This paper explores the effects of extended exposure to salt water fog on the microwave absorption properties of unidirectional carbon-fiber reinforced polymer (CFRP) circuit analog absorbers (CAA). Single-layer CFRP CAAs were fabricated using a wet-layup technique and were then subjected to a controlled salt water fog chamber following B117 standards. A total of ten samples using 305 g/m² areal-weight unidirectional CFRP were fabricated. Three samples were withdrawn from the salt water environment at ten-day intervals and tested, with the final samples being withdrawn after 30 days. The mass of each sample was measured immediately after removal to measure mass-accumulation and after a five-day interval to measure mass-loss. A free-space microwave reflection measurement system was implemented to track and quantify changes to the absorption capabilities of the CAA. A physically-based electromagnetic model was developed to characterize the changes caused by salt water absorption, and good agreement was observed with measured data.

This paper proposes a zero-forcing beamforming design for the energy efficiency optimization of the magnetic resonance based wireless power transfer system with multiple transmitter coils, which aims to secure energy transfer control. A scheme based on beamforming technology is proposed to prevent unauthorized users from accessing the system, which builds a beamforming model consisting of multiple transmitter coils, a target receiver, and a non-target receiver to simulate the actual system. Then to optimize the proposed system's energy efficiency while constraining the target receiver's energy, spectral efficiency, and transmitter's power, the proposed beamforming model is constructed as an optimization problem. To solve this non-convex nonlinear fractional programming problem, the Dinkelbach algorithm is used for fractional conversion, and then the zero-forcing constraints are equivalently replaced. Finally, two solutions of the nonlinear solution and closed-form solution are derived. The simulation results show that the energy efficiency optimization strategies of zero-forcing beamforming with the two derived solutions can satisfy the design requirements.

A dual-band two port MIMO antenna with very high isolation is proposed for 5G/WLAN application. The overall size of the MIMO antenna is (18 × 44× 0.8) mm³. The unequal arm of the Inverted-F Antenna (IFA) is the reason for the dual bands. Bending and extending one of the arms with the staircase shape is responsible for the proposed dual-bands having resonant frequency at 3.45 GHz (3.3 GHz-3.65 GHz) and 5.1 GHz (4.8 GHz-5.5 GHz) respectively with percentage impedance bandwidth of 10% and 13.6% respectively. The proposed antenna uses a simple decoupling structure based on a wide inverted T-shaped slot to achieve good isolation (better than 18 dB and 34 dB respectively for the dual-bands) between the ports. The envelope correlation coefficient (ECC) and channel capacity loss (CCL) are within the acceptable limits.

Artificial material has the feature to realize a controllable effective permittivity, which leads to many potential applications in the RF and optical fields. In this study, an artificial material is proposed for a Resonant Cavity antenna (RCA) to enhance the gain of patch antenna. The artificial material is made of a lot of circular conducting patches in a uniform size hosted in an FR-4 substrate. The fabricated artificial material is in a square shape with a length and width of 52 mm × 52 mm and a thickness of 1.2 mm. The artificial material is set in front of a patch antenna to construct an RCA, and the gain property of the proposed RCA is evaluated with the simulation and measurement methods. The results by both the simulation and measurement methods prove that the gain is enhanced by the proposed artificial material. The maximum gains are 14.5 dBi in simulation and 12.8 dBi in measurement at 15 GHz for the RCA with on slab of the artificial material. The gain is improved compared to the gain of a patch antenna without the artificial material.

Multilayer grid polarizers for millimeter waves produced with photolithographic technology have been simulated. Polarizers have spectral bands of enhanced performance where polarization extinction ratio in decibels grows in proportion to the number of layers. Full-wave modeling is compared with three asymptotic models for subwavelength gratings using adjusted grating parameters. Random variations of interlayer spacings reduce the enhancement of polarizing performance, yet the latter continues to grow in proportion to the number of layers. Broadband signal detection is also considered.

A package-board co-design method was applied for a Narrowband Internet-of-Things (NB-IoT) SiP module. The electromagnetic interference (EMI) generated by the module was studied by improving the transmission quality of radio frequency (RF) signal. The SiP models of the initial design and the optimized design were simulated separately to show that the optimized design significantly increased effective transmission power of the RF signal and suppressed near-field electromagnetic radiation intensity to a certain extent. In addition, the optimized design model was verified by measurement. The measured results show good agreement with the simulated ones and demonstrate that the package-board co-design method can improve the electromagnetic compatibility (EMC) of NB-IoT applications.

