A new method of electrodynamic analysis of gyrotropic (isotropic and anisotropic) media is developed. This method is based on the scalar representation of Maxwell's equations corresponding to 4×4- matrix formulation and coupling equations for gyrotropic medium in the Drude's form. It is utilized by solving the wave equations of second and fourth order, followed by cross-linking the fields at the boundary. The obtained results are experimentally verified by their good matching with the popular benchmark data, such as quartz rotatory power and in comparison with a known standard parameter of an optical element, such as λ/4-plate. This method simply summarizes the polarimetric and ellipsometric calculations.

A novel ultra-wideband (UWB) coupled-line coupler with an operating frequency band from 2 to 22 GHz is presented in this article. The proposed coupler is composed of six coupled-line sections. The continuous zigzag capacitive compensation (CZCC) technology is used to broaden the operation frequency band, which also significantly enhances the isolation and return losses of the coupler. The coupler is built on a multilayer circuit structure. In order to improve the design accuracy of the three-dimensional circuit structure, the combination simulation of EM simulator and circuit simulator are employed. The simulated and measured results of the UWB 10 dB asymmetric directional coupler are presented and discussed, which demonstrate that it is practical to achieve good performances in such a circuit structure.

Two novel microstrip MIMO antennas have been proposed and presented in this paper. The objective is to design a compact and dual-broadband MIMO antenna module appropriate for many wireless devices including WLAN, LTE and WiMax. The presented MIMO antennas have been analyzed, designed, simulated and investigated using CST_MW simulator. They have been fabricated (FR-4 substrate), and their scattering matrices and total efficiencies have been measured. The first MIMO antenna module is composed of four proposed broadband microstrip antennas arranged in two MIMO antenna pairs. The first MIMO pair resonates at 5.2 GHz (5.08-5.313 GHz) while the second pair resonates at 5.8 GHz (5.643-5.96 GHz). This MIMO antenna has a compact size of 40x40 mm², dual-broadband, minimum mutual coupling below -25 dB, bandwidth greater than 225 MHz and gain of 3.8 dBi. The second MIMO antenna module consists of two proposed and modified dual-broadband microstrip monopole antennas, where, each has a dual resonance at 3.7 GHz (3.46-3.94 GHz) and 5.2 GHz (4.99-5.41 GHz). This MIMO antenna has an overall compact size of 20x50 mm², minimum coupling below -22 dB, bandwidth greater than 425 MHz and gain of 2.5 dBi. Good agreement has been achieved between measured and simulated results. The proposed MIMO antennas cover many wireless applications with the following specifications: compact size, dual-broadband, moderate gain, good efficiency and high port-to-port isolation.

A broadband circularly polarized planar antenna based on a quarter-mode substrate integrated cylindrical cavity subarray is presented in this communication. It is composed of two layers: a quarter-mode substrate integrated cylindrical Cavity (QMSICC) subarray and the feeding network comprised of three Wilkinson power dividers. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 5.2 GHz are 40% and 25.5%, respectively. The gain measured for right-hand circular polarization (RHCP) is 4.6 dBi at 5.2 GHz. And it will be used in WLAN operating at 5.2 GHz.

A novel microstrip tri-band bandpass filter is proposed and implemented using hybrid resonator with independently controllable center frequencies and good in-between isolation. This hybrid resonator is constructed by a stepped-impedance stub resonator and a single end shorted resonator. The stepped-impedance stub resonators are applied to achieve the first and second passband, while the third passband is implemented by single end shorted resonators. By applying the even-odd mode approach, the resonance frequency ratio between even mode and odd mode inside the stepped-impedance stub resonators is attained. Furthermore, the filter with multi-path coupling structure can generate the transmission zeros at the edge of the passband, which can effectively improve the filter passband selectivity. Finally, a tri-band filter operating at 1.91, 2.73, and 3.45 GHz is designed and fabricated. The measurement results accord well with the full-wave electromagnetic designed responses.

Underestimation of path loss when planning the deployment of 802.11n APs can lead to coverage gaps and user dissatisfaction. The use of Free Space Path Loss modelling can sometimes lead to underestimation of path loss in urban environments when the effect of small scale fading is not considered. A field experiment was conducted with the aim to investigate the applicability of the ITU-R P.1141-7 Recommendation in path loss estimation of 802.11n signals in an urban environment in Malaysia. The results showed that Section 4.3 of ITU-R P.1411-7 can estimate the path loss of 802.11n signals with very low error margins of between 0 dB and 5 dB for transmitter receiver distances of 50 m and more. At these distances, the average difference of path loss estimation between FSPL and measured path loss is approximately 18 dB. The study concludes that 802.11n APs may need to be placed at closer proximities than previously assumed if FSPL is used to model the path loss. This is to ensure that targeted traffic is actually offloaded; coverage gaps are reduced; user satisfaction is improved.

A novel four-element multiple input multiple output (MIMO) antenna system for LTE 2300 and 2.45 GHz ISM applications is presented. The total size of the proposed MIMO antenna system is 34 mm×18 mm, and the whole antenna system has a wide working bandwidth of 350 MHz (2.19-2.54 GHz). The measured isolation between antenna elements is higher than 15 dB with a close edge-to-edge separation of 0.03λ. Correlation coefficient of the MIMO antenna system is lower than 0.12, which can meet the requirements of 4G wireless systems.

