The advantages and disadvantages of more extended approximated analytical methods of the integral equations solution for the current in thin perfectly conducting and impedance vibrators have been investigated in details in this paper. The solutions of the problem about the electromagnetic waves scattering by the thin vibrators with the distributed surface impedance, obtained with the help of the method of expansion of the searched function for the current in a series on small parameter. The method of consistent iterations and asymptotic averaging method are given. The comparison of the calculated results with the experimental data in the case of excitation of the vi-brator in the centre by the point source of voltage is represented.

Central force optimization (CFO) is a new simple deterministic multi-dimensional search evolutionary algorithm (EA) inspired by gravitational kinematics. This paper evaluates CFO's performance and provides further examples on its effectiveness. A new scheme, the acceleration clipping, is introduced, which enhances CFO's global search ability while maintaining its simplicity. The improved CFO algorithm is applied to the optimal design of two different wideband microstrip patch antennas. Specifically, a microstrip line fed E-shaped patch antenna and a coaxial line fed double-E-shaped patch antenna are designed and optimized using the CFO method. CFO's performance on these antennas is compared to that of the differential evolution (DE) optimization. Both the CFO and DE methods are interfaced with the full-wave IE3D software. It is found that the CFO results are very close to those obtained using the DE technique.

Monopulse antennas form an important methodology of realizing tracking radar. They are based on the simultaneous comparison of sum and difference signals to compute the angle-error and to steer the antenna patterns in the direction of the target (i.e., the boresight direction). In this study, we consider the synthesis problem of difference patterns of monopulse antennas in the framework of Multi-objective Optimization (MO). The synthesis problem is recast as an MO problem (for the first time, to the best of our knowledge), where the Maximum Side-Lobe Level (MSLL) and Beam Width (BW) of principal lobe are taken as the two objectives to be minimized simultaneously. The approximated Pareto Fronts (PFs) are obtained for different number of elements and sub-arrays using a recently developed and very competitive Multi-Objective Evolutionary Algorithm (MOEA) called MOEA/D-DE that uses a decomposition approach for converting the problem of approximation of the PF into a number of single objective optimization problems. This algorithm employs Differential Evolution (DE), one of the most powerful real parameter optimizers in current use, as the search method. The quality of solutions obtained is compared with the help of the trade-off graphs (plots of the approximated PF) generated by MOEA/D-DE on the basis of the two objectives to investigate the dependence of the number of array-elements and the number of sub-arrays on the final solution. Then we find the best compromise solutions for 20 element arrays and compare the results with standard single-objective algorithms such as the Differential Evolution (DE) and Particle Swarm Optimization (PSO) and hybrid techniques like Hybrid Contiguous Partition Method (HCPM) that has been reported in literature so far for the synthesis problem. Our experimental results indicate the MOEA/D-DE yields much better final results as compared to the standard single-objective and hybrid approaches over all the test cases covered here.

The effect of optical radiation on a uniformly doped nanoscale FinFET considering quantum mechanical effects has been theoretically examined and analyzed. The device characteristics are obtained from the self-consistent solution of 3D Poisson-Schrödinger equation using interpolating wavelet method. To our best knowledge this is the first approach for the self-consistent solution to surface potential computations of nanoscale FinFET photodetector using interpolating wavelets. This method provides more accurate results by dynamically adjusting the computational mesh and scales the CPU time linearly with the number of mesh points using polynomial interpolation, hence reducing the numerical cost. A fine mesh can be used in domains where the unknown quantities are varying rapidly and a coarse mesh can be used where the unknowns are varying slowly. The results obtained for dark and illuminated conditions are used to examine the performance of the device for its suitable use as a photodetector.

This paper presents a novel bulk acoustic wave stacked crystal filter (SCF) configuration that improves the inherent narrow bandwidth of this kind of devices and increases their selectivity by means of the allocating of transmission zeros. A set of parallel connected SCFs with their resonant frequencies split along the passband achieves the bandwidth improvement. The SCF detuning is carried out by the thickness of its middle metallic electrode. The filter response covers the 60 MHz bandwidth of a W-CDMA RF application working at 2.14 GHz. The use of SCFs considerably simplifies the layer stack configuration in contrast to other acoustically coupled structures as coupled resonator filters.

In this paper, we propose a method to reduce the length of the narrowband microstrip Uniform Coupled Transmission Lines (UCTLs), which has a general application to compact microstrip circuits. In this method, we use Nonuniform Coupled Transmission Lines (NCTLs) instead of UCTLs. To synthesize the desired NCTLs, their normalized width and gap are expanded as two truncated Fourier series. Then, the optimal values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed method is verified using some examples. Also, an edged-coupled bandpass filter is compacted using the proposed method and then is fabricated and measured.

