Previously derived asymptotics for diffraction by strongly elongated body is generalized to the case of nonaxial incidence. By applying "parabolic" equation method the asymptotics of the field in the boundary layer near the surface is constructed. This asymptotics takes into account the rate of elongation of the body and is applicable both to not too much elongated objects, where it reduces to Fock formulae, and to very elongated bodies.

Magnetic field shielding at low frequencies is a problem of high importance that is known for a long time. Metamaterials, which are known from fancy applications such as the so-called perfect lens and cloaking, also offer a new way to create efficient magnetic shielding by means of anisotropic metamaterials with low permeability in one direction. Such metamaterials can be constructed by assembling arrays of relatively simple LC circuits. In this paper, we analyze different metamaterials and show how they may be designed. We show that typical resistive losses in the coils and capacitors of the LC circuits reduce the shielding quality. Then, we consider the possibility of active electronic loss compensation and discuss the drawbacks of this concept. After this, we propose a purely passive way that benefits from the inhomogeneity of the magnetic field to be shielded. Finally, we present experimental results, which show the performance of metamaterial shields.

A 3-D shaped prolate ellipsoidal dielectric lens is designed to produce multiple asymmetric beams in Ka-band. Such radiation characteristics are useful in applications where the antenna system is mounted on platforms flying above Earth and the shape of the footprints have to be carefully controlled for different elevation angles. A set of design rules is introduced and the final designs are optimized using full-wave time-domain methods. A fully operational Ka-band antenna subsystem has been prototyped and measured. The final antenna lens has axes lengths of 62.3 mm and 57.8 mm and provides a maximum gain of 21 dB. When mounted on a stabilized platform at the altitude of 21 Km (a typical HAPS scenario), this antenna provides 19 circular ground footprints of 5 Km diameter each. Radiation pattern measurements show that such a lens reduces the natural beam footprint elongation unavoidable with traditional spherical lenses and confirm the validity of the proposed system.

This paper presents experimental results in the study of Space-surface Bistatic SAR (SS-BSAR) with global navigation satellite system (GNSS) and stationary receiver. The system uses GNSS as the transmitter of opportunity and a self-built, low cost receiver being set-up and fixed on the earth. It is potentially useful at remote sensing applications such as earth monitoring. The system prototype and signal processing at each stage leading to final image are described. Experimental image analysis is the core of this paper, and therefore performed in details finally.

Space spectral domain approach (SSDA) is a full-wave analysis method that combines the advantages of the spectral domain analysis (SDA) with that of the one dimensional method of lines (MOL). This approach is very efficient to solve 3D MIC/MMIC circuits with higher convergence, higher accuracy and minimized computation time. However, arbitrary shaped structures involving non-homogenous metallization distribution in the resonator patch could hardly be solved using this method. In this paper, the analysis of the space spectral domain approach (SSDA) is developed using non-equidistant MOL discretization as well as modified current basis functions to reduce the computation time window and to sense also accurately the fine metallization details of arbitrary shaped resonators. The modified SSDA approach is applied to solve ten arbitrary shaped resonators with a reduction of computation time less than 10%. Design curves are also presented for these shapes and good agreement is achieved between numerical and experimental results.

It is well known that additional space harmonics in the air-gap magnetomotive force (mmf) distribution of the concentrated non-overlapping windings (CW) cause additional losses in the machine. This is especially so for machines used for traction applications where the machine requires to operate over its rated speed and frequency. In this paper, the authors investigates losses present in an interior permanent magnet (IPM) machine with CW designed to achieve a very wide field weakening range. Losses were quantified analytically and also using finite element methods. Loss estimations were experimentally verified in a constructed prototype machine. Based on the analysis, key losses were identified. The optimization process to minimize these losses and of improving efficiency were discussed in details. The segregation of the losses in the studied machine indicates that the losses in the magnet are much smaller compared to the rotor and stator core losses caused by the slot harmonics. Therefore, core loss minimization techniques for this type of machine will involve reduction of slot harmonics. Also, copper loss is found to be the most dominating component of the total loss. Hence, copper loss minimization should be part of the design optimization process.

In this paper, a new dual band balanced-to-balanced power divider is proposed. By using the dual frequency 90° phase shifter based T model, the proposed balanced-to-balanced power divider can be deduced. By using the method in our previous work, the dual band balanced-to-balanced power divider could be designed with 1:1 power division. This balanced-to-balanced power divider is implemented on microstrip structure. Comparing the results calculated in analytical method with that simulated by the full-wave electromagnetic simulator, and that measured by the network analyzer, the final results show that they have a good mixed mode performance. The pass band 1 is from 2.395 GHz to 2.550 GHz, and the pass band 2 is from 5.245 GHz to 5.30 GHz. The maximum isolations for pass band 1 and pass band 2 are 17.8 dB and 17.6 dB, respectively.

