In this paper, design and simulation of optimized MEMS spiral inductor are presented. The effects of design parameters on characteristics of inductor have been considered. The suspended spiral inductor was designed on silicon substrate using MEMS technology to reduce the metal and substrate losses of inductor. The results show that the quality factor of the inductor is 27 at 5.23 GHz and that the maximum Q-factor is 42 at 26.56 GHz. The dimension of the inductor is 185×200 μm^{2}, which occupies less area on chip than other works. In this work, the high quality factor inductor with small size is obtained.
We present a flat lens design that provides focusing with no aberration. By profiling the refractive index of the lens to generate a spherical wavefront at the exit side of the lens, the transmitted fields converge at a specified focal point. The focusing is achieved using primarily the dispersion phenomenon. We show through numerical examples that focusing without aberration can be achieved at a specific frequency and that focusing is possible over a narrow range of frequencies providing that the dispersion is minimal. Additionally, we show that the same principle used to design the lens can be used to design flat reflectors with a focal point focusing.
Allowing photons to bear mass, the electric and magnetic fields of a steadily moving charge are not no longer perpendicular to each other, as anticipated from Biot-Savart law. The electric and magnetic fields of such a particle depend on the gauge potentials, φ and A. The orthogonality relations of the particle fields and the direction of motion depend on the mass of the photon. The non-relativistic correction to the particle fields was found to be related to the Lorenz gauge condition. It is shown that the existence of magnetic monopoles inside matter is inevitable when magnetic filed is applied in a conductor. Their existence is a manifestation of the massive nature of the photon inside matter. Neither electric nor magnetic current is separately conserved for photons, but their sum is. Massive photons are found to produce electric and magnetic fields. A force proportional to the square of the current is found to act along the wire, F = 1/2μ_{0}I^{2}, where μ_{0} is vacuum permeability.
In this paper, the effect of both uniaxial anisotropy in the substrate and air gap layer on the resonant frequency and bandwidth of circular microstrip patch are investigated. The problem is rigorously formulated based on the spectral domain technic in conjunction with Galerkin approach for computing the resonant frequency, half-power bandwidth, and radiation field of a tunable circular patch antenna which is printed on isotropic or uniaxial anisotropic substrate. The TM set of modes issued from the magnetic wall cavity model theory are used to expand the unknown currents on the patch. Resonant frequency shift due to uniaxial anisotropy is firstly investigated for different anisotropy ratio values of substrate. Then, the effect of inclusion of air gap layer inserted between anisotropic substrate and ground plane on the resonance characteristics is also investigated. The results obtained from this approach are in very good agreement with the experimental results available in the literature.
In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switch-off of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs)and on-time durations (OTDs) of a timemodulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the first positive and negative harmonics of the time-modulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at different harmonics can be simultaneously used as independent communication channels. By employing a differential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a flat-top or a cosec square pattern at first positive and negative sidebands of side-lobe levels (SLL) -20 dB can be synthesized by suppressing the higher sideband level (SBL) to below -10 dB.
This paper presents the development of a novel‘maximum entropy'-based numerical methodology for the solution of electromagnetic problems, where the inputs and system parameters vary statistically. The application of this methodology to the problem of a plane wave impinging on an array of cylindrical conducting rods with stochastic variations in its parameters is then presented. To address this problem, a statistically significant number of replicas of this array of conductors are constructed. The current profiles in these coupled conductors are estimated by using the Method of Moments (MoM). Upon estimation of the current profiles on the conductors, the monostaticradar cross-section is estimated for each replica of the array. The probability density function isthen constructed through the estimation of a finite number of moments from the available output data subject to the constraint of maximum entropy. The methodology is very general in its scope and its application to scatterers with other geometries such as spheres, spheroids and ellipsoids as well as to other application areas would form the basis of our future work.
This paper proposes some approaches to model Ultra Wideband (UWB) antenna arrays. Based on the array factor, often stipulated as not adapted for the description of the properties of UWB arrays in the literature, an analytical expression of the beampattern is developed. The achieved results are coherent with other formulations and empiric studies proposed in the literature. Furthermore, a time-frequency modeling of UWB antenna arrays is proposed using the concept of array factor and antenna effective length.
