A combined analysis method for determining the structural and electrical performance of very-low-frequency (VLF) T-type transmitting antennas with a complex structure is proposed. By using the finite element method for analyzing the antenna's structural performance and the moment method for determining the antenna's electrical performance, the structural entity model of the antenna is transformed into an electrical model by extracting the position and displacement information of the antenna curtain, thereby determining the electrical performance index of the transmitting antenna. An actual VLF T-type transmitting antenna is analyzed using this method. A comparison between the calculated results and the measured data shows that this method is effective and feasible. In addition, by optimizing the sag of the antenna's curtain, it is demonstrated that the radiation efficiency of the transmitting antenna can be further improved using this method, and the radiation patterns of the initial state and optimized antenna stay almost the same. This method provides guidance for the synthesis design of other VLF transmitting antennas with complex structures.

This paper solves the problem of minimizing losses in the stator magnetic core of high-speed electric machines with the use of amorphous iron. A fundamentally new technology for manufacturing of a stator magnetic core from segments of amorphous steel is developed by the authors. The feature of the new stator design is the possibility to use technological ducts located inside the stator as cooling ducts. This aspect significantly improves the heat dissipation from the active zone of the stator and, accordingly, minimizing temperature. The efficiency of this solution was studied using two power generators of 100 kW and 200 kW and rotational speeds of 60,000 rpm and 45,000 rpm respectively in the software complex Ansys Maxwell. Harmonic compositions of currents and voltages, flux density distributions in active elements of the generator in various operating modes were studied: under load, in a three-phase short-circuit and at idle. Also, the obtained data were compared with analogous models of an electrogenerator made of electrical steel. The results of the study showed the operability and effectiveness of the proposed technology. Based on the results of the research, a prototype of the stator magnetic core made from amorphous iron was created. Losses in the generator were experimentally measured. Also the results of experimental studies of aerodynamic losses are presented.

This paper presents a broadband switchable 3D structure, which can be used to protect the information equipment from high intensity microwave wave. Compared to other defending designs, the proposed structure in this paper has wider working band. When the amplitude of incident wave within working band is low, the structure would allow them to pass with little loss. As the amplitude of incident wave is high enough to activate diode, the wave would be reflected. The Full-wave simulations are performed in CST to analyze the transmission performance. The simulated results verify the transmission performance and defending function. Its working principle is explained through change of the effective material parameters at two states. A prototype is fabricated. The protection property of the structure as a function of intensity of incident wave is verified in waveguide simulator.

A research of millimeter wave high order frequency multiplier based on the fierce inductive nonlinearity of avalanche diode is presented. The operation of high order frequency multiplication is introduced, and the high order harmonics generation character under external RF field modulation is analyzed. The characteristc of multiplier circuit is also discussed. Maximum output power of 6 mW and minimum conversion loss of 17 dB are obtained at output frequencies of 94 GHz and 96 GHz with 15th multiplication order. The phase noise of output 94 GHz signal is about -90 dBc/Hz and -94.33 dBc/Hz at 10 kHz and 100 kHz offset.

This communication presents a novel compact and wideband circularly polarized (CP) slot antenna fed by microstrip feedline. The proposed antenna consists of a corner-truncated square-ring slot patch and a novel bent strip. The CP radiation is formed by using the bent strip to excite CP resonance modes. By intruding several open stubs to the corners of the square-ring slot patch, the impedance matching and axial ratio (AR) bandwidth are improved. The measured results show that the proposed antenna has the advantage of wideband characteristics in terms of an impedance bandwidth of 90.59% (3.2-8.5 GHz) and 3-dB axial ratio bandwidth of 84.2% (3.3-8.1 GHz). The principle as well as simulated and measured results of the proposed antenna is revealed.

