Electromagnetic levitation system is commonly used in the field of magnetic levitation system train. Magnetic levitation technology is one of the most promised issue of transportation and precision engineering. Magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. In this paper, a new prototype of the magnetic levitation system is proposed, designed and successfully tested via SIMLAB platform in real time. In addition, the proposed system was implemented with an efficient controller, which is linear-quadratic regulator (LQR) and compared with a classical controller which is proportional-integral-derivative (PID). The present system has been tested with two different criteria: signal test and load test under different input signals which are Sine wave and Squar wave. The findings prove that the suggested levitation system reveals a better performance than conventional one. Moreover, the LQR controller produced a great stability and optimal response compared to PID controller used at same system parameters.
Nowadays everyone needs electronic gadgets in compact size, and single device should accomplish all the tasks. A compact MIMO antenna resonating at multi-band of frequencies is proposed in the current research work. The proposed MIMO antenna consists of two elements. The edge to edge separation between the two antennas is λ0/31 and still maintains low mutual coupling levels between the two antennas. The proposed MIMO antenna resonates at 4.75 GHz, 5.89 GHz, 6.74 GHz, 8.25 GHz and 9.82 GHz. The mutual coupling is reduced by -23.78 dB at 4.75 GHz, -25.71 dB at 5.89 GHz, -29 dB at 6.74 GHz, -32.79 dB at 8.25 GHz and -21.5 dB at 9.82 GHz, respectively. The performance of the proposed MIMO system was evaluated in terms of S-parameters, Envelope Correlation Coefficient (ECC), Voltage Standing Wave Ratio (VSWR), and Radiation Pattern. The measured and simulated results are presented.
In this paper, a 2 to 4 GHz Instantaneous Frequency Measurement (IFM) system is presented. The proposed design uses four band-pass filters to estimate the frequency value of an RF signal. The proposed design is an improvement of that presented in our previously published work. In this work, a new frequency estimator is developed, and a new methodology for designing the frequency response of the band-pass filters is proposed. These two improvements show better accuracy in estimating the frequency value. A closed form for the Standard Deviation (STD) and the bias of the new estimator were derived, and used to adjust the frequency response of the filters. The fabricated system showed a maximum error of about 11 MHz, for practical values of noise and measurements errors.
In this paper a novel evolutionary algorithm is used for the optimization of the performance of a magnetorheological (MR) device, capable to transmit torque between two shafts and powered by a system of Permanent Magnets (PMs). The stochastic, evolutionary, global optimization algorithm is based on a modified version of the self-organizing map. It uses a dedicated simpli ed analytical model of the device, developed in order to obtain a fast and accurate evaluation of the torque. Then, by means this model, the cost function to find the optimal parameters of the device is defined. Once the optimal parameters are identified, the performance of the proposed device is simulated by means of a FEM software. The results in terms of magnetic flux density inside the fluid, the transmissible torque and the actuation torque necessary to perform the device activation are discussed. Finally, a preliminary experimental validation of the proposed device is performed.
Compact wideband flexible monopole antennas are designed and analyzed for its performance for Body Centric Wireless Communications (BCWC). Two antennas with identical radiators on different substrates are designed and fabricated on polyamide and teslin paper substrates, deployinga modified rectangle-shaped radiator. With the aid of modifications in the radiating plane and defecting the ground plane, the polyamide based antenna is designed to operate between 1.8 and 13.3 GHz, and teslin paper based antenna is designed to operate between 1.45 and 13.4 GHz to cover the wireless communication technology frequencies and ultra-wideband range for various wireless applications. The reflection coefficient characteristics of the fabricated antennas on free space and on various sites of the body are measured and match reasonably well with the simulated reflection coefficient characteristics. The specific absorption rate (SAR) analysis is also carried out by placing the antennas on tissue layered model.
