This paper presents an application of integral type optimal control scheme for rotor positioning of a hybrid magnetic bearing (HMB) in one degree of freedom (1-DOF) using low bias current. It is observed that higher biasing current enhances the linearity and disturbance rejection capability but at a cost of higher copper loss in the actuator. So, selection of biasing in an HMB system is very crucial. In the proposed scheme the dc biasing current can be varied by adjusting the axial offset to the rotor magnet. Analysis has been conducted to achieve the optimal biasing current for better performance of the HMB. A prototype of the HMB system has been fabricated and tested which represents quite satisfactory axial vibration characteristics under low biasing current.

In this work, a new design of small microstrip antenna with variable band-notched filtering characteristic for super ultra-wideband (UWB) applications including 5G/IoT networks is presented. In the proposed structure by creating steps with optimized appropriate sizes and angles in the lower edges of the quasi-square patch antenna and by a new technique of modifying the ground plane, more efficient radiation patterns and characteristic impedance are achieved. Moreover, the omnidirection allow cross-polarized H-plane radiation patterns are obtained infrequency band of 3-11 GHz. Also, its radiation patterns are improved between 11 and 14.5 GHz and have better performance especially with tuning capacitors between 14.5 and 20 GHz. In addition, its frequency bandwidth with VSWR<2 is from 3 GHz to 50 GHz which covers 5G networks and both ultra-wideband (UWB) and super wideband (SWB) communications. A rectangular slot on the patch is used to create an integrated band-notch filter in the structure to avoid interference with other wireless systems like wireless local area networks (WLANs), and this specification can be activated or deactivated by a PIN diode. In addition, the center frequency of the filter can be tuned by just a varactor diode or a variable capacitor and/or by changing the position of the capacitors in frequency range of about 3.5-6 GHz, which rejects interference of all WLANs and even lower and upper bands of them and nulls in the radiation patterns can be changed especially in upper bands as well. The final structure simulation results are in good agreement with measurement ones.

The aim of this work is to reduce the torque ripple of a low-speed/high-torque Doubly Salient Permanent Magnet (DSPM) generator for wind turbine applications. To do this, a combined design and control-based approaches are set up to improve the overall machine performance. The design-based approach helps to develop a form of small stator/rotor teeth combination, focusing on the shapes and dimensions of the teeth that will minimize torque ripple. On the other hand, in the second approach, a control technique is designed. It employs indirect torque control (Torque Sharing Function: TSF), including a PI-controller with gains adjusted continuously for regulating the reference current. The obtained results show that by combining these two approaches, the ripple rate of the electromagnetic torque for the studied DSPM is reduced to a minimum when the teeth shapes are trapezoidal in both the stator and rotor, and the command approach also allows an improvement in the total torque shape, such that the ripple rate decreases by about 96%.

A compact differential-fed ultra-wideband (UWB) antenna with single band-notched characteristicis proposed in this paper. The antenna consists of a ground plane etched with an octagonal groove and two symmetrical hexagonal radiating patches. Return loss and isolation of the antenna can be effectively reduced by loading a rectangular stub on the ground plane and etching a semi-circular groove on the radiation patch. In order to achieve a controllable single band-notched characteristic, two pairs of quarter-wavelength stubsare introduced into the grounding plane. The antenna has lower cross polarization and stable gains than conventional single feed antennas. The measured impedance bandwidth with S₁₁ ≤ -10 dB is 114% from 3 GHz to 11 GHz, and the notch characteristic is realized in the 7.2-8.4 GHz band.

The electromagnetic scattering from oil-covered sea surface is investigated by two scale model with the help of Lombardini's oil-covered sea spectrum and the semi-empirical reflection model that takes the oil film into consideration. Firstly, a comparison of the clean and oil-covered sea spectra is made to show the influence of the oil film on the sea surface. Then, the backscattering coefficient from the clean sea computed by the two scale model is compared with the measured data in the reference to validate the accuracy of the two scale model used in this paper. Finally, backscattering features from the oil-covered sea surface are discussed in detail and compared with those from the clean sea. In addition, the influence of the thickness of oil film and fractional filling factor on the backscattering coefficient of oil-covered sea are also studied. The simulated results show that the oil film floating on the sea has remarkable influence on the backscattering coefficient of the sea, compared with those of the backscattering coefficient from the clean sea.