This paper presents designs of novel E-plane spiro meander line uniplanar compact electromagnetic bandgap (E-SMLUC-EBG) and H-plane spiro meander line uniplanar compact electromagnetic bandgap (H-SMLUC-EBG) structures. The proposed EBG has been applied in mutual coupling reduction of a dual-element multiple input multiple output (MIMO) antenna system for WLAN by placing an EBG structure between the radiating antennas. Compact size of EBG helps in reducing the edge to edge distance between Antennas that is 0.14λ₀ in this case, and it increases the compactness of integrated circuit. We get 19 dB and 11 dB simulated mutual coupling reduction in E-plane and H-plane respectively at 5.8 GHz. Measured isolation improvement of 20.3 dB for E-plane and 14.7 dB for H-plane has been achieved. This coupling reduction is also confirmed by surface current and correlation coefficient plots. The four-element (2×2) MIMO antenna system with proposed EBG is also simulated.

Permanent magnet linear synchronous motors (PMLSM) are well known for its high thrust performance. However, such high thrust can be distorted by the existence of cogging force due to the attraction between stator core and permanent magnet (PM). To improve its performance, two parts of the PMLSM structure were considered during the design. They are PM magnetization arrangement on mover side and stator slot opening parameters on stator side. The designed models were simulated by using FEM software, and the performances of the models are then compared. The aim of the design is to achieve high thrust and low cogging force characteristics. Apart from average thrust F_ave and cogging force F_cog, the performance of the PMLSM is also evaluated using average thrust, F_ave to cogging force ratio F_cog, called as thrust ratio. Based on the design, the highest thrust ratio F_ave: F_cog, obtained from radial, axial and Halbach models, are 2.5032, 2.6262 and 1.8437, respectively.

This paper evaluates the effect of glasses on the Specific Absorption Rate (SAR) and the absorbed power in the human head exposed to microwave from wireless eyewear device at phone call state. Due to the sensitivity of eyes to microwave, this paper mainly concentrate on the SAR and the absorbed power in ocular tissues. The calculated results indicate that wearing glasses can obviously increase the maximal SAR and the absorbed power in ocular tissues. Glasses has almost doubled the maximal SAR in ocular tissues. The absorbed power with glasses is about 3.1-4.5 times as big as that without glasses. Furthermore, we find that the maximal SAR and absorbed power are sensitive to the width of glass leg and the thickness of spectacle lens, while variation trends with the varying glasses size are quite different. Hypermyopia patient might suffer from higher risk of getting the oculopathy due to the larger SAR caused by the thicker spectacle lens. In conclusion, wearing glasses may pose higher health risk on eyes of wireless eyewear device user. This paper would provide valuable reference data for the future evaluation of microwave biological effect on eyes.

The salient individual properties of BaFe₁₂O₁₉, MWCNT, and PANI show promise in exhibiting excellent electromagnetic interference (EMI) shielding when they are combined. This research work focuses on developing a composite consisting of all three materials through a simple polymerization process and then evaluating its potential EMI shielding behaviour through electromagnetic measurements. The composite formation was morphologically and structurally verified through XRD, FTIR and FESEM measurements. The presence of main functional groups characteristic to PANI in the composite samples as shown by its FTIR spectra indicates its successful preparation through this method while FESEM micrographs show the random distribution of the composite constituents. The composite is conductive in nature with values reaching as high as 12.43 S/m for the composite with the highest MWCNT wt% (BPM_1_3_25). Electromagnetic measurements done at the X-band show promising EMI shielding behaviour in all prepared composites. The overall highest SEA values are shown by sample BPM_1_3_25 with a minimum shielding value of 65 dB throughout the whole frequency band, far exceeding that of pure MWCNT.

