Nowadays, through wall imaging (TWI) is a emerging topic of research in which one of the most important tasks is to minimize the clutter through which detection accuracy can be improved. Clutter in TWI is due to many reasons like wall coupling, antenna coupling, multiple reflections etc. To analyze the clutter reduction techniques, firstly we indigenously assembled a TWI system (i.e. step frequency continuous wave radar (SFCW)) in UWB range (freq. 3.95 GHz to 5.85 GHz), and different observations have been taken. We have considered metallic plate and one more material with low dielectric constant (Teflon) as a target and kept them behind the plywood wall. A-scan and B-scan observations have been carried out. The observed data are preprocessed for imaging and then different types of clutter reduction techniques like Principal Component Analysis (PCA), Independent Component Analysis (ICA), Factor Analysis (FA) and Singular Value Decomposition (SVD) have been applied, and results were analyzed. Signal to noise ratio (SNR) of the final images (i.e., after clutter removal with different techniques) has been computed to compare the results and know the effectiveness of individual clutter removal techniques. It is observed that ICA has better capability to remove the clutter in comparison to other applied techniques; especially it is found that ICA has a capability to distinguish the difference between clutter and low dielectric target whereas other clutter removal techniques are not showing significant result.

A compact, ultra-broadband coplanar-waveguide (CPW) bandpass filter (BPF) is demonstrated. The proposed CPW-BPF is essentially designed by exploiting CPW short-stub and open-stub structures. Technically, the proposed filter comprises shunt short-stub and series open-stub structures that are connected in a cascade topology. The higher and lower cutoff frequencies are mainly related to the electrical length of the shunt short stub and the series open stub, respectively. In addition, the stopband rejection is enhanced through an incorporation of CPW bandstop structures. The proposed filter design is verified through experimental demonstration. The corresponding lumped equivalent and transmission-line equivalent circuits are provided for circuit design purpose. Compared with the classical CPW-BPFs, the proposed filter is of a relatively simple and compact configuration. The demonstrated CPW-BPF has about 110% 3-dB fractional bandwidth, sharp selectivity, and great stopband rejection.

In this paper, Enhanced Practical Swarm Optimization (EPSO) algorithm is proposed to be applied to pattern synthesis of linear arrays. Updating formulas of global best particle position and velocity are modified to improve the convergence accuracy of classical Practical Swarm Optimization. The developed EPSO is tested and compared with a standard benchmark to be validated as an efficient optimization tool for beamforming applications. Different numerical examples are presented to illustrate the capability of EPSO for pattern synthesis with a prescribed wide nulls locations and depths. Collective multiple deep nulls approach and direct weights perturbations approach are considered to obtain adaptive wide null steering subject to peak side lobe level and minimum main beam width constraints. Starting from initial chebyshev pattern, single or multiple wide nulls are achieved by optimum perturbations of elements current amplitude or complex weights to have either symmetric or asymmetric nulls about the main beam. Proper formation of the cost function is presented for all case studies as a key factor to include the pattern constraints in the optimization process.

Ray-tracing exercise and full-wave analysis were performed to validate the performance of a type of cloak composed of isotropic metamaterials. It is shown that objects inside the 'folded region' of this cloak appear invisible to the incoming light from a ray tracing exercise, but exhibit magnified and shifted scattering under a plane wave illumination from a full wave analysis. Gaussian beams are introduced to resolve this interesting paradox resulted from these two methods. We show that at the time-harmonic state, small energy can be diffracted into the folded region and contribute to the resonant state even when the Gaussian beam is steered away from the cloak with an object inside. A scattering pattern identical to that scattered from the image of the object will be formed, which agrees well with the phenomenon in the plane wave incidence case.

A novel fractal tag antenna constructed with Hilbert-curve and self-complementary configuration is proposed for UHF RFID applications. The main aim of this paper is to merge the meander line and meandered-slot structure of the RFID tag antenna in order to obtain a good performance of compact, broadband, circular polarization and conjugate impedance matching. The tunable inductive and broadband (-10 dB BW = 115 MHz) characteristics of frequency responses and directivity (1.62 dBi) as well as circular polarization (-3dB AR BW = 315 MHz) of radiation patterns for 900 MHz are studied and presented.

