Structure with non-negative effective permittivities in the radial and tangential directions can also perform far-field imaging beyond the diffraction limit since the dispersion curves can be long and flat enough and utilized to transfer the subwavelength information. Thus we propose an impedance-mismatched hyperlens with such a dispersion curve and increasing thicknesses (from the innermost layer to the outermost) to reduce reflection losses due to the impedance difference between the nearby layer pairs. Compared with the hyperlens with same thickness for each period, the resolution ability of the hyperlens with varying thicknesses can be improved dramatically, while the image intensity is weaker. Furthermore, the influence of the layer number on the imaging is also analyzed to improve the performance of the system and an improved hyperlens with repeated thickness setting is also utilized to increase the intensity of the magnified image.

A broadband dual-polarized four-port (DPFP) antenna is presented in this paper, which consists of a radiation element and a feed network. It is very compact in size, with the diameter of 150.0 mm and the height of 47.0 mm, with the following unique properties: (1) it has hybrid beam-forming capability and operates at two modes, which depends on its excitation; (2) its operating frequency range is from 0.96 to1.78 GHz, and the return loss is about 10 dB; (\ref{eq3}) its insertion loss is (3±0.5) dB, with its balanced power splitting over the relative bandwidths of 37% at Mode 1 (180°±5° phase shifting) and 55% at Mode 2 (±5° phase shifting), respectively; (\ref{eq4}) an isolation of 30 dB at Mode 1 is obtained between the dual polarized ports, with the gain of 7.6 dBi and 42° of the 3 dB-bandwidth at 1.25 GHz; and (5) the gain difference between Modes 1 and 2 is about 7 dB, within the angle of -15° ≤ θ ≤ 15° for the same polarization at 1.25 GHz. For the application of DPFP, a hybrid beam forming algorithm is proposed with an angular precision of 3°, as validated by measurement.

In this article, a compact microstrip-fed printed dual band antenna for Bluetooth (2.4-2.484 GHz) and UWB (3.1-10.6 GHz) applications with WLAN (5.15-5.825 GHz) band-notched characteristics is proposed. It is demonstrated that dual band characteristics with desired bandwidth can be obtained by using a fork shaped radiating patch, whereas, band-notched characteristics can be obtained by etching two L-shaped slots and two symmetrical step slots on the rectangular ground plane. The proposed antenna is simulated, fabricated and tested. The structure is fabricated on a low cost FR4 substrate having dimensions of 50 mm (L_sub) × 24 mm (W_sub) × 1.6 (H) mm and fed by a 50 Ω microstrip line. The proposed antenna has S₁₁ ≤ -10 dB over 2.18-2.59 GHz, Bluetooth band, 3.098-5.15 GHz and 5.948-11.434 GHz, UWB band with WLAN band notch. The structure exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation over the desired bands.

This paper studies static effect of communication Low Noise Amplifier (LNA) that utilizes GaAs wafer. It analyzes the Electro-Static Discharge (ESD) effect, which occurs within communication components, such as GaAs LNA, and describes testing standard and methods. In order to find out GaAs LNA's susceptibility to static, two well-recognized communication GaAs LNA IC models were selected to be tested. Commercial program allowed measuring of static energy inserted within LNA's internal circuit by running a simulation about static discharge of GaAs LNA. Then we analyzed malfunctions caused by static and discussed about architectural problem and improvement according to the test and simulation result, from the perspective of GaAs LNA's electro static discharge.

Three distinctively different implementations of convolutional perfectly matched layer for the FDTD method on CUDA enabled graphics processing units are presented. All implementations store additional variables only inside the convolutional perfectly matched layers, and the computational speeds scale according to the thickness of these layers. The merits of the different approaches are discussed, and a comparison of computational performance is made using complex real-life benchmarks.

A novel approach is presented for efficiently solving electromagnetic (EM) scattering problems using proper orthogonal decomposition (POD). As a proof of concept and demonstration of how to use the POD to solve EM scattering problems, two ways of implementing the POD procedure have been proposed and realized for calculating EM scattering from PEC targets. Numerical results obtained show that the POD is quite accurate for reconstructing backscatter patterns over wide range of frequencies and angles of interest based on the given snapshots.

