A compact dual-band high-impedance-surface EBG structure is employed as a reflector for a dual-band annular-slot antenna. The reflector comprises an array of miniaturized EBG cells which utilizes square patches augmented by four S-shaped corrugated arms to reduce the resonant frequency of the proposed EBG structure. In order to broaden the bandwidth and adjust the frequency ratio for the dualband EBG structure, a log-periodic spacing between the S-shaped strips is introduced. The combination of microstrip-fed annular slot and EBG reflector provides directional properties for both frequency bands with reduced size and low-profile.

A completely analytical computation of the electromagnetic field produced by an optical fiber helix is presented for the first time. The analysis utilizes the transformation of radially traveling cylindrical waves between two skew cylindrical coordinates systems, that has been previously derived by the author, in order to express the waves radiated by each infinitesimal part of the helix in terms of cylindrical waves around the helix axis and be able to integrate the contributions analytically. Under certain realistic geometrical assumptions, an unperturbed propagation of a single fiber mode is assumed to account for the infinite fiber length, leading to elegant final series expressions in terms of mixed angular-axial Hartree space harmonics, which show clearly the effect of the helical geometry on the field distribution. Analytical formulas are obtained for the field inside and outside the helix cylinder and an interesting two-term decomposition of the outward radiated field is concluded.

A new design technique of microstrip patch antenna is presented in this paper. The proposed antenna design consists of inverted patch structure with air-filled dielectric, direct coaxial probe feed technique and the novel slotted shaped patch. The composite effect of integrating these techniques and by introducing the new multi-slotted patch, offer a low profile, high gain, broadband, and compact antenna element. A wide impedance bandwidth of 27.62% at -10 dB return loss is achieved. The maximum achievable gain is 9.41 dBi. The achievable experimental 3-dB beamwidth (HPBW) in the azimuth and elevation are 60.880 and 390 respectively at centre frequency.

A dual-band enhanced-bandwidth microstrip antenna is presented with a frequency separation of f2/f1=1.33. In order to achieve the dual-frequency operation, a rectangular patch is loaded with a stub at one of its radiating edges. To improve bandwidth at each band, two parasitic patches are coupled to the driven element.

We investigate the electromagnetic properties of three-dimensional (3D) arbitrarily-shaped invisible cloaks based on the analytical field transformation theory instead of the complicated numerical simulations. Very simple closed-form expressions for fields and energy flows have been derived for arbitrarily-shaped 3D cloak, which could help us to investigate the electromagnetic properties of the 3D cloaks rapidly and efficiently. The difference between 2D and 3D cloaks have been compared in detail. Distributions of the fields, power flows and wave polarizations for the 3D case have been discussed inside the cloak. Numerical results have been presented at the cutplanes of cloaks to valid the theoretical analysis, which shows clearly how the incident waves are bent at the inner boundary. In order to further reveal the physical essence of the cloaks, both 3D spherical and ellipsoidal cloaks have been considered based on the analytical method. The common features and the differences for the two structures have been also illustrated in this paper.

This paper proposes a hybrid classifier for polarimetric SAR images. The feature sets consist of span image, the H/A/α decomposition, and the gray-level co-occurrence matrix (GLCM) based texture features. Then, the features are reduced by principle component analysis (PCA). A 3-layer neural network (NN) is constructed, trained by resilient back-propagation (RPROP) method to fasten the training and early stop (ES) method to prevent the overfitting. The results of San Francisco and Flevoland site compared to Wishart Maximum Likelihood and wavelet-based method demonstrate the validness of our method in terms of confusion matrix and overall accuracy. In addition, NNs with and without PCA are compared. Results show the NN with PCA is more accurate and faster.

