In this paper, we present an improved Coulombianbased analytical calculation of magnetic fields created by permanentmagnetic rings. The 3 dimensional (3D) components of two types of magnetized rings (axially and radially) were analytically evaluated. The obtained components of the magnetic field are expressed over complete elliptical integrals of the first and second kind, as well as by Heuman's Lambda function. These expressions permit fast and accurate calculations of the magnetic field at any point of interest, for both regular and singular cases. The presented method gives an improvement of already known expressions for calculating the magnetic fields of the aforementioned magnetized rings, and we consider that these improved analytical expressions are more extendable to numerical applications.

This paper presents a broad-band technique for measuring the dielectric permittivity of isotropic nonmagnetic film-shaped materials at low microwave frequencies. The material under test is the substrate of an open-end coplanar waveguide (CPW) used as sample-cell. The dielectric permittivity is extracted from S₁₁ reflection parameter measurement of the open-end CPW cell using analytical relationships, which allow to decrease the computation time with respect to any full-wave electromagnetic method. Vector network analyzer (VNA) and high-quality on-coplanar test fixture are used for the measurements between 300 kHz and 3 GHz. Measured ε_r data for several nonmagnetic low-loss materials are presented. This technique shows a good agreement between measured and predicted data for the real permittivity over 0.05 GHz-3GHz frequency range.

With development of communication with integration technology, size reduction of microstrip antennas is becoming an important design consideration for practical applications. Here a new microstrip antenna with Koch shaped fractal defects on the patch surface is presented. Using this method, the overall electric length of the antenna is increased largely and hence the size of antenna is reduced to 85%, compared to an ordinary microstrip antenna with the same resonance frequency. Antenna is simulated using high frequency structure simulator (HFSS) V.10 which is based on finite element modeling (FEM). Finally antenna is fabricated on RO4003 substrate. Measurement results are in good agreement with simulated results.

In this paper, a broadband bandpass filter (BPF) with superior spurious suppression over a wide frequency range at least up to 20 GHz at −20 dB has been designed. The proposed broadband bandpass filter has designed using quarter-wavelength short stubs alternating with branch stubs co-via structure, and inserting the bandstop filters to substitute for redundant connecting lines. Compare with some traditional co-via structure, this work by using the branch stubs to construct the co-via structure, not only reduce the size around 70% but also decrease the radiation loss due to some complex meander configurations occurring in the connecting lines. For the prototype broadband filter, center frequencies around 4 GHz were selected. The bandwidth of passband was between 1.95 GHz and 6.25 GHz, in which the insertion-loss amounts to around −1.5 dB. The suppression range of stopbandis between 8.2-20.3 GHz, in which the insertion-loss amounts to around −20 dB.

The 3D probability tomography theory is developed to image polar and dipolar sources of a geophysical field dataset. The purpose of the method is to improve resolution power of buried geophysical targets, using probability as a suitable paradigm allowing all possible equivalent solutions to be included within a single 3D image. The new approach is described by assuming a geophysical field dataset as caused by a discrete number of source poles and dipoles. A few tests are given to show how the combined polar and dipolar tomography can provide a reliable core-and-boundary resolution of the most probable sources of anomalies. An application to the Vesuvius volcano (Naples, Italy) is finally illustrated by analyzing self-potential and geoelectrical datasets collected within the whole volcanic area. A gravity dataset is also analyzed for completeness. The purpose is to get new insights into the Vesuvius shallow structure and hydrothermal system and to outline the features of the deep tectonic depression within which the volcano grew.

A technique to characterize the fields generated by a cell phone, and projected into an area inside a TEM cell for possible biological interaction studies is described. A double-ended monopole antenna is proposed as the lead signal inducer between the inside and the outside areas of the TEM cell. The coupling voltage at the TEM cell ports and the field distribution within the area under test (AUT) were found to be a function of the phone position, polarization, and dialing type. The measurements for a GSM 850MHz cellular phone showed that the optimum setup is achievable when the phone is placed outside the TEM cell and co-polarized with the signal leader. An improvement of the field uniformity is possible with the use of a shorter signal leader but at the cost of decreased field strength. The proposed setup can be utilized in studies and experiments related to the radio frequency effects on biological cells and organs.

In this paper, we present an adaptive beamforming scheme for smart antenna arrays in the presence of several desired and interfering signals, and additive white Gaussian noise. As compared with standard schemes, the proposed algorithm minimizes the noise and interference contributions, but enforces magnitude-only constraints, and exploits the array-factor phases in the desired-signal directions as further optimization parameters. The arising nonlinearly-constrained optimization problem is recast, via the Lagrange method, in the unconstrained optimization of a non-quadratic cost function, for which an iterative technique is proposed. The implementation via artificial neural networks is addressed, and results are compared with those obtained via standard schemes.

