The preliminary design concept, for a low-loss, high-bandwidth electromagnetically coupled vertical transition for use as a via between adjacent levels of a 3D-MCM based on membrane-supported striplines with micro-machined shielding, is presented. The design methodology, modeling using Ansoft HFSS and simulated results are presented and together represent a complete electrical characterization of the vertical transition. The simulated insertion loss of these structures is shown to be as low as 0.12 dB at 60 GHz with a 44 GHz 1 dB bandwidth. Besides studying the vertical transition, the analysis is extended to identify the range of directional coupling which can be achieved using this type of structure, which is shown to be greater than 3 dB. The structures studied rely on a versatile micromachining technique for the fabrication of the micro-shielding which allows for the conformal packaging of lines and devices, with the ultimate aim of realizing 3D system-in-a-package type modules. The concept and proposed fabrication techniques for these modules, including methods of flip-chip MMIC attachment are detailed.
This paper is concerned with a modeling technique of electromagnetic radiations of power electronics circuits during a switching operation of a power electronic component. The electromagnetic radiating loops are formed by PCB traces assumed to be perfect conductor. We complete our study by proposing a technique using passive loops to reduce the magnetic field emitted by the power electronic converter. To achieve this, we propose to solve Maxwell's equations by using the FDTD method where open boundaries, dielectric board and ground plane are taken into consideration. A validation of the model used in our work (solving Maxwell equations using FDTD) is realized by comparison with other theoretical concepts.
The magnetic field of an axially symmetric coil or magnetic material system can be computed by expansion of the central and remote zonal harmonics, using the Legendre polynomials. This method can be 100-1000 times faster than the more widely known elliptic integral method and is more general than the similar radial series expansion. We present the zonal harmonic method for field, scalar and vector potential calculation of circular current loops, of general axisymmetric coils and magnetic materials, and of special coils with rectangular cross section, with various source representations: currents, magnetic dipoles and equivalent magnetic charges. We discuss in detail the convergence properties of the zonal harmonic expansions, and we show the generalization of the method for special three-dimensional magnetic systems.
The electric potential and field of an axially symmetric electric system can be computed by expansion of the central and remote zonal harmonics, using the Legendre polynomials. Garrett showed the usefulness of the zonal harmonic expansion for magnetic field calculations, and the similar radial series expansion has been widely used in electron optics. In this paper, we summarize our experience of using the zonal harmonic expansion for practically interesting axisymmetric electric field computations. This method provides very accurate potential and field values, and it is much faster than calculations with elliptic integrals. We present formulas for the central and remote expansions and for the coefficients of the zonal harmonics (source constants) in the case of general axisymmetric electrodes and dielectrics. We also discuss the general convergence properties of the zonal harmonic series (proof, rate of convergence, and connection with complex series). Practical considerations about the computation method are given at the end. In our appendix, one can find many useful formulas about properties of the Legendre polynomials, various derivatives of the zonal harmonic functions, and a simple numerical integration algorithm.
In this paper, the transverse equivalent network (TEN) model based on the transmission line theory is employed to analyze and calculate the far-field radiation properties of the Fabry-Perot Resonator (FPR) antenna with perfect magnetic conductor (PMC) ground plane in detail, then the comparative study of the radiation property of FPR antenna with PMC and PEC ground plane is presented. The closed-form expressions for the radiated fields, field peak values, pattern beamwidths and pattern bandwidth of this type of antenna in the E- and H-planes are derived, respectively. The results demonstrate that in theory the radiation property of FPR antenna with two kinds of ground plane is not the same unexpectedly. An interesting characteristic of this type of antenna is that when the PMC acts as the antenna ground plane, the beamwidth and bandwidth of the antenna is increased by a factor of two in general cases, while its peak value of far field is the same as that of the conventional antennas of this class having PEC ground plane. Some results are validated through full-wave simulations of an actual antenna. The original results obtained here lead to a design method for getting the maximum directivity and keeping the bandwidth of this kind of resonant antenna, which is of great significance for antenna designing.
In this paper, the electromagnetic properties of two different High Impedance Surfaces (HIS) with or without Electromagnetic Band Gap (EBG) in different configurations are investigated for mutual coupling reduction in small antenna arrays. The resonant mechanisms of these structures are studied using transmission calculations in a parallel plate waveguide. An optimum configuration is then proposed. It is shown that a good isolation performance can be achieved without the need of metallic vias when the structure is embedded in a metallic cavity, which limits significantly the number of HIS cells needed to perform a good isolation and the cost of manufacture.
