A modified Gysel power divider with arbitrary power dividing ratio is proposed in this letter. The power dividing ratio of the proposed circuit is determined by both the electrical lengths and characteristic impedances of transmission lines. The proposed circuit is analyzed based on transmission line theory, and design equations are derived. For verification, two prototypes operating at 2 GHz with power dividing ratios of 1:1 and 4:1 are designed, fabricated and measured, respectively. The measured results are in good agreements with the simulated ones.

The aim of this work is to study the parameter estimation of a nonlinear medium in terms of scattered electromagnetic fields.The surface parameters are defined in terms of linear and nonlinear components of susceptibility and permeability. A set of Maxwell's equations are derived for an inhomogeneous medium using Green's function and the scattered Electromagnetic fields solving integrodifferential equations. Mathematical formulas are simplified using wavelet based method. Susceptibility and permeability is assumed as a function of wavelet basis. For parameter estimation, least square method and inner product methods are used with wavelets as a basis function, which gives solutions for nonlinear integrodifferential equation. Both time and spatial domain analysis is done using wavelets, and parameter coefficients are obtained. It is found that in both the parameter estimation methods, least square estimation gives better results. At the end of the paper statistical analysis of the scattered signals is included by calculating the mean and covariance of the signals.

In this article, a couple of monopole line-fed UWB antennas with different configurations are presented. Antenna shapes include a big circle overlapped with four small circles, and a two overlapped circles in the horizontal direction. Configurations include single element antenna, single element antenna with dual band reject filters, and polarization diversity antenna version. Measurements show that all antennas work well within almost the whole UWB. The polarization diversity version has a practical port isolation (S₁₂ and S₂₁) better than -15 dB, an Envelope Correlation Coefficient lower than 0.019 and a diversity gain higher than 9.96 dB.

An ultra compact microstrip wideband bandpass filter (BPF) using a quadmode stub-loaded resonator is presented in this letter. The resonant characteristics of the quadmode resonator are explored by adopting odd- and even-mode analysis. The four resonant frequencies of this resonator can be controlled independently. For demonstration purpose, a wideband BPF is designed, fabricated and measured. The measured results are in good agreement with the full-wave simulation results. The realized wideband filter exhibits a 3 dB fractional bandwidth (FBW) of 45% with good in-band filtering performance and sharp out-of-band rejection skirt.

Magnetic field and eddy currents in a cylinder of finite length are calculated by separation of variables. The magnetic field outside the cylinder or inside the bore of the hollow cylinder and shell is expressed in terms of Bessel functions. Both axial and transverse applied fields are considered for the solid and hollow cylinders. The equations for the vector potential components are transformed in one-dimensional equations along the radial coordinate with the consequent integration by the method of variation of parameters. The equation for the scalar electric potential when required is also integrated analytically. Expressions for the magnetic moment and loss are derived. An alternative analytical solution in terms of scalar magnetic potential is derived for the finite length thin shells. All formulas are validated by the comparison with the solutions by finite-element and finite-difference methods.

This paper presents a miniaturized Wilkinson power divider (WPD) with higher order harmonics suppression. The proposed power divider is designed for global system for mobile communication (GSM) application. The quarter wavelength lines of the conventional WPD are replaced by stub loaded transmission line in order to miniaturize the circuit size. A solution, operating at 1.8 GHz center frequency, has shown that the 2nd and 3rd order harmonics are well suppressed by a level < -15 dB. Further, two differently shaped defected ground structures (DGS) are embedded with the design to suppress the higher order harmonics. Therefore, overall 31% size reduction is achieved, and higher order harmonics are suppressed up to the 9th order (16 GHz) by a level < -15 dB compared to reference WPD. The return loss and isolation performance of the proposed WPD are < -15 dB and < -20 dB, respectively.

