A planar, handheld device size compatible, multiple-input multiple-output (MIMO) antenna design is proposed. The antenna system has five antennas which cover multiple wireless bands. One pair of elements covers the frequencies below 1 GHz (559 MHz to 828 MHz) for Long term evolution (LTE) and Cognitive radio (CR) applications and frequency bands 1.68 GHz to 1.77 GHz, 2.48 GHz to 2.63 GHz, 3.3 GHz to 3.4 GHz, and 5.79 GHz to 6 GHz for Internet of Things (IoT). The other pair is a modified truncated tetrahedron wideband antenna which covers multiple bands like 854 MHz to 958 MHz, 1.38 GHz to 1.56 GHz, 1.75 GHz to 1.87 GHz, 2.08 GHz to 2.49 GHz, 3.29 GHz to 3.47 GHz and 4.09 GHz to 6 GHz including the triple radio frequency identification (RFID) bands. The antenna is designed and simulated using CST microwave studio simulator and antenna prototype is fabricated to obtain the experimental results.
A new unterminating method for coaxial to waveguide transitions is presented. The coaxial to waveguide transitions are modelled and the ABCD matrices of the transitions are obtained. The measured scattering parameters for the thru and short-circuit calibration standards match well the simulated scattering parameters computed from the ABCD matrices. To complete the validation of the proposed unterminating method, this method is applied to the measurement of complex relative permittivity for three different dielectric materials, by using the Nicolson-Ross-Weir (NRW) transmission/reflection method. The dielectric samples are inserted one by one into a waveguide section, which is connected between two coaxial to waveguide transitions. The two transitions are de-embedded from the measured scattering parameters of the embedded waveguide section, by using the method proposed in this paper. The values obtained for the complex relative permittivity are in good agreement with those reported by other authors, for all three dielectric materials. The results presented in this paper were obtained for a frequency band ranging from 25 to 40 GHz.
Raindrop sizes were measured in Douala, Cameroon (4˚03N, 9˚42'E) using a Parsivel disdrometer. The data obtained are used for the analysis of the drop size distribution (DSD) and specific rain attenuation modeling in the 5-150 GHz frequency range. The Lognormal and gamma distribution models are employed using the method of moments estimation, considering the third, fourth, and sixth-order moments. The parameter fits for the two DSD models proposed here for different values of rain rates are investigated. The specific rainfall attenuation using the Douala DSD models is compared to the ITU-R models in vertical and horizontal polarisation and models for some countries with different climates such as semi-arid, tropical, and subtropical ones in Africa. The comparison with the ITU-R model shows significant differences occurring at high frequency with both high and low rainfall rates. The comparison with other regions of Africa also shows that Douala is characterized by equatorial climate, and Durban characterized by subtropical climate shows similar rainfall attenuation characteristics at operating frequency range 10 ≤ f ≤ 150 GHz, especially at a lower rain rate. At a higher rain rate, specific rain attenuation at Douala is always higher than in other African locations. The proposed models are very important for the determination of rainfall attenuation for terrestrial and satellite systems.
In this paper, a novel wideband gyrator based on a ferrite coupled line design approach and realized in coplanar waveguide configuration is presented. The ferrite coupled lines are proved to demonstrate typical unique properties. The design of the optimum coupled lines has shown an almost 1 dB/3 dB insertion loss for even/odd modes excitation, respectively. Also, for single excitation, the power is divided at output ports with insertion loss almost equal to 3 dB and 5 dB, good matching and isolation between output ports (less than -15 dB). The bandwidth of the designed coupler is proved over the bandwidth of 7 GHz-11 GHz. As an application, a novel gyrator is introduced and covers the same coupler bandwidth. The performance of the gyrator is optimized using full-wave simulations.
A hexagonal cavity backed antenna based on HMSIW is proposed to operate at 5.2 GHz and 5.8 GHz frequencies. The TM010 and TM110 modes of the hexagonal cavity resonator have been chosen to excite the structure. Afterwards, an HMSIW hexagonal cavity is formed by splitting conventional hexagonal cavity resonator along a magnetic wall. This enables a 50% reduction in size without affecting the antenna operating frequency. A rectangular slot is etched at the centre of the magnetic wall to curtail TM110 mode operating frequency. The dimensions of the slot are optimized to adapt TM110 resonant frequency to the desired frequency. In free space, the resulting antenna accomplished a peak gain of 5.5 dB and 4.3 dB at centre frequencies of 5.2 GHz and 5.8 GHz respectively. In the vicinity of pork tissues, the antenna exhibits a peak gain of 4 dB at 5.8 GHz along with an efficiency of 87.2%.