Fresnel lenses are low-cost opcitical elements used for focusing sunlight to solar panels to ensure operation under high-flux density. However, the conventional Fresnel lens has a relatively high material usage and hence contributes to additional efficiency degradation. Moreover, traditional design of Fresnel lenses introduces additional prismatic facets, due to deviations in manufacturing, which reflect the light toward the back focal spot, leading to additional losses. In this paper, Fresnel lenses based on finite arrays of Nano Shell-Silver Coated Silica (NSSCS) are proposed to overcome the aforementioned drawbacks from infrared regime through the visible band to the ultraviolet region. To identify reflection losses, material losses of the NSSCS array and rejection bands due to the NSSCS array arrangement, three unique electromagnetic (EM) approaches are invoked: Frequency Selective Surfaces (FSS) to determine reflection bands, Metamaterial (MTM) to specify material losses and Electromagnetic Band Gap (EBG) to locate the rejection band. The EM characteristics of the NSSCS array are evaluated for wavelengths ranging from 0.3 μm to 300 μm, using CST MicroWave Studio (CST MWS), which is based on the Finite Integration Technique (FIT). It is found that the NSSCS array exhibits excellent transmittance within two bands, one from 545 nm to 857 nm and the other from 444.5 nm to 480 nm, for angles ranging from 0^{o} to 180^{o} along the azimuth and elevation. The effective refractive index (n_{eff} spectra showed that the NSSCS array does not provide a negative for its real (n_{eff} part over the considered wavelength band. The imaginary part of (n_{eff} value is found to be almost insignificant, between 0.857 μm to 1.714 μm and 316 nm to 414 nm and lossy elsewhere. In general, the NSSCS array shows no specific stop band over the considered frequency region. Fresnel lenses based on a 9×9 NSSCS array configuration with planar, concave and convex profiles are presented in this paper. The beam width and power density of the emerged beams are evaluated at different wavelengths for different lens sizes. In general, it is found that the power density spectrum is largely dependent on the imagery part of n_{eff}. Nevertheless, the beam width decreases by increasing the lens size, while it decays for wavelengths longer than 500 nm. The concave and convex profiles are introduced to further enhance beam width. The effects of increasing the lens size from 9×9 to 11×11 on the beam width are reported for the concave and convex profiles. It is found that the concave design provides almost a constant beam width at 666.7 nm, 461.5 nm and 316 nm with changing array size, while the convex design does not. Characteristics of the emerged EM beams, in terms of beam waist, depth of focus and phase retardation, are evaluated based on Gaussian optic formalisms for the 9×9 NSSCS array. It is found that the beam waist and the depth of focus for the flat profile vary from 334.03 nm to 387.90 nm and 105.16 nm to 285.65 nm, respectively. The beam waist changes from 365.12 nm to 381.41 nm, while the depth of focus changes from 125.65 nm to 289.45 nm for the convex profile. Finally, the beam waist changes from 313.36 nm to 318.19 nm, and the depth of focus changes from 925.49 nm to 201.45 nm for the concave profile.
We investigate a new mean of decreasing leakage and material loss from coaxial cables using different metallic shield and central conducting part geometries. The suggested model is composed of a central conductor surrounded by 40 metallic wires circularly disposed. The proposed cable is also a hybrid one allowing simultaneous transmission of optical as well as radio frequency (RF) signals. The fabrication techniques for the proposed cable are similar to the one applied in the realization of optical fibers. Besides the fact that the attenuation along the proposed cable is reduced, the most important result of this study is that the interference generated by this source on external cables is also lowered.
This paper presents the unified efficient fundamental alternating-direction-implicit finite-difference time-domain (ADI-FDTD) schemes for lossy media. The schemes presented include averaging, forward-forward, forward-backward and novel exponential time differencing schemes. Unifications of these schemes in both conventional and efficient fundamental forms of source-incorporated ADI-FDTD are provided. In the latter, they are formulated in the simplest, most concise, most efficient, and most fundamental form of ADI-FDTD. The unified update equations and implementation of the efficient fundamental ADI-FDTD schemes are provided. Such efficient fundamental schemes have substantially less right-hand-side update coefficients and field variables compared to the conventional ADI-FDTD schemes. Thus, they feature higher efficiency with reduced memory indexing and arithmetic operations. Other aspects such as field and parameter memory arrays, perfect electric conductor and perfect magnetic conductor implementations are also discussed. Numerical results in the realm of CPU time saving, asymmetry and numerical errors as well as specific absorption rate (SAR) of human skin are presented.
