In this article, the Modal Expansion Theory (MET) is applied to 3-D metamaterial waveguides. The equivalent surface impedances of the metamaterial are computed thanks to an open software: GetDP, based on a 3-D Finite-Element-Method (FEM). This program is called during the MET algorithm, which allows considering the frequency and incidence angle dependency of the surface impedances of the metamaterial to compute the dispersion diagrams and the field cartography. To validate the dispersion diagrams obtained with this technique, another FEM commercial software (HFSS) is used as a reference.

In order to improve the efficiency of transformer fault diagnosis and monitoring in power systems, and to realize fault diagnosis of unmanned remote adaptive transformer equipment, we present a method of multi-sensor and multi-direction optical image integrated monitoring in this paper. By monitoring and collecting transformer fault information combined with the changing characteristics of transformer temperature and electrical signals, we establish a transformer calculation model based on multi-level fault and multi-characteristic parameters. According to the characteristics of transformer faults, we use a deep belief network identification (DBNI) algorithm for the transformer and construct the training samples of the transformer diagnosis model using an optimum weight fusion algorithm. The experimental results show that the DBNI model can fully explore the characteristics of large samples, analyze multiple faults information, and extract the hidden features of fault samples. The DBNI model has higher fault diagnosis accuracy than a BP neural network and a single DBN without data fusion and SVM. The DBNI's fault diagnosis accuracy reaching 99.45%. The experimental results show that this model has good robustness of interference ability and can be used intuitively to carry out remote on-line unattended transformer fault diagnosis and information feedback.

This article investigates the optimal design of a magnetic-planetary-gear permanent magnet (MPG-PM) machine. The key is to develop a design method for the pole shoe thickness, stator outer diameter and coil turns of the MPG-PM machine in such a way that the torque waveform is sinusoidal. The magnetic field distributions is solved by the finite element analysis according to the optimization results. A prototype of MPG-PM machine is used for exemplification in terms of the experiment performance requirement. Both the predicted and measured results are given to illustrate the proposed machine. The theory analysis and the experimental results show that the magnetic circuit of the MPG-PM machine is correct, and the torque satisfies design requirements. It provides reference and application value for developing high performance and low-cost MPG-PM machine.

Concentric circular slots coupled hemispherical dielectric resonator antenna fed by a modified microstrip line for circular polarization is investigated. By adjusting the position of the hemispherical dielectric resonator antenna and the slot properly, the resonance of the slot and the antenna is merged to obtain wider axial ratio bandwidth. Parametric studies have been done on the effect of changing the DRA position on impedance band and axial ratio band. The circular polarization achieved by the antenna offers a very good 10 dB impedance bandwidth of 27.379% and a 3 dB axial ratio bandwidth of 640 MHz. The maximum gain in the operational band is 7.3 dBi. The antenna is suitable for Wi-Max applications.

Slotless double-sided outer armature permanent-magnet (PM) linear motors (SDOPMLs) have high efficiency and low detent force. Despite their simple control strategy and easy manufacturing process, finding an accurate model of these motors to calculate the machine quantities is challenging. It is particularly critical for obtaining the optimum design of these machines which may include too many iterations in a short time. To overcome this challenge, a 2-D analytical model based on the sub-domain method is presented to determine the magnetic flux density components for the motor under the study. According to this analytical procedure, the motor cross-section is divided to 11 sub-regions, then the superposition theorem is utilized to analyze the flux density distribution in all sub-regions due to various magnetization patterns, (i.e.， parallel, two-segment Halbach, ideal Halbach, and bar magnet in shifting directions) as well as armature reaction current, respectively. According to the calculated magnetic flux density components, machine quantities like flux linkage, induced voltage, inductances and electromagnetic force components are explained. Also, the obtained analytical results are compared with those of the finite-element method (FEM) to confirm the accuracy of the proposed model. The proposed model can be used in the design and optimization stage of the linear slotless motor against the numerical model to save time. Finally, a comparative study between the performance of the single-sided and double-sided slotless PM linear motors in the same volume is implemented. This comparison shows the advantage of the double-sided motorin terms of the unbalanced magnetic force (UMF).

This paper analyzes the high-frequency energy distribution of a paraboloid reflector in the presence of a uniform plasma layer. The curved surface of the paraboloid reflector is thought to be coated with a uniform plasma layer. The geometrical optics technique shows a singularity at the focal point of the paraboloid reflector. The singularity is removed with the help of Maslov's method, which also let us derive the integral equations that give the high-frequency energy distribution at the focal point. The analytical integral is solved numerically using a computational technique, and the effects of plasma frequency, collisional frequency, operating frequency, and multiple reflections on energy distribution at the focal point are observed. Under the special conditions our analytical and numerical results are obtained which align with the published literature.

