In this paper a semi-analytical representation of the coupling impedance between coils composed of filamentary turns located between two layered media is provided on the basis of the spectral expansion of the fields involved in the system. Both media are composed of several layers of homogeneous materials characterized by their physical properties occupying, respectively, a half-space bounded by a plane. The domain in the middle, where the coils are placed, has vacuum properties. The development is focused on misaligned circular coils placed in parallel planes with respect to the media boundaries. Two different behavioral descriptions have been considered: first, the system is made up entirely of magnetic insulators and the coupling impedance is therefore purely inductive; second, at least one medium is an electrical conductor and, as a consequence, an additional resistive component emerges when the coupling impedance is evaluated. In the latter case, the coupling impedance exhibits a frequency dependence due to the dispersive effects associated with the induced currents generated in the conductive media. The model developed is verified by means of a comparison between numerical and experimental results.

This paper presents a cavity backed slot antenna design with high gain and relatively small size. The large ground plane of the original design is cut 75%. Mushroom cells, ground plane orientation, and bending edges in the ground plane have been employed to improve the antenna gain. A 19.25 dB maximum gain is obtained with an average gain of 18.2 dB in the entire operating band.

Light scattering from small spherical particles has applications in a vast number of disciplines including astrophysics, meteorology optics and particle sizing. Mie theory provides an exact analytical characterization of plane wave scattering from spherical dielectric objects. There exist many variants of the Mie theory where fundamental assumptions of the theory has been relaxed to make generalizations. Notable such extensions are generalized Mie theory where plane waves are replaced by optical beams, scattering from lossy particles, scattering from layered particles or shells and scattering of partially coherent (non-classical) light. However, no work has yet been reported in the literature on modifications required to account for scattering when the particle or the source is in motion relative to each other. This is an important problem where many applications can be found in disciplines involving moving particle size characterization. In this paper we propose a novel approach, using special relativity, to address this problem by extending the standard Mie theory for scattering by a particle in motion with a constant speed, which may be very low, moderate or comparable to the speed of light. The proposed technique involves transforming the scattering problem to a reference frame co-moving with the particle, then applying the Mie theory in that frame and transforming the scattered field back to the reference frame of the observer.

Forward scattering effects have been studied and compared when nonhomogeneous medium is illuminated by coherent and quasi-noise sources operating in mm-wave and microwave ranges. Double-layers dielectric structure simulating Fabry-Perot resonator properties was employed to develop a relevant model used for comparing transmittances of both coherent and noise signals. Experiments with nonhomogeneous materials such as coal, wood chips, sand and others have proved the basic modeling predictions and the role of noise bandwidth in averaging process important for material characterizations. It was found out that efficient averaging associated with noise nature of probing signal can be reached for the relative noise bandwidth of 25% and more.

A 50 to 550 MHz wideband gallium nitride (GaN) HEMT power amplifier with over 43 dBm output power and 63% drain efficiency has been successfully developed. The demonstrated wideband power amplifier utilizes two GaN HEMTs and operates in a push-pull voltage mode Class D (VMCD). The design is based on a large signal simulation to optimize the power amplifier's output power and efficiency. To assure a wideband operation, a coaxial line impedance transformer has been used as part of the input matching network; meanwhile, a wideband a 1:1 ferrite loaded balun and low pass filters are utilized on the amplifier's output side instead of the conventional serial harmonic termination.

The purpose of this paper is to extend to spinor electromagnetism the differential forms, based on the Cartan exterior derivative and originally developed for tensor fields, in a very compact way. To this end, differential electromagnetic forms are first compared to conventional tensors. Then, using the local isomorphism between the O (3,C) and SL (2,C) groups supplying the well known connection between complex vectors and traceless second rank spinors, they are generalized to spinor electromagnetism and to Proca fields. These differential forms are finally expressed in terms of Hertz potentials.

In this paper, a low cost measurement system with high accuracy for radiated emission evaluation has been proposed. By combining the test data of the current probe at different positions on the harness, the measurement accuracy is improved compared with conventional single probe method For the sake of high accuracy, a transfer function is built to map the relationship between anechoic chamber method and current probe method. Based on experiments for evaluation, the final estimation of radiated emission agrees well with the measured results in anechoic chamber. For the cases tested, the difference between the current probe method and the anechoic chamber method is less than 3 dB.