A new kind of field representation on the far field sphere is presented. This representation is based upon the polarisation states of the field. Polarisation states can easily be obtained upon determining the peculiar loci in the field. Depending on the polarisation state of the field, it is demonstrated that, either one of the magnetic or the electric dipole moments is dominant. Subsequently, criteria which may be applied to determine which dipole moment is responsible for the main radiation are derived. This characterization scheme which is a good figure of merit for an antenna designer may be useful in mobile communications especially in identifying possible adverse effects of RF fields on human health. The approach is also helpful for EMC engineers seeking to characterize and identify radiation sources of equipment under test.
This paper describes the application of two recently developed metaheuristic algorithms known as fire fly algorithm (FFA) and artificial bees colony (ABC) optimization for the design of linear array of isotropic sources. We present two examples: one for broad side arrays and the other for steerable linear arrays. Three instances are presented under each category consisting of different numbers of array elements and array pattern directions. The main objective of the work is to compute the radiation pattern with minimum side lobe level (SLL) for specified half power beam width (HPBW) and first null beam width (FNBW). HPBW and FNBW of a uniformly excited antenna array with similar size and main beam directions are chosen as the beam width constraints in each case. Algorithms are applied to determine the non-uniform excitation applied to each element. The effectiveness of the proposed algorithms for optimization of antenna problems is examined by all six sets of antenna configurations. Simulation results obtained in each case using both the algorithms are compared in a statistically significant way. Obtained results using fire fly algorithm shows better performances than that of artificial bees colony optimization technique provided that the same number of function evaluations has been considered for both the algorithms.
The dynamics of a system comprising of two bilaterally coupled Gunn oscillators (BCGOs) has been examined using a circuit theoretic model of the Gunn oscillator (GO). The effects of coupling factors (k_{ij}) between i-th and j-th oscillators on the frequency-range of synchronized operation and the magnitude of common frequency of oscillation have been examined semi-analytically and by numerical solution of the system equations. The occurrence of chaotic oscillations at the verge of synchronization bands is observed in numerical simulation. The experimental response of the BCGO operating in the X-band is obtained and the results are found to be qualitatively similar to the analytical and numerical predictions.
In this paper, modeling and experimentation of a Rectangular Patch Resonator (RPR) covered with a dielectric superstrate are investigated. The RPR criteria are established theoretically and experimentally, to be used in future prospects as an electromagnetic (EM) sensor for the characterization of superstrates. The theoretical model is based on the moment method (MoM) via Galerkin's approach, in which three types of basis and testing functions are used. These functions as well as the spectral dyadic Green function are efficiently implanted with compact structured Fortran 90 codes. The EM commercial HFSS and CST Microwave Studio softwares are used to simulate the proposed RPR prototypes. The accuracy of the obtained results is assessed using four prototypes of RPRs operating around 6 GHz, taking into account only the resonant frequency of the fundamental dominant mode. The theoretical model is compared to simulation and measurement results, and very good agreements are observed.
A Z-R relation is derived using a data set which consists of nine rain events selected from Singapore's drop size distribution. Rain events are separated into convective and stratiform types of rain using two methods: the Gamache-Houze method, a simple threshold technique, and the Atlas-Ulbrich method. In the Atlas-Ulbrich method, the variability of the rain integral parameters R, Z, N_{w}, D_{0} and gamma model parameter $\mu $ are used for the classification of rain into convective, stratiform and transition. Z-R relations are derived for each type of rain after classification. The changes in the coefficients of the Z-R relations for different rain events are plotted and analyzed. The Z-R relations of the different methods using the Singapore data are compared and analyzed. It is concluded that the coefficient A of the Z-R relation is higher for the convective stage followed by the stratiform and transition stages. The coefficient b values are higher for the transition stage followed by the stratiform and convective stages. Reflectivities are extracted from RADAR data above NTU site for rain events and compared with the reflectivities derived from the distrometer data. Rain rates retrieved from RADAR data using the proposed relations from Singapore's data set are compared with the distrometer rain rates. The RADAR extracted rain rates are found to be constantly lower than the distrometer derived rain rates but matches well.