The SHADE and L-SHADE variants of the Differential Evolution global search and optimization algorithm are used to compute optimized excitations for a Log Periodic Dipole Array antenna and to numerically solve the Pantoja-Bretones-Martin suite of antenna benchmark problems. Comparison to published data shows that SHADE and L-SHADE both are effective and efficient algorithms for solving the array excitation problem and the Pantoja-Bretones-Martin wire antenna benchmarks. L-SHADE clearly is more efficient on the array problem, but overall on the benchmarks the opposite is true, albeit to a lesser degree. The data support the view that neither algorithm is generally better than the other for the type of wire antenna problems considered here. Rather, which algorithm is more efficient is highly dependent on the specific antenna being optimized. In terms of the quality of their solutions, however, both algorithms accurately return the benchmarks' known global optima while both converge on different optimal array excitations that result in very similar objective function fitnesses.

A new compact ultra-wideband (UWB) bandpass filter (BPF) with triple sharply notched bands and good stopband performance has been studied and implemented using a triple-mode stepped impedance resonator (TMSIR). The proposed TMSIR is found to have the advantages of introducing triple-notched bands and providing a higher degree of freedom to adjust the resonant frequencies. To validate the design theory, a new microstrip UWB BPF with three notched bands respectively centered at 5.2 GHz, 6.8 GHz, and 9.2 GHz is designed and fabricated. The simulated and experimental results are provided with good agreement.

By exploiting the micro-motion features of fast rotating targets, wideband radar has been successfully applied to high resolution imaging. However, due to the traditional fixed pulse repetition interval (PRI), the target image may suffer from aliasing in some practical situations. In this paper, under the compressed sensing (CS) radar framework, an efficient wideband imaging scheme with random PRI signal is introduced for aliasing reduction. Considering that direct application of the CS theory will result in large-scale dictionaries and high computational complexity, we firstly generate a low resolution image by applying modified generalized Radon transform on range-slow time domain and then scale down the dictionary column by reserving the atoms corresponding to those strong scattering areas. Simulation results show that this scheme can achieve aliasing-free images with acceptable computational cost.

Metal nanowires have drawn much attention due to the highly confined electromagnetic waves and relatively low propagation loss. With the increasing application potentials, we desire deeper insight into the mode behavior guided by metal nanowires for routing and controlling SPPs modes. Here, we apply the analytical solution for analyzing SPPs modes of metal nanowires. Single mode propagation condition and modes number are studied based on the analytical model. A universal formula of field diameters for all guided modes is presented, and mode field diameters are investigated. Finally, the intensity profiles of allowed guided modes are studied for specific dimensions.

This paper illustrates how inverse source problems are aected by certain symmetry and support priors concerning the source space. The study is developed for a prototype conguration where the field radiated by square integrable strip sources is observed in far-zone. Three symmetry priors are considered: the source is a priori known to be a real or Hermitian or even (resp. odd) function. Instead, as spatial priors we assume that the source support consists of a single or multiple disjoint domains. The role of the aforementioned priors is assessed against some metrics commonly used to characterise inverse source problems such as the number of degrees of freedom, the point-spread function and the ``information content'' measured through the Kolmogorov entropy.

This paper proposes a 77GHz microstrip series-fed patch antenna arrays for automotive radar applications. Based on the Taylor Distribution Principle, we designed a six-units series-fed weighted antenna array. A Wilkinson 1∶8 un-equal divider is employed to connect eight antenna arrays to form a whole planar antenna. In antenna far-field patterns, the E-plane side-lobe level is approximately below -20.15 dB, and the H-plane side-lobe level is about -15 dB. Good accordance is obtained between simulated and measured results. The designed antenna has great value in the application fields of 77 GHz automotive radar antenna.

This paper presents the study of an artificial material, made up of a periodic structure, defined by a unit cell, consisting of a finite number N of periodic layers of thin conducting cylinders placed between two dielectric planes. These artificial materials known as metamaterials can be regarded as a homogeneous material with effective constitutive parameters impossible to achieve with naturally occurring materials, such as negative values for both magnetic permeability and electric permittivity. An analytical model has been developed to study the effective electric permittivity of the whole system in terms of the unit cell dimensions and the frequency of the incident electromagnetic wave. Simulations of the effective electric permittivity of the metamaterial were performed by varying the geometry of the metamaterial. This analysis enables the design and construction of structures with properties that make them an attractive candidate for shielding applications in the range of microwave frequencies. The metamaterial has been constructed with four rows of 5 bronze conducting rods each. We have made experimental measurements of the shielding effectiveness of these materials when subjected to a electromagnetic plane wave with electric field polarized along the direction of the conducting rods, and conversely, with electric field polarized perpendicular to the rods. Non-zero values for shielding effectiveness were observed in the first polarization, and zero values in the second case.

