This paper presents the design and analysis of a wideband circularly polarized resonant cavity antenna (RCA). The antenna structure consists of dual-layer Jerusalem cross type partially reflective surface (PRS) above a two-port wideband circularly polarized patch antenna. The PRS enhances the gain of the feeding patch antenna over wide range of frequencies. The structure provides left hand as well as right hand circular polarizations. Parametric analysis of the structure is also presented. The measured 10 dB return loss bandwidth and 3 dB axial ratio bandwidth of the RCA are 25 % (8.24-10.63 GHz) and 28.8% (8.3 GHz-11.1 GHz), respectively. Isolation more than 10 dB is obtained for the frequency range 9.15-10.61 GHz. Measured results show peak realized gain of 9 dBi in the operating band.
Tropical cyclone (TC) is part of the most serious natural disasters. Western Pacific is the region with the highest frequency of tropical cyclones (TCs). By simulating and correcting the brightness temperatures (TBs) of the microwave humidity and temperature sounder (MWHTS) onboard the Fengyun-3C (FY-3C) satellite, a method is proposed to observe the TCs in the Western Pacific. The Weather Research and Forecasting Model (WRF) and the fast Radiative Transfer model for TOVS (RTTOV) are adopted in our method. Then, simulated TBs are linearly corrected based on the field-of-views (FOVs), channels and latitude bands. After that, the biases of all channels are within 2 K and close to zero, and the RMSEs are less than 10-K except Channels 10 and 15. Therefore, this WRF/RTTOV method can be implemented in other TCs in the Western Pacific region. In addition, a precipitation detection algorithm is proposed and used to detect precipitation in the TC area. Compared with the FY-3C MWHTS and Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) precipitation products, the results indicate that our precipitation detection algorithm has reached better indicators. The potential application can lay a foundation for precipitation rate retrieval and further research.
The electromagnetic wave diffraction from the modified cone formed by a circular truncated cone whose aperture is closed by a spherical cap is considered. The problem is reduced to the solution of the mixed boundary value problem for the Helmholtz equation. The axially symmetric version of the problem, where the cone is excited by a radial electric dipole (E-polarization wave diffraction problem), is analyzed. A new approach to the solution is proposed. The solution includes the application of the Kontorovich-Lebedev integral transformation, the nonstandard procedure for derivation of the Wiener-Hopf equation and its reduction to the set of linear algebraic equations of the second kind. Their solution ensures the fulfillment of all the necessary conditions including the edge condition. The approximate equation for the sharp truncated cone terminated by the spherical cap is analyzed. The low frequency approximation as well as the transition to the plane which incorporates the hemispheric cavity is analysed. The numerical calculation results are presented.
This paper proposes a morphological ultra-wideband (UWB)-radar-based respiratory signal model. According to the detection theory, it is crucial to set up an appropriate model to fulfil the detection purpose. Previous models pay less attention on the time dimension of the respiratory signal, but the frequency domain cannot precisely describe it because of its non-linearity and non-stationarity. This model uses a morphological operator to dilate or erode the base wavelet, and the length and value of the digit in the structure element serve as the parameters in this morphological model. The result of the experiment carried out on 10 human targets with impulse radio ultra-wideband (IR-UWB) radar proves the efficiency of this model. As the UWB radar sensed human respiratory signal is nonlinear and non-stationary, the parameters in the model can be regarded as a measure of non-linearity and non-stationarity. An experiment is carried out with the simulated respiratory signal generated with the proposed model. The result shows that the detection algorithm based on Ensemble Empirical Mode Decomposition (EEMD) method has a better performance than that based on Adaptive Line Enhancer (ALE) and with the value of the digit in the structure element increases, the performance of the ALE method declines, while the EEMD method stays in a good performance, which indicates that the EEMD method has a good potential to deal with the nonlinear and non-stationary respiratory signal.
Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, low efficiency resulting from resonant frequency drift is a main obstructing factor for promoting this technology. In this paper, a novel method of coordinating the operating frequency and load resistor is proposed to prevent frequency drift. The system efficiency and input impedance are obtained by solving the system equivalent equations. In addition, the new resonant frequencies can be obtained by solving the input impedance equations. Moreover, the process of the coordination method is illustrated. When resonant frequency drift occurs, the system can now operate at the resonant state, and the efficiency can be improved by using the proposed method. The WPT system via magnetic resonance coupling is designed. Simulated and experimental results validating the proposed method are given.
