A nonlinear metamaterial composite structure with tunable tunneling frequency is presented. Based on theoretical calculation results, a nonlinear metamaterial sandwich structure constructed by epsilon negative metamaterial (ENM), mu negative metamaterial (MNM) and nonlinear double negative metamaterial (NDNM) is designed, and its nonlinear properties are investigated. The measured results show that the tunneling frequency of the sandwich structure ENM-NDNM-MNM can be controlled conveniently by signal power.

In scattering experiments, incident fields are usually produced by aperture antennas or lasers. Nevertheless, incident plane waves are usually preferred to simplify theoretical analysis. The aim of this paper is the analysis of the electromagnetic scattering from a perfectly electrically conducting polygonal cross-section cylinder when a Gaussian beam impinges upon it. Assuming TM/TE incidence with respect to the cylinder axis, the problem is formulated as electric/magnetic field integral equation in the spectral domain, respectively. The Method of analytical preconditioning is applied in order to guarantee the convergence of the discretization scheme. Moreover, fast convergence is achieved in terms of both computation time and storage requirements by choosing expansion functions reconstructing the behaviour of the fields on the wedges with a closed-form spectral domain counterpart and by means of an analytical asymptotic acceleration technique.

Metasurfaces, due to its designable surface electric and magnetic impedances, have largely enhanced electromagnetic wave manipulation techniques. The conventional approach to realize the surface magnetic impedance requires non-planar structures, such as metallic loops, which is not easy to fabricate, especially at optical frequencies. In this work, we theoretically and rigorously prove that eective surface magnetic and electric impedances can be obtained using parallel electric metasurfaces. A synthesis method is presented which allows independent designs of surface electric and magnetic impedances. Finally, a polarization converter with high energy efficiency is designed using the proposed impedance synthesis method for verification. The proposed synthesis method is favorable for reducing fabrication complexities.

Analytical expressions that include arbitrarily directed fields on all laminate boundaries can be used for calculation of the fields inside the laminate when the boundary fields are known from, e.g., measurements. A linear laminate block could be used in non-destructive testing for comparisons between different laminates. This article contains derivation of Fourier series of harmonically time varying, traveling electromagnetic fields in homogeneous, anisotropic approximations of laminates. The component of the magnetic field strength in the stacking direction is used as a source term in twodimensional Poisson equations for the magnetic field strength in other directions. This approximation is here used in three dimensions under the precondition that the conductivity is much smaller in the laminate stacking direction than in the other directions. Sine interpolation and different choices of types of boundary conditions are discussed. Different alternative subdivisions of the Poisson boundary value problems are treated. Shorted derivations of simple analytical expressions are given for both traveling and standing waves in two dimensions. Results from Fourier series in the three-dimensional case are compared with results from finite element calculations.

An intentional focusing of High-Power Microwave (HPM) energy on microelectronic systems can produce effects that will potentially upset or damage the target. However, the physical mechanisms at work within the device are not often well understood. We provide a detailed understanding of the physical mechanisms involved in a common-source Metal Oxide Semiconductor (MOS) transistor inverter when Pulsed Microwave Excitation (PME) in a frequency range from 10 MHz to 1 GHz is applied on the gate terminal. Our study is based on the measurements of the current waveforms on all transistor access and explains the MOS response with and without the Radio-Frequency (RF) interference.

A compact triple-band monopole antenna covering WLAN/WiMAX bands is investigated in this Paper. The proposed antenna has a compact size of 36 x 25 mm² and consists of a circular ring, a split ring radiator and a trapezoid coplanar waveguide-fed structure. The antenna covers three distinct bands of 2.27-2.55 GHz, 3.23-4.14 GHz, and 5.08-6.03 GHz for WLAN and WiMAX applications. To validate the proposed design, prototype is fabricated, and measurement is carried out. Good performances of gain, radiation pattern and efficiency have also been obtained.

For the purpose of two-dimensional (2-D) imaging in the Terahertz (THz) near field through 2-D synthetic aperture radar technology, Fourier transform (FT) is one of the most popular imaging ways. However, FT-based algorithms would encounter performance loss either when spatial sampling is under Nyquist frequency or there are off-grid scatterers in the scene of interest. Therefore, by exploiting the theory of matrix enhancement and continuous parameter estimation, we propose to use matrix enhancement and matrix pencil (MEMP) method and matched filter to deal with arbitrarily located scatterers when spatial under-sampling is adopted. Through constructing a specifically expanded matrix, the information of the scatterers involved in the small data set can be enhanced. Then, highresolution grid-independence 2-D imaging can be achieved by the combination of MP and matched filter. Simulation results verify the effectiveness of the proposed algorithm.

Influence of surface impedance on radiation fields of spherical antennas excited by radially oriented electric dipole is investigated by using a Green's function for a space outside a spherical scatterer. This approach allows us to obtain analytical expressions for radiation fields of an impedance spherical antenna in the wave zone. The spherical antenna with the scatterer coated with a metamaterial layer is also considered. The surface impedance required for radiomasking of the spherical scatterer of resonant dimensions was estimated by mathematical modeling.

