The radiation characteristics of dielectric slabs over a transmission waveguide, based on the concept of spoof surface plasmons, are studied in this paper. The proposed structure can be used to control the radiation over a wide band of operation, whilst retaining low Side Lobe Levels (SLLs) and cross-polarization. Leaky modes, broadside radiation and directive beams at fixed angles can all be obtained using various configurations (utilising homogeneous or gradient index dielectric slabs). The proposed antenna design has attractive performance for THz detectors and transmitters.

This paper discusses performance improvement with the integration of an artificial magnetic conductor (AMC) into array antennas. An AMC with defected ground structure (DGS) was designed to construct the AMC ground plane and in-phase superstrate. The two distinguishable structures were integrated into an array antenna, which serves as a reference antenna at 5.8 GHz. The impedance bandwidth (BW) of the reference antenna significantly improved to 287% when integrated with an AMC ground plane and with 37% reduced size. On the other hand, the integration of in-phase superstrate effectively enhances the gain and BW of the reference antenna by 1 dBi and 44%, respectively. The effects of air gaps on the reference antenna with both the AMC ground plane and in-phase superstrate are discussed. The antenna performance factors, such as return loss and radiation pattern, are also discussed for the reference antenna, the reference antenna with the AMC ground plane, and the reference antenna with in-phase superstrate, respectively. There is satisfactorily good agreement between the simulation and measurement results. The proposed antenna is useful in WLAN (5.15-5.35 GHz and 5.725-5.825 GHz) and WiMAX (5.725-5.825 GHz) applications.

The purpose of this paper is to propose analytical and finite element method (FEM) designs of a novel three-phase Seven Layers Switched Reluctance Motor (SLSRM) for the applications which dictated by the performance with the total torque per volume as a key marker indicator. The introduced motor consists of seven magnetically independent stator layers, which each layer includes a set of 4 by4 stator/rotor poles. In this SLSRM, the three layers are energized together to produce high torque and also decrease the torque ripple in comparison with the one layer conventional SRM. Since each layer has its independent phase in the motor, the isolation problem of coils and cooling troublesome existing in conventional SRMs is solved. In addition, these types of SLSRM have some other advantages, like simpler configuration, cooling in easier way, etc. Firstly an analytical design is carried out to illustrate the design procedure and then three-dimensional (3-D) magneto static simulation analysis of the SLSRM and the one layer SRM is performed using 3-D FEM, to obtain and verify the flux-linkage, flux density and torque profiles. Also, the proposed motor is compared with a conventional one layer SRM with a same size and volume.

In this paper, we have addressed three major problems of uniform linear array in case of a sensor failure at any position. We assume that sensor position is known. The problems include increase in sidelobe levels, displacement of nulls and diminishing of null depth. The desired null depth is achieved by making the weight of symmetrical counterpart element passive. Genetic algorithm (GA) along with pattern search (PS) is used for reduction of sidelobe levels, and adjustment of nulls. Fitness function minimizing the error between the desired and estimated beam pattern along with null constraints is used. Simulation results for diversified scenarios have been given to demonstrate the validity and performance of the proposed algorithm.

We propose a methodic approach to design Artificial Magnetic Materials (AMM) with desired magnetic properties. The design procedure is defined based on a novel formulation for characterizing AMMs. The employed formulation expresses the effective permeability and the magnetic loss tangent (MLT) in terms of the geometrical and physical parameters of the inclusions. The method comprised four steps. In the first step, the feasibility of the design is checked through a set of constraints. The second and third steps provide an iterative procedure to capture the desired magnetic properties. Finally, the geometrical elements, i.e., the area and perimeter of inclusions, are calculated. The technique is applied to design of an AMM structure based on Rose curve resonators. The design based on the proposed methodology is verified by the numerical simulation of the AMM.

