In order to improve the robustness of the fractional order sliding mode controller (FSMC) for permanent magnet synchronous motor (PMSM) sensorless control, a fractional order sliding mode controller based on T-S fuzzy inference algorithm (FFSMC) is proposed to observe the rotor speed and position information. Based on the mathematical model of PMSM and sliding mode controller, a fractional order sliding mode controller is designed, and its stability is proved. The T-S fuzzy inference algorithm is used to tune the reaching law parameters of the FSMC, so that the reaching law parameters are no longer fixed values, but change with the state of the system. The correctness of the proposed method is verified by MATLAB simulation software. The effectiveness of the simulation results is verified by building a PMSM sensorless control experimental platform. The results show that the PMSM sensorless control based on FFSMC achieves parameter self-tuning and improves the observation accuracy. And the robustness of the control system is enhanced.

An advanced 2D mode theory of plane electromagnetic wave diffraction by a transmission dielectric grating (rectangular relief or planar sinusoidal one) is considered. On the bases of this theory, a new model of diffraction of a spatially inhomogeneous light field (a Gaussian beam) by a transmission grating with arbitrary thickness is developed. It provides the opportunity to compute the transverse spatial structure of radiation diffraction orders and to estimate character of their distortions in comparison with the initial Gaussian beam structure. It is shown that such distortions appear under abrupt variations of intensity of all orders and can be caused by transformation of a certain diffraction order from the radiation regime of propagation into the waveguide regime and inversely (Wood's anomalies), and also it can be induced by a set of additional reflections on the boundaries of a thick substrate.

The numerous high-power devices and cables gathered around the subway vehicle will aggravate the deterioration of the electromagnetic environment, which may cause the train to fail to operate normally or threaten the health of passengers with a pacemaker or defibrillator. In order to study the distribution characteristics of low-frequency magnetic field of the subway in complex electromagnetic environment and the influence of various factors on human electromagnetic exposure, the magnetic flux density nephograms of the subway train with different vehicle body materials, with or without windows and with the shielding layer are calculated and analyzed. Specific energy absorption rate (SAR) values have been calculated in a standing voxel model from exposure to electromagnetic fields at 2.4 GHz, frequencies commonly used by Wi-Fi devices. The numerical results show that the average value of magnetic flux density in the stainless-steel carriage is less than that in the aluminum alloy carriage and the carbon fiber reinforce plastic (CFRP) carriage. Compared with the vehicle with windows, the average value of magnetic flux density in the vehicle without windows is less. The added shielding layer decreases the average value of magnetic flux density from 10.5 uT to 3 uT. The maximum value of magnetic flux density in the carriage under different factors is about 10 uT, which is far less than the magnetic flux density reference limit of 0.1 mT of the International Commission of Non-Ionizing Radiation Protection (ICNIRP) standard. Whenthe Wi-Fi device is closest to the human body, the highest Specific Absorption Ratio (SAR) value of human tissue is 0.00749 W/kg, which is far less than the electromagnetic exposure limit of 1.6 W/kg of IEEE standard.

A novel and efficient method to overcome the barriers of conventional diffraction limit using a specially designed metamaterial Split Ring Resonator (SRR) structure as an imaging sensor at microwave frequency is proposed. The topology of the proposed sensor is ingeniously designed to identify imaging objects having dimensions much less than the interacting wavelength λ. The split gap field region of the conventional SRR, used as the sensing region of the imaging sensor, is modified for enhancing the resolution capacity, by slightly raising the split region of the outer ring structure perpendicular to the plane of the resonator (Projected Split Ring Resonator - PSRR) which will reduce the area of the sensing region of the SRR probe considerably. The isolation of the structural parts of the SRR other than projected split region helps in using the localized evanescent field at the split region of the PSRR for imaging of minute objects having dimension ranges up to 0.0001λ by precisely choosing the split gap. The required projection height of the split region and the possible resolution limits of the PSRR sensor probe are evaluated by simulation. Experimental 2-dimensional sub-wavelength images obtained for various dielectric objects using a typical PSRR test probe having resolution capability up to 0.01λ are also presented.