An innovative radar imaging system, based on the capability of a fixed UWB array to radiate short pulses in different directions along time with the principle of electronic beam steering, is presented in this paper. To demonstrate its concept, the analysis presented in this paper is based on simulation results. As function of the use of either only one antenna or several antennas in reception, two radar imaging algorithms have been developed and are detailed in this paper. These algorithms permit to obtain an image of the analyzed scene thanks to the transient beam pattern of the array used in emission. Finally, with a same analyzed scene, these algorithms have been compared with the time reversal method and the back projection algorithm, in association with a SAR imaging system. The conditions of applicability of these methods are also discussed.
Simple normalized dispersion relations for transverse magnetic (TM) and transverse electric (TE) propagating modes in parallel-plate waveguides filled with DPS/DPS or DNG/DNG, and DNG/DPS bilayers are presented. The evanescent TE_{0} mode of the waveguide filled with a DNG/DPS bilayer is characterized also by a simple normalized dispersion relation. Since an important behavior of the modes in the waveguide filled with a DNG/DPS bilayer is the existence of a turning point (TP) at which the power carried by the respective mode on the propagation direction equals zero and changes the sign, we present also implicit relations for determining the normalized parameters of the TM and TE modes at that TP. We show that the TP begins to exist at certain values of the normalized parameter v_{2} characterizing the DPS layer. For both the TM and TE modes, the higher is the mode order, the greater is the v_{2} parameter at which the TP begins to exist, but the behavior of the TP is different for the TM and TE modes.
In this work, we analyze modified bowtie nanoantennas with polynomial sides in the excitation and emission regimes. In the excitation regime, the antennas are illuminated by an incident plane wave, and in the emission regime, the excitation is fulfilled by infinitesimal electric dipole positioned in the gap of the nanoantennas. Several antennas with different sizes and polynomial order were numerically analyzed by method of moments. The results show that these novel antennas possess a controllable resonance by the polynomial order and good characteristics of near field enhancement and confinement for applications in enhancement of spontaneous emission of a single molecule.
Modeling of a ferroelectric interdigital capacitor (IDC) and its incorporating in composite right/left-handed (CRLH) unit cells is represented. To evaluate the capacitance of a multi-layered IDC structures, conformal mapping and partial capacitance methods are utilized. Furthermore, the partial displacement method is utilized to calculate the electric field distribution and the its relation in the ferroelectric layer to applied voltage is obtained. Using this relation in a phenomenological model, dependency of the relative permittivity of ferroelectric on the applied voltage is obtained. The designed unit cell is comprised of IDCs and spiral inductors. To alter the propagation constant of the unit cell by varying the applied voltage, a thin layer ofBa_{0.5}Sr_{0.5}TiO_{3} (BST-0.5) ferroelectric is incorporated underneath an IDC, called BST-0.5 varactor. The periodic structure based on the designed unit cell leads to a CRLH LWA. The Tunability of the periodic structure with three unit cell is demonstrated by varying the relative permittivity of the ferroelectric layer.
In the present paper, we deal with the performance analysis of the Adaptive Normalized Matched Filter (ANMF) detector in compound-Gaussian clutter with inverse gamma texture model and unknown covariance matrix. First, the maximum likelihood estimate (MLE) of the covariance matrix for this clutter model is derived. The MLE is then plugged into the ANMF test and compared to the well known normalized sample covariance matrix estimate (NSCM) and the approximate maximum likelihood estimate (AML). The performance in terms of CFAR behavior and detection probability is evaluated in the presence of simulated clutter and real sea clutter data, which is collected by the McMaster IPIX radar.
Thinning is a technique by which the total number of active elements in an antenna array is reduced without causing major degradation in system performance. Dynamic thinning is the process of achieving this under real time conditions. Stochastic techniques have been useful in the design of thinned arrays. However while applying the technique to large 2-D arrays, under changing conditions problems arise due to the very large and rugged solution space. Also, evaluation of the objective function in such cases requires large computational resources, thus reducing the rate of convergence. This paper suggests a technique using Genetic Algorithm which is useful for overcoming these problems. After discussing the basic concept involving dynamic thinning and application methodology, simulation results of applying the technique to linear and planar arrays are presented.