The bearingless switched reluctance motor system based on active disturbance rejection control has good anti-interference performance and robustness, but it is easy to lose stability due to the influence of measurement noise in actual engineering. The main reason for the sensitivity of active disturbance rejection control to noise lies in the noise amplification of its extended state observer. To solve this problem, a novel reduced-order extended state observer based on predictive linear tracking differentiator is proposed. First, the general form of the observer is given, and then active disturbance rejection controller is designed based on suspension system of the hybrid excitation bearingless switched reluctance motor. The suspension force is used as the hysteresis loop to eliminate the estimation of the disturbance feedforward gain, and the stability of the control system is analyzed by Lyapunov equation. Finally, the simulation comparison is conducted through Matlab. The results show that this method can effectively suppress the influence of measurement noise and reduce the error of disturbance estimation when the observer is in a low bandwidth.
To explore the problem that the frequency characteristics of a magnetically coupled three-coil wireless power transfer (WPT) system are affected with different positions, in this paper, the expressions of the resonant frequency and the frequency corresponding to the maximum output power are deduced based on equivalent circuit theory. It is concluded that not only the resonant frequency is changed with different positions, but also the frequency corresponding to the maximum output power is changed with different positions. The WPT system always features a maximum efficiency point and a maximum output power point. The frequencies of the two points are almost the same. Finally, a three-coil experiment setup is built, and experimental results are well consistent with calculation and simulation results, which verifies the correctness of the proposed method. Proposed method provides a feasible scheme for simultaneously achieving high efficiency and high output power, and also provides a useful reference for the further research on the frequency tracking and optimization control algorithms.
In this paper, the problem of determining the depth and radius of a circular pipe along with the soil characteristics is studied, using electromagnetic waves with a fuzzy support vector machine as well as a fuzzy support vector machine. To this end, three neural network based fuzzy support vectors are used to determine the soil, depth and dimensions. Also, using the 2D time domain numerical simulations of electromagnetic field scattering, along with MATLAB software, 1030 data are generated for training as well as neural network verification. Given the fact that for each of the three parameters the nature of the problem is different, separate neural networks are considered with different parameters, thus the number of different data for the network training is considered. In all three cases, the neural network parameters are optimized using genetic algorithm to reduce the error and also reduce the number of support vectors. It should be noted that the objective function of the genetic algorithm consists of two components of the error, as well as the number of membership functions, which can be determined by determining a control parameter. For soil permittivity, the algorithm can accurately predict 93% of permittivities, and it decreases to 89.8 for the pipe depth determination. For diameter it is seen that for 69.3 of the cases the algorithm can correctly classify the pipes.
A wideband resonance-based reflector (RBR) is proposed in this paper. It has an in-phase reflection band from 2.61 GHz to 5.59 GHz (72.68%), while high reflection magnitude is also obtained in the band. The proposed RBR was applied to an elliptical monopole antenna, and then, the omnidirectional radiation patterns are transformed to be unidirectional ones. The antenna profile is only 0.12λ. The proposed antenna has a measured impedance band of 2.12 GHz to 6 GHz (95.57%), and a measured front-to-back ratio band (FBR > 10 dB) of 2.2 GHz to 4.68 GHz (72.09%). The maximum FBR is up to 27.21 dB, and the antenna has good radiation performances. In addition, the proposed antenna is applied to investigate the electromagnetic characteristics of a human head. The transmission characteristics of electromagnetic wave in human head and the interactions between the human head and the electromagnetic wave were studied. The field distribution and specific absorption rate (SAR) are also discussed. Research found that the antenna matched well with the human head as good field distribution and propagation characteristics were obtained, and the antenna meets the safety standards.