A low-profile half-mode substrate integrated waveguide (HMSIW) filtering antenna with high frequency selectivity is proposed in this letter. The proposed antenna with a height of 0.014λ₀ (λ₀ is the free-space wavelength) consists of a slot-loaded HMSIW cavity, two parasitic patches, and five shorting pins. An upper-edge radiation null is generated by the interaction between the HMSIW cavity and parasitic patches. A rectangular slot etched on the HMSIW cavity is adopted to generate another null to improve the filtering performances at the upper stopband. Besides, the radiation in the lower stopband is suppressed by two nulls which emerge due to placing shorting pins under two parasitic patches. Thus, four radiation nulls can be obtained to enhance the frequency selectivity. The measured results illustrate that the proposed antenna provides an impedance bandwidth of 4.3% ranging from 2.74 to 2.86 GHz and a peak gain of 6.76 dBi during the operating frequency band. Moreover, four radiation nulls appear at 2.34, 2.56, 3, and 3.24 GHz in the lower and upper stopbands.

This paper proposes a novel bandpass filter for L-band based on CRLH TL, which is mainly formed by coupling a high-pass characteristic module with a low-pass characteristic module in a cascade. The high-pass module consists of an interdigitated coupled line and a grounding via, owning to its singular characteristics, which the miniaturization is realized. The low-pass module is composed of a C-type resonator with high-low impedance lines, which can realize great sideband attenuation characteristics. To further improve its out-of-band rejection characteristics, a complementary split-ring resonator (CSRR) defective ground structure with single-pole attenuation characteristics is loaded, and a transmission zero is introduced at 2.5f₀ out-of-band. The test results are in great agreement with the simulation ones, and the dimensions are only 0.20λ_g*0.22λ_g. Compared with other similar types, the filter proposed in this paper has miniaturization, great passband selection characteristics, stopband characteristics, and the advantage of low insertion loss.

This paper presents a star-shaped compact dielectric resonator antenna for wideband and multiband wireless applications. The slots in the dielectric slab have been created to achieve wider bandwidth. The star-shaped alumina dielectric is placed on a low cost FR-4 substrate and fed using a microstrip line. The electrical dimensions of the proposed dielectric resonator antenna are 0.86λ₀×0.86λ₀×0.13λ₀. The proposed design resonates at multiple frequency bands of 5.04-6.13 GHz, 6.87-7.97 GHz, and 8.58-9.63 GHz having the fractional bandwidths of 20.76%, 15.3%, and 11.4%, with peak gains of 3.71 dBi, 6.20 dBi, and 8.10 dBi, respectively. The design was fabricated to validate the simulation results. Good agreement can be seen between the measured and simulated results.

An efficient analysis and optimization method is proposed to compensate the influence of asymmetric radome on an antenna by correcting amplitude and phase of the excitations. The asymmetrical and heteromorphic radomes are inevitable for the radar on high-speed aircraft. Many previous researches focused on the optimization of the radome structure and thickness to reduce the influence of radomes. However, the influence of complex streamlined radome cannot be compensated by merely optimizing the structure and thickness of the radome. Therefore, an alternative optimization method, optimizing amplitude and phase of feeds, is used in this paper. This paper adopts the active element pattern (AEP) technique, utilizing full-wave simulation method to extract the AEP for each antenna element and computing radiation patterns of array antenna by using vector composition of AEP. In combination with hybrid genetic algorithm-particle swarm optimization (HGAPSO), the antenna radiation characteristics can be obtained by updating excitations, which avoid the repeated full-wave simulation in the optimization process. Furthermore, the speed updating formula of PSO algorithm is improved combined with prior information, and the convergence speed is further increased. Finally, a 64 elements array antenna-radome system was optimized as an example in the cases of continuously adjustable phase and digital discrete phase.

