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Showing papers in "Electromagnetics in 2006"


Journal ArticleDOI
TL;DR: In this paper, the authors studied the statistical properties of the impedance and scattering matrices of open electromagnetic cavities with several transmission lines or waveguides connected to the cavity, and they mainly discussed the single port case.
Abstract: We study the statistical properties of the impedance (Z) and scattering (S) matrices of open electromagnetic cavities with several transmission lines or waveguides connected to the cavity. In this paper, we mainly discuss the single port case. The generalization to multiple ports is treated in a companion paper. The model we consider is based on assumed properties of chaotic eigenfunctions for the closed system. Analysis of the model successfully reproduces features of the random matrix model believed to be universal, while at the same time incorporating features which are specific to individual systems as treated by the Poisson kernel of Mello et al. Statistical properties of the cavity impedance Z are obtained in terms of the radiation impedance (i.e., the impedance seen at a port with the cavity walls moved to infinity). Effects of wall absorption are discussed. Theoretical predictions are tested by direct comparison with numerical solutions for a specific system. (Here the word universal is used to denote high frequency statistical properties that are shared by the members of the general class of systems whose corresponding ray trajectories are chaotic. These universal properties are, by definition, independent of system-specific details.)

94 citations


Journal ArticleDOI
TL;DR: In this paper, the authors generalized the statistical model proposed in an accompanying paper to treat multiport scattering problems and derived the average transmission and reflection coefficients in terms of the port radiation impedance.
Abstract: The statistical model proposed in an accompanying paper is generalized to treat multiport scattering problems. Attention is first focused on two-port lossless systems and the model is shown to be consistent with Random Matrix Theory. The predictions are then tested by direct numerical simulation for a specific two-port cavity. Formulae are derived for the average transmission and reflection coefficients in terms of the port radiation impedance. The cases of cavities with multiple ports, and with a single port and distributed losses are compared.

77 citations


Journal ArticleDOI
TL;DR: A combination of FEM and other methods (such as state-space, which can compensate the above-mentioned drawbacks) can be used as a precise, flexible and widely applicable technique for fault diagnosis of faulty induction motors.
Abstract: Statistics show that 80% of faults are due to eccentricity in induction motors, promoting many research efforts still devoted to the eccentricity in these motors. This paper classifies different common faults in the stator and rotor. It then presents analysis techniques for faulty induction motors. Four more applied methods in the diagnosis and detection of faults in induction motors are investigated and critiqued. The finite difference method is introduced, and its drawbacks are noted. An equivalent magnetic circuit method is then discussed as a fast but less accurate method. The reduced accuracy of the latter method is due to neglect of the spatial harmonics, the relationship between these harmonics, and time harmonics, and particularly non-linearity of the magnetic materials. An analytical method of winding functions is investigated for the analysis of faulty induction motors. This method also neglects the spatial harmonics and their relationship with time harmonics, which could considerably influence ...

69 citations


Journal ArticleDOI
TL;DR: An efficient search technique based on a touring ant colony optimization algorithm is presented for the shaped-beam pattern synthesis of a linear antenna array and the frequency memory feature of tabu search is used.
Abstract: An efficient search technique based on a touring ant colony optimization algorithm is presented for the shaped-beam pattern synthesis of a linear antenna array. The element excitations of equally spaced array and the element positions of uniformly excited array are determined to closely approximate the desired pattern. In the touring ant colony optimization algorithm, the frequency memory feature of tabu search is used. Illustrative examples of cosecant, flat-topped and pencil beam patterns are given to verify the validity and accuracy of the technique.

45 citations


Journal ArticleDOI
TL;DR: In this article, a survey of the most widely used approximation methods in the wave propagation studies is made for the specific case of microwave propagation assessment under tropospheric ducting conditions.
Abstract: A survey is made of one of the most widely used approximation methods in the wave propagation studies—the parabolic wave equation method—applied for the specific case of microwave propagation assessment under tropospheric ducting conditions. A brief review of the methods for tropospheric refractivity profiling, the average refractivity modeling, and the applicability of the often-assumed lateral homogeneity of the refractivity is given. The parabolic wave equation derivation and the numerical methods for solving it are summarized with special emphasis on transparent boundary conditions for the upper computational window boundary. Results are reported which illustrate the application of the finite element method and split-step Fourier-based solutions of parabolic wave equations for different cases of tropospheric ducts, concerning radar and communications links performance.

