We detail the optimization of a nanobeam design and show how the fabrication imperfections can affect the optical performance of the device. Then we propose the design of a novel configuration of a photonic crystal nanobeam cavity consisting of a membrane structure obtained by sandwiching a layer of Flowable Oxide (FOx) between two layers of Silicon-Nitride (SiN). Finally, we demonstrate that the presence of a low refractive index layer does not impair the performance of the nanobeam cavity that still exhibits a Q factor and mode volume V of the order of 10⁵ and 0.02 (λ/n)^{3<\sup>, respectively.}

In this paper, a new configuration of Tapered Slot Antenna (TSA) with improved radiation pattern is proposed and studied. This antenna is designed in the form of a substrate integrated waveguide (SIW) array with respect to side lobe level constraints. For side lobe reduction, a simple quasi-triangular distribution is proposed and is accomplished uniquely by means of 3 dB power dividers. A 12-way series feed network with T-junction is designed and demonstrated. Radiation features of the antenna array are discussed to illustrate the accomplishment of a low side lobe level (-19 dB) of the array. The proposed antenna demonstrates the ability of the SIW technology to achieve a very low side lobe in a simple, compact and planar structure.

This paper proposes a simple semi-analytical method for designing coil-systems for homogeneous magnetostatic field generation. The homogeneity of the magnetic field and the average magnitude of the magnetic flux density inside of the volume of interest are the objective functions chosen for the selection of the coil-system geometry (size and location), number of coils and the number of turns of each winding. The spatial distribution of the magnetostatic field is estimated superposing the magnetic induction numerically computed from the analytical expression of the magnetic field generated by each coil, obtained using the Biot-Savart's law and the current filament method. The homogeneous magnetic field is synthesized using an iterative algorithm based on TABU search with geometric constraints, which varies the design parameters of the windings to meet the requirements. The number of turns of each coil and gauge of wire used for the windings is adjusted automatically in order to achieve the target average magnitude of the magnetic induction under the constraints imposed by power consumption. This method was used to design a coil arrangement that can generate up to 10 mT within a volume (0.5 × 0.5 × 1) m with 99% of spatial homogeneity, with square loops of length less than or equal to 1.5 m, and with a power dissipated by Joule effect less than or equal to 1 W per coil. The synthesized magnetic field distribution was validated using Finite Element Method simulation, showing a good correspondence between the objective values and the simulated fields. This method is an alternative to design magnetic field exposure systems over large volumes such as those used in bioelectromagnetics applications.

A wideband slotted multifunctional reconfigurable antenna is proposed for WLAN/WiMAX/UWB/PCS-DCS/UMTS applications. The proposed antenna consists of monopole and spiral sections and microstrip feeding. A microstrip patch on FR4 substrate provides wideband return loss for each application. Total area of the antenna is 34×45 mm² that satisfies all the requirements for different applications in a low profile structure. Reconfigurable design is used in this antenna using RF MEMS switches. The proposed antenna has a nearly omnidirectional radiation patterns (doughnut shape) in different frequency bands. The notch is embedded in the ground plane to improve the impedance matching, and the dimensions of this notch are optimized. Moreover, the variation of group delay is about ±2 ns in UWB application. Also a prototype of the proposed antenna is fabricated, and the results are compared with those obtained from simulations. Measured return losses are in good agreement with simulated ones. The proposed antenna has the advantages of multifunctional operation, low profile, low cost and omnidirectional pattern.

A new structure is suggested for simultaneous microwave chirped pulse generation and array antenna beam steering. It is based on using a multi-channel fiber Bragg grating in a photonic microwave delay-line filter. The paper presents a feasibility study of the idea, discussing the main performance parameters of both signal generation and beam steering functions. Specifically, it focuses on the effects of wavelength tuning, resolution and accuracy. The study shows that custom off-the-shelf components could be used to implement an all optical system capable of generating chirped pulses while steering the radiation pattern of a small sized antenna array. The advantages of the structure for avoiding single sideband modulation difficulties and also for the compensation of the multichannel fiber Bragg grating inaccuracies are also discussed.

