A low-profile wideband multiple-input-multiple-output (MIMO) antenna is presented. The proposed antenna is suitable for mobile terminals applications, as its measured -10 dB bandwidth ranges from 1.56 GHz to 2.77 GHz. The overall antenna efficiency ranges from 68% to 83% over the operating bandwidth. The overall size of the proposed antenna is 60×97×0.8 mm³. A novel isolation structure is employed to achieve isolation range of -26 dB to -16 dB. The radiation patterns are measured, and envelope correlation coefficient is evaluated. The simulated and measured results are in good agreement.

This paper describes the concept and design of a novel compactself-supported cup feedantenna for parabolic reflectors. The feed antenna consists of an open waveguide cup which is excited by a disk loaded dipole. This structure is fed by a coaxial waveguide through a split-coaxial balun and has a rear radiation pattern toward the reflector antenna. Two different types of this configuration are designed in this paper: a linearly-polarized grid reflector antenna fed by a single dipole excitation, and a circularly-polarized solid reflector antenna fed by a cross dipole excitation. The measurement is done for the former, and simulation results of the latter via two different software packages CST and HFSS are compared in this paper. Analyzing the results shows that both types of cup feed antenna have an excellent aperture efficiency and low side lobe level.

A highly efficient hybrid method of single integral equation (SIE) and electric/magnetic current combined field integral equation (JMCFIE) is presented, named as SJMCFIE, for analysing scattering from composite conductor and dielectric objects, in which, SIE can reduce one half unknowns in dielectric region. The resultant matrix equation of SJMCFIE can be represented in the iteration form, which makes the computation complexity reduced further, and coupling mechanism of composite model becomes more explicit. For accelerating matrix-vector multiplications (MVMs), Multilevel Fast Multipole Algorithm (MLFMA) is employed to combine SJMCFIE to formulate SJMCFIE-MLFMA at last, which is the extension of SIE-MLFMA in the proposed reference. Finally, some examples verify the new hybrid method on accuracy, memory storage, computation efficiency compared to SIE-MLFMA and JMCFIE-MLFMA. Besides, SJMCFIE-MLFMA can also be used to analyse the complete coated model's scattering.

In this paper, we propose a systematic simulation-based approach to estimate the reading distance of an RKE system. In our electromagnetic (EM) simulation, a receiving RKE antenna and a vehicle structure, including both exterior and interior, are modeled as piece-wise mesh triangles to obtain accurate radiation characteristics of the antenna mounted inside the vehicle. The reading distance is then estimated by a two-ray propagation model that includes effects of space loss, ground properties, and antenna polarizations for various orientations and heights of handheld devices. The estimated distances are compared to the measurement, and results show that the proposed approach is suitable to replace the measurement-based approach with an average error of less than 2 m.

The main section of this paper comprehensively analyzes electrical shielding effectiveness (ESE) of enclosures with rectangular apertures for producing valuable information used in electromagnetic interference and compatibility guiding enclosure designers of electronic devices. Firstly, results of conventional analytical equivalent circuit model, measurement and simulation with computer simulating technology (CSTTM) of ESE for an enclosure with a single aperture size are compared to improve closeness in different models at 0-1 GHz. After getting a suitable simulation model, all possible parameters with detailed cases are examined to approach beneficial conclusions. Especially, size of enclosure, aperture size, aperture shape, configuration and number of apertures, probe position parameters that affect ESE are investigated. Also, some double parameters are analyzed together to achieve detailed review as two enclosure dimensions, two aperture dimensions and probe position with enclosure depth. Therefore, three-dimensional graphical investigations are performed. Obtained results of these parametric approaches are explained with acceptable reasons. Finally, detailed and itemized comments are given about simulated results of ESE parameters, which are collected from previous sections.

A planar wideband balun is proposed. The proposed balun consists of a novel slotline T-junction and three microstrip-slotline transitions. Similar to the principle of the E-plane waveguide T-junction, the slotline T-junction acts as a phase inverter. With the microstrip-slotline transition, the device employs microstrip as feedlines. The radiation loss of the slotline is reduced to improve the insertion loss by loading the slotline with a superstrate and adding via holes along the slotline. An experimental balun with a bandwidth of 128% from 2.2 GHz to 10 GHz is designed, fabricated, and measured for validation. The measured results have reasonable agreement with the simulated ones.

