In order to effectively improve the communication quality in the extremely-low frequency (ELF) communication, a whole model of analog circuits and transform domain algorithm is constructed. Analog circuits include a pair of magnetic antennas, an amplifier and a group of filters. The distributed capacitance of the magnetic antenna is effectively reduced by the segmented winding method. Analog circuits used to amplify and filter received signal are designed. Besides, a magnetic sensor with high sensitivity is produced. The Karhunen Loève transform (KLT) algorithm applied to the field of interference suppression is deduced in detail. The transform successfully passes the received signal along the basis vector in sub-band, but the interference signal along the vector is attenuated. Therefore, the problem of the optimal filter converted into the solution of transform factor for each sub-band. Then the relationship between the KLT transform and the time domain algorithm in the interference suppression problem is given. Based on the KLT algorithm, Fourier transform (FT) that makes the correlation matrices of the received signal diagonalized approximately is applied to the interference suppression algorithm. Based on the deduction results, the final optimal filter expressions are basically the same as the KLT algorithm. Finally, the experiments are carried out by using the simulated signal and real collected data in the laboratory, respectively. The schematic diagram of the real collected device is presented. The experimental result shows that, no matter the analog signal or the real collected data, the proposed algorithm can effectively suppress the interference. For the simulation, the performance of KLT algorithm is basically same as that of FT algorithm, but KLT algorithm is obviously better than FT algorithm for real collected data.

In this paper, based on different saliency ratios ρ, three interior permanent magnet (IPM) synchronous machines respectively owning a large ρ, a low ρ and an inverse ρ are proposed for the potential applications of electrical vehicles (EVs). To grasp the impacts of saliency ratio on machine performances, comparative studies are conducted at low speed operation (constant torque region) and high speed operation (constant power region), respectively. In particular, the overload capability referring to magnet demagnetization is emphasized in low-speed heavy-duty operation region. And in high speed, the constant power speed range (CPSR) and high efficiency range are investigated. The main results put in evidence the different behaviors of the three machines in terms of EVs operating conditions. Though all three machines reveal considerable behaviors in CPSR, the inverse saliency ratio machine shows a larger high efficiency region and extends the high efficiency region to a wider speed-and-torque range due to its unique characteristic of L_q<Ld.

A novel and compact conformal printed dipole antenna with geometrical modifications in ground plane is proposed in this paper for 5G based vehicular communications and IoT applications. The proposed antenna consists of a printed dipole as defected ground structure and a staircase structured offset fed integrated balun to attain wideband operation. It yields a better -10 dB impedance bandwidth of 17.65 GHz and 2.24 GHz over the frequency ranges 24.3 to 41.95 GHz and 49.91 to 52.15 GHz. Antenna projects the peak gain of 6.81 dB with 98.82% of peak radiation efficiency. The measured results of the proposed model are in good agreement with the simulation obtained from HFSS. The conformal models of the proposed antenna are developed to embed the antenna in different curved surfaces on vehicular body. The analyzed conformal characteristics of the antenna support excellent constant reflection coefficient with respect to planar structure of the antenna over the operating band at different angles.

Effects of a superstrate layer on the resonant frequency and bandwidth of a high T_c superconducting (HTS) circular printed patch are investigated in this paper. For that, a rigorous full-wave spectral analysis of superconducting patch in multilayer configuration is described. In such an approach, the spectral dyadic Green's function which relates the tangential electric field and currents at various conductor planes should be determined. Integral equations are solved by a Galerkin's moment method procedure, and the complex resonance frequencies are studied with basis functions involving Chebyshev polynomials in conjunction with the complex resistive boundary condition. To include the superconductivity of the disc, its complex surface impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results are compared with experimental results of literature as well as with the most recent published calculations using different methods. A very good agreement is obtained. Finally, superstrate loading effects are presented and discussed showing interesting enhancement on the resonant characteristics of the superconducting antenna using combinations of Chebyshev polynomials as set of basis functions.

In some cases, such as at a boiler tank and other large-size mechanical systems, it is more realistic to employ a non-contacting sensor to detect small displacement or vibration. In this paper, a non-contacting sensor for monitoring small displacement or vibration based on measurement of antenna reflection coefficient is proposed. A theoretical and numerical study is performed to investigate the proposed method and to determine the post processing method associated with the antenna reflection coefficient data. To avoid the ambiguity in the measured data, the detection of both the magnitude and phase components of the antenna reflection coefficient is required to compute the small displacement of the target. The distance between antenna and target has to be determined in order to minimize the ambiguity range in the data. The frequency domain observation is more appropriate for determining the amplitude and frequency of the target vibration. Magnitude detection, phase detection and Fourier analysis are used as main tools in the post-processing part of the proposed method.