Analytical investigations of the problem of dielectriccoated thin-wire antenna structures have invariably focused on the physics of developing appropriate models for the dielectric insulation on the thin-wire conductors that serve as antenna for the structure. These include the frequency domain moment-method-based approaches in which the dielectric insulation is replaced by equivalent volume polarization currents; and the time-domain analysis based on the `equivalent radius' concept. An earlier paper gave a physical interpretation to the frequency-domain solutions to suggest that the volume polarization currents derive from an equivalent static charge distribution, which excites an essentially radially-directed quasi-static field, confined to the region associated with the dielectric insulation. It is the main objective of this paper to investigate the veracity of the claims made in open literature as they concern the physics of the model for the dielectric insulation in terms of the electric field excited in the dielectric region. And to that end, simulation experiments were carried out, using a commercial Transmission Line Matrix (TLM) Method code, with which the characteristic features of the radial and axial components of the electric field within the dielectric region were investigated. The simulation results obtained from the experiments suggest that the field in question is not only of the quasi-static variety, but that it is also characterized by an axial component that meets the boundary condition of vanishingly small values on the surface of the conducting wire, to support the theory proposed.

For multi-channel SAR system, since the minimum antenna area constraint is eliminated, wide swath and high resolution SAR image can be achieved. However, compared to mono-channel SAR system, there exist many deleterious factors in multi-channel SAR system which significantly degrade the quality of SAR image. In this paper, all the deleterious factors in the system are analyzed and classified according to their impact on the SAR imaging processing, in addition an new array error estimation method is presented. The validity of the proposed method is verified by experimental results of measured Tri-channel SAR data.

A highly miniaturized 2.45/5.7 GHz dual-band bandpass filter is presented in this paper. It shows that the proposed filter which combines different sizes of open-loop resonators can excite two desired passbands. With the meandered technology and fractal geometry, the overall size is extremely compact compared with the published dual-band bandpass filters. Furthermore, the skirt selectivity of the proposed filter with two transmission zeros locating at both sides of the passbands is much improved. The rejection of the spurious response from 6.7 GHz to 14.5 GHz is successfully suppressed to the level lower than -15dB. The occupied area of the proposed filter is 9.8×8.7 mm². The measurement is in good agreement with the simulation

This research presents the implementation of the Finite-Difference Time-Domain (FDTD) method for the solution of 3-dimensional electromagnetic problems in dispersive media using Graphics Processor Units (GPUs). By using the newly introduced CUDA technology, we illustrate the efficacy of GPUs in accelerating the FDTD computations by achieving appreciable speedup factors with great ease and at no extra hardware/software cost. We validate our approach by comparing the results with their corresponding simulated results obtained from Remcom's XFDTD software.

A WiMedia compliant CMOS RF power amplifier (PA) for ultra-wideband (UWB) transmitter in the 3.1 to 4.8 GHz band is presented in this paper. The proposed two-stage PA employs a cascode topology on the first stage as driver while the second stage is a simple common source (CS) amplifier. In order to improve the efficiency and output power, the output impedance of the driver amplifier (first stage) is optimized so that it falls on the source-pull contours of the second stage amplifier. On-wafer measurement on the fabricated prototype showed a maximum power gain of +15.8 dB, 0.6 dB gain flatness, +11.3 dBm of output 1 dB gain compression and up to a maximum of 17.3% power added efficiency (PAE) at 4 GHz using a 50 Ω load termination, while consuming only 25.7 mW from a 1.8 V supply voltage. Measurement results obtained are used to create a non-linear powerdependent S-parameter (P2D) model for wideband input and output matching optimizations and co-simulations with the UWB modulated test signals. Using the created P2D model, the PA achieved a maximum output channel power of +3.48 dBm with an error vector magnitude (EVM) of −23.1 dB and complied with the WiMedia mask specifications.

Recent research on the array geometrical configuration shows that the two L-shaped array (TLSA) has a lower Cramer-Rao Low-Bound (CRLB) of two-dimensional (2-D) directions-of-arrival (DOAs) estimation than other array configurations. However, in this array configuration, there are some problems to note: i) three electric angles are independently obtained from three uniformly linear subarrays on three axes, so they must be matched before solving elevation and azimuth angles from them; ii) Similar to other array geometries, the effect of mutual coupling in the TLSA on the estimation performance cannot be ignored; and iii) the conventional elevation estimators may encounter estimation failure. In this paper, we develop a new TLSA-based 2-D DOAs estimation algorithm. The key points of this paper are: i) using some particularly selecting matrices, a trilinear model is constructed to compensate the effect of mutual coupling on three subarrays. In addition, the steering vector is restored using the trilinear alternating least square method; ii) 2-D DOAs are estimated from the properly chosen elements of the restored steering vector to avoid pairing parameters and the severe performance degradation resulted from the failure in pairing; and iii) a new elevation estimator is designed to avoid estimation failure. Simulation results are presented to validate the performance of the proposed method.

