Vol. 70

The use of dual orthogonal polarizations to optimally conserve frequency spectrum in microwave link, otherwise known as cross polarization, has received considerable interest in the recent time in the field of electromagnetic wave propagation in sand and dust storms. Cross polarization in dust storms occurs due to the non-sphericity of the falling dust particles and the tendency of the particles to align in a direction at a time i.e. canting angle. The realization of a dual-polarized system is however limited by degree of cross polarization discrimination (XPD) that can be achieved between the two orthogonal channels. Therefore, theoretical investigation has been carried out in this work to estimate the cross polarization at microwave and millimeter wave bands by non-spherical dust particles in dust storms. The XPD being the parameter for characterization of cross polarization, is predicted using propagation constants' differentials and canting angles, as inputs. Apart from both differential phase rotation and attenuation, it has been found that the cross polarization produced by ellipsoidal dust particles strongly depend on the particle canting. XPD decreases with an increase in canting angle. It has also been observed that the values of differential attenuation increase with increasing frequency for visibility and thus depends directly on frequency. Lastly, the obtained results show that cross polarization is significant during severe visibility and for dry dust storm; the XPD is good and acceptable for dual polarization systems.

The meteorological parameters along the overhead line change significantly, which have an effect on the surrounding electromagnetic environment. The analysis method of meteorological parameters impacting the electromagnetic environment is presented in this paper. Firstly, the conductor temperature is solved iteratively by the heat balance equation. Secondly, the power flow model involving the conductor temperature is established based on the relationship between line parameters and conductor temperature. Finally, the electromagnetic environment surrounding the line is analyzed based on the changes of line voltage and current. In the case study, the electromagnetic environment of the IEEE 5-bus system under the three cases is analyzed and compared. It is proved that the changes of meteorological parameters along the line have an important impact on the surrounding electromagnetic environment. The calculation of electromagnetic environment considering the changes of meteorological parameters is more accurate.

Air-gap magnetic energy variation with angular position produces cogging torque, which may results in mechanical vibration, acoustic noise, and torque ripple. Various cogging reduction methods of design modifications viz. skewed magnets, skewed slot, asymmetrical displacement of magnets/slots etc. are reported in the literature. All such methods adversely affect machine performance in terms of air-gap magnetic field, back emf, and induced voltage. This paper introduces the cogging torque reduction by skewing of slot opening. In order to obtain machine performance, the no load magnetic field of the proposed machine is determined using combined methods of two-dimensional subdomain analytical analysis method and multislice method. The machine is considered as a stack of slices along axial direction. The adjacent slices differ in relative location of slot openings. The analytical field solution of each slice is obtained by use of subdomain method, and algebraic summation of slices is taken as field solution of actual machine. The analytical analysis developed is compared with finite element analysis (FEA). The close agreement of analytical results with FEA results confirms the validation of analytical solution. Furthermore, the machine parameters viz. cogging torque, back emf, and induced voltage are evaluated analytically, and results are compared with FEA solution. To demonstrate the effect of skewed slot opening on machine's performance, a machine of same rating without skewing of slot opening is investigated, and their performances are compared.

In this paper the analysis and investigations are carried out on portable antennas for worldwide interoperability for microwave access (WiMAX) applications of flexible coplanar waveguide (CPW)-feed split-triangular shaped patch (STSP). The proposed STSP antenna is fabricated from polyimide substrate material having the dimension of 18×20×0.1 mm³ (volume is 36 mm³). It resonates at 3.55 GHz frequency of a reflection coefficient (S₁₁) of -24.45 dB and offers impedance bandwidth of 580 MHz (3.3-3.88 GHz) with a gain of 2.06 dBi. The STSP antenna has small size, light weight, low volume, and is flexible for WiMAX applications. Simulation and measured results of the proposed STSP antenna are in close agreement.

The reliable detection of geometrically-based stealth targets using a conventional single sensor radar system may be extremely difficult. This is because low Radar Cross Section (RCS) from certain angles results in a low Signal to Noise Ratio (SNR). In the present work, multi-target tracking of stealth targets is investigated in a multi-static radar with passive receivers. The Directions of Arrival (DOA) of targets are estimated by the receivers without knowing the number of targets, and their positions are obtained based on the transmitter beam direction. The B2 bomber aircraft model has been used as a stealth target. The RCS of the model has been simulated for all collection of incident and reflected angles from an oblique impinging plane wave. Probability of Detection (Pd) is modeled using a Toeplitz-based method for different SNRs due to different RCS patterns and is fed to an Iterated Corrected Probability Hypothesis Density (IC-PHD) filter. In spite of considering the transmitter and receivers resolution in our input data generation, the proposed algorithm is able to track the targets individually when they are much close to or even cross each other. Simulation results show the improved performance of the proposed method compared to other existing approaches.