It is generally considered that increasing the carrier frequency of radar is an important way to improve the precision of micro-motion measurement. However, the increase of the center frequency may raise the phase noise intensity of the radar transmitting signals and make the extraction more difficult; therefore, it is particularly necessary to study the influence of phase noises on the extraction of micro-motion characteristics. In this paper, a specific study about the effect of phase noises on the extraction of m-D features is carried out. The effect of phase noises on the extraction performance of the m-D features is evaluated based on the parameter of MSCR. The results of simulation experiments indicate that increasing the carrier frequency will not improve the extraction performance of micro-motion features in the case of using both the classic time-frequency analysis method and the new developed sinusoidal frequency modulation Fourier transform (SFMFT) method. Increasing the frequency of the vibration will not help to improve the extraction performance of the m-D features when using the SFMFT method. However, increasing the vibration frequency can have an improvement effect through the time-frequency method with the increase of Doppler frequency. At last the empirical formula is put forward based on which the exact value of the estimation accuracy can be calculated.

The use of dual orthogonal polarizations to optimally conserve frequency spectrum in microwave link, otherwise known as cross polarization, has received considerable interest in the recent time in the field of electromagnetic wave propagation in sand and dust storms. Cross polarization in dust storms occurs due to the non-sphericity of the falling dust particles and the tendency of the particles to align in a direction at a time i.e. canting angle. The realization of a dual-polarized system is however limited by degree of cross polarization discrimination (XPD) that can be achieved between the two orthogonal channels. Therefore, theoretical investigation has been carried out in this work to estimate the cross polarization at microwave and millimeter wave bands by non-spherical dust particles in dust storms. The XPD being the parameter for characterization of cross polarization, is predicted using propagation constants' differentials and canting angles, as inputs. Apart from both differential phase rotation and attenuation, it has been found that the cross polarization produced by ellipsoidal dust particles strongly depend on the particle canting. XPD decreases with an increase in canting angle. It has also been observed that the values of differential attenuation increase with increasing frequency for visibility and thus depends directly on frequency. Lastly, the obtained results show that cross polarization is significant during severe visibility and for dry dust storm; the XPD is good and acceptable for dual polarization systems.

A method is proposed for a half-mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) to obtain dual-band below the cutoff frequency. Complementary split-ring resonators (CSRRs) and microstrip open-stubs are integrated on the top of an HMSIW cavity. The structure produces two center frequencies both below the cutoff frequency of the originalHMSIW without increasing the cavity size. Results indicate that the center frequencies are 2.95 GHz and 3.99 GHz, and 3 dBfractional bandwidths (FBWs) are 9.1% and 4.6%, respectively. There is a transmission zero between the two frequencies, which enhances the out-of-band suppression performance. The measured results are in good agreement with the simulated ones. This new combination not only obtains two usable passbands below the cutoff frequency, but also makes the filter more compact. The filter has some practical and application significance.

The meteorological parameters along the overhead line change significantly, which have an effect on the surrounding electromagnetic environment. The analysis method of meteorological parameters impacting the electromagnetic environment is presented in this paper. Firstly, the conductor temperature is solved iteratively by the heat balance equation. Secondly, the power flow model involving the conductor temperature is established based on the relationship between line parameters and conductor temperature. Finally, the electromagnetic environment surrounding the line is analyzed based on the changes of line voltage and current. In the case study, the electromagnetic environment of the IEEE 5-bus system under the three cases is analyzed and compared. It is proved that the changes of meteorological parameters along the line have an important impact on the surrounding electromagnetic environment. The calculation of electromagnetic environment considering the changes of meteorological parameters is more accurate.

In this paper, a quad-band wearable slot antenna with low specific absorption rate (SAR) is presented. By cutting an inverted V-shaped slot with its arms further extended towards the center of the circular patch, multiple resonant modes of the antenna can be excited to operate on 1.8 GHz DCS, 2.4 GHz WLAN and 3.6/5.5 GHz WiMAX bands. The measured peak gains and impedance bandwidths are about 4.91/7.84/2.58/4.12 dBi and 320/60/80/180 MHz for the 1.8/2.4/3.6/5.5 GHz bands respectively. The SAR of the proposed antenna has been measured using a three layer human tissue model. The estimated SAR values at all the resonant frequencies are well below the threshold limit of 2 W/Kg, which ensures its viability for wearable applications. In order to approximate different parts of the human body, the SAR values have been estimated for three surface sizes, 120 × 120 mm², 220 × 220 mm² and 320 × 320 mm², of the human tissue model, and results are compared. Frequency detuning of the proposed antenna due to bending along x, y and x-y planes has also been carried out and discussed. Further, on arm effect on the antenna performance is investigated, and results are presented. The simulated and measured results are in good agreement, which validates the use of proposed wearable antenna in DCS/WLAN/WiMAX bands.

