A novel planar circular Apollonian fractal shaped UWB monopole antenna with band rejection capability is presented in this paper. The antenna performs satisfactorily in the frequency range 1.8-10.6 GHz which gives a wide impedance bandwidth of 142% for VSWR within 2. The proposed antenna has the capability to reject the frequency band 5.125-5.825 GHz assigned for IEEE802.11 a and HIPERLAN/2. This is achieved by a pair of narrow band resonant L-shaped slots in the CPW ground plane. The antenna exhibits satisfactory omnidirectional radiation characteristics throughout its operating band. The measured peak gain varies from 2 dBi to 6 dBi in the entire UWB band except the notch band. The performances of time domain characteristic is satisfactory with a group delay variation of 1 ns that shows the antenna is non dispersive. To ensure the usefulness of the proposed antenna in pulse communications systems, the correlation between the time-domain transmitting antenna input signal and the receiving antenna output signal is calculated. This antenna can be effectively used for medical imaging and military radar system along with other common UWB applications.

A microstrip tri-band bandpass filter (BPF) based on three embedded bending stub resonators (EBSRs) is proposed in this paper. Three resonant paths that resonate at three different frequencies can achieve three passbands. The lumped circuit models of the proposed filter are given for designing. The filter is extremely compact, whose area is about 0.047λ_g×0.12λ_g. There are two transmission zeros located between the first two passbands and a transmission zero between the second and third passbands, which results in good selectivity. For demonstrating the proposed filter structure, a filter at 0.9/2.14/3.6 GHz is designed and fabricated. The measured results are well agreed with simulated ones, which indicate the validity.

The paper presents an assessment of human exposure to extremely-low-frequency (ELF) electric field generated by a power line using the rotationally-cylindrical body model. The formulation is based on the Laplace type continuity equation. The induced current density in the three-dimensional (3D) model human body is obtained by solving the Laplace equation via the Finite element method (FEM). The main objective is to highlight some parameters influencing the distribution of the induced current density, such as the ohmic contact between the feet and the soil due to the soles of the shoes, and the electrical parameters of the soil. Furthermore, the influence of internal organs (the human model) to the induced current density distribution. The human body is represented by a homogeneous model and also by an inhomogeneous model composed of several organs namely brain, heart, lungs, liver and intestines, whose shapes were spheroid. The proposed model has been validated through comparison to either the experimental results or the theoretical results available in literature being computed by the aid of a homogeneous body model.

We propose a balanced frequency tripler scheme for millimeter-wave and submillimeter-wave application, in which double-sided suspended stripline is adopted. Two arms of Schottky diodes are mounted on the upper side of the substrate, and the other two arms of diodes are mounted on the lower side. The diodes are DC biased without bypass chip capacitor, which is essential in the common used balanced tripler scheme. Furthermore, the numbers of the diodes are doubled as there are only two arms of diodes in the common balanced tripler scheme, and this will double the power handling capability of the tripler. A W-band frequency tripler is designed according to the proposed scheme with commercial Schottky Varistors. The output power is from 2.9 to 5.7 dBm at the frequencies from 89.7 to 94.8 GHz, with the conversion efficiency from 1.95% ~3.7%.

This paper presents a structured model of the dielectric properties of the corneal tissue at microwave frequencies, based on the fine structure and chemical composition of its constituents. This is accomplished by appropriately combining the known properties of tissue substructures using mixing rules, in order to obtain the effective macroscopic properties of the medium. The presented approach is multi-scale: it begins from the microscopic scale and derives the macroscopic properties after several scale-steps. The predictions of the model agree with the existing measured data in the literature. Verification and analysis of the model sensitivity to input parameters has been presented. The model is expected to find application in non-invasive medical sensing where it can relate dielectric response to pathological structural changes in the tissue. The model is also useful for the prediction of dielectric properties for high-frequency computational dosimetry, and for understanding the physical mechanisms behind the macroscopic dielectric behaviour in general.