This manuscript presents a UWB filter with three notch bands for WiMAX, WLAN, and X-Band Satellite Communication by introducing inverted E- and T-shape resonators shorted at the center, designed and fabricated for the use of UWB applications authorized by the US Federal Communications Commission. First, a UWB filter ranges from 2.8 GHz to 10.6 GHz is designed by employing four λ/4 wavelength short-circuited stubs and then couples E- and T-shape resonators on either side of the main transmission line of the proposed UWB filter to achieve notch bands response centered at the resonance frequency of 3.3 GHz for WiMAX applications, 5.1 GHz for WLAN wireless applications, and 8.3 GHz for X-band satellite communication systems, respectively. The proposed filter is able to produce three individually control stopband frequencies centered at 3.3 GHz, 5.1 GHz, and 8.3 GHz with minimum attenuation levels of -28 dB, -19 dB, and -15 dB, respectively. This indicates that the presented filter can efficiently reject superfluous bands at 3.3 GHz in WiMAX system, 5.1 GHz in WLAN system, and 8.3 GHz in satellite communication systems to improve the performance of the UWB communication systems. Finally, the proposed filter with circuit area 34 mm × 12 mm × 0.762 mm between the simulated and fabricated measurements.
Due to certain conditions, electrical motor (EM) that operates at high speed may lead to magnetic saturation, thermal issue and stress to rotor structure. Magnetic gear (MG) designed for speed multiplier enables the prime mover from EM to operate at lower speed while the output gear multiplies the speed by its designated gear ratio at reduced torque. In this paper, a new coaxial magnetic gear is designed for speed multiplier. The role between inner yoke with PM and pole piece is switched. The inner part of magnetic gear is made to be stationary while the pole piece becomes inner rotor. The working principle is presented analytically. It used flux modulation techniques for torque and speed transmission. Torque characteristic and gear efficiency is analysed using finite element, and compared with existing speed multiplier magnetic gear with the same gear ratio of 7/3. Based on the simulation result, the proposed speed multiplier MG offers 16% better torque density and 12% higher gear efficiency at higher speed range. The structure of the inner rotor was also found to be more robust as only pole piece ring together with plastic is rotated instead of yoke with PM.
This work is a contribution to the characterization of the electromagnetic properties of high temperature superconductors (HTS) made of Bismuth Strontium Calcium Copper Oxides (BSCCO). The electromagnetic proprieties (critical current density and self-field AC losses) of a tape and a coil are determined experimentally at different frequencies, and compared to analytical models and finite element simulations for a better analysis of the physical phenomena. As shown in this work, the transition from the element to the system is not straightforward, and the characterization of such a material at the system scale is necessary due to their high sensitivity to the magnetic field. Solutions to some measurement problems are also highlighted.
For reducing the computational complexity of direction-finding algorithm in sparse multiple-input multiple-output (MIMO) radar, a low-complexity partial spatial smoothing (PSS) algorithm is presented to estimate the directions of multiple targets. Firstly, by dealing with a partly continuous sampling covariance vector in PSS technology, an incomplete signal subspace can be obtained. Then, a special matrix can be obtained by using this incomplete signal subspace. Meanwhile the incomplete signal subspace can also be repaired by the special matrix. At last, the multiple signal classification (MUSIC) algorithm is used to obtain direction estimations. In the process of obtaining signal subspace, no eigenvalue decomposition (EVD) needs to be performed. Compared with the traditional spatial smoothing (SS) technology, the proposed algorithm has lower computational complexity and higher estimation precision. Many simulation results are provided to support the proposed scheme.
According to theory, once certain conditions are fulfilled, current and voltage pulses propagate along ideal transmission lines with the speed of light. One can reach such a conclusion only when the conductors are assumed to be perfectly conducting, which cannot be realized in practice. A wave can only propagate along a transmission line with the speed of light if no energy has to be spent in establishing the current in the conductor. However, in establishing a current in a transmission line, energy has to be supplied to the electrons to set them in motion since they have a mass. The energy transfer to the electrons manifests itself in the form of an inductance which is called the kinetic inductance. The effect of the kinetic inductance has to be taken into account in signal propagation along high carrier mobility conductors including super conductors. In the case of transmission lines, the kinetic inductance leads to a change in the characteristic impedance and a reduction in the speed of propagation of waves along the transmission line. The goal of this paper is to show that the kinetic inductance will set an upper bound to the speed of propagation of waves along transmission lines, which is smaller than the speed of light.