Mining and mineral exploration are very important in the global economy. In mining operations, communication systems play vital roles in ensuring personal safety, enhancing operational efficiency and process optimization. Multiple Input Multiple Output (MIMO) systems have been widely used in the mine environment to suppress the multi-path problem of the tunnel and enhance the capacity of the channel. In order to realize the optimal performance of MIMO system, spatial characteristics of wireless signal in an underground tunnel must be considered. In this paper, the wave propagation model combined with the modal theory and ray theory is used to simulate mine underground wireless channel. Meanwhile, the theoretical models of the signal Angular Power Spectrum (APS) and Angular Spread (AS) are constructed. After simulation and comparison, the following conclusions can be drawn: the APS distribution of the wireless signal is similar to the Gaussian distribution; the position of the antenna in the cross section of the mine tunnel has a small influence on the signal AS, which can be neglected; the roughness of the mine tunnel wall can change the characteristic of the signal AS to some extent.

Air-gap magnetic energy variation with angular position produces cogging torque, which may results in mechanical vibration, acoustic noise, and torque ripple. Various cogging reduction methods of design modifications viz. skewed magnets, skewed slot, asymmetrical displacement of magnets/slots etc. are reported in the literature. All such methods adversely affect machine performance in terms of air-gap magnetic field, back emf, and induced voltage. This paper introduces the cogging torque reduction by skewing of slot opening. In order to obtain machine performance, the no load magnetic field of the proposed machine is determined using combined methods of two-dimensional subdomain analytical analysis method and multislice method. The machine is considered as a stack of slices along axial direction. The adjacent slices differ in relative location of slot openings. The analytical field solution of each slice is obtained by use of subdomain method, and algebraic summation of slices is taken as field solution of actual machine. The analytical analysis developed is compared with finite element analysis (FEA). The close agreement of analytical results with FEA results confirms the validation of analytical solution. Furthermore, the machine parameters viz. cogging torque, back emf, and induced voltage are evaluated analytically, and results are compared with FEA solution. To demonstrate the effect of skewed slot opening on machine's performance, a machine of same rating without skewing of slot opening is investigated, and their performances are compared.

In this paper the analysis and investigations are carried out on portable antennas for worldwide interoperability for microwave access (WiMAX) applications of flexible coplanar waveguide (CPW)-feed split-triangular shaped patch (STSP). The proposed STSP antenna is fabricated from polyimide substrate material having the dimension of 18×20×0.1 mm³ (volume is 36 mm³). It resonates at 3.55 GHz frequency of a reflection coefficient (S₁₁) of -24.45 dB and offers impedance bandwidth of 580 MHz (3.3-3.88 GHz) with a gain of 2.06 dBi. The STSP antenna has small size, light weight, low volume, and is flexible for WiMAX applications. Simulation and measured results of the proposed STSP antenna are in close agreement.

A flexible fully textile-integrated bandstop frequency selective surface working at a central frequency of 3.75 GHz and presenting a 0.6 GHz bandwidth has been designed, manufactured and experimentally characterised. The frequency selective surface consists of a multilayered woven fabric whose top layer presents periodic cross-shaped conductive resonators, and due to its symmetries, its performance is largely independent of polarisation and angle of incidence. These properties make the prototype very interesting for shielding applications. The designed frequency selective surface is based on a layer-to-layer angle interlock 3D woven fabric. This technology provides the prototype with flexibility, portability and the possibility of manufacturing it in a large scale production by the use of existing industrial weaving machinery, in contrast to conventional frequency selective surfaces manufactured using rigid substrates. The proposed textile frequency selective surface has been simulated and experimentally validated providing good agreement between the simulations and measurements. The measured maximum attenuation has been found to be higher than 25 dB under normal incidence conditions.

^nullA quasi-octave bandwidth arbitrary-angle compact waveguide twist using a single matching step is presented. The proposed twist, based on a single intermediate ridge waveguide section that broadens its mono-mode operation, exhibits a similar wave impedance to the rectangular waveguide connected to its ports thus facilitating the reflections minimization in an extended frequency range. An exemplary 45° twist has been manufactured in the 10 GHz to 19.3 GHz frequency range (~64%) for demonstration purposes. The measured data are in concordance with those predicted by the simulation. This result represents, to the authors' knowledge, today's state-of-the-art in terms of compactness and bandwidth performance.