An analytic model is proposed to estimate the electromagnetic field transmission line coupling for both radiated emission and immunity using TEM cell measurements. Further, a coupling impedance is introduced to determine the domination between electric and magnetic fields of the field-line coupling. Comparison of measurement and calculation results confirms the accuracy of the model. The model and coupling impedance can be helpful for the suppression of radiated emission and the enhancement of radiated immunity of transmission lines in electromagnetic compatibility design of electronic systems.

A benchmarking procedure for sparse linear array synthesis methods is proposed. Our approach is based on the comparison of the performance of the array synthesis algorithm under test with the performance of a reference equispaced array. The benchmark procedure is discussed considering some examples regarding sparse synthesis method proposed in literature. Guidelines for the correct comparison of synthesis methods and some ``tough problems'' for the test of new sparse synthesis algorithms are also provided.

An ion beam propagating through a magnetized plasma having positive ions K⁺ (Potassium ions), electrons and negative ions SF₆^- (Sulphur hexafluoride ions) drives Kelvin Helmholtz Instability (KHI) via Cerenkov interaction. For two modes, K⁺ and SF₆^-, the frequency and the growth rate of the unstable wave increase with the relative density of negative ions. It is observed that the beam has destabilizing effect on the growth rate of KHI in the presence of negative ions. However, at the large concentration of the negative ions beam stabilizes the growth rate of KHI. An increase in mass of negative ions also stabilizes the growth rate of KHI modes. It is also observed that increase in ion beam velocities and densities play a significant role in changing the growth rate of KHI modes. Moreover, the finite geometry effects tend to modify the dispersion properties and growth of KHI modes.

The corrosion and anti-corrosion current of a ship modulated by the shaft can be equivalent to a time-harmonic current. Based on Maxwell's equations and boundary conditions of electromagnetic field, the Helmholtz equation of magnetic vector potential and the magnetic field expressions of the time-harmonic current in air are deduced. Then, the fast Hankel transform filtering algorithm is applied to solve the equations which contain Bessel integral. The theoretic calculation indicates that the magnetic induction intensity and its attenuation rate decrease along with the increase of distance. The three components of magnetic field have different distribution. At last, it is verified that the shaft-rate magnetic field can be observed by the experiments of carbon electrodes and ship model carried in a sea pool.

In this paper, hyperbolic metamaterials slot waveguides based on graphene have been proposed to explore the optical characteristics. The hyperbolic metamaterials are composed of graphene-dielectric alternating multilayer. It has been verified in our proposed structure that the optical field is enhanced efficiently in the slot region, which results in the optical gradient force becoming larger as the distance of slot region becomes smaller. Both numerical simulation and theoretical analysis systematically reveal that the stronger gradient force can be achieved through smaller slot gap or lower chemical potential. Furthermore, the optical properties of two coupled waveguides have been studied under the relation of incident wavelength, chemical potential of graphene, composition of graphene-dielectric multilayer (eg., number of periods, filling factor of graphene) of the waveguides in this work. We find that a larger gradient force can be obtained by adjusting the height of waveguides, either decreasing the thickness of dielectric with constant number of periods or compressing the number of periods with fixed graphene filling factor. Our results will be helpful to the study of the optical field in the infrared region and also has great potentials in nanoscale manipulation and plasmonic devices.

In this paper a multiple input multiple output (MIMO) radio channel measurement system is presented that utilizes several software defined radio (SDR) platforms at the transmitter and at the receiver. The system hardware buildup and its calibration technique are presented. The channel measurement results are afterwards exploited for a special antenna synthesis method that was already proofed by raytracing channel simulations. The antenna synthesis method is applied to a mobile single and to a mobile multiple channel receiver. The resulting synthesized antenna systems are evaluated in terms of antenna radiation patterns and the corresponding channel capacities. The results reveal the superiority of synthesized antenna systems compared to conventional omnidirectional antenna systems in the considered urban street scenario. Moreover, the findings from the antenna synthesis based on dynamically measured MIMO radio channels confirm the results from the raytracing channel simulation based antenna synthesis.

