In this article, design and analysis of a modified circular slot antenna is discussed. The proposed antenna design is attractive because of two important reasons: (i) modified circular slot creates dual operating bands; (ii) stable radiation characteristics over the operating frequency bands. The complete analysis of proposed radiator has been done on Ansys HFSS simulation software. For verifying the simulated outcomes, a prototype of antenna structure is fabricated and tested. Measured results show that the proposed antenna operates over two frequency bands i.e., 2.88-3.92 GHz and 5.26-6.28 GHz with the fractional bandwidths of 31% and 17% respectively. Experimentally measured average gain of the proposed radiator is 3 dBi and 6 dBi in lower and upper frequency bands, respectively. All these features of the proposed antenna make it appropriate for WiMAX (3.5 GHz) and WLAN (5.8 GHz) applications.
In this paper dual segment half Cylindrical Dielectric Resonator Antennas (DS h-CDRA), deploying homogenous elements, are designed and analyzed for wide-band applications. At first a single element is analyzed followed by two element DS h-CDRA. Further, Radar Cross Section (RCS) analysis is performed for different angles and frequencies. The proposed antennas are excited from the center of the ground plane using a coaxial probe feed, which results in TM01δ as a mode of excitation in cylindrical DRA. The input impedance and radiation characteristics are determined and compared with measured results, which shows good agreement. The proposed DS h-CDRA provides measured wide bandwidth (≈ 98%) from 5.0 GHz to 11.5 GHz with gain of 4.85 dBi, and it is found constant throughout the operational band (with omnidirectional radiation pattern). The designed antennas performance has also been compared with two element h-CDRA and found even better for the same volume and effective radiation area. The RCS analysis has been performed for monostatic and bistatic mode at different frequencies and angles. The proposed antenna has been found suitable for 5.0 GHz WLAN and WiMAX wireless application.
By combining the theory of mechanical flux-adjusting with the advantages of an interior permanent magnet synchronous machine (PMSM), a new type of auto-rotary PMs mechanical flux-varying PM machine (ARPMMFVPMM) is creatively proposed in this paper. The operation principle and mechanical flux-adjusting mechanism were deeply investigated. The relationship between deformation of spring and auto-rotary angle of gear against speed was obtained by Automatic Dynamic Analysis of Mechanical System (ADAMS). Meanwhile, the electromagnetic characteristics of the machine were numerically analyzed by Finite Element Analysis (FEA). The simulation results show that the auto-rotary of cylindrical PMs is realized by the centrifugal force of mechanical device, and the range of speed regulation is expanded by adjusting the magnetic field distribution.
The echo signal of wide-band monopulse radar spreads in multiple range cells. Thus, effective utilization of echo signal is an important issue for this kind of radar. Based on parameter estimation model, maximum likelihood method is proposed in this paper, which collects all the energy spreading in multiple range cells. Cramer-Rao low bound of angle estimation is deduced in theory. Simulation results demonstrate maximum likelihood method which performs better than both dominant scatter estimate method and weighted estimate method.
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.
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.
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.
Random arrays have been typically studied by considering real uniform excitations. This is suited for single-beam radiation patterns but does not allow for more sophisticated patterns. Indeed, only even patterns, with respect to the steering angle, can be achieved. To overcome this limitation, we recently proposed a new model whereby the excitation coefficients are not uniform and are determined by means of two random variable transformations. In this paper, we deal more extensively with the properties of this model, highlighting things that have not been pointed out previously. In order to get analytical results, we just consider symmetric random arrays. For such a case, we determine the design error, that is the cumulative distribution function of the supremum of the the difference between the actual and desired array factors. It is shown that general shaped beams can be actually achieved but at the cost of an increase of the design error as compared to the single-beam case. Numerical analysis validates the presented theory.
