When an implantable medical device is in radio energy transmission, due to eddy current effect, the temperature of the device will rise, causing a safety risk. In order to study the distribution law of its temperature field, this paper adopts the analysis method of electromagnetic-thermal-fluid-solid multi-physics coupling, and establishes a two-dimensional transient equivalent model of an implantable medical device radio energy transmission system, adopting the analysis method of the electromagnetic-thermal-fluid-solid multi-field full coupling. Among these, electromagnetic heat is applied as the heat source, considering the influence of factors, such as heat conduction and convection. By means of simulated calculation, this paper acquired one-dimensional, two-dimensional and three-dimensional images, whose temperature and efficiency changed with frequency Moreover, their distribution laws are also obtained. In order to verify the correctness of the simulation, this paper conducts infrared temperature measurement experiments to prove the rationality of the analysis through comparing the simulation results. The research findings of this paper can provide a basis for the design of radio energy transmission system for the implantable medical device, improve the safety of implantable medical devices, and reduce the occurrence of medical accidents. Meanwhile, it has certain reference value to the clinical application of implantable medical devices.
An analytical approach for calculation of the dyadic Green's functions inside the rectangular cavity over a broad range of frequency is presented. Both vector potential and electric field dyadic Green's functions are considered. The method is based on the extraction of the Green's function at an imaginary wave number from itself to obtain a rapidly convergent eigenfunction expansion of the dyadic Green's function. The extracted term encompasses the singularity of the Green's function and are computed using spatial expansions. Results are illustrated for rectangular cavity up to 5 wavelengths in size with thousand of cavity modes obtained by the 6th order convergent expansion. It is shown that for an accurate and broadband simulation, the proposed method is many times faster than the Ewald method.
This paper presents a multi-band annular ring antenna that is obtained from a single-layer probe-fed substrate integrated waveguide based on a graphene material, with three top plan slits. In order to create a multi-bands antenna, we conduct simulation of the antenna structure based on CST/HFSS, so we use parametric tuning to adjust TM modes. Simulations show a good results between the two methods (finite element method and integral method) CST and HFSS Simulators. The bandwidths for three modes are 340 GHz in first mode, 346 GHz in the second mode, and 104 GHz in the third mode. The simulation gains at TM11, TM02, and TM12 are 8.2 dB, 8 dB, and 11 dB, respectively. The proposed antenna can be used in therahertz applications.
This paper demonstrates a three-port coaxial fed antenna system for wireless local area network (WLAN) access points, consisting of two dipoles and a patch, radiating at 5.2 GHz with impedance bandwidth of 150 MHz. The antennas are designed for pattern diversity in the end-fire and broadside orientation with an individual gain of 4.5 dBi, which is further enhanced to 6 dBi after integrating with unit-cell structures. The gain enhancement for individual antennas is achieved by strategically integrating transmission type and reflective type sub-wavelength structures for patch and dipoles respectively. The realized ground plane is shared among the three antennas. The measured results show that the return loss of the antennas is unaffected by the unit-cell loading and has an isolation of less than 26 dB throughout the band and across the ports for a port-to-port distance of 0.25λ.
This paper provides a sound wireless power transfer (WPT) recharging solution for on-road automated guided vehicle (AGV) system. In this solution, multiple transmitting coils serve as power transmitters (TXs), and a receiving coil in AGV serves as a power receiver (RX). The multiple TXs are along a straight track for dynamic charging to AGV. The circuit model of multiple-TX and single-RX WPT system is first constructed based on circuit theory (CT), and then current-optimized scheme based on Lagrangian multiplier method is proposed to tune the currents in multiple TXs to maximize the power delivered to the load (PDL). The equal current (EC Case) flowing through each TX is compared with the optimal current (OC Case). Through contrastive analysis, the OC Case shows its advantages in PDL. Finally, the theoretical analysis results are confirmed by the results of full-wave electromagnetic simulation.
In recent years, through-wall imaging (TWI) has gained much research interest because of urgent needs of civilian, security, and defense applications. TWI based on compressive sensing (CS) method can produce high resolution, assuming that the wall parameters are known in prior. However, it is difficult to know the exact wall parameters in actual scenarios. With unknown wall parameters, the dictionary matrix is not a fixed one. Therefore, CS theory cannot be directly applied in the TWI. This paper presents a parametric sparse recovery method for TWI with unknown wall parameters. The original reconstruction problem is reformulated into a joint optimization one which can be solved with an alternating minimization algorithm. Specifically, the proposed method performs the wall parameter estimation and sparse image reconstruction in an iterative procedure. With the estimated wall parameter which is or close to the true one, the high fidelity and high-resolution image is obtained. Experimental simulations show that the proposed method can obtain an autofocus image and improve the image quality.
