A phenomenological theoretical model of grain dielectric properties is presented for radio and microwave frequencies. On the bases of this model, an inverse problem is solved to determine the dielectric permittivity of bound water inside kernels of winter wheat using results of complex permittivity measurements for bulk grain carried out by other authors. The character of the water complex permittivity dependence on frequency and kernel moisture content is studied. For this, the permittivity was considered as a sum of five different functions, depending on moisture content explicitly, and with coefficients being subject to determination. The frequency dependence of these coefficients was analyzed, and the regions typical for the ionic conductivity and for the dipole-orientational polarization mechanism were detected. For this polarization mechanism, the relaxation frequencies are differ from those of free water. It was concluded that water microparticles inside kernels are formed not by pure water, but by aqueous solution of four different substances coming from the kernel solid phase. It is shown that bound water, for the most part, is in a state that is intermediate between that of free water and that of molecules in the monomolecular water layer on the solid phase boundary.

Deterministic blind beamforming algorithms try to separate superpositions of source signals impinging on electromagnetic vector sensor array by using deterministic properties of the signals. This paper links electromagnetic-vector-sensor-array beamforming problem to the parallel factor (PARAFAC) model, which is an analysis tool rooted in psychometrics and chemometrics. Exploiting this link, it derives a deterministic blind beamforming algorithm. The blind beamforming algorithm doesn't require DOA (direction of arrival) information and polarization information. The simulation results reveal that the performance of the blind beamforming algorithm for electromagnetic vector sensor array is close to nonblind MMSE method, and this algorithm works well in array error condition.

In the present communication, we investigate theoretically and study a different type of photonic structure called metallic star waveguide (SWG) structure. The proposed structure, having single homogenous metallic material, is composed of a backbone (or substrate) waveguide along which finite side branches grafted periodically. In order to obtain the dispersion relation and hence the photonic band gaps (PBGs) of the SWG structure the Interface Response Theory (IRT) have been applied. Such types of structures show the band gaps without the contrast in the refractive index of the constituent materials. We also show that the range of forbidden bands can be tuned to different value by varying the number grafted branches of the SWG structures, without changing the other parameters. Moreover, the effects of variation of absorption of metals and plasma frequency on the band gaps of the proposed structures have been investigated.

This paper presents a circularly polarized (CP) GPS/DCS loop-like antenna with a microstrip feed. The proposed antenna comprised of a quasi-C antenna, an inverted-L sleeve strip connected with the ground plane and an L-shaped slit embedded in the ground plane. The C-like antenna generates a resonant mode with a poor impedance matching condition. The inverted-L grounded strip and the embedded L-slit are not only capable of modifying two orthogonal electric fields with equal amplitude and phase difference of 90 degree for radiating circular polarization at 1.575 GHz, but the impedance characteristics is also improved and the operating frequency is reduced. Both simulated and measured results are provided to validate the impedance and CP performance of the proposed antenna. For the optimized antenna case, the measured bandwidth with an axial ratio (AR) of less than 3 dB is larger than 19% and the measured impedance bandwidth of reflection coefficient S₁₁ < −10 dB is about 30.1%.

In this paper, a new compact circular monopole ultrawideband antenna with multiple narrow bands notched is proposed, which is implemented by using the existing techniques, such as loading a L-type band-stop filter, inserting a split ring resonator (SRR), and the method we proposed that connecting L branches on the radiation disk. Four sharp notches at 2.4GHz, 3.5 GHz, 5.5 GHz, and 7.6 GHz are achieved separately. The measured VSWR shows a good agreement with the simulation results. The radiation patterns are obtained from Ansoft HFSS simulations and verified by CST Microwave Studio. The results prove that this kind of antenna can be applied in the UWB communication systems to avoid interference with other wireless systems, such as the 2.4GHz WLAN, 3.5 GHz WiMax, and 5.8 GHz WLAN etc. The parameters determining the antenna's band notched characteristic are discussed.

In this paper a novel ultra-thin radar absorbent material (RAM) using HIGP is presented and investigated. Owing to the high impedance property of the HIGP, the thickness of the RAM is about several tenths of the centre wavelengthof the absorption band, considerably thinner than conventional absorbers. The absorption band of the RAM is about several hundred megahertz. In the new RAM, lumped resistances are soldered between the patches of mushroom-like high-impedance surface (HIGP). And the metal ground plane of waveguide slot antenna is covered by this new type of RAM. As compared to the slot antenna with a metal ground plane, the measured results show that the radar cross section (RCS) of waveguide slot antenna reduces significantly. This proves that the new HIGP RAM has a good radar absorbing characteristics. The simulations and experiment results have shown that the RCS of antenna is reduced by 7.9 dB and gain is only reduced by 0.9 dB.