The electromagnetic characterization of layered materials is applicable to many different applications. In previous work it has been shown that reflection-only techniques - which vary the underlying structure of the sample stack to obtain two independent measurements - are a variation of a single unifying scheme such that there is a single set of closed-form unifying extraction equations for the electric permittivity and magnetic permeability. In this paper, the error propagation method is applied to this single set of closed-form extraction equations in order to derive an accompanying set of closed-form equations to predict the measurement uncertainty of electric permittivity and magnetic permeability. An error analysis is performed on the layer-shift method, and results are compared to a Monte Carlo simulation to prove the viability of the general error analysis equations.

A simple, compact, contactless, and high sensitivity metamaterial-inspired sensorhas been developed to detect and classify precious transition metals in the S- and C-band regime, using reflection coefficients. A multi-band metamaterial, quadruple concentric circular split ring resonator, is specifically designed as a sensing enhancer, where the additional bands can effectively trigger the electromagnetic properties, as well as enhance the differentiation between the testing metal samples. The proposed sensor was tested on precious transition metals, silver, platinum and gold thin slabs of various thicknesses, from 0.5 μm to 3 mm. Five resonances were established in the frequency range of 2-8 GHz. Distinguishable frequency responses generated from different metal samples at those five resonances specify the capability of classifying the metal contents and thicknesses.

A new compact nonuniform leaky-wave antenna (LWA) with left-handed elliptical polarization (LHEP), based on composite right/left-handed (CRLH) metamaterial operating in the range of 7-10.2 GHz is presented in the work. The nonuniform structure of a CRLH transmission line (TL) is realized by the placement of different configurations of inter-digital capacitor (IDC) in the form of sinusoid (SIN-IDC), on the top of metal wall of a half-mode substrate integrated waveguide (HMSIW). Balanced condition of the unit cells is provided by the change in slit width, amplitude and the number of SIN-IDC periods, as well as by relocation of two additional transition apertures arranged by both sides of SIN-IDC. Based on the known Hensen-Woodyard criterion, the optimal number of the unit cells was determined, when the gain coefficient varied from 7.5 to 9.8 dB in all of the operational range of antenna. The developed prototype of nonuniform CRLH LWA has the size of 8.1x115.2 mm. It is characterized by a continuous scan angle range equal to 117°. The maximum angle of rotation radiation pattern is -66° for backward radiation and +51° for direct radiation. The maximum efficiency of the antenna radiation is 85%, while the total one is 68%.

In this work, a diversity antenna with a high level of isolation is presented in this paper. To make the antenna compact, the radiating parts are arranged on opposing sides of the substrate. The isolation between the ports is sufficient for the use of a MIMO system, which is achieved through the orthogonal positioning of radiating elements. Wideband and narrowband antennas are placed on opposite sides of the substrate. The suggested monopole antenna has an impedance bandwidth of 3.1 GHz to 14.9 GHz, whereas the rectangular narrowband antenna has an impedance bandwidth of 5.4 GHz to 5.62 GHz. More than 16 dB of isolation exists between the two ports. The proposed antenna has a maximum gain of 2.9 dB. The diversity nature of the proposed MIMO antenna is studied in terms of Envelope Correlation Coefficient (ECC), Diversity Gain (DG), and Total Active Reflection Coefficient (TARC).

When a substation is struck by lightning, it will cause the ground potential to rise, which will further cause serious interference to the secondary cable. This article is based on the grounding grid established in the testing ground. The grounding copper bar is laid in the cable trench to connect with the grounding grid. At different grounding grid points, use a lighting current impulse generator to apply high current. At the same time, the grounding grid model is established by using the ATP-EMTP software. Through the combination of test and simulation, the influence of different lighting inflow locations on the protection effect of grounding copper bar is studied, and combined with the connection method of the grounding copper bar and the grounding grid, the protective effect of the grounding copper bar on the secondary cable under the impact of lightning current was analyzed. The research results showed that the laying of grounding copper bars can reduce the influence of interference voltage on the secondary cables under certain circumstances, but when there are multiple connection points between the grounding copper bar and the grounding grid, the current injection position is different, which will affect the voltage between the cable core and the shielding layer. At the same time, it will also affect the ground potential rise of cable grounding point in different degrees.