33 citations


Journal ArticleDOI
TL;DR: In this paper, the propagation of a surface electromagnetic wave at the interface of identical uniaxial dielectric half-spaces with a relative twist in their orientation about an axis perpendicular to the interface is formulated as a boundary value problem, the direction of propagation being along the bisector of the relative twist angle and both optic axes being tilted to the interfaces.
Abstract: The propagation of a surface electromagnetic wave at the interface of identical uniaxial dielectric half-spaces with a relative twist in their orientation about an axis perpendicular to the interface is formulated as a boundary value problem, the direction of propagation being along the bisector of the relative twist angle and both optic axes being tilted to the interface. Only positive uniaxiality supports surface-wave propagation. When the optic axes in both half-spaces are tilted relative to the interface, the range of the relative twist angle which supports surface waves diminishes and eventually disappears at some maximum value of the tilt angle which depends on the degree of uniaxiality. At optical frequencies and with relatively large degree of uniaxiality, the surface waves are localized within 10's to 100's of nm of the interface.

28 citations


Journal ArticleDOI
TL;DR: In this paper, a higher-order large-domain hierarchical finite-element technique using curl-conforming vector basis functions constructed from standard Legendre polynomials on generalized curvilinear hexahedral elements is proposed for electromagnetic modeling.
Abstract: A novel higher-order large-domain hierarchical finite-element technique using curl-conforming vector basis functions constructed from standard Legendre polynomials on generalized curvilinear hexahedral elements is proposed for electromagnetic modeling. The technique combines the inherent modeling flexibility of hierarchical elements with excellent orthogonality and conditioning properties of Legendre curl-conforming basis functions, comparable to those of interpolatory techniques. The numerical examples show the reduction of the condition number of several orders of magnitude for high field-approximation orders (e.g., 14 orders of magnitude for entire-domain models) when compared to the technique using field expansions based on simple power functions and the same geometrical elements.

25 citations


Journal ArticleDOI
TL;DR: The PSO algorithm is used to synthesize an optimal linear array in the Chebyshev sense and the objective function is formulated to take into consideration both the lobe level and the main beam width.
Abstract: In this article, the particle swarm optimization (PSO) algorithm is used to synthesize an optimal linear array. The technique is applied to synthesize a linear antenna array in the Chebyshev sense or to eliminate a grating lobe. This is may be achieved by optimizing the excitation currents and/or the relative locations of the array elements. These various design parameters are considered in this paper. In synthesizing equiripple radiation patterns, two approaches were used. The excitation currents feeding the array or the spacing between the array elements are optimized. It is to be noted that the desired equal side lobes level is achieved simultaneously with the narrowest possible beamwidth. Although the optimization problem may become nonlinear, convex, or nonconvex, especially if the interelement distances are the optimized parameters, it can be handled using the PSO algorithm. The PSO is simple to implement and does not require evaluation of gradients or coded parameters. In order to effectively utili...

25 citations


Journal ArticleDOI
TL;DR: In this paper, the behavior of periodic plane arrays of split ring resonators (SRRs) and of complementary split ring Resonators (CSRRs) when they are illuminated by a plane wave is analyzed.
Abstract: The behavior of periodic plane arrays of split ring resonators (SRRs) and of complementary split ring resonators (CSRRs) when they are illuminated by a plane wave is analyzed. The effects of the angle of incidence and polarization are considered. A surface admittance approach is used for the analysis. Experimental results in free space are provided in order to check the theory. Good qualitative agreement is observed between theory and experiment, although some quantitative disagreements still remain and need explanation. Application of the studied devices as frequency selective surfaces and polarization converters can be envisaged as a consequence of the high variety of the reported resonant and cross-polarization effects