A higher order analysis is applied to solve the problem of a class of inhomogeneously-filled conducting waveguides. This includes an arbitrary but smooth hollow conducting waveguides and waveguides filled with layered inhomogeneous materials. The method employs a set of spline-harmonic basis functions and leads to one-dimensional integrals for system matrix elements. This fact along with the higher order nature of the basis functions provides an accurate method for the analysis of the aforementioned waveguides. The accuracy and the convergence behavior of the method are studied through several numerical examples and the results are compared with the exact solutions and with the results of Ansoft HFSS simulator to establish the validity of the proposed method.

In this paper, synthesis of unequally spaced linear antenna arrays based on an inheritance learning particle swarm optimization (ILPSO) is presented. In order to improve the optimization efficiency of the PSO algorithm, we propose an inheritance learning strategy that can be applied to different topology of different PSO algorithms. In ILPSO algorithm, each cycle contains several PSO optimization processes, and uniform initial particle positions, part of which inherited from the good results in pre-cycles, are adopted in post-cycles. ILPSO enhances the exploration ability of PSO algorithm significantly, and can escape from the trap of local optimum areas with greater probability. The results demonstrate good performance of the ILPSO in solving a set of eight 30-D benchmark functions when compared to nine other variants of the PSO. The novel proposed algorithm has been applied in 32-element position-only array synthesis with three different constraints, simulation results show that ILPSO obtains better synthesis results reliably and efficiently.

The mathematical approach for the calculation of the membrane functions of a coaxial gyrotron cavity with an arbitrary corrugated inner rod is proposed. It is utilized mainly for two aims. First, it is shown that for typical parameters of the coaxial gyrotron cavity with the corrugated inner conductor the shape of corrugations only slightly influences the eigenvalues of competing eigen-modes. However, it can significantly influence the density of ohmic losses in the inner conductor. In particular, it is shown that the density of ohmic losses can be reduced almost twice by the proper choice of the corrugation shape. Second, it is shown that the usual idealizations of the corrugated surface of the inner conductor (the surface with rectangular grooves, having rounded edges, is approximated by a surface with wedged groves that have sharp edges) are correct. The physical interpretation of the obtained results and their practical meaning are discussed.

We discuss the applicability of the Linear Sampling Method (LSM) to GPR surveys carried out using array-based configurations. Since the images achieved via LSM are known to get worse when using a small number of antennas and a limited aperture, we introduce an analytic tool to foresee the expected LSM performance for a fixed array size and number of antennas. Notably, such a tool allows us to support (and appraise) the adoption of LSM to data collected with short arrays moved above the investigated domain, which is the configuration most viable in applications.

A novel microstrip-fed ultra wideband (UWB) elliptical antenna with dual band-notched characteristics is proposed. Dual band-notched characteristics are achieved by employing a pair of U-shaped slots on the ground plane and a T-shaped parasitic strip on the backside of the substrate. The operation bandwidth of the designed antenna is from 2.9 to 12 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.2-3.9 GHz for WiMAX system and 4.9-6.1 GHz for WLAN system. Moreover, the proposed antenna provides good radiation patterns across the working bands and a relatively flat gain over the entire frequency band excluding the rejected bands.

A concurrent multi-band low-noise amplifier (LNA) for both WLAN and WiMAX applications covering 2.4-2.7 GHz, 3.3-3.8 GHz and 5.1-5.9 GHz is mainly investigated. The proposed LNA consists of two cascaded common-source stages and employs stepped-impedance transformers and series and shunt feedback techniques to obtain good return loss, low noise and high linearity simultaneously. Test results show that the LNA features input and output return loss of 12 dB, gain of 21 dB, and noise figure of 2\,dB across the three bands of operation, which are the state of the art among the counterparts.

A key feature of upcoming 4G wireless communication systems is multiple-input-multiple-output (MIMO) technology. To make the best use of MIMO, the antenna correlation between adjacent antennas should be low (< 0.5). In this context, we propose a correlation reduction technique suitable for closely spaced antennas (distance, d < λ/40). This technique reduces mutual coupling between antennas and concurrently uncorrelates antennas' radiation characteristics by inducing the negative group delay at the target frequency. The validity of the technique is demonstrated with a USB dongle MIMO antenna designed for LTE 700 MHz band. Measurement results show that the antenna correlation is reduced more than 40% using the proposed technique.

In this work, a matrix method is applied to study the propagation of electromagnetic waves inside a non-slanted reflection grating. The elements of the matrix which characterizes the periodic medium are obtained in terms of Mathieu functions and their derivatives, and the expressions of the efficiencies of reflected and transmitted orders are calculated in terms of the elements of the matrix. In addition the band structure of a general reflection grating is studied with the layer matrix of one single period. The results obtained by this matrix method are firstly compared to the results obtained by Kogelnik's expressions in index-matched media showing good agreement. The comparison is also made for a reflection grating embedded in two media with different refractive indexes, showing good agreement with an FDTD method, but slight differences with respect to Kogelnik's Coupled Wave Theory.