In this paper we present an analytical method, employable with commercial full-wave electromagnetic CADs, which allows full-wave simulations of electromagnetically (EM) large structures, in terms of wavelength, such as linear accelerator cavities (LINACs) and a very accurate estimation of their operating frequency. The proposed technique is based on the exploitation of rotational symmetry through the definition of equivalent axially-symmetric volumes which replaces the non axially-symmetric ones inside the structure being analyzed. After a theoretical study, we show the successful application of the method in the real case study of a Drift Tube Linac (DTL) cell.
In this paper, a switchable beam and super-directive Electrically Small Antenna (ESA) dipole deployed at an IoT network gateway at 868 MHz is presented. It consists of one fed dipole and one loaded parasitic dipole. The nature and value of the load are obtained using the Uzkov equations, allowing determining current weighting coefficients in the case of two separately fed antennas, in order to maximize the gain and the directivity in a given direction. Reconfigurability in two directions is achieved using a pair of anti-parallel PIN diodes to steer the beam to the desired direction. The array final dimensions are 109 × 43 mm2 (0.3λ × 0.1λ) generating a high directivity of 6.8 dBi in simulation and 6.7 dBi in measurement at 868 MHz for each beam in the azimuth plane.
An electrodynamically rigorous mathematical model of a combined vibrator-slot structure consisting of a narrow radiating slot cut in a rectangular waveguide end wall and several thin impedance vibrators placed over the infinite screen is presented. Numerical results concerning internal and external electrodynamic characteristics of the antennas with optimized structural parameters have confirmed the possibility of constructing the Yagi-Uda combined radiating structures in the microwave and extremely high frequency (EHF) bands.
A novel compact patch antenna with Defected Ground structure (DGS) operating for Wireless applications is proposed and investigated. This proposed antenna generates four separate resonances to cover 3.271 GHz (WiMax), 4.92 GHz (WiFi), 6.35 GHz (Space applications) and 11.04 GHz (Fixed Satellite applications) while maintaining overall compact size of 32 × 32 × 1.6 mm3 using an FR-4 substrate commonly available with a permittivity of εr = 4.4. The proposed microstrip patch antenna (MSPA) consists of a square radiator in which a Log Periodic slot is etched out along with square defects on ground surface and a microstrip feed line. The log periodic slot with DGS modifies the total current path thereby making the antenna operate at five useful bands. Structure displays the impedance bandwidth of 8.34% (3.10-3.37 GHz), 2.00% (4.88-4.98 GHz), 14.68% (6.27-7.194 GHz), and 5.41% (10.79-11.39 GHz) with gains 3.25 dB, 0.85 dB, 5.65 dB and 4.47 dB respectively. The antenna performance is analyzed using numerous parametric optimization studies, field distributions, and currents. Excellent agreement is obtained between measured and simulated results.
We present an analytical analysis of a metasurface-based ambient electromagnetic energy harvesting system in which the bi-anisotropic particles loaded with a resistor are used. The proposed metasurface composed of an array of bi-anisotropic particles referred to as an electromagnetic energy harvester that can capture the ambient incident electromagnetic wave energy with a radiative to AC conversation efficiency of around 100%. The captured energy by metasurface is delivered to the load. The load acts as the input impedance of a rectification circuit in a rectenna system. The derived optimal polarizable inclusions can be applied to design bi-anisotropic metasurfaces which can be used for electromagnetic energy harvesting. Finally, the optimal dimensions of a typical chiral structure have been calculated to achieve maximum efficiency for circularly polarized propagating waves.
In this work, an elliptical planar monopole Penta band-notched ultra-wideband (UWB) antenna is proposed. Band rejection at 2.4-2.6 GHz IEEE 802.11 b/g/n, 3.3-3.75 Wi-MAX, 3.9-4.2 GHz C-band satellite communication, 5.15-5.85 WLAN, and 7.9-8.4 GHz X-band satellite communication frequencies is achieved by etching slots in the radiating patch, feed line, and ground plane. The effect of the slot length on the notched band is also studied. The proposed antenna has been fabricated and tested. The measured impedance bandwidth of the antenna is 2.15-12.5 GHz, which covers bands of Bluetooth and UWB applications. The peak gain of the proposed antenna is 8 dB and drops drastically at notched bands. The proposed antenna shows good omnidirectional radiation patterns in the passbands.