Design, simulation and measurement results of the integrated compact up-converter MMICs (microwave monolithic integrated circuits) are presented and discussed. The design is performed to achieve low cost and high performance transmitter system for the Ka-band frequency applications. It is designed using anti-parallel diode pair sub-harmonic single sideband mixer and three stage RF (radio frequency) amplifier. Microstrip lines and lumped elements are used together to achieve a compact chip size. The layouts of the circuits are designed with careful EM (electromagnetic) simulations to avoid inter-component couplings and effect of the microstrip bending discontinuities. The chip is operated for the wide bandwidth of the RF frequency from 22-38 GHz. Due to sub-harmonic mixing the required local oscillator frequency (LO) is reduced to half (10-19 GHz) to that of the RF frequency. The conversion gain of the chip is 9-15 dB and P-1dB output power is 7-12 dBm. The single sideband and anti-parallel diode pair suppress the in-band unwanted sideband and second harmonic of the local oscillator (2LO), respectively. The suppression of sideband and 2LO signals is typically 20-35 dB and 20-30 dB, respectively. The size of the chip is as compact as 4.2 mm² on a 100 μm-thick GaAs substrate.

This paper presents a rigorous approach for the propagation of electromagnetic (EM) fields along a helical waveguide with arbitrary profiles in the rectangular cross section. The main objective is to develop a mode model to provide a numerical tool for the calculation of the output fields, output power density, and output power transmission for an arbitrary step's angle and the radius of the cylinder of the helical waveguide. Another objective is to demonstrate the ability of the model to solve practical problems with inhomogeneous dielectric profiles. The method is based on Fourier coefficients of the transverse dielectric profile and those of the input wave profile. Laplace transform is necessary to obtain the comfortable and simple input-output connections of the fields. This model is useful for the analysis of dielectric waveguides in the microwave and the millimeter-wave regimes, for diffused optical waveguides in integrated optics. The output power transmission and the output power density are improved by increasing the step's angle or the radius of the cylinder of the helical waveguide, especially in the cases of space curved waveguides.

In this article, the harmful radiation level of electric field strength from the hostile low-power radio devices causing the intermodulation interference to the AMPS receiver has been predicted. The predicted level becomes the upper limit to avoid the intermodulation interference on the victim device. Our findings show that the quantified upper limit was 79.13[dBμV/m] to mitigate the adverse influence from these low-power radio devices. Our results are based on the calculation, simulation, and measurement for the commercial AMPS chip. Resulting values are in a good agreement within less than 3[dB].

A small 3-Dimensional (3-D) multi-band antenna of "F" shape is proposed for portable phones' applications. The designed configuration of the proposed antenna is different from traditional Planar Inverted-F Antenna (PIFA) radiators. The proposed antenna has the good characteristics of wide band. The ratio of impedance bandwidth to the central frequencies 2.5 and 5.1 GHz is 28.6 % and 9 %, respectively. It can be applied to Bluetooth (BT) 2.4 GHz and Unlicensed NII - 5 GHz, UNII-1 5.1 ~ 5.25 GHz and UNII-2 5.25 ~ 5.35 GHz. The experimental results have fairly good agreement with the simulation data by High Frequency Structure Simulator (HFSS).

We demonstrate complete tunneling of light through large-scale mu-negative media, which has negative permeability but positive permittivity, by constructing a quasi-one-dimensional structure with side branches. For the structure with a single side branch, there always exists a transmission peak which can be easily tuned by varying the parameters of the side branch. For the structure with periodic array of side branches, the transmission peak is enlarged to a band, which exhibits left-handedness, and can be tuned by changing the distance between two neighboring side branches and the length of the side branch.

The concept of Scale-Changing Network is reported for the electromagnetic modeling of complex planar structures composed of a collection of metallic patterns printed on a dielectric surface and whose size covers a large range of scale. Examples of such multi-scale structures are provided by multi-band frequency-selective surfaces, finitesize arrays of non-identical cells and fractal planar objects. Scale-Changing Networks model the electromagnetic coupling between various scale levels in the studied structure and are computed separately. The cascade of Scale-Changing Networks bridges the gap between the smallest and the highest scale levels and allows forming a monolithic (unique) electromagnetic formulation for the global electromagnetic simulation of complex planar structures. Derivation of these networks is presented and key advantages of the electromagnetic approach are reported.