Study of snow is an important domain of research in hydrology and meteorology. It has been demonstrated that snow physical properties can be retrieved using active microwave sensors. This requires an understanding of the interaction between electromagnetic (EM) waves with natural media. The objective of this work is two-fold: to study numerically all physical forward models concerning the EM wave interaction with snow and to develop an inverse scattering algorithm to estimate snow depth based on radar backscattering measurements at different frequencies and incidence angles. For the first part, the goal is to solve the scattering calculations by means of the well-known electromagnetic simulator Ansoft High Frequency Structure Simulator (HFSS). The numerical simulations include: the effective permittivity of snow, surface scattering phenomena in layered homogeneous media (air-snow-ground) with rough interfaces, and volume scattering phenomena when treating snow as a dense random media. For the second part, the study is extended to develop a retrieval method to estimate snow thickness over ground from backscattering observations at L- and X-band using multiple incidence angles. The return signal from snow over ground is influenced by: surface scattering, volume scattering, and the noise effects of the radar system. So, the backscattering coefficient from the medium is modelled statistically by including a white Gaussian noise into the simulation. This inversion algorithm estimates first the snow density using L-band co-polarized backscattering coefficient at normal incidence and then retrieves the snow depth from X-band co-polarized backscattering coefficients using dual incidence angles.

In this paper, a design of compact monopole antenna with defected ground plane for wideband applications has been investigated. Initially, the partial ground plane is used which yield the impedance bandwidth (S₁₁ ≤ -10 dB) of 23.87% and 17.54% ranging (4.00 GHz-5.11 GHz) and (8.48 GHz-9.84 GHz) respectively. The bandwidth of the proposed monopole antenna is enhanced by employing the defects in the partial ground plane. Antenna is designed and simulated by using Ansoft HFSS v13 simulator; moreover, the antenna is fabricated to validate the simulated results with the measured results. Measured proposed monopole antenna with DGP (Defected Ground Plane) exhibits the impedance bandwidth (S₁₁ ≤ -10 dB) of 72.87% ranging (3.89 GHz-8.35 GHz), which covers different wireless standards such as WiMAX (3.3 GHz-3.7 GHz), WLAN (5.15 GHz-5.85 GHz), X-band satellite applications (7.1 GHz-7.76 GHz) and point to point high speed wireless communication (5.925 GHz-8.5 GHz).

Due to the increase in the data rates for modern wireless communications and recent generation standards, the switched beam approach and multiple-input multiple-output (MIMO) direct conversion transceiver (MIMO-DCT) have become promising techniques to satisfy these requirements. The combining of switched beam and MIMO-DCT through the use of multiple antenna elements has been investigated to overcome the high complexity and high spatial directivity of the conventional system. In this paper, a low cost miniaturized beam-switching array antenna with a MIMO-DCT system has been proposed, designed and analysed. The entire proposed system structure has two design stages. The first is the design of MIMO-DCT via the integration of microstrip antenna element, hybrid coupler, Wilkinson power divider and single-pole double-throw (SPDT) transmitter/receiver (T/R) switch. The second has the switched beam array antenna design using a Butler matrix feeding network and four distributed subarrays (DSs) of the MIMO-DCT. The entire proposed design structure components have been optimized using a commercial software to evaluate each component and meet the desired performance. The final proposed two-stage design has been fabricated, integrated, and the radiation characteristics have been demonstrated, using the Agilent FieldFox network analyser, to meet the requirements for LTE and wireless communication applications.

The purpose of this paper is to examine whether a generalised range-based sliding window detector provides any improved detection performance relative to a single order statistic based counterpart. This is for non-coherent target detection in an X-band maritime surveillance radar environment, and as such the intensity clutter is modelled by a Pareto distribution. It will be demonstrated mathematically that a single order statistic detector is in fact sucient. Some numerical examples are also provided to clarify the theoretical results.