To study electromagnetic scattering from dielectric rough surfaces, a hybrid finite element method (FEM) combined with boundary integral equations (BIE) is extended to the scattering problem with two half-open regions. Integral boundaries, as truncated boundaries of the FEM region, are employed as artificial boundaries of dielectric rough surfaces above and below the rough surface. In the hybrid method, conformal integral boundaries are introduced to reduce the computational region. The validity of our hybrid method is examined by available solutions got from the method of moment (MoM), which indicates the feasibility of our scheme in simulating the scattering from dielectric rough surfaces. Bistatic scattering coefficient from dielectric rough surfaces is studied in this paper for both polarizations, and functional dependence upon different parameters are numerically discussed.
In various technological and scientific applications, different types of coil systems are being used to produce uniform alternating magnetic field. The dimensions of these coil systems are considerably larger than the volume of interest. There is a necessity to reduce the dimension of the coil system without sacrificing the extent of uniformity of the magnetic field. This problem has a wide audience and still remains as a topic of contemporary research in the development of miniaturized devices especially for calorimetric measurements of nano-particles, cancer therapy, and detection of minute surface defects by eddy current probes, etc. In this paper we present how we can modify the shape of a miniature solenoid to produce uniform magnetic field. A Genetic algorithm has been implemented to get the optimum dimension of the miniature solenoid. Our distinct shape design has achieved 97% uniformity for a 60% volume of interest.
A mathematical model of a spherical antenna excited by a slot cut in an impedance endwall of a semi-infinite rectangular waveguide was built using a rigorous solution of the problem. Control of energy characteristics is accomplished by changing impedance distributed on the end-wall of the waveguide section. If the waveguide is excited by the wave H_{10}, the wavelength tuning reaches (30-35)%, i.e. about a half of the wavelength range of single mode waveguide regime.
We present Coplanar-Planar Goubau Line (PGL) transitions designed on high-resistivity Silicon to characterize a PGL using microwave probing. These transitions are optimized in the 57-64 GHz frequency band to present excellent electrical performances despite the field disturbance of the measurement setup. As the transitions are positioned on a probe station chuck, a glass substrate is added between the transition under test and the metallic chuck to minimize the disturbance. 3-D full-wave electromagnetic field simulations performed on a commercial software and on-wafer measurements show almost comparable results in term of scattering matrix parameters. Low losses are attained with a measured average transmission parameter of 2.5 dB at 60 GHz for a length of 8 mm of a back-to-back structure with the transitions at the extremities. The measured average insertion loss and return loss per transition are better than 1.36 dB and 11 dB, respectively, with a bandwidth greater than 7% at 60 GHz for a length of 1 mm (about a half of the wavelength at 60 GHz).
A goal of this work is to find a possible explanation of the experimental results of [1] where the wireless power transfer between two coils is investigated. We show that this wireless power transfer is provided by the longitudinal component of the EM field. Using Jefimenko's approach of solving the Maxwell equations we show that under specific conditions the longitudinal component drops with the distance as 1/R. This result dependence can explain the experimentally detected dependence of the transferred power in the experiment.
In this paper, we introduce plane wave modulators that are designed using one-dimensional photonic crystals (1DPC) containing radial gradient refractive index (r-GRIN) defect layers. Three kinds of r-GRIN materials with different refractive index distribution functions are applied in numerical analysis. The properties of the phase and intensity of the transmitted plane wave beam through propoesed structures are studied using the transfer matrix method. Radially-dependent defect modes, modulated phase and intensity are obtained according to the refractive index distribution functions. The results are predictable by regarding the Bragg condition and destructive interference, which are the origins of the photonic band gap. Due to the radial-dependency of the defect layer's refractive index, the rays passing through different transverse positions experience different optical pathways. Therefore, the defect modes and transmitted spectrum (phase and amplitude) vary transversely. This study demonstrates another ability of the artificial PC structures to design plane wave modulators and manipulate its phase and intensity.
Ground control point (GCP) extraction is an essential step in automatic registration of remote sensing images. However the lack of quantitative and objective methods for analyzing GCP quality becomes the bottleneck that prevents the broad development of automatic image registration. Although several measurements for evaluating the number, accuracy and distribution of GCPs have been proposed in recent years, some of them are redundant and the evaluation of dispersion is not effective enough. In this paper, a method for an objective and quantitative evaluation of GCP quality is proposed. The proposed method consists of three parts: measurement calculation, cost function calculation and final validation. In the first part, two new measurements are proposed to evaluate the number, dispersion and isotropy of GCPs, and the root mean square of GCP residuals using leave-one-out method (RMSloo) is used to evaluate the accuracy. In the second part, seed cost functions are utilized to transform the measurements into a limited value range as well as to be desired on the ascending direction. Subsequently, all the seed cost functions are combined by a total cost function to provide an integrated evaluation. In the third part, the GCP scenario is validated by the accepted threshold depending on the value of the total cost function. To evaluate the performance of the proposed method, experiments using four typical emulated scenarios of GCP distribution and two sets of real GCPs in SAR images are considered. The results demonstrate that the proposed GCP evaluation method performs more effectively than the existing methods, especially in the evaluation of dispersion quality.
