In this paper, a dual-band circularly polarized (CP) patch antenna with left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the higher band is proposed. On the basis of aperture coupled feed, the dual-band circular polarizations are achieved by adopting two rectangular patches with different rotation angles on the front and back of a substrate. A good agreement between the simulated and measured results is obtained. The 10-dB impedance bandwidths and 3 dB Axial Ratio (AR) bandwidths are 18.4% (1.93-2.32 GHz) and 3.2% (2.14-2.21 GHz) in the lower band and 12.4% (2.58-2.92 GHz) and 1.7% (2.84-2.89 GHz) in the higher band, respectively. The proposed antenna with its simple structure, compact size and excellent performanceprovides a reference forcommunication system applications.

This paper presents a method for improving Angle-of-Arrival estimation accuracy in multipath environments using a sliding antenna array consisting of only two antennas. The proposed method is then experimentally validated by means of a dual channel Software-Defined Radio receiver and a wireless microphone.

We present an extremely sub-wavelength negative index metamaterial structure operating at radio frequency. The unit cell of the metamaterial consists of planar spiral and meandering wire structures separated by dielectric substrate. The ratio of the free space wavelength to unit cell size in the propagation direction is record breaking 1733 around the resonance frequency. The proposed metamaterial also possesses the most extreme refractive index of -109 that has been recorded to date. Underlying magnetic and electric response originate from the spiral and meandering wire, respectively. We show that the meandering wire is the key element to improve the transparency of the negative index metamaterial.

A scheme for efficiently solving the nonlinear electromagnetic inverse scattering problem on sparse investigation domains is described. The proposed scheme reconstructs the (complex) dielectric permittivity of an investigation domain from fields measured away from the domain itself. Least-squares data misfit between the computed scattered fields, which are expressed as a nonlinear function of the permittivity, and the measured fields is constrained by the L₀/L₁-norm of the solution. The resulting minimization problem is solved using nonlinear Landweber iterations, where at each iteration a thresholding function is applied to enforce the sparseness-promoting L₀/L₁-norm constraint. The thresholded nonlinear Landweber iterations are applied to several two-dimensional problems, where the ``measured'' fields are synthetically generated or obtained from actual experiments. These numerical experiments demonstrate the accuracy, efficiency, and applicability of the proposed scheme in reconstructing sparse profiles with high permittivity values.

This paper proposes a double negative metamaterial surface as a superstrate for a multilayer cylindrical dielectric resonator antenna (MCDRA). The aim is to achieve a broadband and high gain Electromagnetic Band Gap (EBG) antenna that can be used in harsh propagation areas to satisfy all the requirements for the 60 GHz wireless communications offering a bandwidth of 7 GHz in the unlicensed ISM band (57−65 GHz), permitting to reach data rates of 10 Gbit/s and more. To meet these objectives various techniques are combined. Numerical and experimental results showed satisfactory performances with achievable impedance bandwidth of more than 10.5% (from 58.1 to 64.2 GHz) and a 18 dBi gain, an enhancement of 13 dBi compared to a homogenous DRA without metamaterial superstrate. The proposed antenna exhibits directive and stable radiation pattern in the entire operating band.

Extracting instantaneous frequency (IF) of Micro-Doppler (M-D) is the key to estimating Micro-motion parameters. In this paper, firstly, the micro-motion model of the coning was set up. Meanwhile, the theoretical analysis and derivation of the micro-Doppler were performed. Then we introduced occlusion effect and Time Frequency transform to better accord with the complexity and reality of feature extraction of Micro-Doppler in the real world. Besides other computational complex separation methods, we extended the Viterbi algorithm for some cases and proposed two novel means, selecting local maximum value and extracting central position, to solve the dilemma which unable the Viterbi algorithm. Finally corresponding simulation correct the performance of the two methods in different Signal to Noise Ratio (SNR).The simulation analysis showed that the methods were effective if time-frequency map was not polluted seriously by noise.

Perfectly Matched Layer (PML) is modeled by Split-Field FDTD (SF-FDTD) in order to simulate Radar Cross Section (RCS) of a plasma slab. PML is used as an absorbing boundary, and discrete plane wave (DPW) is employed to generate plane wave. DPW method has a power isolation of -300 dB between scattered-field and total-field regions. The dispersive media is modelled by shift-operator FDTD. In this article, the SO-FDTD and DPW are combined, and it is proved that this combination shows a good stability. Finally, two different plasma profiles (exponential and polynomial) are used to prove reflection coefficient of a conductive layer can be reduced by choosing true profile of covering layer. By using Near-to-Far-Field Transformation, all fields are transferred to far-field region to calculate RCS.

In this paper, a novel wideband single-feed circularly polarized patch antenna is presented. The antenna consists of an L-shaped probe, four parasitic patches perpendicular to the probe, and a planar reflector. By modifying the structure of the patches, two orthogonal radiation modes are created to realize the circular polarization in the broadside direction. This antenna exhibits a wide impedance bandwidth of 82.4% from 2 GHz to 4.8 GHz for the voltage standing wave ratio (VSWR) ≤ 2 and a 3-dB axial ratio (AR) bandwidth of 56.2% from 2.11 GHz to 3.77 GHz, over which the antenna gains vary from 5.7 dBic to 9.7 dBic. The measured results agree well with the simulated ones.

Covariance matrix adaptation evolutionary strategy algorithm is applied to optimize a dielectric loaded microstrip patch antenna. The optimization process performance is enhanced by not considering the symmetrical factor of the antenna structure. The antenna is optimized to work for IEEE 802.11a WLAN 5-6 GHz band. Experimental measurements have also been performed to validate the performance of the proposed antenna.

This paper presents an analytical solution for capacitance and characteristic impedance of CPW with defected structures (CPW_DS) in signal line. The first category of incomplete elliptic integrals F(φ, k) is employed for calculation, and the capacitance and characteristic impedance of CPW_GS in signal line are first time achieved by the analytical solution. FEM simulation results are used toverify the results of analytical solution,which shows a good agreement. All calculations are completed in software Wolfram Mathematica, and CPW structures are simulated in software HFSS.

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.