A compact multiband antenna for frequency bands of 2.45 GHz (ISM), 3.3 GHz (5G), and 5.8 GHz (ISM) is proposed. Modified Complimentary Split Ring Resonator (CSRR) and the cross-shaped stub is introduced in the hexagonal radiator to achieve triple-band operation including both ISM bands applications of 2.45 GHz, 5.8 GHz and WiFi/WLAN. The stubs in the radiator also improve the bandwidth and impedance matching of the antenna. The 10 dB impedance of the proposed antenna varies from 2.43 GHz to 2.64 GHz, 3.02 GHz to 3.85 GHz, and 4.88 GHz to 6.82 GHz. The antenna is analyzed on a human phantom model for wearable applications, where simulated SAR and theoretically calculated SAR are 0.3251 W/Kg and 0.3299 W/Kg, respectively. The antenna is used on a human breast model for cancer detection applications, where the SAR value is used to analyze and validate the performance of the antenna; therefore, the antenna has effectively worked for biomedical and wearable applications.
This paper presents a novel method of multiple input multiple output (MIMO) communication on the basis of a passive repeater that achieves enhanced performance in both line-of-sight and non-line-of-sight environments. The passive repeater is implemented as a back-to-back antenna system. The advantage of the proposed system is an increase in the effective aperture of the base station, which allows to sufficiently extend the communication distance and ensure spatial resolution. The configuration of the passive repeater is simple, based on two connected antennas with parabolic reflectors. This configuration helps to avoid phase controller that allows to spread repeaters in the communication environment. This spreading provides multipath propagation and improves MIMO performance. In this paper we suggest to implement the proposed passive repeater with optimal placements to create multipath wave propagation and ensure spatial resolution in a line-of-sight environment, and to enhance coverage and access blind spots in a non-line-of-sight environment. The numerical analysis is performed to verify the validity of using the proposed repeater, and it is found that the proposed method helps to ensure features in the propagation environment which leads to enhanced MIMO performance.
This work is devoted to the development of a high gain Frequency Selective Surface (FSS) reflector backed monopole antenna using Machine Learning (ML) techniques for 5G applications. It analyzes and solves the complexity of the determination of the optimum position of the FSS reflector and the ground dimension of the monopole in this composite antenna structure since there are no solid and standard formulations for the computation of these two parameters. ML modelling is involved in the development process for the sake of gain enhancement. It is applied to get the optimum position of the FSS reflector layer and the ground dimension of the monopole antenna. The proposed antenna structure is 50 mm × 50 mm, implemented on a Rogers 5880 substrate (thickness = 1.6 mm). Two different patch antenna structures, with and without FSS, are developed and considered in the current work. The antenna performance in terms of operating frequency, return loss, and gain is analysed using the finite element methods. The design is optimized for a targeting frequency band operating at 6 GHz (5.53 GHz to 6.36 GHz), which is suitable for 5G Sub-6 GHz applications. The obtained results show that the integration of the FSS layer below the antenna structure provides a simple and efficient method to obtain a low-profile and high-gain antenna. Finally, the proposed design is fabricated and measured, and a good agreement between the simulated and measured results is obtained. A comparison with similar studies in the literature is presented and shows that the current design is more compact in size, and the obtained radiation efficiency and gain are higher than other designs.
Fast evaluation of the array response matrix and its vector or matrix products play a central role in several applied electromagnetics and array processing applications. In this context, the Kronecker Array Transform (KAT) has been introduced by Ribeiro and Nascimento as an efficient factorization technique that can be applied when the elements of a planar array and the wavevectors exhibit separability. The computational savings leverage on the decomposition of the full array response matrix in the Kronecker product of two smaller array response matrices. In this contribution we extend and apply the generalized Kronecker product introduced by Fino and Algazi to the array response matrix decomposition problem. The resulting Generalized Kronecker Array Transform (GKAT) broadens the class of problems that can be addressed while achieving the same computational savings. The complexity of GKAT is compared with Non-Uniform Fast Fourier Transform (NUFFT), and optimal integration of the two techniques is elaborated.
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.
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.
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.
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.
The unique bow-tie shaped pentagonal slit microstrip patch antenna has been particularly developed, manufactured, and tested for defense applications such as gunner training systems. The substrate is made of 3.2 mm thick FR4 material with a dielectric constant of 4.3. With a conductivity of 5.96×107 Siemens/m copper is used as a pentagonal bow tie patch. During the training period of MANPADS, previously wired system is used, and it is replaced by a completely wireless system with a specially designed antenna along with an ultrasonic sensor and processor unit. The innovation of antenna is pentagonal slit created on patch, and it increases fringing effects. It attains 6.523 GHz with a return loss of -22.5 dB, maximum gain of 5.84 dB, and better VSWR of 1.16. CST Microwave Studio 2016 simulates the proposed antenna characteristics such as gain, return loss, radiation pattern, and VSWR.