Space time adaptive processing (STAP) is a signal processing technique for detecting slowly moving targets using airborne radars. The traditional STAP algorithm uses a lot of training cells to estimate the space-time covariance matrix, which occupies large computer memory and is time-consuming. Recently, a number of compressed sensing based STAP algorithms are proposed to detect moving target in strong clutter situation. However, the coherence of the sensing matrix is not low due to the high resolution of the DOA (direction of arrival)-Doppler plane, which does not guarantee a good reconstruction of the sparse vector with large probability. Consequently, the direct estimation of the target amplitude may be unreliable using sparse representation when locating a moving target from the surrounding strong clutter. In this study, a novel method named similar sensing matrix pursuit is proposed to reconstruct the sparse radar scene directly based on the test cell, which reduces the computing complexity efficiently. The proposed method can efficiently cope with the deterministic sensing matrix with high coherence. The proposed method can estimate the weak elements (targets) as well as the prominent elements (clutter) in the DOA-Doppler plane accurately, and distinguish the targets from clutter successfully.

The emission of electromagnetic radiation from charged particles spiraling around magnetic fields is an important effect in astrophysical and laboratory plasmas. In theoretical modeling, issues still not fully resolved are, among others, the inclusion of the recoil force on the relativistic electron motion and the detailed computation of the radiation power spectrum. In this paper, the cyclotron radiation emitted during the nonlinear interaction of relativistic electrons with a plane electromagnetic wave in a uniform magnetic field is examined, by analyzing the radiated power in both time and frequency domain. The dynamics of the instantaneous radiation and the emitted power spectrum from one particle, as well as from monoenergetic electron ensembles (towards a picture of the radiation properties independent of the initial conditions) is thoroughly studied. The analysis is performed for several values of the wave amplitude, focusing near the threshold for the onset of nonlinear chaos, in order to determine the alteration of the radiation in the transition from regular to chaotic motion.

Electronically switchable microwave filters are attracting more attention for research and development because of their importance in increasing the capability of wireless communication and cognitive radios. In this paper, novel switchable microwave band-stop to all pass filters are designed by using stepped impedance resonator. Commercially available Pin diodes are used in order to allow the fastest switching between band-stop and all pass responses. The theoretical analysis is presented in this paper, and its feasibility has been experimentally verified with a micro-strip prototype. The design was also characterized by measuring the filter performance with increasing power levels of 20, 15, 10, 5, and 0 dBm. The results have shown that the switchable filter is immune to power saturation effects. Nonlinear measurements at higher power levels are also performed and the switchable filter produced low power inter-modulation product. The main advantage of this filter is its capability to switch between band-stop and all pass mode of operation. Other advantages include being small in size, and low in cost.

Efficient and compact wireless power transfer (WPT) systems are proposed and designed for recharging small implantable medical devices. They use the magnetic resonance coupling scheme to transfer power over a relatively large distance. The receiver resonator coil and the load loop are designed in correspondence to size restriction of implantable devices. The dimensions of the coils are optimized and effective values of the lumped capacitors are investigated and fine-tuned for efficiency enhancement. Three design configurations of the WPT system, each consisting of two coils at the transmitter and two coils at the receiver, are designed and fabricated. The transfer efficiency is measured over different transmission distances and with different orientation angles of the receiver coils. The measurement results show good agreements with the simulations and illustrate that the proposed WPT systems exhibit nearly omnidirectional radiation performance. Furthermore, the receiver coils are implanted inside of a biological object to show the power can be transferred effectively.