A two-layer dual-waveguide probe measurement geometry is proposed to nondestructively measure the complex permittivity and permeability of planar materials. The new measurement structure consists of two rectangular waveguides attached to a PEC flange plate that is placed against the material under test, followed by a known material layer backed by a PEC. The purpose for this new measurement geometry is to improve the permittivity results obtained using the existing dual-waveguide probe geometries, namely, the PEC-backed and free-space-backed geometries, by permitting a larger electric field into the material under test and increasing the field coupling between the two rectangular waveguide apertures. The theoretical development of the technique is presented extending the existing single-layer PEC-backed method to the proposed two-layer dual-waveguide probe method. The new measurement structure is theoretically analyzed by replacing the waveguide apertures with equivalent magnetic currents as stipulated by Love's equivalence theorem. Making use of the magnetic-current-excited two-layer parallel-plate Green's function and enforcing the continuity of the transverse magnetic fields over the waveguide apertures results in a system of coupled magnetic field integral equations. These coupled magnetic field integral equations are then solved for the theoretical reflection and transmission coefficients using the Method of Moments. The desired complex permittivity and permeability of the material under test are found by minimizing the root-mean-square difference between the theoretical and measured reflection and transmission coefficients, i.e., numerical inversion. Last, experimental results utilizing the new two-layer technique are presented for two magnetic shielding materials and subsequently compared to the existing PEC-backed and free-space-backed dual-waveguide probe geometries.

The shooting and bouncing rays (SBR) method has been widely used to predict the radar cross section (RCS) of electrically large and complex targets. SBR computation time rapidly increases as the size and the complexity of a target increase. The angular division algorithm (ADA) can be applied to reduce the number of intersection tests in SBR, which facilitates faster RCS prediction. However, ADA has an error in its table construction step, resulting in incorrect prediction for multiple scattered fields. In this paper, the error is described, and the modified ADA (MADA) is proposed to correct the error and to enhance accuracy. Numerical results show that MADA can achieve good RCS prediction accuracy.

A modeling of the metallic wires susceptibility facing to the disturbances caused by electromagnetic (EM) near-field (NF) radiated by electronic structures in radio frequencies (RF) is introduced by using a hybrid method. This latter is based on the use of the given EM-data calculated or determined from the standard computation tools associated with basic analytical methods expressing the coupling voltages at the victim wire extremities and the EM-NF radiations. In difference to the classical methods based on the far-field radiations, the main benefit of this method lies on the possibility to take into account the evanescent waves from the disturbing elements. The basic principle illustrating the hybrid method principle is explained. To verify the relevance of the method proposed, we consider a metallic wire having cm-length above the ground plane disturbed by the EM-near-waves from the electronic circuits in proximity. For that, we model the EM radiation of the disturbing electronic circuits and then, apply the hybrid method to evaluate the coupling voltages induced through the wires. By considering the radiations around hundreds MHz, we demonstrate that the hybrid method proposed enables us to generate voltages in good agreement with the simulations performed with the commercial tools. Two types of realistic configurations are studied. First, with a microstrip loop circuit radiating at about 0.7 GHz, we calculated induced voltages at the extremities of the structures. Then, the same analysis was made with a 3D-model coil self for the large band from 0.1 GHz to 0.5 GHz. The results are in good accordance between the terminal voltages of the wire. The relative error in the second configuration falls less than 10%. This investigation is important for the EM compatibility (EMC) analysis of the radiating coupling between wires and complex electrical and electronic systems disturbed by RF harmonics.

Efficiency often constitutes the main goal in the design of a power system because the minimization of power losses in the magnetic components implies better and safer working conditions. The primary source of losses in a magnetic power component is usually associated with the current driven by the wire, which ranges from low to medium frequencies. New power system tendencies involve increasing working frequencies in order to reduce the size of devices, thus reducing costs. However, optimal design procedures involve increasingly complex solutions for improving system performance. For instance, using litz-type multi-stranded wires which have an internal structure to uniformly share the current between electrically equivalent strands, reducing the total power losses in the windings. The power losses in multi-stranded wires are generally classified into conduction losses and proximity losses due to currents induced by a magnetic field external to the strand. Both sources of loss have usually been analyzed independently, assuming certain conditions in order to simplify the derivation of expressions for calculating the correct values. In this paper, a unified analysis is performed given that both power losses are originated by the electromagnetic fields arising from external sources where the wire is immersed applying the decomposition into transversal magnetic (TM) and transversal electric (TE) components. The classical power losses, the so called conduction and proximity losses, can be calculated considering the TM modes under certain conditions. In addition, a new proximity loss contribution emerges from the TE modes under similar conditions.