Aiming at the focusing of near-field electromagnetic (EM) energy, a design approach of multi-type focusing (MTF) based on 1-bit metasurface is proposed in this paper. The surface electric field required for multi-focus is actually obtained by the superposition of the surface electric field of each single focus. This method can flexibly design the number, position, and energy distribution ratio of the focus according to the phase arrangement of the metasurface. Dipole structure is used as ``0'' and ``1'' unit of 1-bit metasurface. The phase difference of reflection is 180°, and the reflection coefficient is over 90% in 7.4-21.9 GHz. Using this 1-bit unit, the linear focus metasurface, multi-focus metasurface and metasurface generating two foci with different energy distribution are realized respectively. The energy distribution metasurface was manufactured and measured, and the measured results are consistent with the simulations. The design method used in this paper is simple and effective to realize multi-focus metasurface design and has potential application value in microwave imaging, radio frequency identification (RFID), and wireless power transmission.
Beamforming at mm-Wave and beyond is expected to be a critical need for many emerging applications such as Internet of Things (IoT), vehicular networking systems, and unmanned aerial navigation systems as well as 5G/6G backhaul communications. A new technique is proposed using quasi-optical beamforming that will address the shortcomings of existing beamforming approaches. These structures are passive (or nearly passive) having low cost, low power consumption, compact size and weight, have bandwidth advantages, and are expected to be able to operate at higher frequencies. The proposed structures give sufficient degrees of freedom to control the beamsteering angles by varying the dielectric constants and geometries of these structures and can form simultaneous multiple low overlapping beams. This approach increases the gain of the radiating source resulting in highly directive beams; our studies suggest that sufficient dielectric and shape parameters are available so that electrical tuning of beamformer parameters is possible. These structures are designed for a 1x3 microstrip patch antenna to demonstrate the formation of three simultaneous low overlapping beams. The effects on bandwidth are negligible upto 4.4%, and scanning angle of 180° has been achieved by using vertically oriented dielectric wedges. 6 dB gain enhancement and the capability to scale to larger 2D arrays have also been demonstrated. Full wave simulation results in Ansys HFSS are provided to demonstrate the proposed techniques, and validation is done in CST MWS.
In this paper, the effect of flux modulation pole (FMP) number on the performance of a spoke array fault tolerant permanent magnet vernier rim driven machine (SA-FTPMV-RDM) is studied. Firstly, a hybrid stator is adopted in this machine in which armature teeth and isolation teeth are arranged alternatively, and the winding type is single-layer fractional slot concentrated winding (SL-FSCW). Spoke array magnet is employed in the rotor of the machine to achieve flux focusing effect. Then the parameter scanning method is used to optimize the FMP pitch ratio, isolation tooth width ratio, FMP height, and permanent magnet thickness under different numbers of FMPs. It is concluded that there is an optimal FMP number for 12 slots SA-FTPMV-RDM to maximize the torque. Finally, the electromagnetic performances of the optimized machines with different number of FMP are compared by using the finite element analysis (FEA). The results show that the machine with the optimal number of FMPs has the highest torque density and efficiency, strong fault tolerance, but relatively large torque ripple.
In this paper, a novel high-sensitive mid-infrared photonic crystal-based slotted-waveguide coupled-cavity sensor to behave as a refractive index sensing device is proposed at mid-infrared wavelength of 3.9 µm. We determine the sensitivity of our sensor by detecting the shift in the resonance wavelength as a function of the refractive index variations in the region around the cavity. Comparison between mid-infrared photonic crystal-based slotted-waveguide coupled-cavity with mid-infrared photonic crystal-based slotted-waveguide shows a higher sensitivity to refractive index changes. The sensitivity can be improved from 938 nm/per refractive index unit (RIU) to 1161 nm/RIU within the range of n = 1 - 1.05 with an increment of 0.01 RIU in the wavelength range of 3.3651 µm to 4.1198 µm by creating a microcavity within the proposed structure, calculated quality factor (Q-factor) of 1.0821 x 107 giving a sensor figure of merit (FOM) up to 2.917 x 106, and a low detection limit of 3.9 × 10-6 RIU. Furthermore, an overall sensitivity is calculated to be around S = 1343.2 nm/RIU for the case of higher refractive indices of analytes within the range of n = 1 - 1.2 with an increment of 0.05 RIU. The described work and the achieved results by performing 2D-finite-difference time-domain (2D-FDTD) simulations confirm the capability to realize a commercially viable miniaturized and highly sensitive mid-infrared photonic crystal based slotted-waveguide coupled cavity sensor.