In this paper, a triple-band printed dipole tag antenna is proposed for Radio Frequency Identification (RFID). The triple-band printed dipole antenna is designed to operate at 0.92 GHz, 2.45 GHz and 5.8 GHz using Computer Simulation Technology (CST) software. In order to achieve triple-band operation, the proposed antenna contains two branch elements, which act as an additional resonator. The designed antenna is fabricated using Taconic RF-35 substrate with a dielectric constant (ε_r) of 3.5 and thickness (d) of 0.508 mm. The antenna's parameters for triple-band operation are investigated and discussed. Then, this fabricated antenna is integrated with a UHF microchip to become a passive UHF tag. This tag is tested by measuring the reading distance and it is found that the proposed tag can be used for RFID application.

In this paper, a new kind of 3D transition and power divider based on half mode substrate integrated circular cavity (HSICC) is proposed. This novel HSICC transition and power divider can be easily integrated into microwave and millimeter-wave multilayer circuits using LTCC technology. What is more, it can reduce nearly half size of normal SICC resonator and has the advantages of high flexibility, low insertion loss and amplitude imbalance. Two different 3D simulation tools are employed to validate the design method of this novel structure.

The passing center swing back grids (PCSBG) technique, in conjunction with the method of characteristics (MOC), was proposed to model electromagnetic problems featured with rotating objects. The drive of this proposal lays mainly on the fact that MOC defines all field components in the center of grid cell. Its practicability was validated by exhibiting the radiated EM fields from a rotating cylinder which carries surface currents with Gaussian profile and flowing in the axial direction. To clearly demonstrate that the cylinder is rotating and radiating EM fields simultaneously, the following arrangements were made. The cylinder may be equally sliced into an even number of segments that are with and without currents alternatively since a rotating circular cylinder yields no relativistic effects. The computational results showed that the radiated electromagnetic fields bear vortex structures as the cause of rotating cylinder, which serves as the evidences that PCSBG works properly.

μThe surface wave modes in the chiral negative refraction grounded slab waveguides in which the slab or cladding consists of chiral negative refraction metamaterial are investigated. The dispersion relations, electromagnetic fields, energy flow distribution and the total power of surface wave modes are presented. Some novel features have been found. The energy flow of surface wave mode is in opposite directions in the core and cladding. The total power is negative (corresponds to backward wave) in the grounded chiral negative refraction metamaterial slab waveguides.

A two-port antenna with high isolation for digital television system (DTV), global system for mobile communication (GSM), and universal mobile telecommunications system (UMTS) indoor applications is presented. The antenna consits of a disk loaded sleeve monopole antenna and an inverted-L plate antenna, which are combined into one radiation structure. In addition, by using a choke tube and C-shaped slot inserted into the plate, the isolation between the two ports is impoved. A prototype is constructed and tested. The simulated and meseasued results are given.

This paper presents a radio wave propagation prediction method for low-rise buildings using 2-D aerial images taken from actual areas. The prediction procedure was done in three steps. Firstly, the images were classified in order to identify the objects by Color Temperature Properties with Maximum Likelihood Algorithm (CTP_MLA). The objects in the images consist of buildings, trees, roads, water and plain. These objects influence wave propagation highly. The MLA classification is a common supervised image segmentation technique in remote sensing domain. However it still needs human editing in case of classification errors. Secondly, the appropriate path loss models were selected to predict path loss. The original Xia path loss model was modified to include the effects of airy buildings and vegetation around the buildings. Finally, preliminary tests provide a better solution compared with measured path losses with the root mean square error (RMSE) and maximum relative error (MRE) of 3.47 and 0.16, respectively. Therefore, the positions for micro-cell base stations could be designed on a 2-D aerial map.

A new method called Expanded Cholesky Method (ECM) is proposed in this paper. The method can be used to decompose sparse symmetric non-positive-definite finite element (FEM) matrices. There are some advantages of the ECM, such as low storage, simplicity and easy parallelization. Based on the method, multifrontal (MF) algorithm is applied in non-positive-definite FEM computation. Numerical results show that the hybrid ECM/MF algorithm is stable and effective. In comparison with Generalized Minimal Residual Method (GMRES) in FEM electromagnetic computation, hybrid ECM/MF technology has distinct advantages in precision. The proposed method can be used to calculate a class of non-positive-definite electromagnetic problems.

The potential to implement microwave filters with special properties, by loading a waveguide with artificial Single Negative (SNG) or Double negative (DNG) materials was investigated. The SNG or DNG medium was structured with dielectric spherical particles of high permittivity embedded in a dielectric material of much smaller permittivity. Numerical analysis of the frequency response of the waveguide loaded with slabs of this type of composite dielectrics reveals that filtering performance, with attributes like very sharp attenuation at the bounds of frequency pass or stop band can be obtained. The central frequency as well as the bandwidth of the filtering can be controlled via the size and the dielectric constants of the particles, the dielectric constant of the hosting material and the size of the slab.