A novel printed dipole antenna was designed for the L-band satellite communication system INMARSAT (Downlink: 1525--1559 MHz, Uplink: 1626.5--1660.5 MHz). Several structural parameters were experimentally studied with care to establish a design procedure. The measured results show that the impedance bandwidth for return loss below -10 dB is about 170 MHz and that the half-power bandwidth (HPBW) can be up to 110°. The antenna can be used in high latitudes because of wider HPBW.

Exact formulas for internal impedance per unit length of tubular cylindrical conductors energized by time-harmonic current involve Bessel functions. These functions are defined by infinite series, which yield unstable and often erroneous results for complex arguments of large magnitudes. Although it is well known how to evaluate Bessel functions numerically and many routines are now available to perform the actual computation, the available software routines often fail when computing equations that consist of a product and a quotient of Bessel functions under large complex or real arguments. For such cases, different approximate formulas can be used. In this paper, three types of approximate formulas for internal impedance of tubular cylindrical conductors are compared with respect to numerical stability and accuracy.

We have developed an array antenna consisting of 12 elements of simple square-shaped, corner-truncated patches for circularly polarized synthetic aperture radar (CP-SAR) operated in the L-band. The corporate feed design concept is implemented by combining a split-T and a 3-way circular-sector-shape power divider to excite circularly polarized radiation. The fabricated antenna based on the simulation using moment method gives a good circular polarization at the center frequency of 1.27 GHz with an impedance bandwidth of 6.1% and 3-dB axial ratio bandwidth of 1.0%, satisfying the specification for our circularly polarized synthetic aperture radar intended for use onboard an unmanned aerial vehicle and a small satellite.

A novel type of ultra-wide band (UWB) crossed semi-ring monopole antenna with band notched characteristics is presented. The proposed antenna consist a wideband crossed semi-ring monopole and four L-shaped slots, producing band-notched characteristic. Effects of the various parameters for antenna performances are discussed. The central frequency and bandwidth of the notched band can be controlled easily by adjusting three key design parameters. The time domain responses are simulated and studied. A prototype is constructed and measured finally.

A theoretical study of optical properties of phase shift defects in one-dimensional asymmetrical photonic structures consisting of two rugate segments with different periodicities at both normal and oblique incidence is presented. Using the propagation matrix method we numerically calculated transmittance spectra, defect wavelengths, energy density distributions, and group velocities for TE and TM waves, respectively. Our study shows that by adjusting the periodicity of one rugate segment, the defect wavelengths can be shifted toward either a shorter wavelength or a longer wavelength. The differences of the energy density distributions of TE and TM waves at different angles of incidence are explained with the help of group velocity. Effects of the change of the period of one rugate segment on the peak energy densities of defect modes and minimum group velocities at different angles of incidence are also investigated.

Recently, the use of the particle swarm optimization (PSO) technique for the reconstruction of microwave images has received increasing interest from the optimization community due to its simplicity in implementation and its inexpensive computational overhead. However, the basic PSO algorithm is easily trapping into local minimum and may lead to the premature convergence. When a local optimal solution is reached with PSO, all particles gather around it, and escaping from this local optima becomes difficult. To overcome the premature convergence of PSO, we propose a new hybrid algorithm of particle swarm optimization (PSO), simulated annealing (SA) and tabu search algorithm (TS) for solving the scattering inverse problem. The incorporation of tabu search (TS) and simulated annealing (SA) as local improvement approaches enable the hybrid algorithm to overleap local optima and intensify its search ability in local regions. Reconstructions of dielectric scatterers from experimental inverse-scattering data are finally presented to demonstrate the accuracy and efficiency of the hybrid technique.

The characteristics of guided modes in the four-layer slab waveguide containing chiral nihility core have been investigated theoretically. The characteristic equation of guided modes is derived. The dispersion curves, energy flux and normalized power of guided modes for three cases of chiral metamaterial parameters are presented. Some abnormal features are found, such as the existence of fundamental mode and surface wave mode, unusual dispersion curves, positive energy flux in the chiral nihility core, and zero power at some normalized frequencies.