The tremendous proliferation of mobile smartphone handsets and their usage worldwide makes human life comfortable, while the radiation hazards associated with them are alarming, especially among children. There is a necessity to minimize the Electro Magnetic Field (EMF) radiation levels. For the evaluation of Radio Frequency (RF) radiation from the mobile phone, one of the dosimetric parameters used is the Specific Absorption Rate (SAR). The RF radiation can be mitigated by incorporating a barrier or a shield of suitable material in the mobile handset design. In the proposed work, the analysis of SAR evaluation absorbed by the human head is determined with the performance of the shielding material called Shielding Effectiveness (SE) using Transmission Line Method (TLM) mathematically. The proposed shielding materials are composed of flexible and transparent thin films. Flexible and transparent thin shielding materials are advantageous over the other shielding materials in reduced size, less weight, non-corrosiveness, and easy processing. These materials include highly conductive Silver film, Silver Nanowire(AgNW) doped with PDDA (poly(diallyldimethyl-ammonium chloride)) polymer single shields, and a laminated shield comprising AgNW/PDDA with PEDOT:PSS (poly(3,4-ethylenedioxythiophene)poly-styrene sulfonate) polymer as lamination. The SARs of planar multi-layered human head models for different ages are estimated at various mobile frequencies with these shields. Under four-layered head models at 6 GHz, adult and child heads absorb 0.0006 W/Kg and 0.000024 W/Kg of RF radiation using pristine Silver film as a single shield. Using a single shield of Ag nanowire and PDDA, the adult and child heads absorb SARs of 0.00058 W/Kg and 0.000023 W/Kg, respectively. With the laminated shield of AgNW/PDDA and PEDOT:PSS as coating material, the same models are exposed to minimal amounts of 0.00054 W/Kg and 0.000012 W/Kg of SAR. At 6 GHz frequency, under seven-layered head models, an adult and a child's head absorb 0.000047 W/Kg and 0.000002 W/Kg of power, respectively, using Ag film. With AgNW/PDDA shield, the adult and child heads absorb a SAR of 0.000046 W/Kg and 0.0000019 W/Kg, respectively. The SARs of 0.000043 W/Kg and a negligible value of 0.0000018 W/Kg are absorbed by adult and child heads individually with the help of AgNW/PDDA/PEDOT:PSS laminated shield. The results exhibit a significant amount of reduction in Specific Absorption Rate with transparent shielding materials compared to SAR absorbed by the head without any shield. This maximum RF exposure rate reduction from mobile phones with the Ag Nanowire/PDDA/PEDOT:PSS laminated shield is achieved for a seven-layered child head model.
In this paper, a coupled-line based dual-band branch-line coupler with port-extensions is presented. The configuration of the coupler consists of a single coupled-lines section, two transmission lines, and an easy to analyze L-section impedance matching network at all four ports of the coupler. A detailed theoretical analysis is carried out to obtain the closed-form design equations to determine the design parameters of the coupling structure. It is observed that the proposed dual-band coupler can support wide band-ratio and arbitrary power division. To validate the proposed design concept, a prototype working at 0.9 GHz and 1.8 GHz is fabricated on a 60 mil Rogers 4003C substrate exhibiting excellent match between the simulated and measured results.
This paper proposes an absorption-transmission-absorption (A-T-A) type frequency-selective rasorber (FSR) with high selectivity that is loaded above a polarization conversion structure (PCS) and applied to a circular polarization (CP) slot antenna array for ultra-wideband radar cross section (RCS) reduction. Outside the operational frequency band (out-of-band) of the antenna, the energy of the incident electromagnetic (EM) wave is directly absorbed by the FSR, whereas from within the operational frequency band (in-band) of the antenna, the incident EM wave penetrates the FSR and irradiates it on the PCS placed on the lower layer of the FSR structure, which meets the phase cancellation condition and is diffused at the same time, thereby realizing the in-band RCS reduction. Due to the lower insertion loss in the passband, higher quality factor (Q value) in the transmission band, and wider absorption band, the proposed FSR can minimize the gain loss (only 0.2 dB) of the CP slot antenna array and widen the RCS reduction bandwidth to 135.5% (5-26 GHz). In addition, due to the central symmetry of the FSR and PCS structures, the CP slot antenna array has monostatic RCS reduction performance for both horizontally polarized (HP) and vertically polarized (VP) incoming waves.
Assis predicted that based on Weber's electrodynamics, an alternative direct-action model formulated before Maxwell, a charge accelerating inside a sphere at constant electric potential, should have a measureable effective mass. Although initially some experiments appeared in the literature that indeed claimed such an effect, all recent studies found no evidence. All experiments so far used either discharges or electrons with non-constant accelerations that could mask the existence of Assis's prediction. We performed an experiment using a Perrin tube, which produces a beam of electrons with a constant velocity that can be deflected by Helmholtz coils to hit a Faraday cup. The tube assembly was put inside a spherical shell, which could be charged up to 20 kV. Any effective mass of the electrons would have changed their position on the Faraday cup. We found no variation of the electron position within our experimental accuracy, which rules out Assis's effect by two orders of magnitude. This confirms Maxwell's theory and the fact that electrostatic potential energy cannot be localized to individual charges.