The position perturbations of linear antenna elements are used for designing non-uniformly spaced reconfigurable antennas radiating with multiple pattern such that the same amplitude distribution and perturbed positions produces either a pencil or a flat topped beam, the difference being dependent upon phase distribution of the array. The perturbation method consists of inducing small perturbations in the element positions of a linear array to obtain the desired patterns and offer the flexibility of simple design and is similar to other adaptive techniques like phase only or phase/amplitude synthesis. The problem of finding the element position perturbations is treated as a non linear problem and has been solved using a the generalized generation gap steady state genetic algorithm (G3-GA) using parent centric crossover. In the G3-GA approach the population diversity versus selection pressure problem considers both the parent selection and the replacement plans of GA. The positionphase synthesis method using the G3-GA approach is compared with the G3-GA phase-only synthesis technique. It is seen that, an optimal set of element-perturbed positions in a constrained position range with uniform amplitude, unequally spaced elements with unequal phases has the potential to overcome the design challenge of phase only syntheses that uses a larger number of elements to get the same desired side lobe level. Further when the main beam is scanned it is found that the proposed method can maintain a sidelobe level without distortion during beam steering for the angular positions studied.

For maneuvering target Doppler-bearing tracking with signal time delay, a novel approach called ISE-IMM is proposed in this paper. The iterative state estimation (ISE) method is designed to eliminate the negative influence of time delay effect and an interacting multiple model (IMM) filter is embedded to estimate the state according to the measurements of the delayed signal. The nonlinear filter preferred in this paper is a particle filter (PF) with an improved resampling procedure. Performance of our proposed method is evaluated in Monte Carlo simulations. Results show the effectiveness and stability of ISE-IMM-PF in combating the negative effect of signal time delay.

A time domain integral equation approach for analysis of transient responses by 3D composite metallic-dielectric bodies is proposed, which is formulated using the surface equivalent polarization and magnetization as unknown functions. The time domain electric field integral equation is adopted for the metallic part, while the time domain Piggio-Miller-Chang-Harrington-Wu integral equations are adopted for the dielectric part. The spatial and temporal basis functions are the Rao-Wilton-Glisson functions and quadratic Bspline functions, respectively. Numerical examples are provided to demonstrate the stability and accuracy of the proposed method. No late-time instability is encountered, and the results are found in good agreements with analytical or moment method solutions.

Simulation and realization of an active metamateial cell are presented. This metamaterial cell has a power loss due to resistance in the coils. This paper presents a new nanometer negative resistance MOSFET (NR-MOSFET), which is used as a controllable negative resistance to compensate for the nanometer metamaterial losses. The negative resistance was about -320Ω. A form of a lumped circuit model with active and passive resonance is presented. A negative real part of the refractive index exists in a band width from 1.11 GHz to 1.22 GHz. This model can be used as a core cell for mobile communication smart antenna.

This paper applies He's Energy balance method (EBM) to study periodic solutions of strongly nonlinear systems such as nonlinear vibrations and oscillations. The method is applied to two nonlinear differential equations. Some examples are given to illustrate the effectiveness and convenience of the method. The results are compared with exact solutions which lead us showing a good accuracy. The method can be easily extended to other nonlinear systems and can therefore be found widely applicable in engineering and other science.

A new and efficient proposal for all-optical tunable devices and systems using electromagnetically induced transparency (EIT) is proposed. For this purpose a slab doped with quantum dots for realization of three-level atomic system is considered. Density matrix formulation for evaluation of the proposed structure is used. The reflection and transmission coefficients of the considered slab are calculated and the related amplitude and phase quantities studied versus parameters of the structure. We show that some nanometer tuning with application of the control field is obtained. So, the proposed idea can open a new realization method of all-optical tunable devices and systems towards all-optical systems.

The critical-points method is adopted for measuring unloaded Q-factor of microwave resonators in the presence of phase shift caused by the feed line. The result is calculated from four frequencies of three points in the resonator's impedance trace. In fact, the resonator's impedance trace rotates in Smith Chart by the phase shift. If Q-factor were gotten directly from the measured impedance including feed line rather than the equivalent impedance of the resonator without feed line, the performance of measurement will be impaired. To de-embed the phase shift, objective function was introduced to find the proper rotation angle caused by the feed line instead of calibration using extra measurement. Another advantage of the proposed method lies in the fact that no special attention is needed to distinguish magnetic coupling and electric coupling. The effectiveness of the proposed method was demonstrated by one set of simulation data and two measurement examples, namely, a low Q dielectric resonator and a high Q hollow cylindrical cavity.