A novel design of an enhanced Yagi-Uda antenna is introduced for dual-band operation at 28/38 GHz. The antenna is constructed by a corrugated dipole strip and a capacitively end-coupled extension strip as the driving element, two reflectors, and one director. Periodic parasitic elements are added in front of the reflectors to enhance the antenna gain and improve the impedance matching. The driving dipole is fed through a coplanar strip line, and in order to facilitate the experimental measurements using a coaxial feed line, a microstrip to coplanar strip (CPS) line transition is employed. A four-port MIMO antenna system is constructed using the proposed Yagi-Uda antenna arranged at the edges of the mobile handset. Numerical and experimental investigations are achieved to assess the performance of both the single-element antenna and the four-port MIMO antenna system. It is shown that the simulation results agree with the experimental measurements, and both show good performance of the single antenna as well as the MIMO antenna system. The bandwidths achieved around 28 GHz and 38 GHz are about 3.42 GHz and 1.45 GHz, respectively, using the microstrip feed line. Each antenna has a maximum gain of about 9 dB. The four antenna configuration shows radiation pattern diversity required for MIMO system. The envelope correlation coefficient (ECC) and diversity gain (DG) are calculated, and the results show that the proposed MIMO antenna system is suitable for the forthcoming 5G mobile communications.

Reconfigrable antennas that are able to provide a high spatial diversity are increasingly adopted in many wireless applications. An original design of a planar printed compact antenna that achieves an electronically controlled beam steering by using metamaterial hybridization is presented in this paper. The designed antenna, made of coupled split ring resonators, is able to switch between 8 radiation patterns steering in 8 different directions at the working frequency of 2.45 GHz. The spatial diversity is assessed from the analysis of the correlation matrix between the patterns. This concept would provide a promising and compact alternative for low power telecommunication systems.

In this paper, an ultrawide band (UWB) notch antenna with electromagnetic bandgap (EBG) structure for WiMAX and satellite applications is proposed. The proposed design contains an inverted-π model slot and EBG element which create lower and upper notch frequency bands respectively. The designed antenna is fabricated on a Rogers RT/duroid 5880 with the dimensions of 18 mm × 21 mm × 1.6 mm³ which is fed with a 50 Ω transmission line. The proposed antenna has a range frequency from 2 GHz to 12 GHz, in which lower notch covers 3.3-3.7 GHz (WiMAX), and upper notch covers 5.9-6.9 GHz (satellite uplink application). The proposed antenna measured and simulated results are in good correlation. It has good radiation characteristics in the required frequency bands.

A general resonant condition for rectangular waveguide junctions operating in the single mode regime of the main waveguide is formulated based on previously developed mathematical models. We will consider three types of junctions with various side arms: T-oriented semi-infinite waveguide with an impedance end wall, semi-infinite waveguide oriented in line with main waveguide, and infinite perpendicularly oriented waveguide. The main waveguide is coupling with the side arm through a narrow slot, and it has a dielectric inclusion in the coupling region. As a result of the analysis of the resonance characteristics for the indicated types of waveguide devices, the correctness of the application of the general resonance condition is substantiated. The possibility of neglecting the imaginary part of the permittivity of the inclusion material in calculations is confirmed by a satisfactory agreement between the numerical results and experimental data for an isolated inclusion.

This paper presents a hierarchical saliency detector for ship detection in synthetic aperture radar (SAR) imagery. First, the nonlinear anisotropic diffusive process has been adopted to eliminate clutter, while preserving the target edge feature in SAR image. Second, each pixel in the filtered image is assigned to its corresponding super-pixel region via an adaptation of optimization technique. Third, Gamma manifold for feature representation has been presented for the modeling of intensity of all super-pixels in SAR imagery. Fourth, a threshold segmentation method is used to realize ship detection. The proposed method is an automatic detection process without any sliding window. Experimental results accomplished over real SAR images demonstrate that the proposed detection method can achieve a good performance.

This letter proposes a novel single-layer fourth-order balanced bandpass filter based on two coupled dual-mode loop resonators. Two pairs of balanced input/output (IO) feeding lines with unequal arms are employed to excite the outside dual-mode loop resonator, and the inside dual-mode loop resonator with meander lines is coupled to the outside one. Under differential-mode (DM) operation, three finite transmission zeros (FTZs) can be produced and controlled. Under common mode (CM) operation, the rejection level can be controlled by the length of IO feeding arms. For the demonstration, a balanced dual-mode loop filter with the center frequency of 5.2 GHz is designed, fabricated, and measured. The proposed balanced filter has the advantages of compact size, high selectivity, wide stopband of DM response, and good CM suppression.

In this article, a new wideband bowtie shaped slot antenna is realized on a flexible polyethylene terephthalate (PET). The slotted bowtie design is implemented with an asymmetric bow-tie flare angle and a larger feeding neck with a metal strip inside the bowtie slot to achieve a wider bandwidth and a higher gain. The designed free space antenna is fabricated using inkjet printing and tested. The fabricated antenna operates over 2.1-4.35 GHz frequency range (69.77% fractional bandwidth) which covers WLAN, WiMax, and most of the 3G and 4G frequency bands. Further, the antenna exhibits an omnidirectional radiation pattern with a peak gain of 6.3 dBi at 4.35 GHz. The bending test of the fabricated device reveals adequate flexibility without significant antenna performance degradation. Moreover, the antenna tunability for any mounting structure application is also investigated by simulating another version of the parent antenna (free space antenna) for drywall mounting applications. The tuned antenna covers a similar frequency band as a free space antenna maintaining the desired radiation performances. The compact size, higher bandwidth, omnidirectional pattern with a higher peak gain and flexible properties make the antenna design suitable for mounting structure for Internet of Things (IoT) applications.