25 citations


Journal ArticleDOI
TL;DR: This study investigates the susceptibility levels and frequency ranges of RFI to the clock network of a digital device, an 8-bit ripple counter, designed and fabricated using AMI 0.5 μm process technology and shows the sensitivity of a flip-flop, the basic building block of clock network, which explains the experimental results.
Abstract: Radio frequency interference (RFI) can have adverse effects on commercial electronics. Current properties of high-performance integrated circuits (ICs), such as very small feature sizes, high clock frequencies, and reduced voltage levels, increase the susceptibility of these circuits to RFI, causing them to be more prone to smaller RFI levels. Besides, recent developments of mobile devices and wireless networks create a hostile electromagnetic environment for ICs. Therefore, it is important to generalize the susceptibility of ICs to RFI. In this study, we investigate the susceptibility levels and frequency ranges of RFI to the clock network of a digital device, an 8-bit ripple counter, designed and fabricated using AMI 0.5 μm process technology. Our experimental setup is designed to couple a pulse-modulated RF signal using the direct pin injection method. Our experiments show that relatively low levels of RFI (e.g., 16.8 dBm delivered RF peak power with carrier frequency of 1 GHz) could adversely affect t...

17 citations


Journal ArticleDOI
TL;DR: In this article, three different types of metamaterial superstrates, viz., multilayer dielectric slabs, electromagnetic band gap (EBG) materials, and frequency selective surfaces (FSSs), are discussed.
Abstract: In this paper, we present some applications of metamaterial superstrates for directivity enhancement of printed antennas. Three different types of superstrates, viz., multilayer dielectric slabs, electromagnetic band gap (EBG) materials, and frequency selective surfaces (FSSs) are discussed. We first present the design of a multilayer dielectric slab, consisting of high and low permittivity dielectric layers and air-gap tuners for suppressing the grating lobes of patch array antennas. Next, a dielectric-rod EBG-type superstrate with two defect frequencies is proposed for dual-band directivity enhancement of a patch antenna at a boresight. With this design we can increase the degrees of freedom that adjust the level of directivity enhancement and operating frequency location, relative to those of the multilayer dielectric slab type. Finally, an FSS superstrate consisting of two-layered FSS screens for dual-band directivity enhancement is introduced as an alternative to an EBG type of dielectric superstrate...

Journal ArticleDOI
TL;DR: In this paper, the spatial statistics formalism is applied to electromagnetic field analysis, where fields are considered as realizations of a random function and their spatial structure is studied by a method known as variographic analysis.
Abstract: The spatial statistics formalism is applied to electromagnetic fields analysis. Fields are considered as realizations of a random function. Their spatial structure is studied by a method known as variographic analysis. To infer unknown values of the fields, an interpolation method called kriging is then used. It is shown how kriging can be performed on experimental or numerical data to speed up the fields estimation process.

Journal ArticleDOI
TL;DR: In this paper, the authors present RF applications of metamaterials combining ferromagnetic and dielectric structures for planar devices, and a theoretical explanation of defect modes operation in a magnetic photonic band-gap (PBG) structure is proposed.
Abstract: This paper presents RF applications of metamaterials combining ferromagnetic and dielectric structures for planar devices. Materials under scope are periodic dielectric substrates including ferromagnetic inclusions or not with planar metallic patterns, forming microstrip photonic band-gap (PBG) structures. These topologies are modeled, fabricated, and measured in order to design planar sensors and filters up to millimeter wave frequencies. In addition, defect modes that make the spectral properties of the PBG devices more attractive for narrow bandpass filters and high Q resonators are also investigated. A theoretical explanation of defect modes operation in a magnetic PBG structure is proposed.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the temperature increase in a realistic human head model exposed to five different cellular phone models by a bioheat equation and the finite-difference time-domain (FDTD) method at 900 and 1800 MHz, respectively.
Abstract: The temperature increase in a realistic human head model exposed to five different cellular phone models is investigated by a bioheat equation and the finite-difference time-domain (FDTD) method at 900 and 1800 MHz, respectively. These five cellular phone models are greatly differ from each other in structure. The realistic human head model is used to investigate the temperature increase in the head affected by varying factors including; electric properties of human head tissues, hand absorption power effect, cellular phone models, homogeneous and inhomogeneous head models, cellular phone material, and the distance between the cellular phone and the head. Computed results show that the temperature increase in the head reaches the steady-state value for exposure time of about 20 minutes. For worst-case, the maximum temperature increase in the head is found to be 0.19° C at 900 MHz and 0.055° C at 1800 MHz for the inhomogeneous human head with six tissues exposed to a metallic handset held by a hand, with a...