ƒA comparative assessment of power absorption in adult and child heads exposed to a small helical antenna at 1710 MHz, is presented, emphasizing the effect of age related parameters. Finite Difference Time Domain simulations are employed to study the interaction between MRI-based head models and a mobile communication terminal equipped with a small helical monopole. A semi-analytical method, based on Green's function theory and the Method of Moments, is used to study the absorption in three-layer spherical head models exposed to a small helical dipole. SAR patterns in child head models derived by non-uniform scaling of adult ones were assessed against SAR patterns computed in child heads derived by uniform downscaling procedures. In both realistic and canonical exposure scenarios, comparable levels of absorbed power (maximum difference: 12%) in adult and child head models were observed. Dependence of SAR values upon separation distance and tissue dielectric properties was quantitatively assessed. In realistic exposure scenarios, the reduction in peak SAR values was 60-80% for a 1 cm increase in distance and up to 16% for a 110% to 90% decrease in dielectric properties values with reference to the nominal value of 100%. These trends were respectively less (55-65%) and more (up to 24%) emphasized in the corresponding canonical exposure scenarios.

In this paper, a fractal dual-polarized aperture-coupled microstrip antenna is presented. The proposed antenna adopts 1st Minkowski fractal patch and is fed by the aperture-coupled structure with H-shaped and H-shaped loaded capacitance. The size of Minkowski fractal patch is reduced by 20% compared with a square patch. Results show that the T/R isolation is better than 35 dB, improved by 2 dB compared with the double H-shaped slots. The gain is more than 8 dB, and the front-back ratio is greater than 20 dB in the operating frequency range. Both simulated and experimental results are in good agreement.

A novel design of printed sleeve monopole antenna is presented in this paper. Because of using double-sleeve and CPW-fed technique, this antenna has advantages of ultra-wideband (UWB) impedance characteristic, simple structure, easy fabrication and low cost. The details of simulated and experimental results for the proposed design are presented and discussed. This antenna can be designed for UWB wireless communication applications.

A novel circularly polarized array designed for millimeter wave digital radar module was proposed and validated in this paper. The circularly polarized array was designed with single feeding point for easily integrating with front-end module. A new kind of medium filled circular cavity was employed as transition to connect the output of the T/R module and the feeding point of the array. TM₀₁₀ mode was selected as the operating mode of the circular cavity based transition for its special field distribution. Good performance of flexibility, return-loss, axial ratio and radiation pattern were observed.

In this paper, simulated annealing algorithm (SA) is applied to the synthesis of cylindrical conformal arrays in order to suppress the peaks of side lobes by acting on the elements' positions. There are multiple optimization constraints including the number of elements, aperture and minimum element spacing. A constraint matrix is designed to make the solution meet the restriction on the minima distance between elements, and the individual matrix which forms on the basis of constraint matrix is used to express array configurations. The SA does not act on the elements' positions directly but on the variables in a smaller solution space, this indirect description method makes the SA more computationally efficient. The simulation results confirm the great e±ciency and robustness of the proposed method.

Radiation pattern, impedance characteristics, and gain of a probe-excited rectangular ring antenna are investigated by the Method of Moments with the Rao-Wilton-Glisson (RWG-MoM) basis functions. The analysis is carried out for different lengths and positions of the probe as well as various lengths, widths and heights of the ring. In addition, the distribution of the surface current is also illustrated. Consequently, the suitable parameters are determined. It is obvious that the proposed antenna offers a bidirectional pattern with the impedance bandwith (|S₁₁|< -10 dB) of 17%. Along the direction of the ring aperture, the gain is 5.28 dBi. Furthermore, the prototype antenna was fabricated and measured to verify the validity of the numerical calculation. It is found that the numerical and measured results are reasonably in good agreement.

The dispersive behaviour of an artificial Transmission Line is investigated demonstrating the existence of a negative group velocity region. More specifically, the propagation of amplitude modulated signals in a microstrip line coupled with Split Ring Resonators is analyzed, investigating the influence of the propagating pulse shape on the possibility to observe a negative group delay.