In this paper a theoretical investigation of electromagnetic field transmission through dielectric plano convex lens placed in chiral medium is analyzed. The chiral medium is described electromagnetically by the constitutive relations D = ε(E+γ∇×E) and B = μ(H+γ∇×H). Transmission's coefficients for chiral-dielectric and dielectric-chiral interfaces are derived analytically. The analytical field expressions for right circularly polarized (RCP) and left circularly polarized (LCP) waves are obtained using Maslov's method. Numerical computations are made for the field patterns around the caustic region using Mathcad software to observe the effect of chirality parameter.

We investigate the characterization of defect modes in one-dimensional ternary symmetric metallo-dielectric photonic crystal (1DTSMDPC) band-gap structures. We consider the defect modes for symmetric model with respect to the defect layer. We demonstrate reflectance with respect to the wavelength and its dependence on different thicknesses and indices of refraction of dielectric defect layer, angle of incidence and number of periods for both transverse electric (TE) and transverse magnetic (TM) waves. Also, we investigate properties of the defect modes for different metals. Our findings show that the photonic crystal (PC) with defect layer, made of two dielectrics and one metallic material, leads to different band-gap structures with respect to one dielectric and one metallic layer. There is at least one defect mode when we use dielectric or metallic defect layer in symmetric structure. And, the number of defect modes will be increased by the enhancement of refractive index and thickness of dielectric defect layer.

We present new designs of waveguide components in photonic crystal structures used for routing light exhibiting high transmission. In particular, we focus on the design of a brick that will form the PhCs network, i.e., a double bends and Y-shaped splitter. Photonic crystals are considered a good way for realizing compact optical bends and splitters. The PhC consists of a triangular array of holes etched into InP/GaInAsP/InP heterostructure. Propagation characteristics of the proposed devices are analyzed utilizing two-dimensional finite difference time domain (FDTD) method. The FDTD simulations confirm their unprecedented efficiency and robustness with respect to wavelength and structural perturbations. The PhCs transmission properties are then presented and discussed. Numerical results show that a total transmission of about 75% at output ports is obtained.

In this paper, on the basis of proposing a novel complementary split-ring resonator (CSRR) using Koch fractal curve, a bandpass filter based on such a new structure is designed To validate the designing method. Transmission characteristics and reflection characteristics of the presented filter are given by both software simulation and experiment measurement. Consistent results have confirmed the design concept and excellent performance of the new structure and indicated that the proposed filter has a low insertion loss a high selectivity and small size.

This paper introduces a new design technique for a capacitive gap-coupled bandpass filter (BPF) using non-uniform arbitrary image impedances. Based on the proposed BPF equivalent circuit model, the filter's design equations are derived, and they are validated from comparisons of the calculated and simulated results. For this theoretical verification, the BPF using non-uniform arbitrary image impedances is designed using the specifications of: center frequency (f_c)=5.8 GHz, fractional bandwidth (FBW)=3.5%, and filter stage (N)=3. The calculated and simulated results of the designed filter show good agreement. The BPF using the proposed design method could provide an advantage that one can arbitrarily determine two different image impedances, which ultimately affects the BPF's coupling gaps and line widths. This could result in suitable filter dimensions, i.e., gaps and line width, for a conventional low resolution photolithography fabrication although a low or high dielectric constant substrate is used for the design.