A MIMO/Diversity antenna with triple notch characteristics is proposed in this article. The proposed antenna has triple notches in the WiMAX band (3.3-3.6 GHz), WLAN band (5-6 GHz), and X-band satellite communication (7.2-8.4 GHz) band. Defected Ground Compact Electromagnetic Band Gap (DG-CEBG) is a design used to accomplish band notches. Defected ground planes are utilised so as to achieve compactness in conventional EBG structures. The proposed WiMAX band, WLAN band, and X-band satellite communication band DG-CEBG structures show a compactness of around 46%, 50%, and 48%, respectively, over a conventional EBG structure. In these structures, decoupling strips and a slotted ground plane are used to enhance the isolation between two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with a stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing the current path length. |S₂₁| or mutual coupling is found to be less than 15 dB over the whole UWB frequency range. The Envelope Correlation Coefficient (≤0.5) is within the acceptable limits over the whole UWB frequency range. Notched frequency depends on the parameters of DG-CEBG structures; when there is a change in these parameters notch frequency is also changed. A low cost FR-4 substrate with thickness (h) = 1.6 mm, permittivity (ɛ) = 4.4 and loss tangent (δ) = 0.02 is used for the proposed antenna, and it has a compact size of 58×45×1.6 mm³.

A novel design of Meandered Coplanar waveguide (CPW) fed CSRR loaded multiband antenna is presented in this paper. A compact triple band antenna is designed by etching CSRR slots on the radiating element. The proposed antenna shows good performance at all resonant frequencies. The simulation results are discussed and compared with the measured ones. The effects of CSRR loading on the radiating element are explained. Parametric studies are carried out and explained in detail. The proposed antenna is fabricated and measured, and the results are compared with the simulated ones. CSRR permittivity characteristics are explained to validate the results. The proposed antenna can be used for C-band, Wireless Local Area Network (WLAN) and International Telecommunications Union (ITU) applications.

This paper presents a compact slotted MIMO cube antenna operating at 5.8 GHz, consisting of three orthogonal slots, each with a distinct main direction of radiation. Each slot produces linear polarization enabling the structure to radiate three orthogonal polarizations. This provides spatial diversity which helps mitigating the effects of multipath propagation and enhances the diversity gain. The cube is filled with a dielectric with a relative permittivity, ε_r thus reducing the minimum dimension of the cube by a factor of 1/√ε_r . The antenna has a return loss of 20 dB and a coupling of less than -26 dB between the ports. This paper describes the principle operation as well as the design and manufacturing process of the proposed antenna.

A simple and compact diagonal matched feed structure is proposed for offset reflector antenna, which includes a square choke to radiate the desired conjugate mode (TE₄: a higher order rectangular coaxial cable mode) for suppressing the cross-polar power of an offset reflector antenna when the reflector is illuminated by the dominant diagonal mode (TE_V^D: a linear combination of rectangular TE₀₁ and TE₁₀ modes) radiated from the aperture of a central diagonal waveguide. Square choke is excited by two identical slots on the central diagonal waveguide using the longitudinal magnetic field of main operating mode TE_V^D. Wideband conjugate matching as well as impedance matching for broadband operation can be achieved by such radiating main mode and conjugate mode from apertures which are spatially separated. Based on the above configuration, a J-band matched feed structure is designed using HFSS software for a given offset reflector geometry. The proposed matched feed structure is fabricated and measured. The measured results are compared with simulated ones, and close agreements are found.