This paper presents a new approach for solving accurate approximate analytical solution for strong nonlinear oscillators. The new algorithm offers a promising approach by Hamiltonian for the nonlinear oscillator. We find that these attained solutions are not only with high degree of accuracy, but also uniformly valid in the whole solution domain.

On the base of conductor-backed coplanar waveguide (CBCPW) structure, a novel CB-CPW structure is proposed and analyzed, which is realized by using the UC-PBG structure to replace the back conductor of CB-CPW. From 1.3 GHz to 2.8 GHz, The transmission characteristic of the proposed CB-CPW is better than that of CBCPW, and is similar to that of CPW, therefore, this novel CB-CPW not only owns the advantage of CB-CPW, such as good mechanical strength and good heat yield, but also owns the advantage of CPW, such as good transmission characteristic. At last, a dual-band antenna based on this novel CB-CPW is designed and computed, the numerical results validate that this novel CB-CPW is feasible in microwave application.

A band pass filter with a linearly periodic refractive index profile is discussed in analogy with Kroning Penney model in band theory of solids. The suggested filter is a one-dimensional ternary periodic structure and provides better control in dispersion relation as compared to a binary structure because it has two more controlling parameters relative to those of the binary one. Since three layers are involved in the formation of band gaps a much broader range of dispersion control is obtained. Both refractive index modulation and optical thickness modulation are considered. A mathematical analysis is presented to predict allowed and forbidden bands of wavelength with variation of angle of incidence. It is also possible to get desired ranges of the electromagnetic spectrum filtered with this structure by manipulating the value of the lattice parameters.

In the view of measuring directional fluctuations of a thin laser beam sent through a heated turbulent jet, an optical method using interference and diffraction with the out coming beam is proposed. The experimental set-up is described. A new technique for separating directional fluctuations of the laser beam is explained. From the measurement of the interference pattern perturbations, are deduced the Rms of the laser beam deflection angle, the spectrum of directional fluctuations of the laser beam, and the value of a scattering coefficient characterizing the heated turbulent jet. The measured spectrum reveals a -8/3 power law and the value obtained for that coefficient is nearly equal to that found in previous works. This agreement enables to conclude that the experimental technique used is efficient and satisfactory.

We experimentally studied the guidance properties of the S-shaped metamaterial slabs. A peek of transmitted power due to the bulk guidance modes is observed in the negative band of the metamaterial, which is larger than a conventional dielectric waveguide made of FR4. The peek transmission frequency is shown related with the change of the negative band of the S-shaped metamaterial slab. Our results show good agreement with the theoretical predictions.

Ametho d based on concurrent neuro-fuzzy system (CNFS) is presented to calculate simultaneously the resonant frequencies of the rectangular, circular, and triangular microstrip antennas (MSAs). The CNFS comprises an artificial neural network (ANN) and an adaptive-network-based fuzzy inference system (ANFIS). In a CNFS, neural network assists the fuzzy system continuously (or vice versa) to compute the resonant frequency. The resonant frequency results of CNFS for the rectangular, circular, and triangular MSAs are in very good agreement with the experimental results available in the literature.

A novel slot antenna that consists of an H-shaped slot encompassed by a rectangular metallic wall and a pair of C-shaped slots outside the wall is proposed. It features a unidirectional pattern, small electrical dimensions and medium gain. The H-shaped slot radiates as an inductively loaded magnetic dipole while the induced electric currents on the vertical wall radiates as electric dipoles. The front-to-back ratio (FBR) of the antenna can be controlled by proper constructive and destructive interferences of radiating fields of the magnetic and electric dipoles. The size of the ground plane can be reduced by the use of the C-shaped slots that confine the currents to the proximity of the metallic wall. Two prototype antennas operating at 2.4 GHz were designed. By adjusting the structure parameters, the front-to-back ratio of the antenna can be conveniently altered. The first prototype has an impedance bandwidth (BW) of 3.8% for SWR ≤ 2, a 4.6 dBi gain, a 10-dB FBR and a ground size of 0.84λ₀ × 0.64λ₀ where λ₀ is the free-space wavelength at the center frequency. The corresponding figures of the second prototype are 1.83%, 4.1 dBi, over 20 dB and 0.64λ₀ × 0.64λ₀. Both antennas have a height of 0.128λ₀.