In this paper, a single-fed high-gain circularly polarized microstrip antenna is proposed. The circular polarization is obtained by two unequal-length arc-shaped radiation patches, which excites two orthogonal linearly polarized modes with a 90° phase difference. The antenna is excited by coaxial feed. The proposed circularly polarized antenna consists of two arc-shaped radiation patches and a ground plane, which has a simple structure and a higher gain than 10.0 dB. The antenna is fabricated and measured to verify the design. The measured results are in good agreements with the simulated ones. The measured results show that the impendenceb and width (IBW) for S₁₁<-10 dB is 16.7% (3.78-4.47 GHz), and the axial-ratio bandwidth (ARBW) for AR<3 dB is 3.6% (4.09-4.24 GHz). Further, the gain from 4.09 to 4.24 GHz is higher than 10.0 dBi. The antenna radiation pattern performs well over the whole band, and the peak gain can reach 10.67 dBi at 4.11 GHz. It is a good candidate for advanced wireless communication systems.

The scattering problem of time-harmonic electromagnetic plane waves by an impedance and a dielectric ellipsoid is considered. A low-frequency formulation of the direct scattering problem using the Rayleigh approximation is described. Considering far-field data, an inverse electromagnetic scattering problem is formulated and studied. A finite number of measurements of the leading-order term of the electric far-field pattern in the low-frequency approximation leads to specifying the semi-axes of the ellipsoid. The orientation of the ellipsoid is obtained by using the Euler angles. Corresponding results for the sphere, spheroid, needle and disc can be obtained considering them as geometrically degenerate forms of the ellipsoid for suitable values of its geometrical parameters.

A wideband microstrip open-slot antenna with dual-frequency dual-sense circular polarization (CP) is presented in this paper. A bent feeding structure and three radiating slots, including a modified cross-shaped, an inverted F-shaped, and an inverted L-shaped slots, are designed to excite two orthogonal electric fields with a quadrature phase difference for a radiating right-hand circularly polarized (RHCP) wave at 2.5 GHz and left-hand circularly polarized (LHCP) wave at 3.3 GHz. To improve the axial-ratio (AR), a bent parasitic element is introduced near the microstrip line. Multiple resonances are merged to achieve a large bandwidth of 2620 MHz (104.8%) from 2.2 GHz to 4.82 GHz. The measured AR bandwidths are 460 MHz (18.4%) at the lower band (2.5 GHz) and 2150 MHz (65.1%) at the upper band (3.3 GHz).

A simple, compact, and capacitively coupled triple band planar inverted F antenna for wireless applications is presented in this paper. By arranging two metal patches in a stacked manner and using capacitively coupled feeding method three resonant modes are generated. The three operating bands 1.8 to 1.9 GHz, 2.5 to 2.6 GHz, and 3.3 to 3.4 GHz for GSM 1800, LTE 2500, and WiMax applications, respectively with -10 dB return loss bandwidths of 5.4%, 3.9%, and 2.98% around the resonances. The antenna occupies a size of 40 mm × 5 mm × 6 mm and is printed on an FR4 epoxy substrate of dielectric constant 4.3.

Feature extraction is of significant importance for final results of the through-wall detection procedure. High resolution range profile (HRRP) is related to target reflectivity coefficients which can be used as a new feature for object detection. Compressive sensing (CS) is an emerging technique which enables a sparse signal to be recovered using much fewer measurements. This method can provide a novel way for achieving the HRRP since the target reflectivity coefficients are often known to be sparsely distributed in range cells. In this paper, after a set of input-output patterns that consist of target position and HRRP are obtained, through-wall detection problem is reformulated into a nonlinear regression one, which can be solved by support vector machine (SVM). Numerical simulations demonstrate that the prediction accuracy of target position is related to the number of range cells, the number of observations, and signal-to-noise ratio (SNR). Furthermore, the proposed method performs better than the one using signal amplitude as a feature in terms of smaller estimation error and shows better robustness against noise.