The thermal characteristic of a new out-rotor fault-tolerant permanent-magnet (FTPM) motor is modeled and predicted in this paper. Flow characteristics and thermal characteristics of this FTPM motor are calculated by using computational fluid dynamics method. The key is that an equivalent model is developed to replace the real motor, offering the merits of simplified meshing progress and convenient thermal calculation. Furthermore, the effectiveness of the developed equivalent model has been verified by simulation and experiment. In addition, the temperature distribution of the entire motor is given by using equivalent models. The results can be provided to improve motor thermal performance.

This paper is a continuation of our previous published work in which a water-loaded metal diagonal horn antenna has been designed at 2450 MHz for hyperthermia application and simulated results are compared with those measured. In the present study, theoretical investigations of Specific Absorption Rate (SAR) distribution in a homogeneous biological phantom (muscle) due to direct contact water-loaded metal diagonal horn antenna at 915 and 2450 MHz for hyperthermia application is presented. It is estimated theoretically that, at both the operating frequencies, a reasonable impedance matching is achieved at the interface between the antenna aperture and the biological phantom, where a computation of aperture admittance and reflection coefficient has been performed. Furthermore, it is confirmed through theoretical and simulation studies that the proposed horn antenna gives circularly symmetric SAR distribution in transverse plane in the biological phantom at 915 and 2450 MHz. The simulated and theoretical SAR distributions at 2450 MHz are compared with those determined at 915 MHz. In addition, thermal simulation results based on Pennes' Bio-heat equation (BHE) are applied to the realistic muscle model at 915 and 2450 MHz. The reduction of blood flow rate on temperature distribution is also studied.

A method to design a miniaturized two-element quasi-Yagi antenna (QYA) with size and gain requirements is presented for portable ultra high frequency (UHF) radio frequency identification (RFID) reader applications. The antenna consists of a driver dipole and a ground reflector, and these elements are serially connected with a coplanar strip line. The ends of both elements are folded back toward each other to reduce the lateral size of the antenna. A detailed design procedure of the proposed antenna is explained, along with a performance comparison for the input impedance, voltage standing wave ratio (VSWR), broadside gain, front-to-back (F/B) ratio, and total efficiency. A prototype antenna, covering the 860―960 MHz UHF RFID band with a gain > 4 dBi, is fabricated on an FR4 substrate with dimensions limited to 90 mm by 90 mm. The total width of the proposed antenna is reduced by approximately 41% compared to the conventional QYA without miniaturization, and an F/B ratio is improved by 1―8 dB in the band. Experiment results show that the proposed antenna has the desired impedance characteristics with a frequency band of 853―1,098 MHz for a VSWR < 2, and a stable broadside gain of 4.0―5.3 dBi in the UHF RFID band. Moreover, a measured F/B ratio > 13 dB is obtained.

This paper presents a novel approach for bandwidth enhancement and gain improvement of a microstrip patch antenna array for IEEE 802.16a 5.8 GHz Wi-MAX applications. A split ring resonator (SRR) has been designed to load the microstrip patch antenna array. The unloaded antenna array resonates at 5.8 GHz with gain of 4.3 dBi and bandwidth of 425 MHz, whereas when loaded with split ring resonator the gain approaches to 5.7 dBi and bandwidth increases to 610 MHz which corresponds to bandwidth enhancement of 3%. The electrical dimension of the patch is 0.23λ x 0.3λ.

A more realistic model is developed to predict the specific attenuation when electromagnetic signals propagate through dusty media (dust storms). The model is based on Mie approximation for the scattering of electromagnetic signal by a spherical particle. Variation of the dust particles dimensions is considered in this model. Reliable published values for dust dielectric constant are used for computations over the frequency range from 2 GHz to 100 GHz, (i.e. S-band, X band, K-band, Ka-band, Ku-band and W-band). The model outcome is compared with the results from other models suggested in literature. The effect of air humidity on specific attenuation is also investigated.

An integrated eight-element antenna array has been proposed for ultra-wideband (UWB) applications. It consists of eight UWB antenna elements and an eight-way binary-tree modified Wilkinson power divider. Any two adjacent elements in the array are connected to each other and share a common side, thus leading to a connected antenna array. Moreover, this arrangement can be utilized to avoid grating lobe level at higher frequencies. Each antenna element comprises a square ring patch and is excited by a tapered balun to achieve low cross-polarization levels. In order to validate the design, a prototype has been fabricated and measured. Both simulated and measured results confirm that the proposed integrated antenna array achieves a good performance of a reflection coefficient below -10 dB from 2.9 GHz to 10.8 GHz, including stable radiation patterns with low side lobe and cross-polarization levels, thus the antenna is promising for applications in UWB imaging systems.

