Radar scattered time domain response can be modeled by natural poles using singularity expansion method (SEM) in resonance region. In this paper, limitation of the conventional Extinction pulse method is brought out, and a hybrid of conventional Extinction pulse and auto-regressive (AR) method is proposed for robust discrimination of radar targets. A new target discrimination number (TDN) is suggested, which gives very good discrimination margin for enhanced decision process. The Hybrid Extinction pulse technique is applied on the free space targets as well as subsurface canonical metallic targets and the result obtained shows good discrimination margin. The free space target response was obtained using FDTD simulation and the subsurface target response was obtained using frequency domain measurement done for the targets buried under dry sand.
The purpose of this paper is to describe a model predictive direct torque control (MPDTC) with load angle limitation for surface-mounted permanent magnet synchronous motor (SPMSM) drive system. In this paper, an exact discrete-time state-space model of SPMSM is presented, which improves the state prediction accuracy comparing to simple Euler approximation. A finite control set type MPDTC is used to select the optimum voltage vectors applying to the voltage source inverter (VSI). It makes full use of the inherent discrete nature of VSI, and according to the predefined cost function it chooses the optimal solution from the possible switching states. It has been found that with the proposed scheme SPMSM drives show adequate dynamic torque performance and considerable torque ripple reduction as compared to traditional direct torque control (t-DTC). With the load angle limitation in the cost function, the proposed scheme can prevent the PMSMs falling from synchronism.
Gaussian beam techniques are efficient asymptotic methods for field radiation computation. In these techniques, the initial field is first expanded on a chosen surface in elementary Gaussian beams which can propagate and/or interact with surrounding structures. However, the expansion cannot take into account surface and leaky waves propagation. In this paper, we propose an appropriate hybridization method using surface equivalent currents to overcome this limitation. The equivalent current formulation is written on grounded dielectric slab in spectral domain and can model surface and leaky waves which propagate from the surface expansion. The hybridization is carried out on the expansion surface, on which the distribution of elementary Gaussian beams and equivalent currents must be chosen in a relevant way. We study the influence of hybridization parameters and define a set of them leading to good results for general cases.
Permanent-magnetmotorsare widely usedin-wheel motors of electric vehiclesand hybrid vehicles. Based on a movable stator design, this paper presents a new type permanent-magnet motor, whose torque can be adjusted in order to meetdifferent driving requirements. The stator geometryis varied by means of changing movable stator positions.Accordingly, the air-gap lengthin permanent-magnet motorsis changed so that torque can be adjusted. To derive an analytical model, Fourier series expansions are employed to formulate air-gap geometry variation. The analytical modelis validated by finite element numerical results.Concerning motor torque variation capability achieved in this study, the ratio of the largest vs. the smallest torque is 2.3.
Partial Discharge (PD) measurements may be affected by external noise and disturbances of various natures such as interference from broadcasting stations, stochastic noise, pulses from power electronics, etc. Extracting PD pulses from such a noisy environment is therefore a crucial issue. This paper presents a wavelet based technique for automatic noise rejection. The core of the paper is the use of an improved methodological approach for the selection of a suitable wavelet, which aims at summing up the benefits and overcoming some limitations of previous techniques. Firstly, a very wide set of training signals is used for the identification of the decomposition level and for the calculation of suitable performance parameters that identify each wavelet; then a Performance Fingerprint is introduced in order to summarize the ability of a specific wavelet to reconstruct a partial discharge waveform, and a distance criterion is used for the selection of the most suitable wavelet. Afterwards, useful information is collected for the reconstruction of the PD signal, and finally, results on the application of the algorithm for a set of numerical and experimental signals are presented.
In order to improve the reconstruction accuracy of near-field SAIR, a novel regularization imaging algorithm based on an accurate G matrix is proposed in this paper. Due to the fact that the regularization reconstruction is usually an underdetermined problem, inaccurate operation matrix G will lead to great reconstruction error in the imaging results, or even the normal imaging cannot be obtained. In this paper, we establish an accurate G matrix based on the accurate imaging model of near-field SAIR. Compared with the traditional G matrix with some unnecessary approximations, the proposed G matrix without approximation can improve the reconstruction accuracy effectively. For improving the accuracy of matrix G further, the corresponding parameters are corrected according to the RMSE between the imaging results of the regularization method and modified FFT method which is not sensitive to the parameters' change. The effectiveness of this calibration method has been tested by 1D simulation experiments. Moreover, the 2D simulation experiments demonstrate that the proposed accurate G matrix can improve the imaging accuracy of regularization method effectively. Finally, the 1D imaging experiment is performed to test the effectiveness of the proposed method for the actual synthetic aperture imaging further.
A compact UWB bowtie-slot antenna (36×23 cm2) fed by a CPW transition is proposed for an improved ground-coupling radar. The antenna has an operating frequency band in the range [0.46 ; 4] GHz. Full-wave modeling using the FDTD approach has allowed to study in details the antenna radiation characteristics in air and in the presence of a soil. Afterwards, a radar system made of a pair of independent shielded bowtie antennas has been considered to probe the sub-surface very close to the air-soil interface. The polarization diversity in the E and H-planes is an important aspect which has been studied in order to further detect the orientation of damages (cracks, delaminations…) in civil engineering structures. Measurements in a dry and wet sand in different system configurations have allowed to first characterize the GPR system and to draw comparisons with numerical results. The ability of the radar to detect small buried objects is investigated.