In this paper, electromagnetic scattering from multi-impedance body of revolutions (BORs) is formulated using self-dual integral equations (SDIEs) and is solved numerically by the method of moments using BOR basis functions. Using the axial symmetry advantage of BORs, a 3D problem is converted to a 2D one, and a significant reduction in unknowns is obtained. This in turn leads to an increase in the speed of scattering problem solving. Numerical results show that monostatic and bistatic RCS calculation with the proposed method is about 85 and 18 times faster than the commercial software, respectively.
This article aims at discussing computational approach to design magnet-free nonreciprocal metamaterial. Detailed mathematical derivation on Floquet mode analysis is presented for Faraday and Kerr rotation. Non-reciprocity in the designed metasurface is achieved in the presence of biased transistor loaded in the gap of circular ring resonator. Based on the derived mathematical model, co- and cross-polarized components have been extracted, which helps find Faraday and Kerr rotation and compare/contrast the reciprocal and nonreciprocal systems.
This paper presents an optimal duty cycle model predictive current control (ODC-MPCC) strategy based on the internal model observer (IMO) for permanent magnet synchronous motor (PMSM). First, in order to be able to control the current quickly and better, the partial derivative of the cost function with respect to the optimal duty cycle is directly used. On this basis, a five-segment algorithm is used to allocate the optimal duty cycle, and output voltage with arbitrary amplitude and direction. In addition, to reduce the current static error under parameter mismatch, the IMO is designed to estimate the system disturbance caused by parameters variation, which is used for feedforward compensation. Finally, experiments show that the proposed method can effectively reduce the current ripple and static error and improve the steady-state performance of the system.
A newly synthesis method of planar array antenna for wireless power transmission (WPT) is introduced in this paper. The whole array aperture is divided into several subarrays which can reduce the complexity of the feed network and the cost of the array antenna. Invasive Weed Optimization (IWO) algorithmis used to optimize the subarray division and the excitation amplitude of each subarray. The maximum beam collection efficiency (BCE) and maximum sidelobe level outside the receiving area (CSL) are considered as the evaluation index. The synthesis results show that the proposed method can obtain higher BCE and lower CSL.
Pattern synthesis usually involves determining the strengths of the current sources in a given array that yield a specified pattern. Demonstrating that this pattern can be produced by an actual array of physical elements is a step that is rarely included in the discussion. The purpose of this article is to examine how well a numerical model of these sources will match the desired pattern when mutual interactions between the array elements are taken into account. An investigation of this process is described here using NEC (the Numerical Electromagnetics Code), although any wire-antenna computer code could be used. Modeling wire antennas in codes like NEC typically involves specifying the input or exciting voltage of the antenna to find the induced current from which the far field can be obtained. The pattern-synthesis problem for a specified array geometry, by contrast, requires instead finding the exciting voltages that will induce the synthesized currents needed to produce the pattern of interest. The radiation pattern that results can then be compared with the desired pattern to determine how well the physical array performs. Several examples of this approach are included here to demonstrate the process.
The proposed work focuses on the mathematical interpretation of Electromagnetic Shielding Effectiveness (ESE) of age-dependent human Head Models (HMs) of seven tissues (Skin, Fat, Bone, Dura, Cerebrospinal fluid (CSF), Gray matter, and White Matter) with the impact of the mobile phone holding position on the RF radiation absorption by the human head. The ESE is first simulated and estimated using the Transmission Line Method approach: a. for only layered human Head Models (HMs) in the absence of mobile position with variation in Oblique Angle of Incidence (OAI) in Transverse Electric Polarization (TEP) and Transverse Magnetic Polarization (TMP), b. in the presence of mobile phone position and Polarization. c. by incorporating the Transparent Conductive Metal Mesh Polyethylene terephthalate (PET) film (Copper grid PET Film) as a shielding material in the presence and absence of Polarization and mobile phone holding positions. The Copper grid PET Film is composed of optical PET film laminated with Copper (Cu) and Nickel (Ni) Transparent Conductive Mesh Coatings (TCMCs) to form a transparent laminated mesh. The radiation absorption characteristic, Specific Absorption Rate (SAR), is evaluated numerically at four Sub-6 GHz frequencies from the obtained ESE data to draw collation at the least SAR absorbed by the age-dependent HMs, considering the water contents of tissues. Out of adult and child HMs, the child HM absorbed the higher RF SAR. However, with the transparent PET/Cu/Ni Laminated Mesh (LM), at 5.47 GHz, the SAR by the brain's white matter in child HM is highest in TEP with no shield considered is 10 W/kg. With transparent LM, the SAR obtained is 2.8e-12 W/kg in TEP in no mobile phone tilt condition at 89˚ OAI. With the user mobile tilt at 15˚ and 30˚, the SAR absorbed by the brain WM is 2.62e-12 W/kg and 2.1e-12 W/kg, respectively at 89˚. Hence, the SAR absorption is the least in any direction (azimuth or elevation) when the mobile phone is tilted to 30˚ in TE Polarization using the transparent PET/Cu/Ni laminated mesh. Therefore, the usage of transparent PET/Cu/Ni laminated mesh in TE Polarization saw the least SAR absorbed, whether the mobile phone is tilted either towards or away from the head when the mobile phone is moved to 15˚ or 30˚ tilted position.