This paper presents a dual-band polarization dependent phase gradient metasurface (PGMS) lens based on phase compesation method. The proposed metasurface (MTS) consists of a multi-layered unitcell with elliptical structures encircled by a square loop. Owing to the elliptical shape, the unitcell produces an independent phase control for different polarizations of incident wave at two operating frequencies. The present work is aimed to design a dual band gain enhancement MTS lens antenna in the broadside direction at 10 GHz and 12 GHz. The proposed MTS is designed by one-to-one spatial phase mapping with major and minor axes of the elliptical unitcell at 10 and 12 GHz for x- and y-polarized incident waves, respectively. The performance of the MTS is validated by placing two linearly polarized patch antennas operating at 10 GHz and 12 GHz at the focal distance. The simulation and measured results show a gain enhancement of 10 dB in the frequency range of [9.5-10.1] GHz and [11.6-12.1] GHz for x- and y-polarized waves, respectively.

This paper introduces a novel planar super-wideband (SWB) antenna with reconfigurable band-notch characteristic. The antenna can work in band-notch mode or band-notch free mode. A good impedance matching is responsible for the SWB characteristic of the proposed antenna by adopting a gradient ground, a gradient feeder line, and a gradient radiating patch. Furthermore, to achieve a reconfigurable notched band function, a 0.3 mm deep slot which is 16 mm in length and 8 mm in width is dug near the antenna feeder for the placement of dielectric plates etched with different sizes of split ring resonator (SRR). The designed antenna has a size of 200 mm × 109 mm × 0.79 mm, and the measured frequency band of bandwidth covers 0.8-26 GHz with a reconfigurable band-rejection characteristic. The dielectric plates with different SRRs reject the part of WLAN band (5.44-5.55 GHz), X-band satellite downlink band (7.65 GHz-7.82 GHz), and 6.33 GHz-6.59 GHz. A good agreement is achieved within the super-wideband frequency range between simulated and measured results.

A compact CPW-fed triple-band Multiple Input Multiple Output (MIMO) antenna is designed for WLAN, WiMAX, and 5G applications in this article. Three resonant frequencies, including 2.4 GHz, 3.5 GHz, and 5.5 GHz are generated by two branches and a rectangle radiation patch. The proposed antenna comprises two antenna elements placed side by side with a meandering neutralization line (NL) inserted between the elements to realize decoupling. To analyze the performance, it is fabricated and experimented. The measured results reveal that it has three impedance bandwidths: 2.38-2.52 GHz (5.7%), 3.28-3.62 GHz (10.1%), and 5.05-6.77 GHz (29.1%) with the measured isolation up to 16 dB. Furthermore, the parameters of diversity performance like envelope correlation coefficient (ECC), diversity gain (DG), efficiency, gain, channel capacity loss (CCL), mean effective gain (MEG), and total active reflection coefficient (TARC) are also analyzed, and the results indicate that the proposed antenna is desirable for integration in WLAN/WiMAX/5G devices.

Various multiple-input multiple-output (MIMO) antenna systems for vehicles are presented in this paper usingtwo uniquely designed elements: low profile wideband Planar Inverted-F antenna (PIFA), and compact wideband monopole for automotive application in the sub-6 GHz 5G systems and Vehicle-to-Everything (V2X) communications that operate on the frequency range from 617 MHz to 6 GHz. This paper presents different MIMO configurations to be used in a low-profile housing or a shark fin style on the vehicle's roof. Each MIMO system achievesa satisfactory MIMO performance across the whole band withsuitable physical dimensions. The envelope correlation coefficient (ECC) and diversity gain (DG) are calculated using MATLAB in each MIMO configuration as they represent the two key factors in the MIMO performance. Simulation results are presented along with measured data on 1-meter rolled-edge ground plane (GND) and on vehicle's roof from properly cut metal sheet prototypes. The results are discussed in terms of VSWR, passive isolation between elements, combined radiation patterns, port-efficiencies, ECC and DG.

In this paper, a design method of spaceborne multi-beam antenna array is proposed. Multi-beam is achieved by rotating subarrays. A high efficiency circularly polarized horn antenna array working in Ka band is designed and processed. The antenna array has 16 large axial ratio elliptical beams, which can achieve the beam coverage range of 53°×49.1°. The simulation results are basically consistent with the test results, verifying the effectiveness of the proposed method. The design method of multi-beam antenna proposed in this paper can meet the requirements of multi-beam seamless coverage.