This paper deals with the design and experiments of a dual-band circularly polarized rectenna at 1.85 and 2.45 GHz. It uses a single antenna and a single RF-to-dc rectifier. The circuit contains a dual-band circularly polarized antenna and a dual-band RF-to-dc rectifier based on a miniaturized 180° hybrid ring junction. The ring junction is used to independently match the sub-rectifiers at each frequency. The proposed rectenna was experimented with single-tone and multi-tone incident waves. It achieves more than 300 mV and 40 % efficiency, across a 4-kΩ resistive load, at very low power density of 1.13 µW/cm² at 1.85 GHz and 1.87 µW/cm² at 2.45 GHz. It also achieves more than 150 mV under the same load condition and in the critical case when receiving only one of the two frequency bands. It is dedicated to harvest RF energy in the GSM 1800 and the 2.45-GHz ISM bands, regardless the polarization angle of the incident waves.

Traditional passive millimeter wave imaging (PMMW) mechanism measures intensity-only radiometric energy of the scene, and the limited information restricts the subsequent process of target detection and recognition. Polarimetric phenomena provide an extra dimension of information and are utilized to improve the PMMW imaging performance. Based on linear polarization characteristics for terrain identification in our previous work, the horizontal, vertical and 45 degree linearly polarimetric images are obtained by manually changing the polarization orientation of the radiometer with a selfdesigned rotating installation. Then the related Stokes parameters and the linearly polarized angle are calculated for principal component analysis (PCA). Pixels with similar polarimetric characteristic are clustered in the score-plot feature space. Then the clusters are extracted to realize object segmentation of the raw image. Three types of objects including metallic stuff, lawn and concrete park are finally segmented, demonstrating that the proposed segmentation is feasible and effective.

Usually, knowledge of material's dielectric properties, as a function of frequency, represents a key issue in scientic elds and several industrial applications. At LNE-CETIAT, in partnership with Institut Fresnel UMR 72792, a set of capacitive and coaxial cells, dedicated to the measurement of complex dielectric permittivity, have been developed. The present paper focuses on the experimental calibration and validation of two cells using low and medium dielectric loss materials. It gives the main measurement results obtained on three dierent materials: decanol alcohol, polytetra uoroethylene (PTFE) and polyvinyl chloride (PVC) in the frequency range from 3 MHz up to 2 GHz.

In this work, a quad-band omnidirectional slot antenna array is proposed. The structure consists of two closely-spaced radiating elements fed using coplanar waveguide (CPW) line. This combined structure is then integrated in a tapered slot etched on the antenna to enable operation in four frequency bands (0.8, 1.8, 2.6 and 3.45 GHz) for LTE and WiMAX applications with at least -10 dB of reflection coefficient. The antenna dimensional parameters are also studied to understand its behaviour and eects on its performance in facilitating the optimization process. Measurements of the fabricated antenna on a low-cost FR4 substrate validate its operation centred at 0.845 (from 0.77 to 0.92 GHz), 1.74 (from 1.59 to 1.9 GHz), 2.655 (2.59 to 2.72 GHz) and 3.49 GHz (from 3.28 to 3.7 GHz). Meanwhile, simulated and measured radiation patterns of the proposed antenna in all bands agree well and are omnidirectional, making is suitable for application in mobile terminals.

This paper talks about a simple printed reconfigurable antenna for cognitive radio. This antenna can be switched between ultra-wideband (UWB) and two other narrow bands. To achieve frequency reconfigurability, horizontal slots are inserted in the partial ground plane, and their lengths are varied by using ideal switches. These switches are incorporated so that they can be turned ON/OFF independently. The proposed antenna is suitable for cognitive radio as it is capable of sensing whole UWB from 3.1 GHz to 10.6 GHz (7.5 GHz bandwidth) and switching between two different narrow bands viz. 3.1 GHz and 8.23 GHz, and the corresponding observed gain and radiation pattern are also as per the requirement.

The paper presents a study of dynamic thermal processes in ultra-high-speed microgenerators power of 55 W with the rotational speed of 800,000 rpm for UAV. A large-scale study of current works devoted to this topic were done where the main shortcomings were identified. A mathematical description of heat exchange processes in microelectromechanical energy converters with a flight time of no more than 10 minutes was developed in a non-stationary formulation. A study of the thermal state of the microgenerator operating in a short-term mode without a special cooling system is conducted. An experimental study of the heating dynamics of its active parts is carried out using the method of physical analogies. On the basis of experimental studies, the FEMM model is verified. Afterwards, combined electromagnetic and thermal calculations of microgenerator are conducted.