Efficiency of high frequency surface wave radars may be improved by inserting a metamaterial in the vicinity of transmitting antennas that will reinforce the propagation of surface waves. This paper deals with the first and second order derivations of the surface impedance boundary conditions (IBC) applied to model such a metamaterial, which is equivalent to a bounded ground with a low negative permittivity. The goal of this paper is to extend an approach previously based on the classical Leontovich IBC which is usually restrained to high permittivity grounds. As shown here, a simplification in the expression of the surface impedance is possible in the case of a planar and homogeneous surface. That allows to have a first order impedance boundary condition substituted for the required second order impedance boundary condition.
In this paper a compact antipodal Vivaldi antenna with dimensions of 40×85 mm2 for Ka band is presented. To enhance the antenna gain, epsilon near zero metamaterial (ENZ) unit cells are embedded at the same plane of the Vivaldi flare aperture. These ENZ unit cells have the advantage of confining the radiated fields with additional compact size. The obtained antenna exhibits an ultra-wide bandwidth from 23 GHz to 40 GHz with a reflection coefficient less than -10 dB. This is suitable for 5G applications at both 28 and 38 GHz. The antenna gain in this frequency band is found in the range from 14 to 17.2 dBi. The proposed antenna is designed by using CST-MW Studio, and the results are verified with experimental measurements.
For the first time, the concept of combinational use of subwavelength metasurfaces and plasma media is introduced in this paper for being utilized in practical radio frequency (RF) shielding applications. Using an equivalent circuit model, it is demonstrated that the simultaneous use of the lossy characteristic and special dispersion of plasma in low-frequency regime and the transmission zeros provided by spatially homogeneous metasurfaces in the upper frequency band results in superior shielding performances. The designed coating layer has an ultra-thin profile while exhibiting a super wide reject band ranging from 1 to 20 GHz (|S21|<-10 dB). A fair comparison is also performed to elucidate that the proposed plasma-metasurface composite (PMC) shield outperforms the previously reported RF shielding FSSs in both bandwidth and thickness. The numerical results show that while maintaining a low profile, the shielding bandwidth of the designed PMC can be set to surprisingly include all the UHF, L, S, C, X, Ku, and K bands. Moreover, the designed coating layer provides a stable and polarization-insensitive reject band for different incident wave angles up to 45°. These superior performances, as well as the shielding tunability enabled by plasma, confirm the promising capabilities of PMC structures for various applications.
In this paper, a new formulation is proposed to solve an inverse scattering problem for locating isolated inclusions within a homogeneous noise-free and noisy biaxial anisotropic permeable background using MUltiple SIgnal Classication (MUSIC) algorithm. Locations of the dielectric, permeable, lossless and lossy electromagnetic or both dielectric and permeable inclusions with arbitrary ellipsoidal shapes in a noise-free or noisy background can be restored. The numerical study of different inclusions is illustrated, and accuracy of the method is investigated. The proposed formulation is also investigated for extended inclusions in both noise-free and noisy backgrounds.
To improve the power transfer efficiency in a magnetically-coupled resonant wireless power transfer (MCR-WPT) system, an efficient particle swarm optimization (PSO) algorithm based on the change of particle swarm scale is proposed. The transfer efficiency and frequency are used as the fitness function and particle position, respectively. Therefore, the optimal frequency can be obtained by adjusting the position of particle. Five types of optimizing process are presented and compared with the traditional PSO algorithm. It is found that the proposed method has faster convergence speed than the traditional PSO algorithm. Additionally, the proposed five types of optimizing process with different regulation parameters are investigated. The results indicate that Type 2 with n=3 is the best alternative in finding the optimal frequency with the fastest speed of convergence. Experimental prototypes have been set up for validation.
