal design). The GNSS antenna is implemented on a PVC (Poly Vinyl Chloride) substrate. The measured results of S₁₁ parameter show that the proposed design covers all the required 4G/5G bands with minimum S₁₁ of -10 dB and a radiation pattern in the theta 60-90° range for cellular antenna, while the GNSS antenna has a zenith radiation pattern with axial ratio of <3 dB for theta angles in the 0-30° range and a mutual coupling of -15 dB. The fabricated antenna was measured to validate the simulated results of reflection coefficient, VSWR. All things considered, the suggested design is perfect for automobile applications to satisfy both satellite and mobile communication needs.

In this article the design of an ultra-wideband coplanar monopole antenna with a microstrip parasitic patch having a dimension of 50 mm x 50 mm using a 1 mm thick RT-Duroid substrate (ε_r = 2.2) is explored for wireless applications. Five different coplanar antenna designs are presented, and one of the designs is proposed for fabrication. In simulation the proposed antenna has four resonant bands, 2.043-2.133 GHz, 5.821-7.89 GHz, 10.3-12.027 GHz, and 12.783-17.802 GHz, with a cumulative bandwidth of 8.905 GHz within 1-18 GHz. The proposed antenna is fabricated, tested and validated using Vector Network Analyzer. Fabricated antenna resonates at four different bands, 2.349-2.888 GHz, 5.767-7.926 GHz, 9.725-10.534 GHz and 13.862-16.021 GHz with resonant peaks at 2.529 GHz, 7.116 GHz, 10.084 GHz and 15.391 GHz frequencies respectively. Further the antenna has a cumulative Bandwidth of 5.666 GHz in 1-18 GHz band. Radiation efficiency is above 90% at the resonant band. The acquired results from simulation and measurement are in close match.

In this paper, a novel frock shaped four-port MIMO antenna is designed, and experimental results were verified for UWB applications. The four elements are placed orthogonal to each other to reduce mutual coupling. The proposed novel-shaped antenna is derived from a circular patch antenna. A series of modifications were made on a circular patch antenna to get desired single novelly shaped radiator. Inserting decoupling stubs in the Plus form between MIMO elements lessened mutual coupling. The entire designing procedure of the proposed four-port antenna was carried out by Characteristic Mode Analysis. The proposed model is printed on an Fr-4 substrate with dimensions of 40x40x1.6 mm³. This novel 4-port antenna is well-operated in the UWB range from 2.8 GHz to 11.4 GHz and bandwidth of 8.6 GHz. The novel shape radiators with good decoupling stubs produce a high impedance bandwidth of as 121.8%, radiation efficiency of 91%, high isolation 26 dB, and a gain of 6 dB in the operating band. The diversity parameters are enveloped correlation coefficient (ECC) less than 0.0011, diversity gain (DG) very near 10 dB, capacity channel loss of 0.28 bp/s/Hz, and mean effective gain of -3.1 dB. The experimental results of the antenna are verified with simulated ones and got good agreement between fabricated and simulated results.

This paper presents a low-profile, stub-loaded multi-slot antenna that operates across 850 MHz to 4500 MHz. Remarkably, the new design meets the call of covering wideband frequencies used by many 4G and 5G New Radio bands from UHF to C bands. The antenna consists of two wide slots on the ground plane. Each slot comprises a straight segment connected to a larger circular slot. A novel microstrip feed line loaded with dual circular stubs excites the multi-slot antenna. The slots and the feed lines are printed on each side of the dielectric substrate. This novel design offers pattern diversion capacity based on port excitation. Two prototypes were fabricated and tested to verify multiple simulation results including bandwidth, isolation, and group delays. A close consistent of measured and simulated results validates the design. Concurrently, good isolation between ports and nearly omnidirectional gain patterns are observed over the band. Further, the form factor of the proposed antenna makes it a suitable solution for modern 4G and 5G handheld devices.

To solve the problem of single working frequency of traditional reflective focused metasurface, a dual-band reflective focused metasurface is proposed, which can realize independent focusing characteristics at 7.25 GHz and 20.5 GHz. The metasurface unit is composed of metal elements combined by a split-ring resonant structure working at 7.25 GHz and an elliptical resonant structure working at 20.5 GHz in the same plane, dielectric substrate and ground. Dual-band independent control and 360° phase coverage are achieved by adjusting the dimensions of unit. The surface current distribution also verifies the rationality of the designed metasurface element. Based on the principle of quasi-optical path, a dual-band reflective focused metasurface with independent focusing characteristics is designed. Through full-wave simulation, the focusing efficiency at 7.25 GHz and 20.5 GHz is calculated by Poynting theorem, which are 56.9% and 57.5%, respectively. The proposed dual-band metasurface has the characteristics of simple structure and low profile without multi-layer stacking and metal through-holes.