The radiation properties of a copper-patch antenna designed for resonating at the frequency of 0.7 THz, which is used in aerospace applications, is presented. These properties are then compared to those of a graphene-patch antenna presenting the same dimensions. We show how the use of graphene, as a tunable material, allows to dynamically modify the frequency of operation of the antenna as well as its radiation pattern. Our results show that the return loss peak reaches -29 dB, at the operating frequency, which is almost twice the value obtained with the copper patch. This increase in the return loss peak is also accompanied by an improvement in the gain of the antenna from 5.73 dB in the case of the copper patch to 7.16 dB in the case of graphene. We focus our interest on how the reconfigurable radiation properties of the graphene-patch antenna are directly related to the graphene surface conductivity.

In this work, we study a multichannel filter by using one-dimensional photonic crystal (1DPC) based on Thue-Morse sequence (TMS). We use a dielectric defect layer between binary sequence cells with a TMS structure. First, we show transmission in terms of wavelength for the structure without defect layers. Then, we plot transmission in terms of wavelength for a different number of defect layer periods (N) in normal incidence. The analysis shows that there are two photonic bang gaps (PBG) in visible and infrared regions and two defect modes in each one for N = 1. Moreover, the number of defect modes is increased by increasing N. So, by tuning them, this structure can be used as a multi-channel filter within an optical wavelength range.

A compact dual-band bandpass filter implemented with an embedded coplanar waveguide (ECPW) resonator and a capacitively loaded resonator (CLR) in substrate integrated waveguide (SIW) cavity is presented and analyzed in this paper. Three transmission zeroes (TZs), of which two are located in the middle of the two passbands and one located in the upper stopband, are obtained to improve the inner-band isolation and the selectivity of the filter. The center frequencies and bandwidths of the two passbands can be easily tuned by changing the geometrical parameters of the two resonators. The proposed dual-band SIW filter is demonstrated with center frequencies located at 8.41/14.29 GHz. The measured insertion loss is -1.28/-1.91 dB with the corresponding fractional bandwidth (FBW) of 21.2%/7.3%. The measured results are in good agreement with the simulated ones.

Propagation path loss models are useful for the prediction of received signal strength at a given distance from the transmitter; estimation of radio coverage areas of Base Transceiver Stations (BTS); frequency assignments; interference analysis; handover optimisation; and power level adjustments. Due to the differences in: environmental structures; local terrain profiles; and weather conditions, path loss prediction model for a given environment using any of the existing basic empirical models such as the Okumura-Hata's model has been shown to differ from the optimal empirical model appropriate for such an environment. In this paper, propagation parameters, such as distance between transmitting and receiving antennas, transmitting power and terrain elevation, using sea level as reference point, were used as inputs to Artificial Neural Network (ANN) for the development of an ANN based path loss model. Data were acquired in a drive test through selected rural and suburban routes in Minna and environs as dataset required for training ANN model. Multilayer perceptron (MLP) network parameters were varied during the performance evaluation process, and the weight and bias values of the best performed MLP network were extracted for the development of the ANN based path loss models for two different routes, namely rural and suburban routes. The performance of the developed ANN based path loss model was compared with some of the existing techniques and modified techniques. Using Root Mean Square Error (RMSE) obtained between the measured and the model outputs as a measure of performance, the newly developed ANN based path loss model performed better than the basic empirical path loss models considered such as: Hata; Egli; COST-231; Ericsson models and modified path loss approach.

We propose a novel approach for the broadband generation of orbital angular momentum (OAM) carrying beams based on the Archimedean spiral. The mechanism behind the antenna is theoretically analyzed and further validated by numerical simulation and physical measurement. The results show that the spiral-based antenna is able to reliably generate the OAM carrying beams in an ultra-wide frequency band. Of particular interest is the fact that the mode number of radiated beams is reconfigurable with a change in operating frequency. Prototypes of a single-arm spiral antenna (SASA), a multi-arm spiral antenna (MASA), and a compact multi-arm spiral antenna (CMASA) are investigated and demonstrated to support our arguments. The proposed approach provides an effective and competitive way to generate OAM carrying beams in radio and microwave bands, which may have potential in wireless communication applications due to its characteristics of simplicity, broadband capacity and reconfiguration opportunities.

In this work, reflectarray antennas are proposed for their use as probes in compact antenna test ranges. For that purpose, the quiet zone generated by a single oset reflectarray is enhanced, overcoming the limitation imposed by the amplitude taper of the feed antenna. First, the near field is characterized by a radiation model which computes the near eld of the reflectarray as far field contributions of each element, which are modeled as small rectangular apertures and thus taking into account the active element pattern. Then, a phase only synthesis is performed with the Levenberg-Marquardt algorithm in order to improve the size of the generated quiet zone. Due to the nature of the application, this near eld synthesis takes into account both the amplitude and phase, making it a more challenging task than an amplitude-only synthesis. The optimization is focused on flattening the amplitude while trying to preserve the phase front generated by the reflectarray.