Journal ArticleDOI
TL;DR: In this article, the authors analyzed how the perfect electromagnetic conductor (PEMC) can be used as a component phase in complex material composites and showed that the electromagnetic response of such PEMC material obeys the constitutive equation relating the electromagnetic two-forms by a scalar factor.
Abstract: This article analyzes how the perfect electromagnetic conductor (PEMC) can be used as a component phase in complex material composites. The recently introduced PEMC concept connects the fullest isotropy with complex and nonintuitive material effects in electromagnetics. The electromagnetic response of such PEMC material obeys the constitutive equation relating the electromagnetic two-forms (in the four-dimensional formulation) by a scalar factor. The medium is studied from both the bulk and particulate point of view.

Journal ArticleDOI
TL;DR: In this paper, the rotation of the polarization plane of electromagnetic waves by the metallic helices is experimentally investigated based on the registration of polarization plane rotation of wave reflected by a two-dimensional (2D) lattice.
Abstract: The rotation of polarization plane of electromagnetic waves by the metallic helices is experimentally investigated. The object of investigation is electromagnetic waves scattered by the copper wire one-turn helices. Flat periodic structure consists of 1-turn helices placed on the radio transparent material that is manufactured. The helices are excited by a linear electromagnetic wave. The experimental method is based on the registration of polarization plane rotation of wave reflected by a two-dimensional (2D) lattice. The optimal pitch angle of the helix which is necessary for maximal rotation of polarization plane of waves was calculated previously. The optimal parameters of the helix were taken into account when the 2D lattice was manufactured. As a result even the flat lattice was enough for observation of considerable rotation of the polarization plane of transmitted and reflected waves. For transmitted wave, the resonance behavior of rotation of the polarization plane with sign change of angle of ro...

Journal ArticleDOI
TL;DR: In this article, the scattering from a metal plane with a ridge is considered for the cases of plane wave and line source illumination and both polarizations and exact analytical results are expressed using series that contain products of radial and angular Mathieu functions.
Abstract: The scattering from a metal plane with a ridge is considered for the cases of plane wave and line source illumination and both polarizations. Exact analytical results are expressed using series that contain products of radial and angular Mathieu functions. The exact analytical results are computed and compared with high-frequency approximations and with measurements.

Journal ArticleDOI
TL;DR: It is found that in general the digital circuits will reduce the error bit rates as signals propagate through when the EMI frequency is much higher than the signal frequency.
Abstract: This paper describes the analysis of intentional high-power RF interference on digital circuits. The interference is modelled as a noise in the form of a single-frequency pulse train (sinusoids or square waves) and is superposed to the pulse trains of the digital signals. SPICE simulations for a CMOS inverter and a 4-bit adder are performed to determine error bits at the circuit output with EMI injected at the input port for various interference frequencies and voltage levels. Propagation effect of error bits through the circuits is investigated. It is found that in general the digital circuits will reduce the error bit rates as signals propagate through when the EMI frequency is much higher than the signal frequency. Error bit rate amplifies when the EMI frequency is close to the signal frequency. The phase difference between EMI noise and signal also affects the bit errors. Bit error rate is further related to the external microwave source for the case of a wire penetrating a cavity aperture.

Journal ArticleDOI
TL;DR: In this paper, a solution for the diffraction problem related to a plane wave incident on a semi-infinite periodic structure, representative of a given distribution of equal microstrip patches, was proposed.
Abstract: This paper describes a proposed solution for the diffraction problem related to a plane wave incident on a semi-infinite periodic structure, representative of a given distribution of equal microstrip patches. It belongs to the set of the uniform asymptotic Physical Optics solutions and allows one to account for the edge effects in the design of microstrip reflectarrays. The non-diagonal matrix related to the specular direction of reflection is considered in the Physical Optics approximation of the equivalent electric and magnetic surface currents induced on the illuminated face of the truncated structure. Such current densities are inserted in the expression of the radiation integral and the diffracted field is evaluated by performing a uniform asymptotic evaluation of the resulting integral.