Improvement of properties of polymeric materials through blending is a way to obtain products with highly adapted performance for specific applications. The present work reports the design and preparation of binary blend films of poly (ethylene-co-methacrylic acid) neutralized using sodium salt (EMAANa) and nano polyaniline doped with hydrochloric acid (nano PANI-HCl) or toluene sulfonic acid (nano PANI-TSA) with the aim of achieving improved thermal stability, DC conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of EMAANa. The binary blends were prepared by solution blending using a solvent mixture of toluene/1-butanol (90:10) at 65 °C. The hybrid materials were characterized and evaluated by FTIR, UV-Vis spectroscopy, XRD spectroscopy and thermogravimetric analysis (TGA). The electrical conductivity of the PANI and PANI/EMAANa blends was measured by four-probe method. The EMI shielding effectiveness was studied using a wave-guide coupled to an Agilent Synthesized Sweeper 8375A and a Hewlett-Packard spectrum analyzer 7000 in the X band frequency range (8-12 GHz). FTIR indicates a π-π and hydrogen bonding interaction between PANI and EMAANa, enabling the PANI to be adsorbed in the ionomer. The TGA of the blends show similar weight loss pattern with nano PANI-TSA-EMAANa exhibiting slightly lower weight loss below the decomposition temperature. The TGA results show that thermal stability of the blends is better compared to pure EMAANa. The results of measurements of electrical conductivity and EMI SE demonstrates that PANI was successfully blended into the EMAANa substrate.
With combining the advantages of the hybrid excited synchronous machine and claw pole machine, hybrid excitation claw-pole synchronous machine (HECPSM) exhibits merits of controllable flux operation and independent flux paths. One novel wide range adaptive speed region control strategy is proposed in this paper, based on the analysis of the field control capability of HECPSM and the space vector control. Independent control methods of maximum torque per ampere (MTPA), space vector and minimum copper loss (MCL) control were employed for the proposed machine during three different speed regions in order to obtain satisfied performance in the whole speed range. The correctness and effectiveness of the proposed adaptive speed region control strategy and drive system design were verified by simulation and experimental results, which demonstrated that the proposed control strategy maximized the range of speed regulation while exhibiting the high efficiency.
With the increasing number of mobile phone users, new services and mobile applications, the proliferation of radio antennas has raised concerns about human exposure to electromagnetic waves. This is now a challenging topic to many stakeholders such as local authorities, mobile phone operators, citizen and consumer groups. The study of the spatial and temporal variability of the actual downlink exposure is a very important requirement to find an accurate exposure assessment. In this paper, a concept of exposure areas linked to specific variations of the electric field is introduced. Then a measurement campaign of the temporal variability of the electric field in urban environment is presented, considering different technologies and mobile operators in the previously defined exposure areas. This study allowed to determine updated daytime and nighttime exposure profiles. A second result yielded the averaging duration needed to reach a stable evaluation of the electric field exposure levels, inside each exposure area and according to each technology.
The dispersion characteristics of woodpile three-dimensional (3D) function photonic crystals (PCs) composed of plasma and function dielectric elements are theoretically investigated by a modified plane wave expansion method, respectively, and the formulas to obtain the dispersion diagrams are given. Only two cases are considered, which are the presence and absence of the external magnetic field. The external magnetic field is vertical to the wave vector, which means that only the magneto-optic Voiget effect is considered. For the proposed PCs, the function dielectric square columns are inserted into the plasma background with face-centered-tetragonal symmetry according to the woodpile lattices. The relationships between the parameters of such PCs and the features of the photonic band gaps (PBGs) for the extraordinary mode and electromagnetic wave are studied under two different cases. The calculated results show that the dispersion characteristics of the proposed PCs can be tailored by adjusting those parameters. If the extrinsic magnetic field does not exist, larger PBG can be found in the present PCs than 3D dielectric-air PCs, 3D function dielectric PCs and 3D plasma-dielectric PCs with the same lattices. If there is an external magnetic field, the narrower PBG for the extraordinary mode can be obtained than the 3D function dielectric PCs and 3D plasma-dielectric PCs with the same lattices. The computed results also show us a approach to realize the reconfigurable devices based on the PCs.
The analytical solution of the Biot-Savart equation can be complex in some cases, and its numerical integration is commonly more appropriate. In this paper, it is integrated using the Gauss-Legendre method through 1, 2 and 3-D domains, using first and second-order (curvilinear) isoparametric mapping. In order to verify the gain of accuracy with second-order elements, the results obtained are compared with analytical cases and with the Finite Element Method. Then this paper presents an adaptive method which pro ts from the accuracy along those elements with higher energy values, by reducing the number of Gauss points along the elements with lower energy. This approach reduces the total number of Gauss points evaluated during the integration process and provides a possibility to choose an interesting trade-off between simulation time and accuracy.