In this paper, a novel miniaturized circularly polarized (CP) antenna is proposed for use in B3 band of Compass Navigation Satellite System (CNSS). The primary radiator is a hexagon patch with four bending strips. A shorting pin is loaded with each strip to miniaturize the dimension of the proposed antenna, which achieves a small electrical size of 0.11λ×0.11λ×0.068λ (λ being the wave-length in free space at 1.268 GHz). In order to improve the bandwidth, Y-shaped coupled patches and bending-strips, which act as reactive loading are coupled to an octagon patch. Four coupled bending-stubs with same turning directions of bending-strips, are sequentially placed at the edge of the octagon patch to enhance CP performance. Finally, a prototype of the antenna is implemented and measured. The experimental results reveal that the proposed antenna achieves impedance bandwidth (IBW) of 19.6% (1.175-1.430 GHz) for |S11|≤-10 dB and 3-dB axial-ratio bandwidths (ARBW) of 27.5% (1.000-1.320 GHz). The radiation efficiency is more than 75%, and the gain keeps above 1.98 dBic over the B3 band. Thus, the proposed antenna can be a good candidate for the applications of CNSS.
The aim of this work is to study the parameter estimation of a nonlinear medium in terms of scattered electromagnetic fields.The surface parameters are defined in terms of linear and nonlinear components of susceptibility and permeability. A set of Maxwell's equations are derived for an inhomogeneous medium using Green's function and the scattered Electromagnetic fields solving integrodifferential equations. Mathematical formulas are simplified using wavelet based method. Susceptibility and permeability is assumed as a function of wavelet basis. For parameter estimation, least square method and inner product methods are used with wavelets as a basis function, which gives solutions for nonlinear integrodifferential equation. Both time and spatial domain analysis is done using wavelets, and parameter coefficients are obtained. It is found that in both the parameter estimation methods, least square estimation gives better results. At the end of the paper statistical analysis of the scattered signals is included by calculating the mean and covariance of the signals.
This paper presents a miniaturized Wilkinson power divider (WPD) with higher order harmonics suppression. The proposed power divider is designed for global system for mobile communication (GSM) application. The quarter wavelength lines of the conventional WPD are replaced by stub loaded transmission line in order to miniaturize the circuit size. A solution, operating at 1.8 GHz center frequency, has shown that the 2nd and 3rd order harmonics are well suppressed by a level < -15 dB. Further, two differently shaped defected ground structures (DGS) are embedded with the design to suppress the higher order harmonics. Therefore, overall 31% size reduction is achieved, and higher order harmonics are suppressed up to the 9th order (16 GHz) by a level < -15 dB compared to reference WPD. The return loss and isolation performance of the proposed WPD are < -15 dB and < -20 dB, respectively.
Due to the increase in the data rates for modern wireless communications and recent generation standards, the switched beam approach and multiple-input multiple-output (MIMO) direct conversion transceiver (MIMO-DCT) have become promising techniques to satisfy these requirements. The combining of switched beam and MIMO-DCT through the use of multiple antenna elements has been investigated to overcome the high complexity and high spatial directivity of the conventional system. In this paper, a low cost miniaturized beam-switching array antenna with a MIMO-DCT system has been proposed, designed and analysed. The entire proposed system structure has two design stages. The first is the design of MIMO-DCT via the integration of microstrip antenna element, hybrid coupler, Wilkinson power divider and single-pole double-throw (SPDT) transmitter/receiver (T/R) switch. The second has the switched beam array antenna design using a Butler matrix feeding network and four distributed subarrays (DSs) of the MIMO-DCT. The entire proposed design structure components have been optimized using a commercial software to evaluate each component and meet the desired performance. The final proposed two-stage design has been fabricated, integrated, and the radiation characteristics have been demonstrated, using the Agilent FieldFox network analyser, to meet the requirements for LTE and wireless communication applications.
The purpose of this paper is to examine whether a generalised range-based sliding window detector provides any improved detection performance relative to a single order statistic based counterpart. This is for non-coherent target detection in an X-band maritime surveillance radar environment, and as such the intensity clutter is modelled by a Pareto distribution. It will be demonstrated mathematically that a single order statistic detector is in fact sucient. Some numerical examples are also provided to clarify the theoretical results.