In this paper, a compact, circularly polarized printed monopole antenna is proposed at ISM band (2.4-2.48 GHz) for biotelemetry and implantable applications. The proposed antenna possesses a small dimension (10×10×0.3 mm³) and simple microstrip feeding structure. The circular polarization is easily achieved by introducing an ``L'' shape stub at the ground plane in ISM. The simulated 10 dB impedance bandwidth is around 13.87%, and 3 dB AR bandwidth is around 5.3%. The effect of different body phantoms is discussed to evaluate the sensitivity of the proposed antenna. The simulated peak gain of the proposed antenna is about -7.79 dBi across the operating band. The SAR analysis of the antenna configuration has also been studied.

Axial flux Permanent Magnet (AFPM) machines, due to its high torque capability, high power density and compact size, are the most suitable candidates for in-wheel Electric Vehicle application. However, the presence of cogging torque in AFPM machines, resulting from the interaction of PMs and stator slots, introduces torque ripples, noise and vibrations which deteriorates the performance of the machine. To overcome this, several techniques for cogging reduction are utilized. Out of various techniques, rotor magnet shape variation is most commonly utilized. This paper investigates the effect of some preferred magnet shaping techniques in AFPM machines on several performance parameters such as magnetic flux density distribution in air gap, cogging torque, flux linkage, no load-induced emf, emf harmonics, electromagnetic torque and torque ripple. These parameters were analyzed using 3-D Finite Element Method (FEM) based simulations. It was found that a maximum cogging reduction by 62.49% and output torque ripple by 63.25% were obtained by using short-pitched and skewed rotor magnets. This also resulted in a reduction of induced emf by 14.18% and electromagnetic torque by 15.17%.

In this paper, the effects of the locations of four dual-band antennas on a mobile terminal chassis are investigated in the vicinity of user's hand. To perform this study, a dual band four-port mobile terminal antenna for 5G is designed for operation in between 3.34 and 3.84 GHz (lower band, LB) and 5.15 and 6.52 GHz (upper band, UB), respectively. Due to the symmetry of the antenna elements (AEs), a right hand standard phantom is placed at a fixed position. Meanwhile, the antenna elements are placed at seven different locations across the chassis, with the best possible locations chosen based on the maximum efficiency in data mode. The influence of the human hand on the antenna performance is assessed based on two aspects: 1) in terms of matching (impedance mismatch (IM) and impedance bandwidth (IB)); and 2) in terms of efficiency (radiation efficiency (RE) and total efficiency (TE)). To validate its performance, the proposed antenna has been fabricated and measured. Results showed good agreement between simulations and measurements. Based on the results, a general design guideline for future 5G antennas operating in the sub-6 GHz bands considering user's hand effects can be outlined. The observed maximum variation for the proposed antenna with user's hand in terms of IM is -8 dB and -5 dB, respectively, and 57% and 37% in TE, respectively.

The reliable detection of geometrically-based stealth targets using a conventional single sensor radar system may be extremely difficult. This is because low Radar Cross Section (RCS) from certain angles results in a low Signal to Noise Ratio (SNR). In the present work, multi-target tracking of stealth targets is investigated in a multi-static radar with passive receivers. The Directions of Arrival (DOA) of targets are estimated by the receivers without knowing the number of targets, and their positions are obtained based on the transmitter beam direction. The B2 bomber aircraft model has been used as a stealth target. The RCS of the model has been simulated for all collection of incident and reflected angles from an oblique impinging plane wave. Probability of Detection (Pd) is modeled using a Toeplitz-based method for different SNRs due to different RCS patterns and is fed to an Iterated Corrected Probability Hypothesis Density (IC-PHD) filter. In spite of considering the transmitter and receivers resolution in our input data generation, the proposed algorithm is able to track the targets individually when they are much close to or even cross each other. Simulation results show the improved performance of the proposed method compared to other existing approaches.

A circularly polarized (CP) antenna with simple feeding network for ultra-high-frequency (UHF) radio-frequency identification (RFID) reader application is presented in this letter. The proposed antenna consists of a slot loop etched on the ground and a simple feeding network using bended microstrip lines. And the two parts of the antenna are printed on either sides of a thin substrate, thus a low-profile antenna is obtained. The slot loop is meandered based on the first-order Minkowski fractal technique for antenna size reduction. To generate circularly polarized radiation, two branches of the feeding network are designed to be orthorhombic with 90° phase difference. The antenna is simulated and practically fabricated with a compact size of 80×80×1.6 mm³. The 10-dB impedance bandwidth and 3-dB axial-ratio (AR) bandwidth are measured to be 50 MHz (0.896-0.946 GHz) and 12 MHz (0.916-0.928 GHz), respectively. The measured peak gain exhibits stable value of 3 dBi over the impedance bandwidth. Furthermore, a wide 3-dB beamwidth of 120° is achieved for the proposed antenna. Based on the above, this antenna is well suited for applications in UHF RFID handheld readers.