In recent years, the transmission/reflection (TR) method has been successfully emplolyed to determine the complex permittivity of dielectric material. Based on the principle that different coals have different abilities to absorb microwave energy at different frequencies, it is essential to analyze the electromagnetic property of coal to realize microwave desulfurization. Samples composed of a known dielectric and coal are manufactured in order to obtain the accurate permittivity of coal. In the article, we propose an improved TR method which is insensitive to the position of the sample in its cell. Additionally, we get the suitable mass ratio of the known dielectric and sample under test in the composite sample, and the suitable thickness of the composite sample in the permittivity measurements.

A modified differential evolution algorithm (MDE) for pattern synthesis of antenna arrays is proposed in this paper. By employing the novel strategies of best of random mutation and randomized local search, the convergence of standard differential evolution algorithm (SDE) is significantly accelerated. Five standard benchmark functions are optimized to testify the proposed algorithm by comparison with several other optimization algorithms. The numerical results verify the superior performance of the proposed MDE. Furthermore, the MDE is applied to two pattern synthesis examples, including a linear array and a cylindrical conformal array. Experiment results demonstrate that the proposed MDE has better performance than the other optimization methods in both of these two examples, which indicate the proposed algorithm is a competitive optimization algorithm in pattern synthesis.

Electrical cables of all types are subject to aggressive environments that can create defects or accelerate aging. Many application domains require diagnosis methods and tools. Among many methods, reflectometry has proven to be the best candidate and can be easily applied to the detection and localization of hard defects, while only requiring one access point to the wire. But soft defects are more difficult to track and require new powerful methods. This paper presents a review of the recent state of the art in the field of wired network diagnosis and shows the evolution of future activities in this domain. It provides new perspectives and new research domains are proposed.

A problem of electromagnetic fields excitation by a system of finite-dimensional material bodies in two arbitrary electrodynamic volumes coupled by holes, cut in a common boundary of the volumes, is defined in a rigorous formulation. For the system containing two material bodies and one coupling hole, the problem is reduced to a system of two-dimensional integral equations relative to surface electric currents on the material bodies and equivalent magnetic current in the coupling hole. The resulting integral equations are correctly transformed to a system of one-dimensional equations for currents in a narrow slot and on thin impedance vibrators, which may have irregular electrophysical and geometrical parameters. The resulting equations system for a transverse slot in a broad wall of a rectangular waveguide and impedance vibrators with variable surface impedance is solved by a generalized method of induced electro-magneto-motive forces (EMMF) under assumption that interaction between the vibrators and the slot is absent. Calculated and experimental plots of electrodynamic characteristics for this vibrator-slot structure are presented.

We introduce a data-driven unsupervised classification algorithm that uses polarimetric and interferometric synthetic aperture radar (PolInSAR) data. The proposed algorithm uses a classification method that preserves scattering characteristics. Our contribution is twofold. First, the method applies adaptive model-based decomposition (AMD) to represent the scattering mechanism, which overcomes the flaws introduced by Freeman decomposition. Second, a new class initialization scheme using a histogram clustering algorithm based on a Dirichlet process mixture model is applied to automatically determine the number of clusters and effectively initialize the classes. Therefore, our algorithm is data-driven. In the first step, the Shannon entropy characteristics of the PolInSAR data are extracted and used to calculate the local histogram features. After applying AMD, pixels are divided into three canonical scattering categories according to their dominant scattering mechanism. The histogram clustering algorithm is applied to each scattering category to obtain the number of classes and initialize them. The iterative Wishart classifier is applied to refine the classification results. Our method not only can obtain promising unsupervised classification results but also can automatically assign the number of classes. Experimental results for E-SAR L-band PolInSAR images from the German Aerospace Center demonstrate the effectiveness of the proposed algorithm.