This study investigated the relationship between temperature elevation and spatial-average SAR (specific absorption rate) in a head model of a Japanese male due to a dipole antenna. The frequencies considered are in the range between 800MHz and 3 GHz, which are used in wireless communications. Our attention focuses on the average mass of SAR which maximizes the correlation with local temperature elevation. Computational results suggested that an appropriate averaging mass of SAR did not exist over wide frequencies, which was attributed to the frequency-dependent penetration depth of electromagnetic waves. For most cases considered in this study the SAR averaging over 10 g was better than that for 1-g from the standpoint of correlating the temperature elevation. The dominant factor influencing this averaging mass is the thermal diffusion length which largely depends on the blood perfusion rate. Additionally, the heat evolved in the pinna played an important role in the correlation between spatialaverage SAR and temperature elevation.

In this paper, the Parallel Finite-Difference Time-Domain (FDTD) method based on MPI (Message Passing Interface) is applied to analyze the EMC problems of the electrically large platforms accurately and quickly, which is a full-wave numerical method. The MPI library and domain decomposition method are applied to implement the Parallel FDTD method, so that the computation resource is expanded. The method can analyze the EMC problems by modeling the electrically large platforms accurately. Then the network theory is introduced to compute the isolation between antennas combined with the Parallel FDTD method firstly, which avoids the complexity of sweeping frequency and reduce the computing time greatly. Numerical results show that the method is correct and efficient. Finally, the EMC problems of antennas mounted on electrically large platforms are analyzed and some useful conclusions are obtained.

Exploitation of the backscattered field polarization over the wide electromagnetic spectrum, from visible to microwave frequencies, provides an approach to advanced target recognition in remote sensing applications. The framework for full coherent characterization of the scattered field that is established here, maximizes the extracted target information. It is also shown that such a methodology, which is theoretically similar to the concept of "partial or compact polarimetry", yields comparable results to full or quadrature-polarized systems by incorporating judicious assumptions and assuming/implementing optimal transmitted or illumination field polarizations. On this basis, common characteristic features, interworking and fusion of different polarimetric sensor products in different regions of spectrum, e.g., radar/SAR and Electro-Optical, are investigated and formulated within a robust framework based on full coherent treatment of the scattered field.

This paper deals with the design of beam-forming networks (BFN) for scannable multibeam antenna arrays using Coherently Radiating Periodic Structures (CORPS). This design of CORPS-BFN considers the optimization of the complex inputs of the feeding network by using the Differential Evolution (DE) algorithm. Simulation results for different configurations of CORPS-BFN for a scannable multibeam linear array are presented. The results shown in this paper present certain interesting characteristics in the array factor response for the scannable multibeam linear array and the feeding network implification for the design of BFN based on CORPS.

Effects of different optical losses (auger recombination, cooperative up-conversion, excited state absorption (ESA) and Si- Nc induced loss) on amplification parameters including net gain and population inversion in Si-Nc Er doped fibber are studied. Optical loss due to up-conversion effect has critical role in the mentioned optical amplifiers. Simple modeling of this effect can be done by 2C_upN₂², where C_up and N₂ are up-conversion coefficient and population of level 2 respectively. In traditional considered cases C_up are assumed to be constant, but in practical situation this is hard to be realized. In practice distribution of Er ions is inhomogeneous and especially the Gaussian. So, from our point of view the suitable model should consider position dependence up-conversion coefficient. In this paper we considered this subject and by simulation modeling tries to show effect of inhomogeneous distribution of up-conversion coefficient on optical net gain and population inversion. It is shown that life times of first and second excited states are decreased and so the population inversion is decreased too. Thus optical net gain near to center of the Gaussian distribution is deceased strongly. The observed gain lowering is suitable description of the reported experimental results. Also, it is observed that in high level Si-Nc density the obtained optical gain is decreased against traditional description which C_up is assumed to be constant. The core diameter is considered R = 10μm.

The discrete complex image method is one of the most prominent techniques that handle the Sommerfeld integrals encountered in the integral equation formulations of multilayered media. The extraction of surface waves extends the validity of the method to the far field. These surface waves are expressed in terms of Hankel functions that suffers a singularity problem at the origin which contaminates the results in the near field. In this work,w e use a formulation developed recently by the author to derive a new expression for the surface waves. The new expression is shown to obviate the singularity of the Hankel functions at the origin,and hence leads to accurate results in the near field.

The characteristics of radiating longitudinal slots in a rectangular waveguide have been studied. A moment method solution is used with entire basis expansion and testing functions (Galerkin) including the effect of wall thickness. It is shown in this paper. 1) The determination of different parameters like VSWR, reflection coefficients and insertion loss are calculated with the results of normalize reactance and conductance. 2) The Taylor distribution approach with specific SLL for desired linear aperture array antenna. The resonant conductance or resistances are calculated from desired amplitude distribution. The formulation uses transmission matrix approach. The computed result shows excellent agreement with measured results. CST Microwave studio is used for the simulation and is totally based on FIT techniques.