This paper proposes to use an Aperiodic Fourier Modal Method (A-FMM) to model an outgoing photonic jet from a dielectric loaded waveguide ended by a tip with a speci c shape. The proposed method has several advantages. First of all, the method is fast, which allows to manage optimization investigations. Secondly, the study excitation (and more particularly the impact of plan wave excitation) can be examined precisely. Using our modelling technique, we show, in comparison with an actual optimized elliptical tip, that an optimized rectangular tip improves energy concentration by 8% and reduces the calculation time by a factor of 10. Furthermore, A-FMM allows to show that plane wave excitation modifies the spatial distribution of the jet, especially in the case of TE polarization. This can explain the differences observed, in previous works, where only fundamental mode excitation was used in the modelling. To validate these general results, prototypes have been realized, and measurements in the microwave regime have been compared favorably with simulation results.
An approach to the design and the realization of a broadband multilayer anti-reflection (AR) coating with high transmission is proposed in this study. A binominal multi-section transformer is employed to efficiently determine the thickness and the refractive index of each matching layer, while those layers can be further realized by doping different fractions of subwavelength-size silicon powders (for relatively-high-index layers) or air pores (for relatively-low-index layers) into the low-loss HDPE polymer host. Based on this scheme, we design a ten-layer AR coating for widely used silicon wafer. The designed AR coatings are double-sided integrated with a 375-μm-thick silicon wafer, which can enhance the overall THz transmission to higher than 95.00% from 0.250 THz to 0.919 THz (114.46% fractional bandwidth) for either TE-polarized or TM-polarized THz beam incident from an arbitrary angle below 50˚.
This paper proposes a cascaded multilevel converter to reduce the number of IGBT switches for the purpose of improving system stability and decreasing switching losses. This converter can eliminate second-order ripple caused by energy exchange between grid and batteries, and thus extend battery life. This cascaded connection between the equivalent buck/boost circuit and the half-bridge inverter is also able to reduce the number of switch tubes. A control strategy based on state of charge (SOC) closed-loop tracking is designed to implement the errorless follow-up control of average SOC values for electric vehicle batteries. The equivalent circuit under different working modes of the topology is analyzed, and the effectiveness of the control strategy is verified. Simulated and experimental results show that this converter can effectively achieve grid connection requirements and balance the battery units to meet practical needs.
In this paper, a novel low-cost, high gain dual-polarized antenna design with a suspended cylinder and a ground connected cylinder geometry is proposed. The design structure of the antenna is simple and fabricated with two cylinders, two shorting strips, and a circular ground plane. All these components are easily fabricated from a copper sheet of thickness 0.4 mm, and the antenna is fed by two coaxial probes at the orthogonal planes on the circumference of the cylinders. A prototype is designed, fabricated and measured. The measured results show that the prototype has -10 dB impedance bandwidth of 34.37% at port 1 & 34.21% at port 2. Broadside gain from port 1 is 10.2-10.4 dBi & port 2 is 10.25-10.52 dBi, which indicates that the antenna has flat gain over the impedance bandwidth, and isolation between the ports is more than 15 dB from 2.65-3.6 GHz and more than 20 dB from 2.75-3.55 GHz. The isolation of the proposed antenna is improved by shorting the suspended cylinder to the ground plane by two shorting strips. The resonance frequency and isolation peak are simultaneously tunable with varying the width of the shorting strips. The parameters of the antenna are optimized by using HFSS, and good agreement between the simulated and measured results is obtained. The proposed dual polarized antenna can be used for base station applications such as LTE (Long Term Evolution) and WiMAX (Worldwide Interoperability for Microwave Access).
In this paper, we present a hybrid system consisting of a novel design of a microstrip antenna that can be designed to resonate at various frequencies within the ultra-high frequency (UHF) band (e.g. 415 MHz, 905 MHz, and 1300 MHz), combined with a pair of high frequency (HF) coils (13.56 MHz). The system is designed to be fabricated on an FR4 substrate layer, and it provides a compact solution for simultaneous wireless power transfer (WPT) and multi-band wireless communication, to be utilized in implanted medical devices. The external antenna/coil combination (EX) will be located outside the body on the skin layer. The EX has 79.6 mm-diameter. The implanted hybrid combination (IM) has 31.5 mm diameter. The antenna is designed such that by varying the position of a shorting pin the resonance frequency can be switched among three frequencies; therefore, the same design can be used for various applications. The system was designed using numerical simulation tools, and then it was fabricated and measured. The design was optimized while the performance of the system was numerically simulated at various depths inside a layered body model. Furthermore, the insertion loss (S21) and transmission efficiency (η) for both antenna and coil pairs at different depths were studied through simulation and measurements. The system provides a good solution for the combination of power transfer and multi-band data communication.