We calculated analytic expressions for the absorption coefficient (ACF) of a weak electromagnetic wave (EMW) by confined electrons in cylindrical quantum wires (CQW) in the presence of laser radiation by using the quantum kinetic equation for electrons in the case of electron-optical phonon scattering. The ACF of a weak EMW depends on the intensity E_{01} and frequency Ω_{1} of the external laser radiation (E_{1} = E_{01}sin(Ω_{1}t+φ_{1})); the intensity E_{02} and frequency Ω_{2} of the weak EMW (E_{2} = E_{02}sin(Ω_{2}t)), the temperature T of the system and the radius R of CQW. Then, the analytic results are numerically calculated and discussed for GaAs/AlAs CQW. The numerical results show that the ACF of a weak EMW in a CQW can have negative values. So, in the presence of laser radiation, under proper conditions, the weak EMW is increased. This is different from the similar problem in bulk semiconductors and from the case of the absence of laser radiation.
Excitation of waves at harmonics of electron cyclotron frequency due to utilization of an external alternating electric field is under the consideration. It is proved that they are eigen modes of plasma-dielectric-metal structures in both long (as compared with electron Larmor radius) wavelength range and short wavelength range if an external steady magnetic field is oriented perpendicularly to the plasma interface. It is assumed that uniform external electric field operates at the frequency, which belongs to the range of electron cyclotron frequencies. The problem is solved theoretically using kinetic Vlasov-Boltzmann equation for description of the plasma particles motion and Maxwell equations for description of TM polarized field of these modes. Non-linear boundary condition for tangential magnetic field of these TM-modes is formulated using conception of non-linear surface electric current. Infinite set of equations for harmonics of their tangential electric field is derived due to this condition. This set is solved using approach of the wave packet consisting of the basic harmonic and two nearest satellite harmonics. Simple analytical expression for growth rate of surface electron cyclotron TM-modes' parametric instability is obtained and analyzed numerically.
Based on Bloch-Floquet's theorem and ordinary matrix calculations, a rigorous method for extraction of the eigenmodes of fiber gratings is developed. This method is also applicable to fiber gratings which are either physically multilayer or mathematically divided into layers along the radial coordinate. Although the well-known coupled mode theory (CMT) is accounted a method for extraction of the coefficients of reflection and transmission of finite-length FBGs, its inadequacy for extraction of the Bloch eigenmodes of FBGs is illustrated, even if the modulation depth of refractive index is small and the Bragg condition is satisfied.
Global System for Mobile Communications (GSM) is currently one of the most widely and most demanding telecommunication applications in the world. Researchers have reported that radiation from base stations may be dangerous to public health and that some human diseases are related to RF field exposure. Considering that in the past almost all the EM radiation assessments were focused on the Maximum transmission power of base station, and no statistical analyses have been performed on transmitted power's variation with the traffic. An accurate method for predicting electromagnetic (EM) radiation from GSM base stations is proposed in this paper. It is based on the Poisson distribution of GSM-transmitted signals to calculate GSM transmitted power at different time periods. The theoretical calculation data fits well with the measurement data. Measurement results confirm that electromagnetic radiation varies with changing traffic and power density at different times with varying traffic strength is more accurate than implementing only maximum power (20 W) calculation. In some occasion, maximal power density is about 61 μW/cm^{2} for 15 m in rush hours, but minimum power density is only 0.031 μW/cm^{2} for 15 m in idle hours.
In this paper, a new numerical method of calculating the total impedance of a twin high current busduct consisting of rectangular hollow busbar is proposed. The method is based on the integral equation method and partial inductance theory. Results for impedance of this twin high current busduct have been obtained, and the skin and proximity effects have also been taken into consideration. The validation of the proposed method is carried out through Finite Element Method (FEM) and laboratory measurements, and a reasonable level of accuracy is demonstrated.
Plane-wave excitation fields are not always sufficient for the immunity characterization of wire-type structures operating in the contemporary manmade environment. Following a previous work dealing with straight-wire transmission lines in the presence of nonuniform fields, the present paper examines twisted-wire pairs. Numerical results for the induced load voltages reveal the importance of field nonuniformity for assessing the immunity behavior of twisted-wire transmission lines on a firmer basis.