It is well known that high refractive index contrast is essential to the formation of an omnidirectional Photonic Band Gap (PBG). It is generally cited also that the width of the omnidirectional PBG of a dielectric mirror is determined by the refractive-index contrast. But in this work, we show that this condition is not really general criteria. Dielectric mirror with higher refractive index contrast does not necessarily mean that it has the largest omnidirectional photonic band gap. So, we investigate the necessary conditions on the high and low refractive indices of the quarter wave layers to have the largest omnidirectional bandwidth in the visible range. We present a profound study of the omnidirectional band center wavelength and the bandwidth behaviors versus the layers refraction indices. It is shown therefore that one can modulate omnidirectional photonic band gap center by modulating the optical phase of the mirror.

The present paper investigates the propagation and dispersion of elastic surface waves in an asymmetric inhomogeneous isotropic three-layered plate in the presence of magnetic field and rotational effects. The skin layers are exposed to an external magnetic field force while the core layer is assumed to be in a rotational frame of reference, which are perfectly bounded together with free-ends conditions. The resultant displacements and shear stresses in the respective layers are derived analytically together with the general dispersion relation. Further, the general dispersion relation is analyzed for some physical cases of interest. Finally, the effects of the magnetic field, rotation and electric field on the propagation and dispersion of the present model are presented graphically.

This paper presents a dual-band microstrip antenna for Global System for Mobile Communications (GSM) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The split ring resonators structure driven antenna operates at 900 MHz and 3.3 GHz, respectively. Return losses achieved at the two resonance frequencies are 22.26 dB and 18.97 dB, respectively. The proposed antenna is developed on a cost-effective FR-4 substrate with relative permittivity 4.4, tangent loss 0.002, and partial ground plane. The bandwidths of the proposed antenna are 3.01% and 4.26%, respectively. The design and fabrication procedure along with both simulated and measured results are presented and discussed in this paper. Designed antenna delivers good performance and solution for both applications.

In this paper, a low-profile fractal antenna and its array for DSRC-band applications have been proposed. The proposed single element is a newly designed fractal antenna which is right-handed circularly polarized (RHCP) and derived from the Koch-snowflake 1st-iteration. Moreover, a diagonal slot defect in the ground plane has been implemented for resonating the structure at the desired frequency and, to get a low cross-polarization over the operating frequency. The compact feed-network of the array is designed using s Wilkinson power-divider. A single element and a 4 × 1 antenna array are designed, prototyped and verified. The antenna array is designed by a single-layer microstrip structure with a compact size of 151.70 × 43.50 mm². According to the experimental results, the single element and the antenna array have S₁₁ of -15.27 dB and -13.95 dB, and RHCP gain of 6.14 dBic and 11.98 dBic, respectively. Moreover, the computed radiation efficiencies of single element and array are 78.17% and 71.50%, respectively, while CP bandwidths of single element and array are 49.00 MHz and 58.00 MHz, respectively. The performance of the proposed RHCP antenna is suitable for the DSRC-band application.

In this paper, a new miniaturized switchable band microstrip patch antenna array using PIN-diode is presented for WLAN/WiMax applications. In the first stage DGS has been employed to miniaturize a dual band microstrip patch antenna array simultaneously resonating at 2.2 GHz and 3.8 GHz. Further in second stage RF PIN-diodes has been used to achieve the frequency reconfigurability to serve for different communication systems. The designs are verified through both simulation and measurement of fabricated prototype. The measured results were in good agreement with simulated results.

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a multi-layer dielectric material using a Ku-band rectangular waveguide WR62. The S_ij-parameters at the reference planes in the rectangular waveguide loaded by a multi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the two dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated S_ij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer and one tri-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from multi-layer measurements and mono-layer measurements is presented.

In order to research the temperature distribution of a hybrid excitation double stator bearingless switched reluctance motor (HEDSBSRM), the finite element method (FEM) is used to conduct thermal modeling and analysis. First, 2D FEM is used to calculate the losses of the motor, including the core losses and copper losses of the windings. Then, in the thermal analysis module of ANSYS Workbench software, losses are used for calculation and analysis as the thermal load. Furthermore, in order to enhance the accuracy of modeling, this paper also considers the equivalent thermal conductivity of each part of the motor, and the equivalent insulation of the windings and surface convection heat transfer coefficient are also considered. Finally, the simulation results of motor temperature field distribution are analyzed and studied in detail. The thermal characteristic is also of guiding significance to the optimal design of the motor.