Thermal effects limit the gain, quality, and stability of high power fiber lasers and amplifiers. In this paper, different values of heat conductive coefficients at the core, the first and second clad with the complete form of the heat transfer equation are considered. A quartic equation was proposed to determine the temperature at the fiber laser surface. Using the surface temperature value, the temperature can be determined at the longitudinal and radial position of the double clad fiber laser. The different definitions of heat sources which were previously presented in articles is used to describe the heat generation at a double clad high pump power fiber laser condition. The results were compared to each other, and the percentage of each factor in heat generation was calculated.
This paper describes the radio propagation measurement campaign in the sugarcane field representing a tall food grass characteristic which is one of the common types in outdoor agriculture environments. The measurement was conducted by using a channel sounder having a bandwidth of 45.6 MHz at 2.45 GHz with the aim at investigating the propagation channel characteristics which are useful in deploying of wireless sensor networks in the precision agriculture. By analogy to Ikegami model, the variation of path loss over the relative angles between the plant rows and the line-of-sight direction from the transmitter to the receiver is identified. Utilizing this knowledge, this work justifies the procedure of predicting the path loss at any point in the field by a few measurement efforts. Furthermore, the Rician K-factor and RMS delay spread are investigated in the vegetation depth shorter than 40 m. The result shows that the relationship between the Rician K-factor and its corresponding path loss value in each measurement point can be fitted with the log-linear line. This leads to the possibility of predicting K-factor at any points in the field. In addition, since the result of RMS delay spread is independent to the vegetation depth and the density of the plant, it is represented by the statistical model in which the Weibull distribution provides the best representation.
Ferrite toroids (or clamps) are widely used to reduce common-mode (CM) currents in power systems. The CM impedance of the ferrite depends on the frequency-dispersive permeability and permittivity of the ferrite, the geometry of the system, and the location of the ferrite in it. An analytical model was developed to predict the CM impedance of a wire harness above a return plane with a ferrite on it. The model is based on transmission line theory for a cable, a ferrite, and a return plane. The parameters of the model are calculated using a frequency-dependent quasistatic model for a ferrite toroid. This model accurately predicts the CM impedance of a mock harness within 3 dB up to 1 GHz. The proposed model is also applied to a real power system consisting of an inverter and a motor. Knowledge of the CM impedance of the system in the operating regime is critical to determining the impact of the ferrite on CM currents. The CM impedance is determined using the dual current clamp technique. The impact of the ferrite on the CM impedance and currents of the power inverter system was predicted within 3 dB, demonstrating the usefulness of the modelling approach for analysis of power systems.
Metasheets are ultra-thin sheets built from sub-wavelength resonators designed in order to achieve certain frequency-dependent transmission behaviour. A semi-analytical approach based on an equivalent circuit representation is proposed to calculate the microwave transmission through metasheets which consist of 2D periodic arrays of planar circular metal rings with and without substrate. The electromagnetic response of the metasheet can be controlled by changing the radius and periodicity of the circular rings. In the semi-analytical approach, the equations for impedances of the equivalent circuit are parameterized and fitted to match the values of transmission coefficients obtained by full-wave simulations at selected frequency points. Such an approach permits an optimization of the metasheet design with a very small number of full-wave numerical simulations. It is shown that the results of the semi-analytical approach match well with full-wave simulations and measurements within a reasonable range of radius and periodicity values.
A compact multiple input multiple output (MIMO) antenna with WLAN band-notch filtering function for portable wireless ultra-wideband (UWB) systems is proposed in this paper. The overall size of the antenna is 26 x 40 x 0.8 mm3, and it is fabricated on a low-cost FR4 substrate. The antenna comprises two identical planar monopole antenna elements, namely PM1 and PM2, which are fed by a 50-ohm coplanar waveguide. The PM1 and PM2 are positioned perpendicular to each other to minimize the mutual coupling between them. To further reduce the mutual coupling and to increase the impedance bandwidth, a long rectangular strip is protruded from the ground plane between the PM1 and PM2. To create the band-notch characteristics at WLAN band from 5 to 5.9 GHz, an inverted U-shaped slot is etched on the feed line. The simulated and measured results show that the proposed antenna achieves good impedance bandwidth (S11 ≤ -10 dB) from 2.2 to 11.4 GHz and mutual coupling (S21) of < -20 dB. The measured peak gain of 2.4 to 7.5 dBi and radiation efficiency above 90% are obtained except at notch band. The measured envelope correlation coefficient (ECC) of 0.008 in the whole operating band and omnidirectional radiation characteristics demonstrate that the proposed MIMO antenna is a suitable candidate for portable UWB systems.
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