In this paper detailed numerical results are presented for the estimation of the electric field generated by the first return stroke, in order to reproduce the main characteristics of field waveforms measured at distances beyond 50 km. The effect of parameters such as the lightning channel geometry, distance from the source, return-stroke current speed, its attenuation along the channel is discussed by comparing numerical and experimental results.
In the work presented here, the suitability of an unusual energy storage medium is investigated. The energy storage system is based on the forceful compression of two magnetic Halbach arrays. The mass and volume energy density is obtained and compared to existing common energy storage systems. The charge and discharge times and depths are also discussed. In addition, limits and considerations, which are needed for practical implementation, e.g., risk of demagnetization, internal mechanical stresses, heating of the magnetic structure and financial efficiency are investigated.
The application of a recently introduced microwave imaging technique based on the Huygens principle (HP), has been extended to multilayered objects with inclusions in this paper. The methodology of HP permits the capture of contrast such that different material properties within the region of interest can be discriminated in the final image, and its simplicity removes the need to solve inverse problems when forward propagating the waves. Therefore the procedure can identify and localize significant scatterers inside a multilayered volume, without having apriori knowledge on the dielectric properties of the target object. Additionally, an analyticallybased approach for analyzing UltraWide Bandwidth (UWB) body propagation is presented, where the body is modeled as a 3-layer stratified cylinder with an eccentric inclusion. Validation of the technique through both simulations and measurements on multilayered cylindrical objects with inclusions has been performed.
In this paper, the electromagnetic scattering from two scatterers is analyzed from a rigorous integral formulation solved by the method of moments (MoM). G. Kubicke has recently developed the E-PILE (Extended Propagation-Inside-Layer Expansion) method to calculate the scattering from an object above a rough surface for a two-dimensional problem. This method allows us to calculate separately and exactly the interactions between the object and the rough surface. The purpose of this paper is to extend the E-PILE method to a three-dimensional problem. Such a 3-D problem involves a large number of unknowns and can not be solved easily with a conventional method of moments by using a direct LU inversion. Thus to solve this issue, the E-PILE method is combined with the physical optics (PO) approximation to calculate the local interactions on both the object and the rough surface. By using this hybrid method, the requirements of memory and CPU time can be reduced significantly.
This paper presents a novel design of an egg curve based wide-slot antenna for various wideband applications. The proposed printed antenna consists of an egg curved slot with a similar tuning stub. The egg curve is obtained by introducing an egg shaping parameter into standard elliptic curve equation. The effect on the impedance bandwidth through the variations in antenna design parameters has been investigated and analysed in detail. To validate the theoretical design, various egg curved slot antennas were designed, fabricated and measured. Good agreement between the simulated results and the measured ones is observed. An empirical formula is also proposed to approximately determine the frequency corresponding to the lower edge of -10 dB operating bandwidth. The results demonstrate that the proposed egg curved slot antenna (ECSA) can obtain a measured bandwidth (BW) of 164.46% (1.95-20.0 GHz) for |S11|≤10 dB. A stable realised gain of about 4.1-5.1 dBi with consistent radiation patterns are measured over more than the entire ultrawideband (UWB) bandwidth (3.1-10.6 GHz) which makes it a suitable candidate for wideband and UWB wireless system applications.
We present a simple and straightforward approximate approach to removing resonant artifacts that arise in the material parameters extracted near half-wavelength resonances that arise from transmission/reflection (T/R) measurements on low-loss materials. In order to determine material parameters near one such λ/2 resonance, by means of the 1st-order regressions for the input impedance of the sample-loaded transmission line, we approximate the characteristic impedance of the sample-filled section that is, in turn, dependent either on the relative wave impedance in a coaxial transmission line or on the relative permeability in a rectangular waveguide case. The other material parameters are then found, supplemented with the refractive index obtained from the conventional T/R method. This method applies to both coaxial transmission line and rectangular waveguide measurements. Our approach is validated by use of S-parameters simulated for a low-loss magnetic material, and is also applied to determine the relative permittivity and permeability from S-parameters measured for nylon and lithium-ferrite samples. The results are discussed as compared to those from the well-known Nicolson-Ross-Weir (NRW) method and are experimentally compared to those from the Baker-Jarvis (BJ) method as well.
A new design of dual-port monopole-slot-like microstrip active integrated antenna (AIA) is presented and discussed in this paper. The primary designed passive antenna is capable of supporting two different WLAN bands at 2.4-2.84 GHz and 5.15-5.35 GHz due to its dual-port structure. In order to reduce the transmission coefficient between the two ports of antenna a coupling sleeve-arm and an inverted T-shaped slot are utilized on the ground plane of antenna each beneath one of the corresponding feed-lines which act as filtering structures at desirable frequencies. The proposed passive dual-port antenna is integrated with a power amplifier (PA) and a low noise amplifier forming a dual-port microstrip AIA which can be used as a full-duplex transceiver at its operating WLAN frequency bands. The measured results for both passive and active antennas show that the designed antennas have proper radiation characteristics at their desired operation frequencies. The fabricated passive antenna exhibits dual-band performance at 2-3.42 GHz and 4.5-5.6 GHz while the fabricated AIA covers 2.31-2.82 GHz (at PA port) and 4.45-5.5 GHz (at LNA Port) with 13 dB and 9 dB gain level improvement respectively.