Journal ArticleDOI
TL;DR: Differential-form formalism appears to be an ideal tool for electromagnetic analysis because it allows one to express the basic electromagnetic laws in a most compact and elegant form However, equations involving bi-anisotropic media have practically never been studied in this formalism, which may be due to missing algebraic tools.
Abstract: Differential-form formalism appears to be an ideal tool for electromagnetic analysis because it allows one to express the basic electromagnetic laws in a most compact and elegant form However, equations involving bi-anisotropic media have practically never been studied in this formalism, which may be due to missing algebraic tools Introducing multivector dyadic algebra, a useful toolbox is obtained with which one can formulate medium problems in compact form Analysis of fields in some classes of media is briefly reviewed in this paper, showing that great simplification in the analysis can be attained through the differential-form formalism For convenience, an appendix giving the notation and basic algebraic rules for multivectors and dyadics is added at the end of the article

Journal ArticleDOI
TL;DR: In this article, both cubic-spline method and trigonometric series for shape description are used and compared and a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem.
Abstract: This paper presents a computational approach to the imaging of a perfectly conducting cylinder buried in a slab medium. Both cubic-spline method and trigonometric series for shape description are used and compared. We measure the scattered field in the first and third layers. Based on the boundary condition and the recorded scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is employed to find the global extreme solution of the object function. It is found that the shape described by cubic-spline can be reconstructed. In such a case, Fourier series expansion will fail. Even when the initial guess is far away from the exact one, the cubic-spline expansion and genetic algorithm can avoid the local extreme and converge to a global extreme solution. Numerical results are given to show that the shape description by using cubic-spline method is much better than that by the Fourier series. In addition, the ...

Journal ArticleDOI
TL;DR: In this article, the authors extended the finite element-boundary integral (FE-BI) technique for the analysis and design of cavity-backed antennas and arrays consisting of complex, inhomogeneous, and anisotropic materials.
Abstract: The modeling capability of the finite element-boundary integral (FE-BI) technique is expanded for the analysis and design of cavity-backed antennas and arrays consisting of complex, inhomogeneous, and anisotropic materials. The adaptive integral method (AIM) is implemented to accelerate the evaluation of the time-consuming boundary integrals. The modeling of anisotropic materials, impedance boundary conditions, and resistive boundary conditions is also addressed. Validation examples and comparison data are presented to demonstrate the acceleration and memory reduction achieved as a result of this enhancement.

Journal ArticleDOI
TL;DR: In this article, the study of pulse compression phenomena in periodically dielectric-slab-loaded TE 10 waveguide structures of conductive walls and finite length is carried out using wave analysis techniques when the structure is excited by a stepping frequency input signal waveform.
Abstract: The study of pulse compression phenomena in periodically dielectric-slab-loaded TE 10 waveguide structures of conductive walls and finite length is carried out using wave analysis techniques when the structure is excited by a stepping frequency input signal waveform. The periodically loaded waveguide shows highly dispersive phenomena and keeps losses to a minimum. The aim is to find a properly frequency modulated wave that propagates through this waveguide, so that pulse compression phenomena can take place. An exact Fourier analysis is carried out to compute the compressed wave field intensities.

Journal ArticleDOI
TL;DR: In this article, the operator properties of the generalized scattering matrix of the H-(E-) plane waveguide transformer in an arbitrary shape were examined analytically, and four fundamental laws of electromagnetism were used to derive a new form of generalized energy-conservation statement.
Abstract: This paper examines analytically the operator properties of the generalized scattering matrix of the H-(E-) plane waveguide transformer in an arbitrary shape. Four fundamental laws of electromagnetism are used to derive a new form of the generalized energy-conservation statement. The structure of spectrum of the generalized scattering matrix and the spectrum localization are established. A practical significance of the considered basic properties is illustrated by the example of matrix models of the waveguide bends. The obtained analytical results are useful for testing the correctness of numerical solutions, as well as for the mathematical justification of the methods based on modal analysis.