This work presents a planar handset antenna having a small size 47×15×0.8mm³ and providing four wide operating bands of at least 698-960, 1710-2690, 3100-3900 and 5150-5850 MHz for the 11-band LTE700/GSM850/900, GSM1800/1900/UMTS/LTE2300/LTE2500, WiMAX 3.5GHz/ 5.4GHz, WLAN 5.8GHz. The multi-broadband antenna consists of Br-1, Br-2, Br-3, C-Strip and Ground plane. The structure is analyzed by S11 and surface current distribution. The simulated and measured results agree well. The gain of the proposed antenna is 1.51-4.12dBi, and the radiation efficiency is about 75%-94%.

Different solution techniques, computational aspects and the ways to improve the performance of 3D frequency dependent Crank Nicolson finite difference time domain (FD-CN-FDTD) method are extensively studied here. FD-CN-FDTD is an implicit unconditionally stable method allowing time discretization beyond the Courant-Friedrichs-Lewy (CFL) limit. For the solution of the method both direct and iterative solver approaches have been studied in detail in terms of computational time, memory requirements and the number of iteration requirements for convergence with different CFL numbers (CFLN). It is found that at higher CFLN more iterations are required to converge resulting in increased number of matrix-vector multiplications. Since matrix-vector multiplications account for the most significant part of the computations their efficient implementation has been studied in order to improve the overall efficiency. Also the scheme has been parallelized in shared memory architecture using OpenMP and the resulted improvement of performance at different CFLN is presented. It is found that better speed-up due to parallelization always comes at higher CFLN implying that the use of FD-CN-FDTD method is more appropriate while parallelized.

Since both metamaterials comprised of artificial molecules (inclusions in a host material) and natural molecular materials at optical and greater frequencies can exhibit significant electric quadrupolarization as well as electric and magnetic dipolarization, we determine the passive, causal electric quadrupolarizability for a spherically symmetric molecule, namely a dielectric sphere subject to source-driven applied fields. For source-driven excitations, it is found that two electric quadrupolarizability constants are generally required to characterize the electric quadrupolar response of the sphere, with one of the constants multiplying the divergence of the applied electric field. For source-free fields, such as the fields of the eigenmodes of an electric quadrupolar array, the local electric field illuminating each inclusion is solenoidal. The constitutive relation is characterized by just one quadrupolarizability constant, and the electric quadrupolarization becomes traceless. It is also found that the electric quadrupolarization becomes very large and effectively traceless near the resonant frequencies of electrically small plasmonic spheres with negative permittivity and for somewhat larger spheres with positive permittivity.

This paper deals with the modeling of bistatic scattering from a randomly rough surface. An advanced integral equation model is presented by giving its general framework of model developments, model expressions, and predictions of bistatic scattering for various surface parameters. Extension work to improve the model accuracy is also reported in more detail. In particular, the transition function for the Fresnel reflection coefficient is in more general form. Model predictions are illustrated, demonstrated, and validated by extensive comparisons with numerical simulations. The updated advanced integral equation model remains a compact algebraic form for single scattering and substantially improves prediction accuracy in bistatic scattering that is drawing more emerging applications in earth remote sensing.

In Geosynchronous earth orbit synthetic aperture radar (GEO SAR) working system, the radar signal travelling through the atmosphere is sensitive to the ionosphere. One of the effects is the Faraday rotation under geomagnetic field, which is similar to the phenomenon when the signal traveling through a ferrite medium. So based on the theoretical inference, we semi-physically simulate Faraday rotation of the ionosphere with that of the ferrite in the ground, which is one of the experiments of the ground railway prototype testing for GEO SAR system. The measurements of a mountain without ionospheric Faraday rotation and under the equivalent Faraday rotation of ionosphere are given experimentally. Imaging studies show that the influence of the ionosphere Faraday rotation on the distributed targets imaging is not visually obvious. Our work provides experimental basis for the GEO SAR to successfully image on the satellite.

So far, several methods to reduce the cogging torque of permanent magnet motors have been introduced. Implementation and evaluation of these methods have usually been done on radial flux types of motors. Nowadays, as axial flux permanent magnet motors have more advantages over radial ones, they are more attractive. Therefore, in this paper analytical modeling and calculation of the most effective method impact in reducing the cogging torque in axial flux permanent magnet motors will be studied. In fact, in this method the radial edges of the magnets will be curved to have a significant impact on reducing this unwanted component. This paper introduces a new concept to model this method. Finally, the accuracy of the proposed method will be verified by finite element analysis.

The performance of wireless communication systems is predominantly dependent on propagation environment and respective radiating antennas. Due to the shorter wavelength at Millimeter Wave (MmW) frequencies, the propagation loss through the objects in indoor environments is typically very high. To improve the channel capacity and to reduce inter-user interference, a high gain directional antenna is desired at MmW frequencies. Traditional antennas used in MmW devices are not suitable for low-cost commercial devices due to their heavy, bulky and expensive configurations. This paper focuses on design and development of a very compact (44.61 mm x 9.93 mm x 0.381 mm) high gain Antipodal Linear Tapered Slot Antenna (ALTSA) utilizing Substrate Integrated Waveguide (SIW) technology at 60 GHz. Received signal strength (RSS), path loss (PL) and capacity are studied for MmW based wireless applications utilizing ALTSA with Radio Frequency (RF) measurement equipment in narrow hallway environment.