An air-spaced coaxial-fed patch antenna to be used as a microwave sensor for non-destructive porosity measurements in lowloss dielectric materials is presented. The variation of the patch resonant frequency when it is put on the surface of the material under test is used to estimate the dielectric permittivity. Then, a standard two-phase mixture model is used to derive the material degree of porosity from the above permittivity estimate. Measurements at the 2.4 GHz ISM frequency band have been carried out on a set of polymeric samples with artificially induced porosity. The specific choice for the operating frequency is related to the final goal of applying the above microwave sensor for quality control of ceramic materials during the production process.

In this paper, an extremely fast technique is introduced to evaluate the shielding effectiveness of a rectangular enclosure of finite wall thickness and numerous square or circular small apertures subject to a normally incident plane wave. The technique is based on the traditional waveguide circuit model where the enclosure is replaced with an equivalent shorted transmission line. In the proposed circuit model, the perforated thick wall is represented by an equivalent impedance which is derived from the reflection coefficient. The computation results are in very good agreement with measurements. Additionally, further results are compared to a generalized modal MoM technique which are in excellent agreement as the number of apertures increase. Besides accuracy, the method is extremely efficient and easy to implement compared to the numerical techniques.

A geometrical high-frequency approximation method for solving the propagation of electromagnetic wave through the quartic Wood lens into an uniaxial crystal is presented in this paper. Caustic problem of electromagnetic wave is translated into non-caustic problem by using the hybrid space. The drawback that the solution in the caustic region cannot be obtained with geometrical optics is overcome by this method known as Maslov's method. The high-frequency approximation solution that is valid around caustic region is obtained by using this method which combines the simplicity of ray and generality of the transform method. And the results are compared with those obtained by Huygens-Kirchhoff's expression.

This paper presents the design and construction of an advanced wideband, automated radar system. With the aid of Vector Network Analyzer (VNA), a wideband ground-based system can be achieved with proper Radio Frequency (RF) circuitry integration. The RF circuitry is designed specifically to configure the proposed system to be able to measure full linear polarimetric scattering matrices of the area of in terest. Besides, quasi-monostatic horn antenna configuration is chosen to transmit and receive the electromagnetic wave. The goal of this paper is to demonstrate the real and synthetic aperture capabilities of the system in outdoor measurement with the microwave frequency range from 2 to 7 GHz. Coupled with the integration of the Automatic Antenna Positioning System (AAPS), the constructed system is able to perform real and synthetic aperture radar measurements. A series of measurement was done on real aperture radar measurement using point target for validity purpose. The overall results show good agreement with the theoretical values. On the other hand, the proposed system is capable to performing a radar imaging measurement. A preliminary analysis is done on a 45 days old rice field. A three dimensional (3-D) radar image has also been constructed successfully with Range Migration Technique (RMA). The result shows good potential ofthe system in constructing radar imaging ofnatural target.

Diffraction of an electromagnetic plane wave from a slit in an impedance plane placed at the interface of two different media, has been formulated rigorously. Both the principal polarizations are considered. The method of analysis is Kobayashi Potential (KP). To determine the unknown weighting functions, boundary conditions are imposed which resulted into dual integral equations (DIEs). These DIEs are solved by using the discontinuous properties of Weber- Schafheitlin's integrals. The resulting expressions are then expanded in terms of Jacobi's polynomials. The problems are then, reduced to matrix equations with infinite number of unknowns whose elements are expressed in terms of infinite integrals. These integrals are hard to solve analytically. The integrals contain poles for particular values of surface impedance and are solved numerically. Illustrative computations are given for far diffracted fields and other physical quantities of interest. To check the validity of our work, we compared the far field patterns with those of obtained through Physical Optics (PO). The agreement is good.

The reliable design of a satellite communications network, operating at Ku band and above, requires the exact evaluation of the interference effects on the availability and performance of both the uplink and downlink. In this paper, the case of Uplink Adjacent Satellite Network Interference is examined. We accurately calculate the deterioration of the uplink clear sky nominal adjacent satellite network Carrier-to-Interference threshold, due to spatial inhomogeneity of the propagation medium. At these frequency bands, rain attenuation is the dominant fading mechanism. Here we present an analytical physical model for the calculation of Interference Statistical Distribution between adjacent Broadband Satellite Networks operating at distances up to 500 km. We employ the unconditional bivariate lognormal distribution for the correlated rain fading satellite channels. Useful numerical results are presented for satellite networks located in different climatic regions and with various quality of service (QoS) assumptions.