It is known that electromagnetic resonant tunneling phenomenon can be found in the single-negative (SNG) bilayer, a two-layer coating made of the epsilon-negative (ENG) and the mu-negative (MNG) media. In this work, we report that this resonant tunneling is strongly dependent on the static positive parameters in SNG materials. The values of the static permeability in ENG layer and the static permittivity in MNG layer for obtaining the resonant tunneling are theoretically analyzed and discussed for two possible cases of equal- and unequal-thicknesses. Useful design guidelines in selecting positive parameters for the resonant tunneling are obtained. We also investigate the possible influence in the resonant tunneling due to the losses from the ENG and MNG materials. Additionally, we examine the polarization-dependent resonant tunneling, that is, the dependence of angle of incidence is examined.

This paper presents the design and fabrication of a class of dielectric filled rectangular waveguides using a multilayer photoimageable thick-film technique. The original fabrication technique is modified to shorten fabrication time and improve waveguide thickness to reduce transmission structure losses. The materials used are first characterized before the wave-guiding properties are extracted. The fabricated waveguides show excellent results in term of loss and a 1% variation in permittivity over a wide frequency range of 10-100 GHz. To demonstrate the practical applications of this modified fabrication technique, 5th and 3rd order band-pass filters are designed and fabricated. The different incertitude on the fabrication issues is studied showing an effect on the bandwidth and central frequency. The measurement results of the fabricated prototypes agree well with the simulated ones. A broadband 3 dB coupler is designed and fabricated covering both V and W bands. The measurements results for this circuit show good performance with 23% of bandwidth and are in good agreement with the simulations.

The aim of the paper is to present a simple but well applicable development, to generate the waveform of the magnetic flux density, and so the magnetic hysteresis, for any signal frequency. The proposed approach is based on the knowledge of the signal spectrum for one given frequency. It allows to construct the spectrum for any other frequency. Then, the constructed signal is transformed back to the time domain.

During the last two decades, several simulation tools have been proposed for the modeling of electronic equipments in function of the physical environmental changes. It was stated that numerous electronic components such as semiconductor devices can be affected by the mechanistic effects, humidity or simply the temperature variations. To study the last effect, based on the multilayer perceptron neural network (MLPNN), a characterization method of the passive electronic device thermal effects is introduced in this paper. The method proposed was realized toward the equivalent circuit identification of the under test device (R, L, C components) measured input impedances. To demonstrate the relevance of the method, numerical computations with MLPNN algorithms implemented into Matlab were performed. First, a capacitor modeling from 30 kHz to 1 GHz for the temperature variation from 25°C to 130°C is presented. It was found that a good agreement between the proposed model and the measurement is observed. Then, a commercial EMI low-pass filter was also characterized in RF frequencies through the S-parameter identification. Finally, further discussion on the potential applications of this work, in particular, in the electromagnetic compatibility (EMC) field is offered in the last part of this paper.

The diffraction problem of three-dimensional Gaussian beam on the aperture array of rectangular holes is solved. A new algorithm for calculating scattered fields of the beam is proposed. The conditions under which the distortion of the reflected field pattern and the narrowing of the transmitted field pattern appear are studied.

The objective of this paper is to illustrate how the marching-on-in-degree (MOD) method can be used for efficient and accurate solution of transient problems in a general dispersive media using the finite difference time-domain (FDTD) technique. Traditional FDTD methods when solving transient problems in a general dispersive media have disadvantages because they need to approximate the time domain derivatives by finite differences and the time domain convolutions by using finite summations. Here we provide an alternate procedure for transient wave propagation in a general dispersive medium where the two issues related to finite difference approximation in time and the time consuming convolution operations are handled analytically using the properties of the associate Laguerre functions. The basic idea here is that we fit the transient nature of the fields, the permittivity and permeability with a series of orthogonal associate Laguerre basis functions in the time domain. In this way, the time variable can not only be decoupled analytically from the temporal variations but that the final computational form of the equations is transformed from FDTD to a FD formulation in the differential equations after a Galerkin testing. Numerical results are presented for transient wave propagation in general dispersive materials which use for example, a Debye, Drude, or Lorentz models.