In this article, a theoretical analysis and design are presented for a Microstrip Patch Antenna (MPA) embedded with an inclined rectangular slot supported by a C-shaped Defected Ground Structure (DGS). Dual-band characteristics are achieved at 2.4 GHz and 2.6 GHz with a small frequency ratio of 1.08, which makes the proposed antenna useable for Wi-Fi and WiMAX applications. A theoretical analysis is also proposed for the designed antenna structure using modal expansion cavity model and equivalent circuit approach. The analyzed antenna design is fabricated, and it is found that measured results are in good match with theoretical and simulated results.
A compact dual-band inverted-F filtering antenna with good band-edge selectivity for modern wireless communication systems is presented in this paper. A novel dual-band filter based on open-loop dual-mode resonator loading a T-shaped stub and an inverted-F antenna (IFA) also with a T-shaped open stub are integrated together. The higher band is controllable easily by adjusting the dimension of the T-shaped stub, leaving the lower band unaffected. To minimize the dimension of the filtering antenna, the last stage of the filter is folded. A flat gain response is obtained with steep skirts at both band edges. Simulated and measured results show that the integration makes the proposed antenna operate at 2.4/3.7 GHz with compact size, good band-edge selectivity, and controllable higher band compared with the traditional IFA.
A dual-band shorted annular ring patch antenna with interference rejection at the horizon is presented for GPS timing applications. It is shown that the dimensions of the annular ring can be optimized to make a null in the RHCP pattern at low elevation near the horizon for all azimuth angles. This null attenuates interfering signals originating from ground based sources. The antenna achieves circular polarization utilizing radial shunted stubs. The effect of the stubs on the resonance is analytically derived and verified through simulations. A novel feed configuration that incorporates a coplanar waveguide transition improves the impedance match for both L1 and L2 GPS frequency bands compared to previous designs that present compromises between the feed impedance of the two bands. Additionally, since the shunted stubs reduce the number of required electronic components compared to other antennas with similar horizon nulling capability, the cost is reduced. A prototype antenna operating at GPS L1 and L2 bands has been fabricated and validated through measurements.
In this article, design and analysis of a dual-band ring dielectric resonator based radiator with circular polarization features is explored. The presented ring DRA is excited with the help of a tilted modified square-shaped aperture. Two important attractive features of present article are: (i) two radiating modes originated inside the ring DRA i.e. HEM11δ and HEM12δ mode; (ii) tilted modified square aperture generates circular polarized (CP) wave in both the operating frequency bands. For verifying the simulated results, practical model of the proposed antenna has been fabricated and verified. Experimental outcomes display that the proposed radiator functions over dual frequency bands i.e. 2.8-3.58 GHz and 5.5-5.92 GHz respectively. 3-dB axial ratio (AR) frequency ranges of proposed radiator are 2.8-3.2 GHz and 5.85-6.0 GHz, respectively. These appearances make it appropriate for some important wireless applications such as wireless LAN (2.4/5.2 GHz) and WiMAX (2.5 GHz) applications.
We present a new explanation for a quantum eraser. Mathematical description of the traditional explanation needs quantum-superposition states. However, the phenomenon can be explained without quantum-superposition states by introducing unobservable potentials which can be identified as an indefinite metric vector. In addition, a delayed choice experiment can also be explained by the interference between the photons and unobservable potentials, which seems like an unreal long-range correlation beyond the causality.
The temperature variation throughout overhead transmission lines has an important effect on the line operation. In order to describe the actual operation of transmission lines more accurately, this paper proposes a line segmentation method based on temperature distribution at different locations. Taking the actual transmission line of Shaanxi Province as a test case, the influence of the different temperature calculation methods on the maximum transmission power of lines is studied under the lumped parameter model and the distributed parameter model, respectively. It is shown that transmission line model considering non-uniform temperature distribution at different locations is more accurate for studying the operating state of the system.