We introduce and numerically investigate a high-quality resonant structure formed by a dielectric low-order diffraction grating combining materials with high refractive index contrast. The proposed structure is capable of supporting multiple plasmonic modes owing to hybridization effects, modes having the characteristic of exhibiting remarkable sensing response to the change of the environment refractive index yet limited figure of merit. To improve the figure of merit, the proposed architecture is modified by adding a layer of semiconductor gain medium, as it can compensate the internal losses. The result is an active sensor showing multi-modal lasing behaviour, with very low threshold and large mode spacing. It is found that the device shows switchable response upon modification of the pump amplitude or polarization, a very important feature when it comes to sensing devices. Finally, the achieved figure of merit is 3400 RIU^-1, one order of magnitude higher than the passive case and much higher than the theoretical limit for sensors based on Kretschmann configuration. Thus, the proposed architecture possesses great potentials as an optical sensor for bio-detection and environmental monitoring.

In this work, a radio frequency (RF) micro-electromechanical system (MEMS) based analog phase shifter is presented over 17-30 GHz. The proposed phase shifter is made using two back-to-back single-pole-seven-throw (SP7T) switches and connected through seven distributed MEMS transmission lines (DMTL). The SP7T switch is designed with lateral electrostatic actuation and demonstrates measured average return loss of > 11.3 dB, insertion loss of < 5.94 dB, and isolation of > 22 dB up to 30 GHz. Total area of the SP7T switch is only 0.89 mm² including bias lines and pads. The proposed wide-band phase shifter can be tuned at all the frequencies between 17 and 30 GHz. Phase shifter gives measured average insertion loss of < 6.94 dB, return loss of > 10 dB, and phase error of ~10 at 17 GHz to 30 GHz over 500 MHz bandwidth. All phase shifts can be tracked with a resolution of 22.50 based on predefined actuation voltages. Total area of the fabricated device is ~11.72 mm². In addition, switches and phase shifter work satisfactorily > 1 billion cycles with 0.1-1 W of RF power. The proposed phase shifter bank gives phase shifting performances at each frequency over 17-30 GHz with a constant resolution utilizing analog tuning, and it operates > 1 billion cycles of reliability with 1 W of RF power.

The tapered waveguide as a microwave plasma excitation structure is widely used in the industrial field. However, it needs high input microwave power to ignite and sustain plasma because its electric field is not sufficiently focused in the discharge area. In order to solve this problem, this paper proposes a novel microwave plasma source based on a ridged waveguide. The structure of the proposed microwave plasma source is optimized to focus the electric field in the discharge region by electromagnetic calculations before the plasma excitation. Then, the equivalent circuit model is used to analyze the impedance matching characteristics of the novel device after the plasma excitation. In order to validate this device, a microwave plasma system is built to measure the plasma exciting power and sustaining power in both air and argon at atmospheric pressure. The simulation and experiment are carried out in both tapered waveguide and the proposed device. Simulation results show the electric field of the ridged waveguide is 1.9 times of that of the tapered waveguide when the input power is 1500 W. Moreover, in the experiments, the exciting power and sustaining power of the air and argon plasma in the novel device are lower than those of the tapered waveguide at different gas flow rates.

A compact ultra-wideband Multiple-Input-Multiple Output (MIMO) orthogonal microstrip fed linear tapered slot antenna (LTSA) is planned for frequency notched applications. The projected MIMO antenna comprises of two indistinguishable linear tapered slot antennas excited by two orthogonal microstrip feeds. In this paper, double split-ring resonators (DSRRs) are suggested to develop the isolation between two linear tapered slot antenna elements. A quarter wavelength spur line is entrenched on the feeding part of the micro-strip antenna to attain the notch frequency. The L-shaped spur line adds to the notch frequency at 5.5 GHz targeted to dodge interference from 5-6 GHz WLAN band. The planned antenna is fabricated and labelled in terms of impedance and radiation parameter measurements, compliant with that of properties achieved from full wave simulation. The antenna has congruous gain and well-built radiation pattern. Radiation pattern portrayal confirms high gain in the end-fire direction.

The present paper introduces the analysis and design of a near field RFID tag for IoT in sub-six GHz 5G frequency band. The proposed radio frequency identification technique is based on the near field interaction between the RFID tag and a wideband antenna reader. This near field interaction adjusts the resonances of the wideband antenna according to the used RFID tag. In addition, the far field RCS of the RFID tag is also investigated to study the relation between the near field and the far field responses of the proposed RFID tag. The proposed RFID tag is characterized with adjustable six resonances based on concentric square rings printed on a dielectric slab. For manufacturing and experimental verification, the dielectric slab is assumed to be FR-4. However, the proposed structure can be generalized to other thin and flexible substrates like paper, plastic and textile.