Millimeter-wave (MMW) radiation characteristics of solid targets are very complicated, and this paper starts with the research on modeling and simulation of the simple solid metal target. On the basis of the optical property of MMW, the two-ray propagation (direct reflection and ground secondary reflection of the solid target surface) is analyzed by means of the ray tracing theory in the geometrical optics, the radiation temperature calculation model is established; Furthermore, in combination with the panel-method-based geometric model and in accordance with the spatial analytic geometry and vector algebra theory, model calculation of the intersection movement between the radiometer and the target is analyzed and the MATLAB simulation platform for MMW radiation characteristics of the solid target is built. Under the assumed simulation conditions, simulation experiments on three types of solid metal targets (sphere, cylinder and cone) are performed to verify the proposed method in this paper. Meanwhile, comparative analysis between the MMW radiation characteristics of the circular metallic plate and those of the metallic ball with the same radius indicates that the spherical metallic target is equivalent to the non-ideal metallic circular planar target which is increased about 1.3 times in the linear size, and the result is validated through the measured data, which provides more accurate and effective data and theoretical support for target recognition and location in the millimeter-wave passive detection.

Simple internal multiband monopole antenna with low SAR for most of wireless mobile communication applications is presented in this paper. The proposed antenna is a unequal arms monopole antenna with a meander strip in the other substrate side. The antenna has a simple structure and is sufficiently small in size to be easily fit on the housing of mobile or USB dongle with size 18 × 15 × 0.8 mm³. The antenna is designed to operate at multi-bands to occupy most of allocated wireless communication devices by using high frequency structure simulator ver. 13 (HFSS). The proposed antenna has acceptable gain and efficiency while providing broadside radiation pattern that covers the horizontal plane. The antenna design and experimental results are in agreement. Moreover, the specific absorption rate (SAR) in the human head is investigated by CST 2012 Microwave Studio Hugo Voxel Model.

In this work, near infrared filtering properties in a transmission narrowband filter are theoretically investigated. The filter is a defective photonic crystal of (LH)^ND(HL)^N, where N is the stack number, L is SiO₂, H is InP, and defect layer D is an extrinsic semiconductor of n-type silicon (n-Si). It is found that there are multiple transmission peaks within the photonic band gap (PBG) as the defect thickness increases. The filtering position can be changed by varying the doping density in n-Si. That is, the peak (channel) wavelength is blued-shifted when the doping density increases. In the angle-dependent filtering property, the channel wavelength is also blued-shifted as the angle of incidence increases for both TE and TM waves. These filtering properties are of technical use in the applications of semiconductor optoelectronics.

We propose a novel signal model by combining the sparse stepped frequency signals with chaotic signals, i.e. the sparse stepped chaotic signal (SSCS) model, as well as the corresponding compression algorithm based on compressed sensing. In SSCS, the chaotic signals are modulated to sparse stepped frequencies to compose a transmitting burst. When receiving, the echo signals are demodulated to the baseband and then can be sampled directly at a rate much lower than the Nyquist rate determined by the bandwidth of chaotic signal of each subpulse. Compared with radars using conventional stepped frequency waveforms, the SSCS radar can transmit fewer subpulses in a burst and directly use lower speed ADC next to the receiver. Both simulated and real radar data are processed to demonstrate the effectiveness of the proposed SSCS as well as the compression algorithm by which high resolution range profiles are very well reconstructed.

The effective coefficients for Maxwell's equations in the frequency domain are calculated for a multiscale isotropic medium by using a subgrid modeling approach. The correlated fields of conductivity and permeability are approximated by Kolmogorov's multiplicative continuous cascades with a lognormal probability distribution. The wavelength is assumed to be large as compared with the scale of heterogeneities of the medium. The permittivity ε(x) and the electric conductivity σ(x) satisfy the condition σ(x)/(ωε(x)) < 1, where ω is the cyclic frequency. The theoretical results obtained in the paper are compared with the results from direct 3D numerical simulation.

Numerical methods based on solutions of Maxwell's equations are usually adopted for the electromagnetic characterization of Magnetic Resonance (MR) Radiofrequency (RF) coils. In this context, many different numerical methods can be employed, including time domain methods, e.g. the Finite-Difference Time-Domain (FDTD), and frequency domain methods, e.g. the Finite Element Methods (FEM) and the Method of Moments (MoM). We provide a quantitative comparison of performances and a detailed evaluation of advantages and limitations of the aforementioned methods in the context of RF coil design for MR applications. Specifically, we analyzed three RF coils which are representative of current geometries for clinical applications: a 1.5 T proton surface coil; a 7 T dual tuned surface coil; a 7 T proton volume coil. The numerical simulation results have been compared with measurements, with excellent agreement in almost every case. However, the three methods differ in terms of required computing resources (memory and simulation time) as well as their ability to handle a realistic phantom model. For this reason, this work could provide "a guide to select the most suitable method for each specific research and clinical applications at low and high field".