A co-designed compact dual-band filter-antenna suitable to be embedded inside a wireless access point (AP) in the 2.45/5.2-GHz wireless local area network (WLAN) bands is presented. The proposed filter-antenna comprises a loop-loaded dual-band monopole radiator and a microstrip dual-band pseudo-interdigital bandpass filter. The monopole consists of a uniform width monopole, two identical capacitively loaded magnetic resonators and a top loaded loop. The two magnetic resonators are loaded at the center of the monopole for dual-band operation and the rectangular loop loaded at the top is involved for miniaturization. Instead of using the traditional 50Ω interfaces, the impedance between the filter and antenna is optimized to improve the performance. The filter-antenna and the system circuit board of an AP share the same substrate and ground plane. In this case the design can fully integrate the circuit board of the AP into an internal filter-antenna solution. The proposed filter-antenna provides good selectivity and rejection in out of band regions and omni-directional radiation patterns within the two desired bands. The measured results show good agreement with the simulated ones.

Time-reversal (TR) invariance of the wave equation in lossless transmission line (TL) is here introduced as an improvement for fault-detection techniques in wire networks. This new approach is applied to reflectometry in wire diagnosis. To test the efficiency of this method, the reverse time algorithm simulated with FDTD (Finite Difference Time Domain) is developed in a one dimension space. It uses a new signal processing and an adapted signal to the wire under test for diagnosing the fault in the wire. In addition the interest of the convolution product between the incident signal and the output signal from this reverse time method will be also shown and applied in this paper. Through numerical simulations and experimental results measured on coaxial cable, the benefits of this method have been illustrated.

Guided-Mode Resonance (GMR) effects in transparent periodic gratings possess a number of remarkable phenomena. GMRs exhibit strong features in the optical spectrum, i.e. dips, peaks, cusps, and may attain extremely high Q-factors. In some cases resonant reflection with the efficiency equal to unity can be observed. We demonstrate that the introduction of small losses in the structure can drastically modify its optical response by causing strong absorption resonances. Unity reflection in loss-free structures can be almost completely converted into unity absorption peaks as soon as very small losses are introduced. Even thin absorbing films in the structure (or in its vicinity) can lead to such strong resonant absorption effects. The resonances may exhibit a negligible spectral shift, but a significant variation in the magnitude when losses are slightly altered, which is highly attractive for sensor and switch applications. Absorption peaks experience a resonant behavior with respect to both frequency and material losses. We show that the width of the absorption peaks decreases and approaches the width of the reflection peaks, as losses decrease. Thus, high-Q resonances can be observed. The absorption resonances also possess strong angular dependence; they may split and significantly increase in magnitude for a slightly inclined incidence. We elucidate the resonant reflection/absorption effects theoretically and provide numerical examples.

This paper proposes a compact zeroth-order resonant (ZOR) antenna with improved gain and efficiency. The proposed CRLH unit cell is based on the coplanar waveguide (CPW) structure. The proposed ZOR antenna is designed for a 2.45 GHz frequency band, and it has the characteristic of monopolar radiation. Shunt inductance is implemented by microstrip short-circuit stubs, and a metal-isolator-metal (MIM) capacitator provides series capacitance, where a large capacitance can be achieved in a small footprint. The proposed antenna comprises two interleaving composite right-/left-handed CRLH unit cells, where the size of one unit cell is measured at only 0.12λ₀ x 0.098λ₀. Because the field is loosely confined within the CPW-based unit cell, a good antenna peak gain of 2.03 dBi, and a radiation efficiency of over 68% is achieved when fabricated on a thin substrate. The proposed antenna did not require an additional matching network, reducing the total antenna footprint. This paper presents antenna parameters such as the return loss, radiation pattern, antenna gain, and radiation efficiency to validate the proposed design, which achieved good simulation results.

A broadband circularly polarized (CP) cylindrical dielectric resonator antenna (DRA) is presented. The DRA is excited by an L-shaped microstrip feed line through the coupling of an annular slot in the ground plane. The broadband CP radiation is achieved by using two CP radiators, DRA and annular slot. Broadband impedance match is obtained by introducing an impedance transformer. The optimal configuration offers a 3-dB axial ratio bandwidth of 15.9%, from 6.22 to 7.28 GHz, and a 10-dB impedance bandwidth of 21.3%, from 5.78 to 7.16 GHz. The measured results for the constructed prototype are also exhibited and discussed.