The growing demand for natural fibers in dielectric composite production has accelerated research into plant-based materials, particularly those derived from agricultural waste. Hence, this study attempts to evaluate the effect of processing factors and their elemental composition on the permittivity value of pineapple fiber-based dielectric composites. The dielectric composite was prepared following the randomized experimental conditions of two-level factorial analysis, and the permittivity value was measured using a G-band rectangular waveguide. The most significant factors affecting the permittivity value of the dielectric composites and the best condition were determined. The elemental composition of the dielectric composite was analyzed through an energy dispersive X-ray (EDX) analysis. The best conditions were obtained at a 1:10 ratio of pineapple leaves to distilled water, 50 minutes pulping times with a heating effect, and 5 g of pineapple leaf powder. The highest permittivity value of the composite was recorded at 3.31, with the heating effect as the most significant factor. The elemental analysis of the composite with the highest permittivity value presents that carbon was the dominant element in the composite at 78.05%. The obtained permittivity value exhibited by the composites shows that the pineapple leaf fiber-based dielectric composite could be a potential alternative as an antenna substrate.

Spatiotemporal optical vortices (STOVs) are electromagnetic wave packets that transport a phase line singularity perpendicular to their propagation direction. We address the problem of the transverse orbital angular momentum (OAM) actually transported by STOVs propagating in free space or non-dispersive media, the most frequent experimental situation. An elliptically symmetric STOV of topological charge l and carrier frequency ω₀ carries an intrinsic transverse OAM per unit energy γl/2ω₀, where γ is the STOV ellipticity. Intrinsic stands for the OAM about a moving transverse axis passing permanently through the STOV center. For circular STOVs (γ = 1) this value is half the intrinsic longitudinal OAM of monochromatic light beams of the same charge and frequency. This result agrees with that in Phys. Rev. Lett. 127, 193901 (2021). The formula (γ+1/γ)l/2ω₀ for the intrinsic transverse OAM in Phys. Rev. A 107, L031501 (2023) yields infinite values and is not conserved on propagation for particular STOVs. When STOVs propagate losing their elliptical symmetry, they preserve the intrinsic transverse OAM γl/2ω₀ despite the phase singularity may split, the split singularities may disappear, or even change the sign of their topological charges. The total transverse OAM of a STOV about a fixed transverse axis crossing its center vanishes because the extrinsic transverse OAM is opposite to the intrinsic OAM, which may preclude applications such as setting particles into rotation, but STOVs could transmit their intrinsic OAM to the photons of other waves, as in nonlinear frequency conversion processes.

In this paper, an artificial neural network (ANN) based approach is proposed for the estimation of the target angle using Multiple Input Multiple Output (MIMO) radars operating in Frequency Modulated Continuous Wave(FMCW). The proposed technique operates in two stages, with the first stage being the formation of the range profile at each MIMO element via Discrete Fourier Transform (DFT) and the second stage being the estimation of the target azimuth angle via an artificial neural network. The range profile formed in the first stage is fed to the second stage as a single snapshot angle measurement. The performance of the proposed technique is apprised with other existing methods under different Signal-to-Noise Ratio (SNR) conditions and measurement model uncertainties. The simulations performed show that the learning capability of the model strongly hinges on SNR conditions, and the learning process is ameliorated as SNR in training data increases as anticipated. Under low SNR conditions, the proposed technique performs better than other techniques in terms of Mean Square Error (MSE). We have also shown that our solution remains unaffected by the model uncertainties as it fully relies on the calibration data, while the performance of the model-based angle estimation techniques dramatically degrades as the uncertainty in the underlying model grows.

This paper presents the study of an H- and dual C-shaped planar dipole antenna by adding and etching technique for the triple-band of drone operating frequencies. Tuning the frequency range was performed to cover the VOR standard of 108-118 MHz, the GS standard of 328.6-335.4 MHz and the DME standard of 962-1,231 MHz. The antenna structure was fabricated on a PCB of FR4 with a dielectric constant (ε_r) of 4.4 and thickness (h) of 1.6 mm (material with low cost, compact size, and easy to use). The reflection coefficient (S₁₁) results of the simulation and measurement were in good agreement, which demonstrated the bandwidth frequencies of resonance frequency at 112 MHz (106-118 MHz), 331.50 MHz (323-401 MHz), and 1,087.50 MHz (920-1,301 MHz). The antenna gains were 1.73, 3.43, and 6.31 dBi, respectively, and the antenna radiation pattern was omnidirectional when it was used with H-plane. It was found in experiment that the proposed antenna could be installed in a drone with sending and receiving signals fittingly as desired. Furthermore, the proposed antenna is lightweight at just 0.4 kg, less than the original drone antenna (1.8 kg), and it does not require changing the antenna in each frequency range.