In this paper, a novel view of a switched reluctance motor under dynamic eccentricity fault to provide the precise and reliable electromagnetics model is presented. It describes the performance characteristics and comparison results of the 6/4 switched reluctance motor with dynamic rotor eccentricity utilizing three-dimensional finite element analysis. The results obtained using three-dimensional finite element analysis of the switched reluctance motor includes flux-linkages, terminal inductance per phase, mutual inductances and static torque for various eccentric motor conditions. In this analysis the end effects and axial fringing fields for simulating reliable model are obtained and presented. The paper continues with comparing these results with the ones obtained for the same motor profile but utilizing two-dimensional finite element method. Finally, Fourier analysis is carried out to study the variations of torque harmonics.

This paper proposes a hybrid methodology that combines an extended form of Finite-Deference Time-Domain (FDTD) method with Time Domain Physical Optics (TDPO) for analysis of 3-D scattering of combinative objects in complex electromagnetic compatibility (EMC) problems. Establishing a covariant formulation for FDTD, the extended algorithm introduces a parametric topology of accurate nonstandard schemes for the non-orthogonal div-curl problem and the suppression of lattice dispersion. For complex-combined objects including a small size (SS) and large size (LS) parts, using TDPO is an appropriate approach for coupling between two regions. Thus our technique solves the EMC complexity with the help of higher order FDTD (HOFDTD) and the combinatory structures by using of the TDPO. Numerical validation confirms the superiority of the proposed algorithm via realistic EMC applications.

A new microwave method based on calibration-independent measurements has been proposed for non-ambiguous complex permittivity determination of liquid materials. We have derived a function in terms of the first-reflection coefficient of the sample using raw complex scattering parameter measurements of three measurement configurations. We have verified the proposed method from measurements of two liquid test samples with the available reference data in the literature.

This paper presents a multiband slot antenna with modifying fractal geometry fed by coplanar waveguide (CPW) transmission line. The presented antenna has been designed by modifying an inner fractal patch of the antenna to operate at multiple resonant frequencies, which effectively supports the digital communication system (DCS 1.71-1.88 GHz), worldwide interoperability for microwave access (WiMAX 3.30 - 3.80 GHz), IMT advanced system or forth generation mobile communication system (3.40-4.2 GHz), and wireless local area network (WLAN 5.15 - 5.35 GHz). Manifestly, it has been found that the radiation patterns of the presented antenna are still similarly to the bidirectional radiation pattern at all operating frequencies. The properties of the antennas, for instance, return losses, radiation patterns and gain are determined via numerical simulation and measurement.

Due to the special structure of current carrying planar spiral coils, precise calculation of the forces between them is complicated and time-consuming. To overcome these problems, in this paper a new and fast method is proposed for calculation of the magnetic forces between planar spiral coils. The advantage of the proposed method is that just by having the external dimension of coils and their number of turns, the force between them at different distances and with different currents can be calculated. The results obtained by direct and proposed calculation methods show the efficiency of the latter in simplicity and calculation time. The precision of the proposed method has been confirmed by experimental tests done on constructed coils.

We are developing prototype free electron maser (FEM) that is compact, tuneable and efficient for potential industrial use. Therefore we define the characteristics for the construction of a novel X-band rectangular waveguide pre-bunched free electron maser (PFEM). Our device operates at 10 GHz and employs two rectangular waveguide cavities (one for velocity modulation and the other for energy extraction). The electron beam used in this experiment is produced by thermionic electron gun which can operate at 3 kV and up to 5 mA. The resonant cavity consists of a thin gap section of height 1.5 mm which reduces the beam energy required for beam wave interaction. The prototype design, engineering and construction process are reported in this paper.

In this paper, a time stepping two-dimensional FEM is performed for modeling and analysis of a IM with insulation failure inter-turn fault. FEM analysis is used for magnetic field calculation and the magnetic flux density and vector potential of machine is obtained for healthy and faulty cases. Comparing the magnetic flux distribution of healthy and faulty machines helps to detect the influence of turn fault. The machine parameters (self and mutual inductances) are obtained for IM with inter-turn fault. Finally, the FEM machine model is used for studying the machine under different fault condition. Study results including phases and fault currents express the behavior of machine with inter-turn faults. The symmetrical current components of IM with different fault severity are obtained by FE study and studied. The machine torque in healthy and faulty condition is also obtained and compared. The torque vibration increase upon to degree of fault.