This paper presents the design of a compact-integrated reconfigurable rectenna array containing 2x2 compact microstrip patch antennas based on a fractal model with the rectifier circuit integrated into the same physical structure and usable in practical conditions. In this array configuration, four rectennas were mounted in a planar structure with total dimensions of 85x85 mm using FR-4 dielectric and with recongurable DC output that was tested in three ways: series-association, parallel-association and series-parallel association. In the series-association the rectenna array was able to generate the DC power that reached 6.51 V and maximum efficiency of 64.5%; in the parallel-association it generated the DC power that reached 1.58 V and maximum efficiency of 65.3%; in series-parallel-association it generated the DC power that reached 3.00 V and maximum efficiency of 64.5%. The results showed that rectennas in array configuration are feasible to be used as power supplies to electronic devices in real situations.

A size-reduced quarter-mode substrate integrated waveguide (QMSIW) band-pass filter (BPF) loaded with combination of complementary split ring resonator (CSRR) and capacitive metal patches is presented. The CSRR generates a passband below the characteristic cutoff frequency of the substrate integrated waveguide (SIW) cavity. Improved stopband rejection is also attainable by loading a capacitive metal patch. Thus, a single-layer compact BPF with wide stopband is realized successfully. The equivalent-circuit model has been derived and analyzed. To verify the validity of the presented method, an experimental filter centered at 2.45 GHz is fabricated and measured. The new filter has the return loss of 16 dB and insertion loss less than 0.9 dB. Out-of-band suppression is better than 20 dB from 3 GHz to 11.6 GHz. The whole size of the filter is only 20×17.4×0.508 mm³, achieving 75% size reduction compared to the conventional structure.

A wideband right-hand circularly polarized (RHCP) crossed-dipole antenna with wide impedance bandwidth (IBW) and axial ratio bandwidth (ARBW) is proposed in this paper. A pair of dipoles with modified arms and a novel back-cavity are introduced to enhance both the IBW and ARBW of a conventional crossed-dipole antenna. Simulated and measured results indicate that the proposed structure can improve the circularly polarized (CP) characteristics significantly. The IBW (|S₁₁|<-10 dB) and ARBW (AR<3 dB) are 100% and 89.1%, respectively. The total size is 0.4λ×0.4λ×0.15λ (λ being the corresponding free-space wavelength at the frequency of 2.2 GHz). With both the excellent CP operating bandwidth and compact size, the proposed antenna is attractive for broadband wireless communication systems.

This paper proposes a secure beamforming (BF) scheme for a dual-hop satellite communication system, where a satellite acts as a relay using amplify-and-forward (AF) protocol to assists signal transmission between the terrestrial source and destination, where the target user is intercepted by an eavesdropper (Eve) in the downlink transmission. By assuming that the satellite is deployed with multiple antenna feeds, we rst establish an optimization problem to minimize the on-board transmit power subject to the quality-of-service (QoS) and secrecy performance requirement of the destination. Then, based on the method of penalty function, we propose a secure BF scheme to obtain the optimal BF weight vector with analytical form. Finally, computer simulation results are given to demonstrate the eectiveness and superiority of the proposed algorithm.

This paper proposes the design of wide bandpass filters for Ku and Ku/K band applications. It has wide passband with miniaturization of size using folded substrate integrated waveguide (FSIW) technique. The filter is designed by introducing a C slot and an E slot in central metallic septum of FSIW respectively. The proposed filters are fabricated and tested after optimization. The fabricated E slot filter achieved enhancement in bandwidth with dual band operating in Ku band (14.35 GHz-16.76 GHz) and K band (18.66 GHz-19.61 GHz), respectively. The measured results match quite closely with simulated ones.

Cancer treatment is one of the several new applications which use subnanosecond pulse and picosecond high voltage pulse. In particular, picosecond pulses can introduce important non-thermal changes in cell biology, especially the permeabilization of the cell membrane. The Prolate Spheroidal Impulse Radiating Antenna (PSIRA) is used to radiate very fast pulses in a narrow beam width with low dispersion and high field amplitude. The beamwidth of the radiated pulse is further reduced by using near field focusing lens. In this proposed work, the compact partition lens system is designed for miniaturized PSIRA to focus the radiated impulse to the target (skin) location. The near field focusing lens is used to enhance the resolution on the target location. The PSR with Modified Bicone Antenna (MBA) with lens configuration provides greatly reduced spot size. The spot size on the target(skin) is measured as 3mm along the lateral direction and 6 mm along axial direction.

This letter presents a broadband circularly polarized (CP) crossed dipole antenna with wide axial ratio (AR) beamwidth. The antenna consists of a crossed dipole fed by two baluns, a wideband feed network and a cylindrical metallic cavity. To broaden the beamwidth, circular arms are introduced. Meanwhile, the metallic cavity is utilized to broaden the AR beamwidth. Measurements show that the antenna has an impedance bandwidth of 70.6% (1.87-3.91 GHz) for voltage standing wave ratio (VSWR) ≤ 2 and a 3-dB AR bandwidth of 62.4% (1.92-3.66 GHz). In addition, the 3-dB AR beamwidth of the antenna is larger than 100°, and the gain varies from 4 dBic to 6 dBic over the whole CP operation bandwidth. Owing to the high-gain and wideband operation, the proposed CP antenna is potentially capable for satellite applications and high-gain applications.

The interferometric synthetic aperture microwave imager (IMI) on WCOM is a onedimensional L/S/C tri-frequency microwave radiometer aiming to improve the measurement capability on soil moisture and ocean salinity. An IMI antenna system mainly consists of a parabolic cylinder reflector and a tri-frequency linear patch feed array. At present, an L-band ground prototype with a solid reflector and an 8-element feeds array is completed, with the imaging feasibility being verified by experimental results. In order to improve radiometer performance, this paper presents an improved antenna system, which is dedicated to the next generation of interferometric microwave imager prototype. Improvements made for the antenna system mainly include using deployable mesh reflector and increasing feeds. Simulation results of image reconstruction in viewing a series of near real case ocean brightness temperature maps are used to quantitatively compare and analyze imaging performances of the two L-band IMI prototype antenna systems.

In this paper, a novel miniaturized circularly polarized (CP) antenna is proposed for use in B3 band of Compass Navigation Satellite System (CNSS). The primary radiator is a hexagon patch with four bending strips. A shorting pin is loaded with each strip to miniaturize the dimension of the proposed antenna, which achieves a small electrical size of 0.11λ×0.11λ×0.068λ (λ being the wave-length in free space at 1.268 GHz). In order to improve the bandwidth, Y-shaped coupled patches and bending-strips, which act as reactive loading are coupled to an octagon patch. Four coupled bending-stubs with same turning directions of bending-strips, are sequentially placed at the edge of the octagon patch to enhance CP performance. Finally, a prototype of the antenna is implemented and measured. The experimental results reveal that the proposed antenna achieves impedance bandwidth (IBW) of 19.6% (1.175-1.430 GHz) for |S₁₁|≤-10 dB and 3-dB axial-ratio bandwidths (ARBW) of 27.5% (1.000-1.320 GHz). The radiation efficiency is more than 75%, and the gain keeps above 1.98 dBic over the B3 band. Thus, the proposed antenna can be a good candidate for the applications of CNSS.

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.