The ability to predict rain characteristics at small space-time scales is important, particularly in the planning, design, and deployment of wireless networks operating at frequencies above 10 GHz. For wide area networks, high space and time resolution rainfall data are often not available, and the cost of such measurements is prohibitive. This paper thus presents a new approach to address this problem using rain radar measurements to obtain rain estimates at finer resolutions than that available from the original measured data. This paper proposes three innovative methodologies: 1) the approach is not directly applied to measured rainfall rate data but focuses on the parameters of fitted lognormal distribution parameters and/or computed rain characteristics for each location; 2) to facilitate the application in wireless communication networks operating above 10 GHz, a set of databases and contour maps of rain parameters spanning North West Europe have been created. These conveniently and efficiently provide rain parameters for any location within the area under study; and 3) the proposed 3D space-time interpolation approach can extrapolate rain parameters at space-time resolutions that are shorter than those found in NIMROD radar databases. The results show that the approach presented in this paper can be used to provide {1 km, 5 mins} space-time rain rate resolution from {5 km, 15 mins} data for the whole North West Europe with error percentages of less than 4%. This is far superior to estimates provided by the International Telecommunication Union recommended model.

The aim of this paper is to present a model for a Composite Right-/Left-Handed (CRLH) distributed oscillator. A linear approach is used for the analysis of the circuit. The effects of the losses and of the parasitic elements, both present in the active devices and in the passive components, are included. Analytic formulas for the design of the transmission lines used in the oscillator are given. The model is validated by means of a comparison with previously published measured data.

For most of space-frequency joint anti-jamming algorithms, the solution of adaptive steering vector is a high complexity problem. To solve this issue, a space-frequency combined anti-jamming algorithm based on sub-band energy detection (SF-SED) is proposed. At first, the algorithm performs fast Fourier transform (FFT) on the received data of the array antenna and obtains multi-snapshot data of each sub-band through sub-band decomposition. Then, the interference detection statistic and decision threshold are constructed by the energy of the sub-band to judge whether there is an interference in each sub-band. Finally, different methods are used to solve the adaptive weights of the two types of sub-bands according to sub-band classification results. Compared with the related work, the proposed algorithm not only has lower computational complexity, but also has higher output signal-to-interference-and-noise ratio. Theoretical analysis and simulation results demonstrate the anti-jamming performance of the proposed method.

Angular misalignment is an issue for many potential wireless power transfer (WPT) applications. This paper proposes a resonator as an effort to solve this issue. In the beginning, this paper gives an example of quantitative coupling analysis on angular misalignments. Then, it proposes an omnidirectional resonator for electromagnetic coupling WPT system. The proposed resonator is based on the structure of a regular polyhedron. It is constructed of four planar spiral resonators arranged as a regular tetrahedron. The coupling between the proposed resonator and a planar spiral resonator is verified. Both the simulated and measured results show that the coupling coefficient can be kept at a certain level when the omnidirectional resonator rotates around all x, y, and z axes regardless of the orientation of the planar spiral resonator respect to the omnidirectional resonator.

This paper designs, fabricates, and analyzes an inductively-tuned K/Ka band RF MEMS (Radio frequency micro-electro-mechanical-systems) capacitive switches. The MEMS switch employs a defect ground structure (DGS) and an air bridge. Two different MEMS switches, one with air bridges and the other not, are designed. Surface current distribution results of MEMS switches in different states are simulated and discussed. A novel actuation voltage's calculation approach of MEMS switch is proposed. Measured results indicate that the type MEMS switch's actuation voltage is 20 V. For the MEMS switch without air bridges, the isolation is more than 15 dB at 12.5~20 GHz, and the insertion loss is less than 0.28 dB up to 20 GHz. For the MEMS switch with integrated air bridges, the isolation is more than 15 dB at 18.3~40 GHz, and the insertion loss is less than 0.64 dB up to 40 GHz. Circuit models and measured results of the proposed MEMS switches show good agreements. The pull-in and release time of this switch are 99 μs and 49 μs, and the lifetime of this type of switch is more than three million.