The goal of this paper is to present a semi analytical method which makes it possible the calculation of the dynamic iron losses in a three phase induction machine taking the slotting effect into account. The particularity of this method is that it allows the distinction of the stator and the rotor slot openings contribution in the dynamic and, consequently, in the total iron losses. This analytical study shows that a convenient choice of the stator and the rotor slot openings leads to an iron loss reduction, due to the cancellation of particular flux density slotting harmonics. Theoretical results are confirmed numerically.

A compact and planar dual band antenna for wireless communication is presented. The impedance bandwidth of the proposed antenna can cover Bluetooth (2.4-2.484 GHz) and ultrawideband (UWB: 3.1-10.6 GHz) bands. It is composed of a semi-bevelled-rectangle patch and a bended L-shaped strip and fed by a microstrip line. The antenna is built on a FR4 substrate with only 21×35 mm surface area included the ground plane. Details of the antenna design and the measured results included voltage standing wave ratio, radiation patters, peak gain, etc. are presented and discussed.

The time delay, space shift and widening of wave packet transmitted and reflected by structures with Bragg mirrors have been investigated. The specific structures such as Bragg mirrors, resonators, and structures with chirp variation of thickness of the ``period'' have been considered. The calculation has been carried out under the conditions that carrier frequency, and incidence angle is in the vicinity of the Bragg resonance. Integral (mass center) and differential (group) estimates of the delay time and space shift have been compared. The conditions for the appearance of anomalous (negative) mass center delay or mass center shift (Goos-Hänchen shift) of the reflected wave packet have been determined. The shape transformations of the wave packet illuminating periodic and quasiperiodic apodized Bragg reflectors have been under consideration. Spatial apodization of permittivity contrast yields much smaller shape deformation of the transmitted wave packet upon incidence at angles and carrier frequency near the edges of reflection band, as well in Bragg reflection band, in comparison with phenomena in similar periodic structures. The values of group delay for layered structures with a small chirp variation of optical (electrical) thickness of the period along longitudinal coordinates have been experimentally obtained in microwave range.

Guided-mode resonance filters (GMRFs) are highly compact structures that can produce a strong frequency response from a single thin layer of dielectric. When a GMRF is formed onto a curved surface, the local angle of incidence varies over the aperture of the device and the overall performance significantly degrades. In the present work, we spatially varied the grating period of a curved GMRF to perfectly compensate for the local angle of incidence. The performance of the curved device actually surpassed that of a flat device because it also compensated for the spherical wave front from the source. This paper summarizes our design process and experimental results obtained around 25 GHz.

A Substrate Integrated Waveguide (SIW) planar array is presented using a right handed circularly polarized (RHCP) element with four crossed tilted radiating slots. In addition, a pair of metallic tuning vias is included to really improve the reflection of longest slots. A corporate feeding network over SIW has been designed for distributing the input signal to 128 radiating elements, divided into 8 progressive wave linear arrays of 16 elements each. The designed planar array has been manufactured and measured to verify the antenna performance. 25.5 dB gain, 2.33 dB axial ratio, as well as 85% radiation efficiency values have been experimentally achieved at 17 GHz. A 3% usable bandwidth (16.75-17.25 GHz) is obtained due to the typical frequency main beam tilt dispersion in the elevation plane of the progressive wave arrays.

Maxwell equations can be used to formulate an analytical full time-domain theory of skin effect phenomena in circular cylindrical conductors without any detour into the frequency domain. The paper shows how this can be done and concomitantly provides the means to determine the time-varying per unit length voltage drop along the conductor from a given time-varying conductor current. The developed relationship between voltage and current is not very complicated and led the authors to examine the reasons why it has never been utilized in transient analysis, nor given special emphasis in the literature. Those reasons are thoroughly examined and the conclusion is that the conditions required for the application of a purely time-domain skin effect theory are very restrictive.