Variations of modified E-shape microstrip antennas are proposed which realize wideband and circularly polarized responses inside the same impedance bandwidth but in separate frequency regions. The offset pair of slots in E-shape patch tunes the spacing in between TM02, TM10 and TM11 mode frequencies, and for the design in 900 MHz frequency band, it yields the total impedance bandwidth of 34.15%, in which circularly polarized bandwidth of 4.75% is present towards the higher frequency region. In comparison with the wideband E-shape or its circularly polarized variation, proposed configurations yield larger total impedance and same axial ratio bandwidth, but without overlapping bands for the wideband and circularly polarized regions. A compact half E-shape microstrip antenna is proposed, which yields total impedance bandwidth of 38.8%, with a circularly polarized bandwidth of 5.3%, present towards the higher frequency region. Further, the wideband E-shape variations are presented on a thinner substrate by using a bow-tie shape ground plane profile. Against the conventional ground plane design, it offers more than 12% increase in the bandwidth for 0.03λg reduction in the substrate thickness. Thus, as against the reported E-shape variations, proposed study presents a new design feature of traditional E-shape patch that provides separate regions for the wideband and circularly polarized responses, occupying the same impedance bandwidth.
A compact triple band monopole antenna with a simple modified C-shape structure for vehicle-to-everything (V2X) application is presented. The proposed multiband vehicle antenna with three C-shaped round stubs structure satisfies the worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN), and wireless access in vehicular environment (WAVE) bands. The three resonant frequencies are implemented with three C-shaped round stubs, and they are simply controlled by adjusting the round stub length without influence each other. The presented antenna demonstrated good impedance bandwidth and nearly omnidirectional radiation patterns over the whole operating bands. The field communication tests by connecting the vehicular communication module were also performed and verified in the view of automotive vehicle antenna application.
This work studies the correlation between 14-elements of a sub-6 GHz MIMO antenna for mobile terminal, operating in the 3.10 to 3.85 GHz frequency band. Envelope correlation coefficient (ECC) was used to assess the relationship between MIMO antenna elements. A total of 91 ECC values were considered at every frequency point for the 14-element antenna, which was performed under two propagation scenarios: (i) a uniform environment, and (ii) a Gaussian environment. For the latter, three angular spreads (AS) of 20˚, 30˚, and 40˚ and incident angle of every 10˚ in both elevation and azimuth coordinates are considered. The resulting ECC in the uniform environment is below 0.15 over the entire operating frequency band, indicating that the 14 elements are minimally correlated. However, in a Gaussian environment, the ECC is evaluated at 3.25 GHz. For the AS values of 20˚, 30˚, and 40˚. The average number of ECC values below the 0.3 threshold is 48, 67, and 81 out of 91 total ECC values, respectively. Finally, a relation is derived between the number of ECC values below 0.3 and the lowly-correlated number of antenna elements. It is seen that at a wider angular spread of 40˚, the number of equivalent lowly-correlated elements is 12 with 87% from all considered incident wave directions.
This paper investigates the design method, characterization, and innovative uncertainty analysis of bandpass (BP) type negative group delay (NGD) passive cell. The lumped passive topology under study consists of a resistor and a passive RLC-series network. The voltage transfer function (VTF) based circuit theory introducing the BP NGD specification analytical expressions is established in function of the R, L and C lumped component parameters. The BP NGD performance is evaluated by figure of merit (FOM) formula. To demonstrate the BP NGD function, the design method was applied to a proof-of-concept (POC) operating at 125-kHz RFID standard center frequency. The BP NGD theory is validated by both AC simulation and measurement of POC and discrete component-based circuit prototype. Experimental BP NGD results in good agreement with calculation and simulation are obtained with NGD value of -36.77 μs, 8% NGD bandwidth, and an attenuation lower than -9.6 dB. Innovative expressions of BP NGD parameter uncertainties are established versus the POC circuit parameters. The BP NGD specification variations are interpreted with respect to the influence of constituting component uncertainties via comparison between the established NGD uncertainty theory and co-simulated sensitivity analyses.