The purpose of this paper is to discuss the applicability of the TGn radio channel models in estimating the performance of WLAN transmission. The specificity of the indoor radiowave propagation is first discussed, then TGn models are introduced together with a deterministic propagation model created by the authors for predicting the radio channel higher-order parameters. Intensive WLAN measurements have been carried out in two representative propagation environments and compared to theoretical predictions obtained in four configurations: beginning with the original TGN channel models, then enhancing them by including deterministically simulated pathloss and impulse responses and eventually by generating the channel impulse response on a purely random basis. The obtained results should indicate how accurately the general TGn channel models match measurements in real environments and how they compare to proposed successive modifications.

DRFM (Digital Radio Frequency Memory) is now widely utilized by modern radar jammers due to its high efficiency in jamming generation. However, its jammer structure is somewhat complex, since the up-conversion and down-conversion processes must be included. This paper proposes a new Synthetic Aperture Radar (SAR) jammer architecture utilizing Direct Radio Frequency Processing (DRFP), wherein both the up-conversion and down-conversion modules can be excluded. DRFP has a very compact hardware structure which employs Direct Digital Synthesizer (DDS), phase shifter, and delay lines for jamming modulation. Finally, the performances of DRFP are shown by both the inner-field test and a rail-way SAR experiment to be rather effective in jamming generation.

A novel triple-band single-fed compact microstrip antenna with varied polarization states and radiation patterns is proposed based on two-dimensional artificial metamaterial transmission line (TL). The TL element is composed of complementary split ring resonators (CSRRs) etched in the ground plane and a capacitive gap embedded in the stepped-impedance conductor line. By inserting a 2×2 array of the original element in conventional patch and feeding the resultant structure with an annular-ring slot along the diagonal, an antenna working in three resonant modes (n = -1, n = 0, and n = +2) is engineered at three specific well-separated frequencies f_-1 = 1.5, f₀ = 2.4 and f₊₂ = 3.5 GHz, respectively. As a result, both the numerical and experimental results illustrate that the antenna exhibits a patch-like radiation with pure linear polarization in the n = -1 mode, a monopolar radiation with circular polarization in the n = 0 and also an asymmetric quasi monopolar radiation with a hybrid linear polarization in the n = +2 mode. The antenna features compact whose patch occupying only an area of 0.246λ₀×0.246λ₀×0.03λ₀ at f_-1 and exhibits groups of advantages such as high radiation efficiency. Moreover, the proposed prescription, free of any metallic via, perturbation structure and complicated feeding network, is of practical value and opens an alternative avenue toward new types of antenna with agile polarization capability and versatile radiation patterns.

In this paper, we presents a cost effective method to generate a high-quality quadruple frequency optical millimeter-wave (MMW) signal using an integrated dual-parallel MachZehnder modulator (IDP-MZM). Not only does the method minimize the complication of the central station (CS) and its frequency demand for the devices, but the generated optical MMW signal as well has good transmission performance. By properly adjusting the direct current (DC) bias, modulation index, and using two radio frequency (RF) driving signals with 135° phase delay, a high quality dual tone optical MMW at 60 GHz is generated from a 15 GHz RF local oscillator (LO) with optical sideband suppression ratio (OSSR) as high as 32 dB and radio frequency spurious suppression ratio (RFSSR) exceeding 33 dB without optical filter when an integrated IDP-MZM with 30 dB extinction ratio is utilized. Furthermore, the influences of a number of non-ideal parameters, such as the impact of imperfect extinction ratio, non-ideal RF driven voltage and phase difference of RF-driven signals applied to two sub-MZMs of the integrated DP-MZM, on OSSR are studied through Simulation. Finally, we build a Radio over fiber (RoF) system through simulation, and the transmission performance of the generated optical MMW signal is presented. The eye patterns still clear and keeps open even after 60 km transmission.