A wide-band single-layer EMI shielding material for X-band is developed using an M-type strontium hexa-ferrite nanoparticle filler in LLDPE matrix. Strontium hexa-ferrite nanoparticles with crystalline size of 25.8 nm are obtained by annealing at 850˚C. LLDPE allows a higher wt. % of ferrite inclusions enabling enhanced dielectric and magnetic losses. A peak absorption of 99.39% is achieved at 10.21 GHz when the filler weight in a 3 mm thick sample is adjusted to 60 wt.% while a wide -10 dB absorption bandwidth of 3.36 GHz centered around the same frequency is obtained. The density of the composite is 1.36 g/cm³ and shows negligible water absorption.

This letter presents a new directional dual-band slotted trapezoidal inverted-F antenna (IFA) for indoor Wireless Local Area Network (WLAN) applications. The dual-band performance can be obtained by tuning the lengths of the inner symmetrical trapezoidal slots and the outer trapezoidal arms in a nearly independent manner. The measured results show that the proposed antenna can provide two separate impedance bandwidths (return loss better than 10 dB) around 180 MHz and 750 MHz for 2.4/5.1-5.8GHz WLAN bands, respectively. Good radiation performance and roughly constant in-band antenna directivities are also observed.

A ternary composite, based on the M-type hexagonal barium ferrite, BaFe₁₂O₁₉, conducting polymer, polyaniline (PANI), carbon allotrope, and multi-walled carbon nanotube (MWCNT), was prepared through a facile in-situ polymerization process. The structural properties of the synthesized composite were characterized through XRD and FESEM analysis. PANI particles were found to be able to coat on BaFe₁₂O₁₉ and MWCNT surfaces. The increased MWCNT wt% loading within the composite resulted in the increase of the electrical conductivity with values as high as 2.0320 S/m for sample PBM5 (25wt% MWCNT). The composite inherited the salient properties of its respective components to achieve optimum values of shielding effectiveness. The highest value of SE_A recorded was 42.37 dB at 17.60 GHz. The significantly larger magnitudes of SE_A than SE_R suggest that the mechanism of shielding for all synthesized composites are through absorption.

Hybrid pattern recognition is used to predict the types of insulation materials used inside wall systems of building envelopes. The hybrid pattern recognition features vector is built using the characteristics of UWB signals. UWB signals can penetrate objects, resulting in scattered signals based on the object's dielectric properties. The object's dielectric properties and structure have a signature within the scattered signals. This paper demonstrates that proper hybrid pattern recognition can be used to experimentally detect the existence and the type of insulation material inside wall systems with a high success rate.

By reductio ad absurdum, we show that a perfect power combiner of single-mode waveguides is impossible for incoherent input waves of the same frequency and same polarization as it is against the law of conservation of energy. The inevitable 3 dB loss of a three-port power combiner is explained physically. An incoherent power combiner of nearly 100% efficiency can be realized only if the two input fields have different wavelengths, have different polarizations, or are of orthogonal modes.

This paper analyzes the extremely low frequency electromagnetic wave excited by a horizontal electric dipole immersed in the sea. Analytical solutions in the air from HED underwater are deduced using a three-layer model. The effect of the sea-air interface is studied along two perpendicular directions. The electric field is inversely proportional to the square of r while the magnetic field is inversely proportional to the cube of r along the interface. By decomposing the total response into direct, up-going and down-going components, contributions of each component are discussed, indicating that interference cancellation effect occurs among the arrival electromagnetic signals from multi-paths at specific offsets and frequencies.

This paper proposes a backscattering communication technique based on modulated frequency selective surfaces (FSS) for wearable applications. The FSS is composed of dipoles loaded with varactor diodes to modulate the backscatter response, in order to separate it from the clutter. The paper describes the effect in the transponder response according to the number of dipoles, the separation between them and the effect produced when FSS is placed on-body. An analysis based on simulations of several cases and experimental results is provided.

We present a novel type of pixel antennas that are suitable for fabrication in low-cost setups based on commercial inkjet printers. The proposed antennas involve hexagonal cells that can be removed in accordance with rigorous optimizations via genetic algorithms that are supported by full-wave solutions with the multilevel fast multipole algorithm. Optimal pixel configurations are determined precisely for desired electrical characteristics, such as low power-reflection values at required frequencies. Measurements on fabricated samples demonstrate the effectiveness of the optimizations, as well as the favorable characteristics of the hexagonal-cell pixel antennas that fully benefit from the advantages of low-cost inkjet printing.