This article reports the development and test of a radio-propagation measurement system based on an 8-bit software-defined radio. Tests are performed in an urban area at the frequency of 733 MHz and compared with numerical prediction from the Altair WinProp commercial suite. The system is portable (1.2 kg), low-cost, based on non-proprietary open-source tools and has the capability of tracking the GPS coordinates of the measured points. Frequency limit of the system is bounded by the software-defined radio in use, and the limit of this present case spans 24 MHz to 1700 MHz. The integrated system does not need user intervention after its initial setup can be operated autonomously.

In this paper, a dual-band impedance transforming power divider is investigated for all types of impedance environments at its ports, irrespective of the locations of the ports. The intuitive design approach utilizes conventional single-band Wilkinson Power Divider (WPD) architecture to provide the superior dual-band performance with arbitrary port impedances. The proposed power divider also accords a high degree of design flexibility with high frequency ratios (r) and impedance transformation ratios (k). The presented concept is evaluated and verified by design examples and measurements with a fabricated prototype. The agreement between the simulation and measurement results validates the working of the proposed architecture with arbitrary source and load port impedances at two arbitrary design frequencies.

In this paper, we apply the BBGF-KKR-MST (Broadband Green's function-KKR-Multiple Scattering Theory) to calculate Band Structures and Band Field Solutions in topological acoustics. A feature of BBGF is that the lattice Green's functions are broadband, and the transformations to cylindrical waves are calculated rapidly for many frequencies for speedy calculation of the determinant of the KKR equation. For the two bands of interest, only 5 cylindrical waves are sufficient so that the dimension of the eigenvalue matrix equation is only 5. The CPU time requirement, including setup and using MATLAB on a standard laptop, is 5 milliseconds for a band eigenvalue. Using the eigenvalue and the scattered field eigenvector, the field in the cell is calculated by higher order cylindrical waves. The exciting field of higher order cylindrical waves requires only 11 coefficients to represent the band field solutions in the cell. Comparisons are made with the results of the volume integral equation method and the commercial software COMSOL. The BBGF-KKR-MST method is significantly faster.

Unipolar induction has been a heavily discussed phenomenon in the realm of electrodynamics, with research and experiments proposing and supporting different ways to explain the observed effects. This paper presents a novel model to predict induced electromotive forces in a Faraday generator, based on direct interaction between conductor charges. It is compared with predictions that are usually obtained through considerations of Lorentz force, flux linking or flux cutting rules. A standard apparatus provides additional experimental measurements that show good agreement with the theory.

A 3-dB compact hybrid coupler is presented in this paper in an ultra-wideband frequency range from 1.5 GHz to 3.2 GHz with 90˚ phase deference between the two output ports. The proposed coupler is formed by two notched elliptically shaped microstrip lines and four phase shifters, which are broadside coupled through an elliptically shaped slot. A combination of impedance matching technique and structural modification then has been employed to increase coupler efficiency. The design is demonstrated assuming a 0.51-mm-thick Rogers RO4350B substrate. Results of simulation and measurements show that the designed device exhibits a coupling of 3±1 dB across the aimed bandwidth. This ultra-wideband coupling is accompanied by smooth isolation in the order of better than 25 dB and return loss in the order of better than 17 dB. The manufactured device including microstrip ports and phase shifters occupy an area of 35 mm × 30 mm × 1.1 mm (0.27λ × 0.23λ × 0.009λ) which makes it a compact suitable device for UHF applications and measurements, specifically measuring and determining isolation in in-band full duplex transceivers, because of its smooth isolation versus frequency and ultra-wideband bandwidth.

This article aims to study the behavior of Constant False Alarm Rate (CFAR) detectors for a heterogeneous Weibull clutter and its derivatives. CFAR architectures based on exploitation of the Combined Environmental Knowledge Base (CEKB) have been proposed, called Knowledge Based Systems-Maximum Likelihood-CFAR (KBS-ML-CFAR) and KBS-Log-t-CFAR for nonhomogeneous Weibull clutter at general parameters. A CFAR architecture that uses Geographic Information System (GIS) as a Knowledge Base (KB), called KBS-Forward Automatic Order Selection Ordered Statistics-CFAR (KBS-FAOSOS-CFAR) has been proposed for special Weibull parameters. The performances of the proposed detectors have been studied and analyzed by conducting MATLAB simulations. The simulation results show that the KBS-CFAR based on CEKB outperforms the ML and Log-t-CFAR in terms of clutter edge detection capability in nonhomogeneous Weibull clutter case. Compared with other KB, this KBS-CFAR based on CEKB performs well to preserve the probability of false alarm (P_fa) at a desired constant value. For special Weibull parameters, the proposed KBS-FAOSOS-CFAR based on GIS performs better than KBS-Dynamic-CFAR and KBS-Adaptive Linear Combined-CFAR (KBS-ALC-CFAR) in severe interference case. CFAR techniques have been implemented on the ADSP (Advanced Digital Signal Processor) processing board, and the results have been evaluated and discussed.