A study is made of the electrodynamic characteristics of an antenna having the form of a perfectly conducting, infinitesimally thin, narrow strip located at a plane interface of an isotropic medium and a cold collisionless magnetoplasma. The antenna is perpendicular to an external static magnetic field superimposed on the plasma medium and is excited by a time-harmonic given voltage. Singular integral equations for the antenna current are obtained in the case of an infinitely long strip conductor. Based on the solution of these equations, the current distribution and input impedance of the antenna are found for nonresonant and resonant frequency ranges of the magnetoplasma. The limits of applicability of an approximate approach employing the transmission line theory for determining the antenna characteristics are established. Within the framework of this approach, the results obtained are generalized to the case of a finite-length strip antenna.

An E-shaped printed monopole antenna with loaded resonant elements suitable for penta-band multi-input multi-output (MIMO) application is proposed. The simple E-shaped monopole antenna results in a single resonance, and by loading the vertical arm of the antenna with narrow slots and stubs, a multi-band antenna can be obtained. The slots so placed on the antenna create L-shaped resonance paths which are multiples of λ_g/4, and stubs resonate at λ_g/4. The antenna is designed for operation over the UMTS, WiMAX and WLAN frequencies 2.1, 2.5, 3.5, 5.2, 5.8 GHz. A two element array of such antennas with close spacing of λ_g/15 is suitable for MIMO application. The array has low mutual coupling, low envelope correlation, high efficiency and good radiation patterns over all five frequency bands. Simulation and measurement results are compared and discussed.

Progress in wireless communication requires antennas that work on multi-band simultaneously. This paper presents a design method for a multi-band antenna using printed dipole with L-slots fed by a single coaxial cable. Using this method, a triple-band antenna that operates at 868-915 MHz for RFID (radio frequency identification), 1575 MHz for GPS (global positioning system) and 2.45 GHz for BLE (bluetooth low energy) was designed and manufactured. The antenna's parameters for triple-band operation are investigated and discussed. In this antenna design, ANSYS HFSS software using highly accurate nite element method (FEM) simulation is employed to analyze the entire structure. The designed antenna is manufactured using an FR-4 substrate with a dielectric constant (ε_r) of 4.4 and thickness (h) of 1.6 mm. Many prototypes have been fabricated, and good agreement between simulations and measurements has been achieved. The performance of the prototypes has been measured in a standard far-field anechoic chamber. The proposed triple-band antenna is also tested by measuring the reading distance, and it is found that the proposed antenna can be used for RFID applications.

European smart energy meter applications operate over a smart grid network. These applications operate over ISM frequency bands. The proposed dual-band printed monopole antenna provides a solution to smart energy meter applications. The surface dimension of the planar monopole antenna is 45 x 17 mm². The antenna has strips fabricated on a standard cost-effective FR-4 substrate of thickness 1.6 mm for achieving dual-mode resonance at 868 MHz and 2.4 GHz. The proposed monopole antenna has operating impedance bandwidth of 2.89% and 2.78% for the first and second resonances, respectively. The gain of the presented antenna is in order of 1.18 dBi for lower resonant mode and 2.1 dBi for the higher resonant mode. The antenna resonates in the frequency range which is also useful in smart RFID tags for device identification operating over smart grid. In addition, the antenna can be utilized for the devices functional in Low Rate Wireless Personal Area Networks (LR-WPAN) and WiFi-based smart applications.

This work deals with the optimization of an inverted F dual-band implantable antenna operating in Medical Device Radiocommunications Service (MedRadio, 401-406 MHz) and Industrial Scientific Medical (ISM, 902-928 MHz) applications bands. Artificial neural networks (ANNs) are implemented to minimize the size of the initial design. The ANN's output with the physical and dielectric parameters of antenna as inputs is tested using COMSOL Multiphysics®. The obtained results regarding the return loss S₁₁, resonant frequency and bandwidth of the antenna are presented and discussed. Indeed, the size of the antenna is reduced by 21.48% with respect to the initial size while preserving its initial good performance in both frequency bands.