We measured millimeter-wave dielectric parameters of magnesium fluoride glass wafers at the room temperature in the frequency band of 75--110 GHz by applying the open resonator technique based on the use of Bragg structures and related multi-layer assemblies. Through the comparison of measured and simulated transmission spectra of various structures, the dielectric constant of magnesium fluoride glass is found as ε= 5.50±0.01. The estimate for the loss tangent is found to be tanδ= 0.00005, with a possibility that the actual losses could be smaller than this value.
A quad band-notched compact ultra-wideband (UWB) patch antenna to operate on the industry, scientific, and medical (ISM) bands are presented in this study. A modified hexagonal patch vertex-fed with a coplanar waveguide (CPW) is fabricated on an FR-4 substrate with size of 43 × 28 × 1.6 mm3 and fractional bandwidth of 133%. The compact antenna operates at a frequency of 2.45 GHz, which is often required for the efficient performance of ISM utilisation. The existing bands share the same bandwidth as that of UWB systems. Therefore, a notched band at 3 GHz for worldwide interoperability for microwave access (WiMAX), and a further resonance band at 2.45 GHz for ISM are generated by implementing a meander-line strip on the antenna. Furthermore, the design demonstrates a couple of F-shaped slots and an inverted diamond-shaped slot on the patch. Moreover, a pair of J-shaped slots is loaded on the ground plane. The downlink C-band, wireless local area network (WLAN), and downlink X-band are rejected by the proposed slots, respectively. The current distribution, gain, radiation efficiency, and quad notched parameters of the proposed antenna are studied by using CST software. The demonstrated prototype covers an ISM band at (2.2 GHz-2.6 GHz) with a return loss of -23.45 dB and omnidirectional radiation patterns. A good agreement is observed between measured and the simulated results. This paper has presented a solution for both interference and miniaturised issues.
In this paper, a U-shaped microstrip patch antenna with meandered slots is presented. It is designed for biomedical applications to operate at 2.45 GHz. Based on the simulation experience, two designs of the patch are introduced with and without use of meandered slots. The comparative study between these two is also demonstrated. It is observed that the antenna with meandered slots shows good performance with sufficient bandwidth, low losses and is capable of use in biomedical applications. Furthermore, the proposed antenna has small size of 35*29*1.6 mm3, and the size of the ground is only 14% of the overall antenna size. The measured and simulated results show good agreement with each other. The antenna is fabricated on an FR4 substrate, and simulation is carried out on FDTD based Empire XCcel simulator.
Replacement of conventional bearings by passive magnetic bearings for highspeed applications, in terms of their performance will be effective, if the design is carried out by optimizing the geometrical dimensions in the given control volume. Present work deals with modification and utilization of two-dimensional (2D) analytical equations in optimization of multi rings permanent magnet (PM) thrust bearing configurations. Conventional and rotational magnetized direction (RMD) configurations are selected in optimizing the design variables for maximum bearing characteristics in a given volume with a constant aspect ratio. The design variables chosen for optimization are axial offset of rotor, number of rings, radial air thickness and inner diameter of the rotor and stator PM rings. MATLAB codes for solving 2D equations are developed in optimizing configuration variables. Further, optimized parameter values of the two configurations are compared. Finally, optimized results obtained using 2D and three-dimensional (3D) equations for the conventional configuration with same aspect ratio are compared, and conclusions are presented.
A light micro-deformation monitoring radar based on frequency modulation continuous wave (FMCW) technique is proposed and designed for scenes which are sensitive to micro deformation such as slopes, dams, and high buildings. The mini radar is well suited to measure micro-deformation of buildings or mountains. Meanwhile, interferometric method was used by the radar to obtain high range resolution of the micro-deformation monitoring radar. The radar acquires micro deformation of the target by inversion of phase difference between the transmitted and received waves. To get an accurate micro-deformation measure result, the radar was carefully designed in signal mode and hardware structure. Various experiments are used in the article to verify the radar's deformation measure ability. The experiments prove that the radar can measure micro deformation accurately and timely. For example, railway bridges' vibration can be monitored by the radar in real time. In addition, it can be used in structures monitoring, disaster alarming and other regions.