A wideband circular patch antenna with broadside and conical radiation patterns is proposed. In addition to realizing a wide shared impedance bandwidth of ~48% for both the modes of operation, the unparalleled advantage of the proposed antenna is its reduced sidelobes in the E-plane broadside radiation patterns. The achieved sidelobe-free bandwidth is in the order of 39%, which is much wider than the pertinent art works on wideband pattern diversity antennas using a single radiating patch. The antenna characteristics are validated by fabricating and testing the designed prototype. The proposed antenna is also numerically investigated in front of a parabolic reflector antenna for monopulse radar applications.

Oblique incidence of small-amplitude electromagnetic wave on an anisotropic conductive collision semi-infinite turbulent plasma slab under the influence of a homogeneous magnetic field is considered. The conditions of both the ordinary and extraordinary waves' propagation along and transversal directions with respect to the external magnetic field in a homogeneous absorbing collisional magnetoplasma are obtained. Second order statistical moments of the spatial power spectrum of a scattered radiation in the polar ionosphere are calculated for the arbitrary correlation function of electron density fluctuations using the geometrical optics approximation. External magnetic field, oblique incidence of electromagnetic wave on a plasma slab, anisotropy of both ionospheric conductivity and dielectric permittivity, also elongated plasma irregularities in the auroral region of the terrestrial atmosphere are taken into account. The direction along which these asymmetric factors compensate each other is established. The conditions of the "Compensation Effect" are obtained: the spatial power spectrum not broadens, and its maximum is not displaced. Second order statistical moments of a scattered radiation: the shift of maximum and the broadening of the spatial power spectrum in the main and perpendicular planes are investigated analytically and numerically for the power law spectrum of the anisotropic ionospheric plasmonic structures using the experimental data.

This paper presents, time and frequency domain analysis of a compact tri-band notched UWB (ultra-wideband) antenna with integrated Bluetooth frequency for wireless applications. Modifications in radiating element and DGS techniques are used to achieve high impedance bandwidth. The antenna operates at UWB frequency band 3.1-10.6 GHz as well as bluetooth frequency 2.4 GHz. The band notch characteristics are at Wi-MAX (3.3-3.7 GHz), WLAN (5-6 GHz), X-Band Satellite communication (7.1-7.76 GHz). These notches are obtained by etching different slots in ground plane and in radiating element. Gain, group delay, pulse transmission and radiation patterns of the proposed antenna are also investigated. A prototype of antenna is fabricated and reflection coefficient is measured. A comparison has been made between proposed antenna and previously published UWB antennas.

In this work, we propose a liquid crystal (LC)-based double-dipole phase shifter. By manipulating the electric field, we change the resonant frequency and phase of the electromagnetic wave by deflecting the orientation of LC molecules. We made the LC-based device with a 30 × 30 array of two parallel unequal dipoles on a Quartz substrate. The substrate has an area and thickness of 4×4 cm² and 480 μm, respectively. The experimental results show that the phase shift of 0°-385.4° is achieved at 94 GHz by changing the applied bias voltage on the LC layer from 0 V to 8.4 V. The phase shift is greater than 360° in the range 91.75-94.85 GHz. When the LC molecules are most significantly affected by the electric field, the maximum precision of phase shift is 4.08° with a bias voltage of 2 mV.

With the technology of free space optical communication, information can be transmitted from the transmitter to receiver wirelessly without the necessity of fiber optic cables. This technology offers system security, extended bandwidth, high data rate, and simple installation. This work aims to improve the optical channel based on the optimization of different optical amplifiers and filters. Performance analysis is carried out using a rectangular optical filter (ROF) and two electrical amplifiers named automatic gain control (AGC) and transimpedance amplifier (TIA). The results are presented in terms of maximum quality factor as a function of link range. The proposed systems (represented by ROF and AGC) brought better performance than traditional one (represented by TIA) via the same link range and data rates used. The findings displayed the progress of the AGC which has better quality factor than TIA and ROF. For instance, at 5 m length, the AGC achieves a maximum Q-factor of 12.29, while the ROF and ATI reveal a Q-factor in the range of 9.8 and 7.01 respectively.