Ultra wideband components have been developed using SIW technology. The various newly developed components include a GCPW transition, Y and T-junctions. The GCPW transition covers over 10 GHz bandwidth with less than 0.4 dB insertion loss. The optimized T and Y-junctions have relatively wide bandwidths of greater than 40% that have less than 0.6\,dB insertion loss. The developed transition was utilized to design an X-band eight-way power divider that demonstrated excellent performance over a 4 GHz bandwidth with less than ±4º and ±0.9 dB phase and amplitude imbalance, respectively. Theoretical and experimental results are presented and compared with previously designed SIW power dividers. The developed SIW power divider has a low profile and is particularly suitable for circuits' integration.

A novel coplanar waveguide (CPW)-fed circularly polarized (CP) antenna is proposed. The antenna is composed of a square ground plane with a circular slot and an equiangular tapered-shaped feedline. With the use of a special shaped feedline, the axial ratio (AR) bandwidth of the proposed antenna is about 61.9% (2.9-5.5 GHz), which is larger than most of similar antennas proposed before. In addition, the impedance bandwidth, determined by 10-dB return loss, is between 2.9-20 GHz, which makes the antenna be used for ultra-wideband (UWB) applications.

In this paper, a calibration technique for the position sensor via support vector regression (SVR) is proposed. The position sensor adopts a zero-intermediate frequency architecture based on a six-port network, which is used for directly measuring the phase differences and indirectly reflecting the position. The SVR, which implements the structural risk minimization (SRM) principle, provides a good generalization ability from size-limited data sets. The results indicate that the SVR model can achieve a great predictive ability in positioning, with an accuracy of 2.41 mm over a distance range of 274.5 mm.

A printed monopole ultra wideband (UWB) antenna with frequency band-notched characteristics is proposed and investigated. The antenna consists of a half-disk shaped structure combined with an inverted isosceles trapezoid structure. To achieve the frequency band notched characteristics, an open-ended thin slit with a length of about one quarter guided wavelength is inserted on the radiator. Multiple slits can be employed to realize multiple frequency band notched characteristics. To validate the concept, two prototypes are designed, fabricated and tested. The first is a single band notched UWB antenna whereas the second is a dual band notched UWB antenna. The simulated and measured results of both antennas are presented shown a reasonable agreement between them. The results also confirm the proposed UWB antenna design can achieve superior dual band-notch performance at desired frequency bands.

The design and analysis of a high-power wideband sheet-beam coupled-cavity traveling-wave tube operating at V-band is presented. The interaction circuit employs three-slot doubly periodic staggered-ladder coupled-cavity slow-wave structure, and a 5 : 1 aspect-ratio sheet electron beam is used to interact with the circuit. Combined with design of the well-matched input and output couplers, a 3-D particle-in-cell model of the sheet-beam coupled-cavity traveling-wave tube is constructed. The electromagnetic characteristics and the beam-wave interaction of the tube are investigated. From our calculations, this tube can produce saturated output power over 630 Watts ranging from 58 GHz to 64 GHz when the cathode voltage and beam current are set to 13.2 kV and 300 mA, respectively. The corresponding saturated gain and electron efficiency can reach over 32.5 dB and 15.9%. Compared with the circular beam devices, the designed sheet-beam TWT has absolute advantage in power capability, and also it is more competitive in bandwidth and electron efficiency.

In this letter, a novel compact quad-band microstrip circular slot antenna using edge-feeding is proposed to support the four wireless communication bands of GPS1.575 (1.525-1.625 GHz), WIMAX3.5 (3.3-3.6 GHz), WLAN2.45 (2.4-2.485 MHz)and WLAN5.2/5.8 (5.15-5.825 GHz). To expand the bandwidth of the GPS band and induce the WIMAX/WLAN band to support quad-band applications without affecting the compactness of the proposed antenna, a good method of implanting two T copper slices at the inner boundary of the two circular slots respectively is adopted. By adjusting the diameter of the two circular slots and the size of the T-shaped patch, resonant frequencies and bandwidth of the antenna are controlled and the multiple operating bands are achieved. In order to further reduce the size of the antenna that an edge-fed technology is used. This antenna has a simpler structure for realizing quad-band characteristics. Then, a prototype of the proposed antenna was successfully implemented, and good radiation performance is observed in all desired bands.