In this paper, a fast and efficient method has been proposed to analyze the electromagnetic shielding rooms with electrical large sizes and arbitrary shapes. The ray-tracing method is used to predict the Shielding Effectiveness (SE) of the electromagnetic shielding rooms. The proposed method is based on speeding up the ray tracing algorithm. The performance of the proposed method is verified by a comprehensive example. The effect of additional metal cabinet in the shielding effectiveness of shielding room has been investigated. Also the position of it has been found optimally to produce a ``best" performance for the shielding room.

Novel and computationally e±cient method for optimization of microwave structures is presented. The technique is based on the adjustments of the design specifications and exploits the coarse model --- computationally cheap representation of the structure being optimized, e.g., equivalent circuit. It is demonstrated that the proposed approach allows rapid design improvement while being simple to implement. Limitations and modifications of the technique are also discussed.

In this work we consider the problem of obtaining a capacitive image by scanning a "one-dimensional" surface of a closed conductor of arbitrary geometry. To solve our problem we propose a novel integral numerical method. The method is applied to different geometries by considering deterministic surfaces as complex as those with a fractal structure and random rough surfaces with Gaussian statistics. We find that the images obtained by simulating a prototype of a capacitive microscope, strongly depend on the interaction between the object and the probe. Despite this interaction, important information can be obtained regarding the statistical properties of the random roughness of the object surface.

A novel compact planar antenna with a frequency band-filter characteristic for UWB applications is proposed and investigated. Having a dual-Y-shaped slot on the patch, a frequency-notched characteristic at 5.2 GHz is obtained. The band-notched mechanism of the designed antenna is implemented and experimentally studied.The designed antenna satisfies the voltage standing wave ratio (VSWR) requirement of less than 2.0 in the frequency band between 2.8 and 18.6 GHz while showing the band rejection performance in the frequency band from 5.0 to 5.6 GHz. This technique is suitable for creating ultra-wideband (UWB) antenna with narrow frequency-notched characteristics.

Aiming at the bandwidth enhancement for patch antennas, a new impedance matching scheme is presented. In this design, open-ended microstrip-lines are used as the matching resonators; the gaps between the lines are used as the J inverters. Numerical and experimental studies are executed to demonstrate this new structure. The measured and predicted results are in good agreement. The measured data show that the bandwidth of a sample antenna is increased by a factor of 3.3 after adding two matching resonators. The proposed matching structure is good in performance, and smaller in size than traditional matching structures.

Partial dischagre is the precursor of insulators breakdown. In this work the propagation of electromagnetic radiation emitted from partial discharge in high voltage insulating materials is investigated. Three common dielectric materials used in power industry: polymer, epoxy resin and ceramics are studied. The results obtained are envisaged to support the development of appropriate sensors for partial discharge detection. The radiation pattern is dependent on a multitude of parameters. Among these, the intensity distribution of the source as well as the dielectric material and its geometry are the main parameters. Significant differences in the radiation spectra are obtained for insulators made of ceramic material compare to non-ceramic insulators.

A microstrip dual-mode dual-band bandpass filter using stepped impedance resonators (SIRs) is designed for dual-band wireless local area network (WLAN) applications at 2.4 and 5.2 GHz. By appropriately selecting the impedance ratio (R_z) and length ratio (α) of the SIRs, the harmonic frequencies can be tuned for generating the dual-bandpass response. Based on SIRs, a dual-mode dual-band bandpass filter is designed with one transmission zero. To improve the selectivity, another three transmission zeros in stopbands be created by introducing two stubs in input/output (I/O) lines. Two experimental filters are fabricated. Both simulated resulted and measured resulted are presented.

Agriculture waste has potential to be used as an alternative material for the microwave absorber used in the anechoic chamber. Compared to the current materials used, such as polystyrene and polyurethane, agricultural waste has low cost and is environmental friendly. In this paper, rice husks from paddy are used as the material in the pyramidal microwave absorber design, to operate effectively in the frequency range from 1 GHz to 20 GHz. Urea Formaldehyde (UF) and Phenol Formaldehyde (PF) are the resins investigated, and are used to make the rice husk particle board. There are four main stages in designing the rice husk pyramidal microwave absorber. They are fabricating the rice husk particle board, deriving the dielectric constant value of the resin-rice husk mixture particle board, simulating the rice husk pyramidal microwave absorber using CST Microwave Studio software, and analyzing the performance of the rice husk pyramidal microwave absorber. Various parameters that affect the performance of the pyramidal microwave absorber are investigated, such as the dielectric constant of the material used, mixed resin percentages, source-port distance and angles between the signal source and the surface of the pyramidal microwave absorber. The excellent reflection loss results show that the rice husks can be potentially used as the material in a microwave pyramidal absorber.

