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.

A miniaturized ultra-wideband (UWB) quasi-self-complementary antenna (QSCA) with band-rejection characteristic is presented and discussed. With the tapered microstrip-fed line and flower-shaped QSC structure, a lower cut-in frequency (3.18 GHz) is obtained with a compact size (9x17.5x1 mm³). By embedding a five-star-shaped ring resonator under the radiation patch, a band-notched feature is achieved. The measured impedance bandwidth below 2:1 VSWR is from 3.18 GHz to 13.4 GHz with a rejection band from 5.45 GHz to 5.95 GHz, and the simulated and measured results of the proposed antenna are in good agreement. Thus, the antenna is suitable to be integrated with the space-limited wireless system without electromagnetic interference at the WLAN (5.47-5.825 GHz) band.

The moving chest wall imparts a delay modulation onto the reflected IR-UWB radar signal, making the radar return a nonlinear function of chest wall displacement. Existing theoretical spectral models of the IR-UWB radar reflections from the human chest wall have restrictive assumptions that preclude realistic modeling of chest wall displacement and assume an aliased version of the radar signal. This paper presents novel theoretical analysis of the un-aliased spectrum, without the restrictive assumptions. Potential applications not specifically treated in this paper, but illustrative of the novelty and broader scope of the presented analysis, include heart-induced displacements that are realistically more bursty in nature and breathing-induced displacements consistent with, for example, non-unity inspiration-to-expiration ratios characteristic of asthma; neither of these could be analyzed using previous models. As well known, the un-aliased spectrum cannot generally be recovered from the aliased spectrum. In particular, the paper shows that the clusters of the non-aliased spectrum are not just scaled versions of each other; rather they have complex variations that if measurable, could enable estimation of parameters such as displacement amplitude; such variations are not apparent in the existing aliased spectrum model, which has just one cluster. This paper analyzes the degree to which the aliased model di↵ers from the non-aliased model. The paper also addresses some practical aspects of the spectral model, such as the number of significant components in a spectral cluster and computational complexity of the theoretical model.

In this work, four types of random arrays are compared. In particular, the mean and variance of the array factor are derived. This provides a partial statistical characterisation that allows pointing out some important aspects of random arrays and link them to the number of elements and array aperture. In the absence of a simple and effective analytical apparatus, here great importance is also given to the experimental aspect, especially as far as the side-lobe level is concerned. To this end, Monte Carlo simulations are run to experimentally build the side-lobe distribution as a function of the number of radiators and the average spacing between two adjacent radiators. The obtained results show that random arrays where one is free to impose constraints on the minimum spacing between adjacent elements can obtain performance analogous to those achievable by other schemes which do not put such constraints. However, the former are preferable because they are able to zero the probability that adjacent radiators are separated with less than a certain minimum distance and this allows the mitigation of mutual coupling effects.

We present a method to improve the resolution of available hyperlenses in the literature. In this method, we combine the operation of hyperlens with the recently proposed plasmon injection scheme for loss compensation in metamaterials. Image of an object, which is otherwise not resolvable by the hyperlens alone, was reconstructed up to the minimum feature size of one seventh of the free-space wavelength.

The development of modern communication devices for the latest technologies such as 5G has brought the millimeter wave technology into the spotlight because it offers higher data rates and bandwidth. Since highly directional transmissions are necessary for communication in these frequencies due to high path loss and atmospheric absorption, the use of adaptive antennas is inevitable. Rotman lenses have long been used as analog beam forming networks to support linear array antennas for electronic scanning. Their broad bandwidth and planar structure make them ideal for a variety of applications. However, their overall dimensions can be prohibitive especially for large scan angles. In this paper, we propose a few compact configurations that reduce the overall dimensions of Rotman lens as much as 50% without degrading its performance.