This paper presents a distributed estimation strategy called alternation diffusion LMS estimation (AD-LMS) to estimate an unknown parameter of interests from noisy measurement over wireless sensor network. It is useful in the wireless sensor networks where robustness and low consumption are desired features. Diffusion LMS is introduced in this estimation strategy to improve the performance and reduce the communication burden. With the proposed strategy, whether each node distributes its estimation depends on an alternative parameter. The node only exchanges its estimation when the instant time meets some conditions. Next, each node combines the estimations of neighbors with its own estimation using combination coefficients upon the topology of the network. At last, the nodes update their estimations with a normalized LMS algorithm. The proposed AD-LMS strategy is compared to standard diffusion strategy. The results show that they achieve exactly the same coverage rate and nearly the network performance (network MSD and steady-state MSD) of standard diffusion strategy while reducing the communication burden significantly.

This paper presents a metamaterial loaded interdigital capacitor antenna having fractal geometry. The antenna consists of multiple split ring resonators (MSRR) with shorted ground. The metamaterial loading is achieved by MSRR that enhances the gain. Furthermore, multiband characteristics is obtained by two L-shaped rings providing the fractal geometry. The antenna has the physical dimension of 27 × 39.20 mm for the outer ring and in terms of wavelength has the dimension of 0.486 × 0.707λ. This antenna structure is designed and simulated on an FR-4 epoxy substrate of thickness h = 1.56 mm and dielectric constant ε_r = 4.4. The antenna resonates at multiple frequencies i.e. 1.5 GHz, 2.2 GHz, 2.70 GHz, 4.20 GHz, 4.9 GHz, 5.3 GHz, 7.2 GHz, 7.5 GHz and 8.8 GHz respectively at different matching values with gains of 9.5 dB, 14.5 dB, 11.9 dB, 3.6 dB, 4 dB, 1.5 dB, 3.8 dB and 6.5 dB. The comparison of the simulated and measured return losses shows a good agreement. The antenna finds its applications in GPS, space and satellite communication, radar, body area network (BAN) communication system.

Wireless power transfer (WPT) via coupled magnetic resonances has been in development for over a decade. Frequency splitting occurs in the over-coupled region. In addition, the vibration of the receiver and relay coils is observed in the over-coupled region. The vibration mechanism of the relay coil is investigated in this study. First, the circuit model of a three-coil WPT system is established, and the transfer characteristics of the system are examined by applying circuit theories. Second, the transfer characteristics of the three-coil WPT system are analyzed using simulation software. Third, the energy equation of state of the three-coil WPT system is established with the introduction of entropy variable. Lastly, the experimental circuit of the three-coil WPT system is designed. The experimental results are consistent with the theoretical analysis. The vibration of the relay coil is clearly explained. The transfer characteristics of the three-coil WPT system, particularly the relay coil, may provide ideas to achieve the maximum output power and transmission efficiency under various operating conditions.

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a bi-layer dielectric material using a Ku-band rectangular waveguide WR62. The S_ij-parameters at the reference planes in the rectangular waveguide loaded by a bi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the transmission lines theory, the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated the S_ij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from bi-layer measurements and mono-layer measurements is presented.

Radial flux Dual Stator Dual Rotor Permanent Magnet (DSDRPM) machine can be considered as an exterior rotor PM machine kept over an interior rotor PM machine. This facilitates with a scope for optimization of the relative placement of inner and outer stator slots of the machines to achieve cogging torque minimization. This paper deals with the analytical prediction of flux density distribution in an internal and external rotor PM machines with semi-closed slots and further utilizes it to calculate the cogging torque in DSDRPM machine. An optimal angle of shift between the stator slots of the two machines has been determined to obtain a reduction in the resultant cogging torque of DSDRPM machine. The analytical results are verified with the Finite Element Analysis (FEA) results and found to be in close agreement with each other.

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.

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 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).

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.

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.