In high power applications of wireless power transfer systems as Maglev, both a high transferred power and a high efficiency are essential. However, these two requirements usually show dissimilar profiles over a range of operating conditions. Magnetic and electric models for a capacitor compensated system are used to analyze the problem. Using the analysis outcome, a compromise is made to come to an acceptable design, achieving both requirements. In particular, appropriate design parameters and resonance frequency are obtained. The analytical results are confirmed by 3D FEM analysis.

A method is presented for computing aperture-radiated fields in terms of complex-source type beams. These beams are generated in a natural way by expanding the aperture field spectrum in a sum of complex exponentials. The latter are obtained by using the 2D-GPOF method. Inverse transformation in spatial domain leads to an analytical form in terms of complex source points. Fields radiated by apertures obtained via this approach are validated by direct near field integration and compared with those calculated with spectral-based beam expansion which starts from the Hankel spectrum and uses a 1D-GPOF approach.

A serial resonant antenna for the large field of view (FOV) magnetic resonance imaging (MRI) is presented. It consists of metallic patches cascaded through lumped capacitors in serial on the top layer of a grounded dielectric substrate. The theoretical analysis show that at the resonant frequency, uniformly distributed current with zero phase delay is produced independent of the antenna length, hence a uniform magnetic field for large FOV MRI can be achieved. Integrated with the L-shaped tunable matching network, the antenna can be tuned easily to operate rigorously at the working frequency of the MRI system. The numerical modeling, physical fabrication and measurement, as well as the phantom imaging are carried out to design, characterize and verify the performance of the proposed antenna for MRI.

An extensive error analysis for arbitrary near-field antenna measurements is performed. Expressions are derived to estimate the far-field uncertainty using the available near-field data together with the measurement inaccuracy but, most importantly, without the knowledge of the reference far field. Error analysis techniques presented so far either assume a specific set of antennas or a specific measurement surface and are difficult to generalize. We present a generalized approach providing realistic error estimates using the recently developed Fast Irregular Antenna Field Transformation Algorithm (FIAFTA). FIAFTA utilizes equivalent plane wave sources to represent radiated antenna fields and is able to process near-field data collected on arbitrary measurement grids. The unknown plane wave coefficients are determined by solving a linear system of equations. The error model is applied to planar, cylindrical, and spherical near-field measurements and is also valid for arbitrary measurement grids. The estimated far-field uncertainties show good agreement with the real far-field errors.

In this paper, a novel coplanar waveguide (CPW) fed dual band-notched ultra-wideband (UWB) antenna with circular slotted ground is proposed. In order to achieve two notched bands at 3.3-3.7 GHz for worldwide interoperability for microwave access (WiMAX) and 5.15-5.825 GHz for wireless local area network (WLAN) respectively, a pair of bended dual- L-shape branches are attached to the slotted ground. By optimizing the lengths and positions of the branches, the desired notch-bands of WLAN and WiMAX can be achieved. The prototype of the proposed antenna was fabricated and tested. The simulated and measured results show good agreement over the ultra-wideband. Besides these mechanical features, such as compact in size, easy in fabrication, the proposed antenna also shows good characteristics in its radiation patterns and time-domain behaviors. So it is a nice candidate for modern UWB communication systems.

Dependence of the electromagnetic shielding effectiveness on filler volume fraction has been investigated from attenuation upon reflection measurements over a broad frequency range in hybrids based on Poly(vinylidene fluoride)-Aluminum nanoparticles. The loss of reflectivity with relation to the incident radiation in these nanocomposites compared with the pristine polymeric matrix shows the maximum value for the sample with an aluminum content of 10% in volume. Furthermore, the morphological aspects of all the specimens as well as their thermal properties, viscoelastic behavior and dielectric response have been evaluated. The nanocomposite that incorporates an Al content of 10% in volume exhibits the best balance in properties including, in addition to its shielding behavior, its processability and mechanical performance.

This paper presents a rigorous approach for the propagation of electromagnetic (EM) fields along a straight hollow waveguide with a circular cross section. The objectives are to present the technique to calculate the dielectric profiles and their transverse derivatives in the inhomogeneous cross section of the cylindrical hollow waveguide, and to understand the influence of the spot-size and cross section on the output fields and output power density. The derivation is based on Maxwell's equations. The longitudinal components of the fields are developed into the Fourier-Bessel series. The transverse components of the fields are expressed as functions of the longitudinal components in the Laplace plane and are obtained by using the inverse Laplace transform by the residue method. The separation of variables is obtained by using the orthogonal-relations. These objectives contribute to the application of the model for the straight hollow waveguide.