In order to analyze the influence of three-phase asymmetrical operation of a generator on its stable operation, firstly, taking a 24-MW bulb turbine generator as an example, the 2-D transient electromagnetic field model is established. Through the comparison analysis of the experimental results and simulation data, the correctness of the model is verified. Secondly, the values of air gap flux density, torque and loss in different conditions are obtained by using the finite element method. The effects of asymmetric three-phase current on air gap flux density, torque and loss are determined. Thirdly, the corresponding relationships between the three-phase current unbalance degree and torque ripple, eddy current loss are established, and the variations of torque ripple and eddy current loss are given when the three-phase current unbalance degree is changed. The result shows that the asymmetry three-phase current makes the torque ripple and eddy current loss increase dramatically, which seriously threaten the safe and stable operation of the generator. Finally, the further study on the torque ripple and eddy current loss of the generator under different current distributions and the same three-phase unbalance degree identifies that the content of negative sequence current is a key factor to affect the torque ripple and eddy current loss.
A planar substrate integrated waveguide leaky wave antenna with cross slots is proposed in the frequency range of 10 GHz-15.5 GHz. Moreover, the symmetrical version of the structure is designed and analyzed in terms of the simulated S parameters and E field distribution which shows the existence of the open stopband in the frequency range (12.91 GHz-14 GHz), consequently degrading the radiation beam at broadside. Therefore, asymmetry is introduced in the unit cell design with respect to the position of the cross slots to achieve the continuous beam scanning in the desired frequency range. Unit cell is analyzed with the help of dispersion relation and Bloch impedance for predicting the beam scanning and matching of the proposed LWA respectively. This leaky TL is fabricated by the standard printed-circuit board process. Measured results are almost consistent with the simulation ones with a continuous beam scanning from of -40° to 16° with gain varying from 8.5 dBi to 11 dBi.
An innovative idea of shuffled structure of two quarter wavelength plates is proposed in this paper, which is supported by the numerical simulation results obtained through the application of the method of characteristics (MOC). In contrast to traditional anti-reflective coatings techniques, the proposed structure is a shuffled arrangement of two quarter wavelength slabs which are in theory evenly divided into N+1 and N pieces and then stacked up alternatively. These slabs are made of non-magnetic (μr = 1) dielectric (εr > 1) materials respectively characterized by dielectric constants εr1 and εr2 having the relation of εr2 =(εr1)2 to allow maximum transmission. These 2N+1 pieces are assembled such that there is always an εr2 piece between two εr1 pieces. Therefore, the proposed structure has the advantages of simple components and easy assembly. In the present simulation, the integer number N ranges from one to ten. The computational results are demonstrated in both time and frequency domains exhibiting that the proposed structure functions as a frequency selector.
Statistical moments of a scattered field are calculated in the first and second approximations using modified smooth perturbation method. Analytical expressions of both the variance and correlation function are obtained in the principle plane containing wave vector of an incident wave and external magnetic field. Observation points are spaced apart at small distances taking into account diffraction effects. Numerical calculations are carried out for the anisotropic Gaussian spectral function containing both anisotropic factor and the angle of inclination of elongated anisotropic plasma irregularities using the experimental data. It was shown that 3D surface of the correlation function of the phase fluctuation oscillate and these variations are decreased increasing characteristic spatial scale of plasma irregularities. New peculiarities of the ``Double-humped Effect'' are revealed in the collisionless magnetized plasma. It was shown that spatial scale and the inclination angle of elongated anisotropic plasma irregularities play important role in formation of a gap in the spatial power spectrum. Varying the magneto-ionospheric plasma parameters and values of characteristic spatial scales of anisotropic irregularities the depth of a dip increases and oscillates.
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