Journal ArticleDOI
TL;DR: A didactical sequence of the basic mathematical reasoning and the application of one of the most popular methods used for this purpose is proposed, clarifying several considerations which are usually omitted in textbooks or in previous technical papers on the subject, thus providing a time-saving reference tool for antenna designers who are unfamiliar with the topic.
Abstract: The technique of shaping the surface of satellite parabolic reflectors, illuminated by a single feed, in order to obtain a determined shaped contoured radiation pattern, with corresponding weight and cost savings, has become an important engineering problem. At present there are many sophisticated synthesis methods that have evolved in the last ten years, but a tutorial on the basics of the design procedure is missing in the literature. This article proposes a didactical sequence of the basic mathematical reasoning and the application of one of the most popular methods used for this purpose, clarifying several considerations which are very important but are usually omitted in textbooks or in previous technical papers on the subject, thus providing a time-saving reference tool for antenna designers who are unfamiliar with the topic. Typical surface deformation data for shaped reflectors at C, Ku, and Ka bands are given as a guideline for a set of different footprints, and a comprehensive and user-friendly ...

Journal ArticleDOI
TL;DR: In this article, a full-wave homogenization technique for the computation of the effective permittivity of perfectly conducting wires embedded in a dielectric host is presented. But the technique is illustrated with numerical examples and is compared with predictions from a classical mixing formula.
Abstract: In steel fiber reinforced concrete, steel fibers are randomly oriented in the concrete host. This article presents a full-wave homogenization technique for the computation of the effective permittivity of perfectly conducting wires embedded in a dielectric host. The technique is illustrated with numerical examples and is compared with predictions from a classical mixing formula.

Journal ArticleDOI
TL;DR: A hybrid geometrical theory of diffraction (GTD) method is presented to calculate the radiation patterns of slot antennas on both air-filled and partially dielectric-loaded rectangular waveguides with a finite wall size.
Abstract: This paper examines the effect of a finite ground plane on the radiation patterns of waveguide slot antennas. A hybrid geometrical theory of diffraction (GTD) method is presented to calculate the radiation patterns of slot antennas on both air-filled and partially dielectric-loaded rectangular waveguides with a finite wall size. The electric field distribution along the slot is obtained by a full-wave mode-matching method and then employed to calculate the geometrical optics (GO) field. The GTD is then applied to evaluate the diffraction from all the waveguide wall edges. Radiation patterns are finally obtained by the vectorial summation of the GO field and the diffracted fields. Numerical results obtained by our method are compared with measured data and those simulated by Ansoft's high frequency structure simulator (HFSS). Good agreement is observed for all the cases considered. The backward radiation is also examined for different sizes of waveguide wall on which the slots are cut.

Journal ArticleDOI
TL;DR: In this paper, a generalized dipole-enhanced approximation was proposed to calculate the electric field distributions at the surface of an arbitrarily selected spherical particle in a uniform external field, where the difference between the exact solutions and the ideal dipole approximations reflected the perturbations due to all the other particles.
Abstract: This paper presents a generalized dipole-enhanced approximation, considering the interactions among particles in a dielectric mixture, to calculate the electric field distributions at the surface of an arbitrarily selected spherical particle in a uniform external field. An approximate formula whose calculated results agree well with the exact numerical solutions obtained by the finite-element method is derived. This formula provides analytic solutions for the dielectric mixtures with high-volume fraction particles because it truly reveals the perturbations due to all the other particles. As the difference between the exact solutions and the ideal dipole approximations reflects the perturbations due to all the other particles, the difference calculated based on the dipole-enhanced approximation is applied to the prediction of effective permittivity for dielectric mixtures, and a modified mixing formula is presented.

Journal ArticleDOI
TL;DR: In this paper, a fast iterative method to solve for the fields scattered by thin layers of particles is presented, where the particles are randomly positioned within the layer and are characterized by means of their T-matrix.
Abstract: In this contribution, a fast iterative method to solve for the fields scattered by thin layers of particles is presented. The particles are randomly positioned within the layer and are characterized by means of their T-matrix. The memory complexity of the problem is reduced by dividing the layer into uniform cells. Different preconditioning techniques are applied to yield an iterative solution. The speed and the memory requirements of the presented algorithm are compared to a direct calculation approach. As an example, the scattered fields of up to 6000 dielectric spheres that are excited with a gaussian beam are calculated.

Journal ArticleDOI
TL;DR: An analytical and numerical investigation of the scattering of an electromagnetic wave from a perfectly conducting implant, embedded eccentrically into a dielectric spherical head model, using a dyadic Green's function for spherical vector wave functions.
Abstract: Despite the specific precautionary measures suggested in the media including hands-free operation of mobile phones, use of shields, limiting the duration of mobile phone usage, and choosing a mobil...