This paper presents a convex meshfree framework for solving the scalar Helmholtz equation in the waveguide analysis of electromagnetic problems. The generalized meshfree approximation (GMF) method using inverse tangent basis functions and cubic spline weight functions is employed to construct the first-order convex approximation which exhibits a weak Kronecker-delta property at the waveguide boundary and allows a direct enforcement of homogenous Dirichlet boundary conditions for the transverse magnetic (TM) mode analyses. Three arbitrary waveguide examples are analyzed to demonstrate the accuracy of the presented formulation, and comparison is made by the analytical, finite element and meshfree solutions.

A novel compact microstrip planar slot antenna with triple-band operations for WALN and WiMAX applications is proposed. The antenna, which occupies an overall dimension of 35×19×1.6 mm³, has a simple structure which consists of an asymmetric coplanar strip with a reverse G-shaped slot and a U-shaped open stub. The U-shaped open stub excites a resonant mode at 2.4 GHz. On the other hand the asymmetric coplanar strip could excite the resonant modes at 5.2 GHz. Meanwhile, the reverse G-shaped slot is aimed to excite resonant modes at 3.5 and 5.8 GHz. It has good omnidirectional radiation patterns in the azimuth plane and reaches 1.1 dBi at 2.4 GHz, 2.3 dBi at 3.5 GHz, 3.1 dBi at the band of 5 GHz. The designed antenna is simulated by HFSS software and a good agreement with experimental results is demonstrated.

A through wall image enhancement scheme based on Takagi Sugeno fuzzy system and principal component analysis is proposed. The scheme incorporates spectral properties of image and textural properties of eigen components of image to assign weights. The scheme overcomes the empirical setting of inference engine and output membership functions. Simulation demonstrates the effectiveness of proposed scheme in terms of accuracy.

Within the framework of the composite surface scattering model, analytical formulas for Doppler shift and bandwidth of radar echoes backscattered from time-varying sea surface are derived in the forms of three-dimensional integrals. In our derivations, the influences of the tilt modulation (TM), the hydrodynamic modulation (HM), the shadow and the curvature of large-scale undulating waves are all taken into account for achieving more reasonable results. Comparisons between our theoretical curves and the results obtained directly by exact numerical method demonstrate that our formulas can improve the simulated results. On the other hand, the simulations by our formulas can also help to estimate the effects of the TM, the HM, and the shadow of large-scale waves on Doppler behaviors individually. We find that the predicted Doppler shifts are always larger in HH-polarization than in VV-polarization due to the TM. Meanwhile, the simulations also show that the predicted Doppler shifts for both HH- and VV-polarizations would become larger when the HM is considered. In addition, at low-grazing angles (LGA), the shadow effect results in a rapid increase in the predicted Doppler shift, and on the contrary makes the bandwidth narrower.

In this paper, coupled lines are used in the design of a dual band planar multi-way Bagley polygon power divider to reduce the size is proposed. For the input port matching and transmission characters are affected by the even mode impedance only, analysis of the multi-way Bagley polygon power divider and equivalent circuit based on coupled lines, closed form design equations are presented with even mode impedance, and odd mode impedance is obtained arbitrarily. To validate the design procedure, two dual band three-way Bagley polygon power dividers are designed, simulated, and fabricated using coupled lines with areas of 3.17 cm² and 2.53 cm², and the corresponding conventional divider with areas of 17.86 cm² and 11.74 cm², respectively. When coupled lines are used, the layout is more compact with a reduction in size of more than nearly 80% compared to the conventional design.

In this work, we analyze the effects of an inter-stage capacitor located between the power stage input and the driver stage output on the overall efficiency of a RF CMOS power amplifier and on gate-drain reliability problems. To verify the analyzed effects, we designed a RF CMOS power amplifier with a center frequency of 1.85-GHz. Class-D amplifiers with a feedback resistor are used as driver stages, and a class-E amplifier is used as the power stage. A distributed active transformer is adapted for use in the output power combiner for high efficiency. The inter-stage capacitor between driver and the power stage is removed to enhance the switching operation of the power stage. By eliminating the inter-stage capacitor, the supply voltage of the driver stage can be decreased compared to that in a general amplifier. Accordingly, the power-added efficiency is improved and the gate-drain reliability problems are moderated compared to a general amplifier. The analyzed effect of the inter-stage capacitor is verified successfully using the measured results of the designed amplifiers.