In this paper, we propose the design of multilayer frequency selective surfaces (FSS) waveguide band-pass filters (WBPF). The WBPFs are designed to operate at two different frequency channels, respectively 71-76 GHz (Rx) and 81-86 GHz (Tx). The cross section surface of the FSS is imposed by the WR12 waveguide rectangular section's dimensions. The WBPFs are inserted symmetrically in a T-junction waveguide to design a compact diplexer. This is a basic component developed for an efficient integration in the future E-band millimeter-wave transceiver. The multilayer FSS structure uses only non-resonant sub-wavelength unit cell elements; metallic patch and slot. To reach high channel isolation (≈ 70 dB) a seven order filter was required. Hence, each filter is composed of 13 capacitive and inductive metallic FSS spaced by 12 ultra-thin dielectric substrate layers. The dielectric material is Rogers Ultralam 3850 (Liquid Crystalline Polymer; LCP circuit material). The filter's overall thickness is < λ/4. The numerical studies have been performed using finite element method simulator (HFSS) and CST Studio Suites Tools. The experimental validation has been also done in the X band frequency by developing a fifth order FSS WBPF. Good agreements between simulated and measured results are obtained.
In literature, heuristic algorithms have been successfully applied to a number of electromagnetic problems. The associated cost functions are commonly linked to full-wave analysis, leading to complexity and high computational expense. Artificial Neural Network is one of the most effective biological inspired techniques. In this article, an efficient surrogate model is trained to replace the full-wave analysis in optimizing the bandwidth of microstrip antenna. The numerical comparison between ANN substitution model and full-wave characterization shows significant improvements in time convergence and computational cost. To verify the robustness of this approach, all these concepts are integrated into a case study represented by a rectangular ring antenna with proximity-coupled feed antenna.
Recently researchers have great interest in using multi-core processors for applications requiring intensive parallel computing. In this paper, an approach for the implementation of hybrid parallel Gravitational Search Algorithm (GSA) and Nelder-Mead (NM) algorithm using open Multi-Processing (OPEN-MP) on multi-core processors is proposed for beam-forming applications. The proposed parallel GSA-NM algorithm is used to optimize the complex excitations, amplitudes and phases, of the adaptive array elements to synthesize the array beam-pattern. The array consists of 24-elements uniformly distributed in a circular configuration. To measure the performance of the proposed approach, the results are compared with those obtained using parallel hybrid CFO-NM, and PSO-NM Algorithms.
In this article, the parametric analysis of the slot-loaded microstrip line feed patch antenna is investigated using artificial neural network model. The bandwidths of the proposed antenna obtained at TM01, TM02, and TM03 frequency modes are 10.2 GHz, 13.6 GHz, and 17.2 GHz, respectively. The performance of the proposed antenna is analysed using artificial neural network model. The changes obtained in bandwidth due to the position of slot length and slot width are reported. The antenna parameters such as return loss, VSWR, gain and efficiency are also calculated. The simulated results obtained with the help of IE3D simulation software are trained and tested using ANN. Theoretical results are compared with simulated and experimental ones, and they are in close agreement.
The voltage on a single-turn loop inside an enclosure characterizes the enclosure shielding effectiveness against a lightning insult. In this paper, the maximum induced voltage on a singleturn loop inside an enclosure from lightning coupling to a metal enclosure wall is expressed in terms of two multiplicative factors: (A) the normalized enclosure wall peak penetration ratio (i.e., ratio of the peak interior electric field multiplied by the sheet conductance to the exterior magnetic field) and (B) the DC voltage on an ideal optimum coupling loop assuming the ideal penetration ratio of one. As a result of the decomposition, the variation of the peak penetration ratio (A) for different coupling mechanisms is found to be small; the difference in the maximum voltage hence arises from the DC voltage on the optimum coupling loop (B). Maximum voltages on an optimum coupling loop inside a finite cylinder enclosure for direct attachment and a lightning line source at different distances from the enclosure are given in Table 3.
Imaging is a valuable tool for solving inverse source problems. The achievable image quality is determined by the imaging system. Its performance can be evaluated by using the concept of point spread functions (PSFs). It is common to compute the PSFs using a numerical algorithm. However, in some cases the PSFs can be derived analytically. In this work, new analytical PSFs are presented. The results apply to scalar and dyadic scenarios in 3D originating from acoustics and electromagnetics. Data sets with narrow angular acquisition or complete spherical coverage are considered, where broadband and narrowband frequency domain data is supported. Several visualizations accompany the resulting formulas. Finally, the analytical PSFs are verified using a numerical implementation of the imaging process.