A low-profile circularly polarized (CP) antenna for a handheld Ultra-High Frequency Radio Frequency Identification (UHF RFID) reader is proposed in this paper. The radiating part on the top substrate is composed of three inverted-F elements rotated 120˚ around the center of the structure. A power splitting circuit, placed on the bottom substrate, based on a series transmission line feed delivers equal amplitude to the three IFA with a sequential 120˚ phase shift. Both layers are fabricated on low-cost FR4 material. This design has a disk form factor with a compact size of 35 mm circle radius and an 8.6 mm height. The measurement shows good results with S11 as lower than -10 dB for the whole band, 3 dB-axial ratio around 110˚ (10 MHz of bandwidth), directivity reaching 4.4 dBic, and the total gain of the antenna is 1.9 dBic. In order to validate the proposed antenna performance, a UHF RFID handheld reader is built based on the ThingMagic M6E-Nano module. Different scenarios are investigated to validate the proposed antenna performance in a real environment.
In a brief but brilliant derivation that can be found in Maxwell's Treatise and traced back to his 1861 and 1865 papers, he derives the force on a moving electric charge subject to electromagnetic fields from his mathematical expression of Faraday's law for a moving circuit. Maxwell's derivation in his Treatise of this force, which is usually referred to today as the Lorentz force, is given in detail in the present paper using Maxwell's same procedure but with more modern notation.
A cosecant-squared radiation pattern synthesis for a planar antenna array by using the genetic algorithm (GA) is presented. GA makes array synthesis flexible to achieve two desired features, namely, low peak side lobe level (PSLL) and small deviation (ripples) in the shaped beam region. In order to obtain a desired csc2 pattern with the PSLL constrained, GA optimizes both the excitation amplitude and phase weights of the array elements. Dynamic range ratio (DRR) of the excitation amplitudes is improved by eliminating the weakly excited array elements from the optimized array without distorting the obtained pattern. To illustrate the effectiveness and advantages of GA, the beam pattern with specified characteristics is obtained for the same array by using particle swarm optimization (PSO). Results show that the performances of GA and PSO are comparable when dealing with small-to-moderate planar antenna arrays. However, GA significantly outperforms PSO on large arrays. Moreover, numerical results reveal that GA is superior to PSO in terms of cost function evaluation and statistical tests.
In this article, a compact dual-band antenna system for LTE-M (700-900 MHz) and LTE-2500 dedicated to mobile handsets is presented. The system consists of a dual-band Planar Inverted-F-Antenna (PIFA) for LTE-M and LTE-2500 bands where this designed PIFA is frequency reconfigurable in the LTE-M band. Additionally, another PIFA is designed to cover the LTE-2500 band to enable Multiple-Input-Multiple-Output (MIMO) communication for this band. Frequency reconfiguration between 700 MHz and 900 MHz is performed by a varactor diode biased from the RF port using a decoupling circuit to separate DC and RF signals. The compactness of the system and the good isolation between the two antennas were obtained thanks to the study of the characteristic modes of the mobile phone chassis, where the ideal positions of the antennas can be easily obtained. A prototype of our system was fabricated where good frequency reconfiguration and good MIMO performance (TARC and envelope correlation) were achieved.
A reconfigurable cylindrical dielectric resonator antenna with polarization diversity is proposed for S-band and C-band in this paper. An annular slot is used as the feeding aperture, which can not only excite two orthogonal modes (HEMx11δ and HEMy11δ) of the cylindrical dielectric resonator at 3.2 GHz, but also produce a 90˚ phase difference. Two switches, whose locations are carefully optimized, are used to control HEMx11δ being a phase-lagging or phase-leading component. Thus the antenna can achieve either left- or right-hand circular polarization (LHCP or RHCP) in S band, depending on the switch states. The higher order mode of HEM21δ is also excited at 4.7 GHz for linear polarization (LP), regardless of the switch states. With the advantages of compact structure, simple biasing network and easy fabrication, this antenna can be widely applied to wireless communication systems, especially for polarization diversity applications.
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