This paper presents the design of a Super Wideband (SWB) antenna with enhanced bandwidth for microwave application with a detailed parametric study of the methods used to enhance the bandwidth of the conventional antenna. The proposed SWB antenna has emerged from a traditional circular monopole antenna by experimenting with the inscribed fractal structure with a tapered feed line and partial ground plane with blended corners and achieved a super wideband frequency range from 2.31 GHz to 105.5 GHz with a fractional bandwidth 192.1%, Bandwidth Dimension Ratio (BDR) 2154.88. The antenna has a relatively small electrical dimension i.e. 0.33λ0x0.27λ0, where λ0 corresponds to the lower-end operating frequency and exhibits good gain and efficiency characteristics. In order to observe the signal correlation of the proposed antenna, the time domain analysis using similar antennas in face-to-face and side-to-side scenarios has been performed using the EM simulation tool CST-STUDIO. The simulated gain varies from 1.28 to 9.35 dBi. The proposed antenna can be used for S, C, X, Ka, Ku, V and W bands for microwave and millimetre wave applications. The simulated and measured results of the proposed antenna exhibit a good agreement.
An ultra-wideband (UWB) antenna with dual band notched characteristics verified by characteristic mode analysis (CMA) is presented. The intended UWB radiator is etched on a Rogers RT5880 substrate with a size of 29×35×0.764 mm3, operating over a spectrum of 2.66-14.86 GHz with a fractional bandwidth (FBW) of 139%. Dual notched bands at WiMAX (3.01-3.63 GHz) and WLAN (4.48-5.85 GHz) are achieved by embedding L-shaped stubs in the notched rectangular patch. In addition, the two notched bands of the reported antenna are verified by using characteristic mode analysis (CMA) in terms of modal significance (MS) and characteristic angle (CA). The reported antenna's simulated and tested results are well matched to obtain S11, VSWR, stable radiation patterns, a stable peak gain of 2.65 to 3.6 dBi and the maximum radiation efficiency of 97.86% in frequency domain, which makes the intended radiator suitable for portable UWB applications.
A flux weakening (FW) control method of leading angle for a permanent magnet synchronous motor (PMSM) based on active disturbance rejection control (ADRC) is proposed to solve the problem of large fluctuation of speed, current, and torque in the control process. Firstly, according to the mathematical model of PMSM and its voltage and current constraints, the leading angle FW control algorithm is introduced. Then, according to the ADRC theory and the mathematical model of PMSM, the speed loop ADRC and current loop ADRC are constructed. The controller parameters are combined with the control bandwidth, and the parameter variation ranges are obtained by analyzing the stability of the control system. Finally, the proposed ADRC methods are combined with the leading angle FW control method to realize the ADRC leading angle FW control for PMSM, and the proposed method is verified on the experimental platform. The experimental results show that the proposed method has less speed, current, and torque fluctuations than the proportional integral (PI) controller method, which can effectively improve the motor control performance. At the same time, the controller parameters are combined with the bandwidth, which is convenient for practical engineering application.
This paper presents a comparative study that was done using genetic algorithm, improved particle swarm optimization and the hybrid technique genetical swarm optimizer approaches for the design of one-dimensional photonic crystal selective filters. The three evolutionary methods for synthesizing the geometrical parameters of a fiber Bragg grating structure from its layer thicknesses are proposed and demonstrated. The synthesis of the mono-band 1-D PhC selective filters is designed as a mono-objective problem, and these 1-D PhCs are composed of alternate Si and Air layers with thicknesses on the micron scale. The main contribution of this paper is formed by the solution to this kind of problems. According to the literature, this hybrid methodology genetical swarm optimizer has not been dealt with before, when 1-D PhCs selective filters are considered. Comparison of the GA, IPSO and GSO for the selected set of examples revealed an improvement of paramount importance in terms of error lowering and the number of iteration cycles diminution.
A quad-band (3.5, 5.8, 7.5 & 8.08 GHz), low profile, low Specific Absorption rate (SAR), and circularly polarized (3.5, 7.5, 8.08 GHz) wearable textile antenna (50x30x1 mm3) integrated with a triple-band zero reflection phase Artificial Magnetic Conductor (AMC) surface is presented. The designed standalone antenna exhibits low SAR with 10 mm separation for 0.5 W input power and radiation performance with a gain of >5 dB and Front to Back Ratio (FBR) (<10 dB) at all operating frequencies. The AMC unit-cell is synthesized using PDMS (Polydimethylsiloxane) with footprint of 20×20×1 mm3 to operating at 3.5, 7.5, and 8.08 GHz respectively with in-phase reflection. The designed 3×3 AMC reflector is integrated to improve the radiation performance of the designed antenna with gain to >7 dB, FBR to >10 dB, and withstanding low SAR at increased input power compatibility at separation (d=3 mm) from the body surface. The designed AMC transforms the radiation pattern from omnidirectional to directional with improved FBR, reduced back radiation with low SAR (<0.504 W/kg). The proposed AMC integrated antenna also providing mechanical feasibility in terms of handling the frequency detuning due to bending and the human-body loading feature makes it suitable for wireless body area networks (WBAN) applications.