This paper presents a parsimonious Bayesian indoor wave propagation model for predicting signal power in multi-wall multi-floor complex indoor environments. The received power is modeled as a Bayesian multiple regression model. The parameters of the model are assessed and validated using a two-tier validation strategy in which Bayes factor and posterior probability are used in the first tier and second tier, respectively. The performance of the two-tier strategy is then assessed using Bayesian information criterion. The proposed indoor propagation model is tested in a two-storey building with access points operating at 2.4 GHz.

The ionized field under HVDC transmission lines have an impact on environment and people. With the industrial pollution and environment deterioration, the suspended particles that will influence the ionized field cannot be ignored. So the meshless local Petrov-Galerkin (MLPG) method based on moving least square (MLS) shape function is applied in this paper to calculate the ionized field of unipolar transmission line. Based on the calculation, the analysis of the ionized field within the influences of suspended particles has been done by establishing the charging model of suspended particles. The research shows that suspended particles indeed influence the ionized field by increasing space charge density, reducing corona onset electric field, and reducing the ion mobility.

Deceptive jamming plays an irreplaceable role in electronic counter measures (ECM) due to its flexibility and high power efficiency. Based on digital channelized receiver, this paper proposes a novel deceptive jamming method for linear frequency modulation (LFM) radar, side lobe jamming, which builds decoy group utilizing filter side lobes. Via adjusting the filter structure properly, this method produces false targets at specific positions. Unlike intermittent sampling repeater jamming (ISRJ) which forms a train of symmetric decoys, side-lobe jamming can generate asymmetric false targets, which is more deceptive. On the other hand, it can produce much more false targets than ISRJ, which has a certain suppressive effect on the radar. The experimental results with simulated data verify the effectiveness of the proposed algorithm.

Here, a multi-stopband frequency selective surface (FSS), covering commercial frequency bands CDMA, GSM-900, GSM-1800, LTE-2200 MHz, Wi-Fi, and Bluetooth for mobile communication applications has been proposed employing a pair of concentric square ring patches as a unit cell. Possibilities of annular ring patch type FSS are explored first. Finally, the design comes up with a compact square ring patch type single layer FSS. It is also explored that by increasing the width of the inner ring, operating bandwidth can be enhanced to cover closely spaced commercial frequency bands in a single band. Thereby the mutual coupling between the closely spaced resonators for multiple bands can be minimized. The proposed design is flexible enough to tune the desired resonance frequency by changing the length of the individual ring resonators. The design concept has been formulated using linear polynomial regression (LPR) techniques and validated through proper measurement of the fabricated prototype. This FSS can be used as a mobile back cover to protect mobile users from harmful radiations.

A simple and compact, self-isolated printed antenna able to operate in the 2.4 GHz (2400-2484 MHz) and the 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands in notebook computers is introduced. The design is built on a low-cost substrate with the dimensions 6 mm × 30 mm (about 0.05λ × 0.24λ at 2.4 GHz) and comprises a symmetrical coupled-fed loop and two parasitic shorted strips. For size reduction, the 2.4 GHz loop is loaded with a pair of L-shaped stubs above the feeding and coupling T strip. The parasitic strips shorted on both sides of the coupling T strip are further added to generate the 5 GHz band resonance. The results show that good radiation characteristics can be obtained in the bands of interest. In addition, when grouping three proposed designs with a gap of 4 mm between them, the results for each antenna impedance bandwidth, the isolation between any two of the three designs, and the envelope correlation coefficient (ECC) are also satisfactory.