Hadamard speckle contrast reduction (SCR) is considered to be an effective approach to deal with speckle problems in coherent imaging systems. A Hadamard SCR system is divided into two sub-systems, which implement phase patterns projection and reflected waves imaging respectively. The performances of both sub-systems are discussed with numerical simulations and linked to certain parameters so as to give more insights of this approach. For generality, both optical and millimeter wave imaging systems are discussed. To distinguish from former literature based on Fourier optics, the simulation is implemented via wave optics, which is more physical and more accurate. Moreover, considering the fact that the Hadamard method originates from statistics, the effectiveness of Hadamard SCR is in the first place linked to the texture of the object's surface. Statistical optics is also adopted during qualitative analysis of the results. It is shown that the ratio between the dimension of a resolution cell and the granular size of the object's randomly rough surface is closely linked to the performance of Hadamard SCR. Differences in the roughness model in imaging cases of optical and millimeter waves are discussed, which would help to evaluate the validity of the Hadamard SCR approach in practice. The purpose of this paper is to clarify the misunderstandings of Hadamard SCR in previous literature and to give a guideline to apply this approach.

Millimeter wave High Impedance Surfaces (HIS) based antennas are designed, fabricated, and characterized for high data rate communications at frequencies around 40 GHz. HIS with different finite surface area sizes are used as a ground plane for the microstrip patch antennas to suppress the surface waves. The antenna measurements and full wave electromagnetic simulations demonstrate a wide bandwidth of 12-15% in the frequency range of 38-44 GHz with a high gain of ~6 dB and a very low cross polar contribution better than -20 dB.

A new type of microwave transmission line structure is proposed in order to reduce the crosstalk between transmission line circuits. In this structure, the edge of the metal strip line is periodically corrugated with subwavelength grooves of appropriate geometric parameters, and thus the transmission lines can support highly localized spoof surface plasmon polaritons (SPPs) at microwave frequencies. The theoretical simulation shows that the crosstalk between such a transmission line and a conventional strip line is very low at microwave frequencies, and this is further verified experimentally. This type of transmission line structures has great potential applications in high speed circuit systems.

This paper presents a six-section multi-layer asymmetric 10 dB directional coupler based on offset broadside coupled striplines, using Low Temperature Co-fired Ceramic (LTCC) technology, which operates over a decade bandwidth from 1.8 to 18 GHz. It features high performance transitions between the external signal layer and the buried signal layers, as well as a novel mixed first section to solve the limitations of the coupler access bends. A prototype was manufactured that exhibits a return loss of better than 15 dB, isolation of better than 23 dB and a high coupling accuracy of 10.3±0.6 dB over the 1.8-18 GHz band. This design outperforms previously reported results in terms of bandwidth and shows excellent potential for microwave measurement applications.

The goal of this paper is to use polymer-based materials (instead of hard ceramics) in fabrication of dielectric resonator antennas at millimeter-wave frequencies. The soft nature of polymers facilitates machining of antennas, while the low permittivity of polymers naturally enhances the bandwidth. More importantly, advantageous properties (e.g., flexibility and photosensitivity) of some polymers introduce special capabilities which can not be achieved by ceramics. A photosensitive polymer is utilized in this paper to fabricate polymer-based resonator antennas. As a result, deep X-ray lithography is enabled to produce high quality antenna structures. The proposed dielectric resonator antennas which inherently have very low relative permittivity (usually in a range from 3 to 5) are excited effectively using a slotcoupled feeding method and analyzed in both the frequency and time domains. Impedance and radiation properties are compared with higher permittivity ceramic antennas. Impedance bandwidths up to 32 percent are measured and stable radiation patterns with low cross polarization levels over the entire bandwidth are achieved for the prototype antenna. This method enables lithography-based batch fabrication of structures with fine features and complex geometries.

A novel hybrid adaptive iterative physical optics-method of moments (AIPO-MoM) technique is presented for the electromagnetic analysis of jet engine structures that are both electrically large and complex in both stationary and dynamic cases. In this technique, the AIPO method is used to analyze the smooth inlet region, and the MoM method is used to analyze the electrically complex compressor region, including blades and a hub. It is efficient and accurate by virtue of combining the respective merits of both methods. In the dynamic case, a concept for modified impedance equation is proposed to reduce computational load. Numerical results are presented and verified through comparison with Mode-FDTD and measured and commercial simulation packages results.