This study presents a polarization reconfigurable antenna with frequency diversity function. The antenna incorporates a novel positive and negative perturbation technique to achieve different polarization sense. A square shape slot is loaded on the ground plane to excite circular polarization by creating a negative perturbation. An L-shape segment is integrated to the patch using a switching diode. This segment creates a positive perturbation to eliminate the negative perturbation created by the defected ground slot, and the antenna excites linear polarization. Frequency diversity is achieved by exciting different polarization senses at different frequencies. A 3-dB axial ratio bandwidth of 1.41% is obtained for circular polarization radiation while the 10-dB impedance bandwidth during linear polarization is 1.8%. The antenna shows good radiation performances with high gain at both polarization states, and the performances are confirmed experimentally.

Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, the output voltage fluctuations resulting from lateral misalignments are main obstructing factors for promoting this technology. In this paper, an asymmetric two-coil WPT system is presented. The mathematical model of the proposed topology with lateral misalignments is built based on equivalent circuit method. The expression of the output voltage is then derived by solving the system equivalent equations. In addition, a method of optimization parameters is proposed. The mutual inductance between the receiving coil and transmission coil is nearly constant by the proposed method with lateral misalignments. Therefore, the output voltage can be kept nearly constant. The asymmetric two-coil WPT system via magnetic resonance coupling is designed. Simulated and experimental results validating the proposed method are given.

A novel dual-band and dual-sense circularly polarized coplanar waveguide (CPW) fed planar antenna with an asymmetric rectangular slot is presented. An F-shaped feed line is protruded from the signal line into the slot. Circular polarization is obtained due to the F-shaped feed line and asymmetry in the slot. Axial ratio bandwidth is significantly enhanced by placing parasitic elements adjacent to the feedline. The antenna has a size of 63.5×55 mm². The measured results agree well with simulation. The measured impedance bandwidths are 26.04% (1.57 GHz-2.04 GHz) for the lower band and 18.93% (2.87 GHz-3.47 GHz) for the upper band. The measured 3 dB axial ratio bandwidths of lower band and upper bands are 22.22% (1.6 GHz-2 GHz) and 10.53% (3.15 GHz-3.5 GHz), with respect to 1.8 GHz (RHCP) and 3.325 GHz (LHCP), respectively.

Curved trajectories of traditional navigation satellites limit their performance in bistatic radar imaging system. Instead of using common Inclined Geosynchronous Orbit (IGSO)/Medium Earth Orbit (MEO) satellites in motion, a new global navigation satellite system (GNSS) imaging system based on Beidou geosynchronous orbit (GEO) satellites is presented to deal with this problem. The most prominent feature of GEO satellites is that they are stillrelative to the earth. This work includes three parts. First, a reasonable parallel assumption is provided to simplify the geometric topology of the imaging system, and the relevant path delay formula is deduced. Second, the principle of imaging based on multiple GEO satellites is proposed, and the simulation result is presented. Third, the entire signal processing, which uses a multi-correlator, is designed to improve the range resolution. Two imaging experiments targeting at the trees are described and conducted in Wuhan University to verify the imaging system. The first experiment is targeted at isolated trees, and the second experiment is focused on groves along the road. Conclusion can be obtained: the imaging result is highly consistent with the imaging area, which validates the feasibility of the method and confirms the potential use of GNSS imaging system in forest monitoring.

This paper presents a combinatorial triangle type artificial magnetic conductor checkerboard surface for wideband radar cross section reduction. The structure consists of a combination of a single band and dual band AMC unit cells with 180±370 phase difference from 4.06 GHZ to 11.2 GHz. 10 dB RCS reduction compared to PEC surface is realized from 4.4 GHz to 11.68 GHz (91%) for the proposed structure. The performance of the structure is compared with the conventional checkerboard surface. The distribution of scattered fields from both the structures are analyzed using array theory. The angular stability of the structures are also studied for TE and TM polarized wave incidences. A prototype of the proposed structure is fabricated, and the measured data are in good agreement with simulated results.