Because of the current commutation and the double salient pole structure of bearingless switched reluctance motors (BSRMs), the torque and suspension force have large ripples when traditional current control methods are used. According to the special structure of the double stator BSRM (DSBSRM), the direct decoupling of torque and suspension force is realized. Therefore, the DSBSRM can be controlled separately as a conventional 12/8 SRM and a four-poles active magnetic bearing. In order to achieve the suppression of the torque ripple and improve the robustness of speed, a direct torque control (DTC) strategy using second order sliding mode (SOSM) speed controller is proposed. In order to achieve the suppression of the suspension force ripple and rotor displacement chattering, a direct suspension force control (DSFC) strategy is proposed as well. Then the SOSM-DT/DSFC model is established by simulink. The results of simulation show that the torque ripple, suspension force ripple and rotor radial displacements of DSBSRM can be reduced respectively. Moreover, the proposed control strategy has better robustness and dynamic performance than traditional control strategy.
In this paper, the implementation of convolution perfectly matched layer (CPML) with good absorbing property is proposed for the symplectic multi-resolution time-domain (SMRTD) method, and a side-wall vault-top tunnel model is established by using the equidistant equation. The radian of the tunnel can be selected in the range of 0-π/2 according to actual needs. The absorbing performances of perfect matched layer (PML) and CPML are compared in the proposed tunnel model. In addition, based on the straight tunnel model and curved tunnel model with different radians, the characteristic of field cross-section distribution of electromagnetic pulse (EMP) propagation excited by TE10 mode is studied.
In this paper, a sensor based on a meta-surface absorber loaded with microfluidics is proposed foridentification of edible oil species and provides a non-destructive, rapid and convenient technology for the measured samples. First, a narrow-band absorber with absorption frequency of 9.887 GHz and Q value of 147, which is implemented with four W-shaped meander line resonators, is designed by Finite Element Method. Its corresponding electromagnetic resonance mechanism is explored to reveal absorption characteristics, build its corresponding equivalent circuit model and guide the design of the palindromic microfluidic channel. The sensor shows a high sensitivity of 500 MHz/ε'r, and the corresponding sensing performance is experimentally validated by the fact that the distinguishableresonance absorption frequency shift is 461 MHz, 458 MHz, 449 MHz, 444 MHz and 436 MHz when rapeseed oil, corn oil, peanut oil, sesame oil, and olive oil are loaded into the microfluidic channel, respectively. The identificationis successfully achievedaccording to the resonance absorption frequency shift. Moreover, a good agreement between the simulated and measured results demonstrates that the proposed meta-surface-inspired sensor is a promising candidate to monitor and determine the quality of edible oil to some extent, and is relatively valuable to the modern agriculture and food industry.
This paper introduces an innovative circuit theory of analog voltage compressor (AVC) and decompressor (AVD). This electronic function can also be assumed as an analog voltage converter. Analytically, it acts as power function synthesizer topology designed with an analog nonlinear circuit. The AVC/AVD topologies are based on an operational amplifier associated with resistor and non-linear diode components. Given the positive parameter a>0, the main x-y characteristic of the AVC/AVD is formulated by y=xa for the input and output x and y, respectively. The synthesis formulas allowing to determine the AVC/AVD parameters in function of a are established. To validate the original AVC/AVD concept, static and dynamic simulations and experimentations with a proof-of-concept circuit using operational amplifier UA741 are carried out. As expected, well correlated x1/2-AVC and x2-AVD characteristics are realized with the static testing for the voltage range varied from 0 to 9-V and 0 to 3-V for AVC and AVD circuits, respectively. The simulation and experimentation of dynamic test results are in good agreement for the sine wave voltages with frequency varied from DC to 1-kHz. The simulated and experimental results confirm the relevance of the developed compressor/decompressor analog circuit. The AVC/AVD functions for instrumentation system applications can be potentially applied to the amplitude matching especially for digital systems.
The authors propose a new method based on spatial cumulants for estimating the parameters of multiple near-field and far-field sources. The Toeplitz property used in some studies is not applicable to fourth-order statisticsto separate sources components. Therefore, in this paper, a method is proposed to computeoutput cumulants of specified sensors in special arrangements, by which the components of the near-field and the far-field sources are effectively separated using differencing. The angle and range estimations, as well as the classification of the sources, are obtained based on the data from two spatial cumulant matrices. One of them contains the angle information of all sources, and the other only contains the information of the near-field sources. The parameters extraction algorithm is based on the ESPRIT technique; therefore, the proposed method does not require any spectral search. This leads to a significant reduction in computational complexity. Unlike some approaches, the proposed method does not suffer from array aperture loss. Also, the parameters pairing procedure is done automatically. Analysis and simulation results confirm the good performance of the proposed method in terms of computational complexity, estimation accuracy, correct classification of signals, and aperture loss.
Gauss integral theorems for electric and magnetic fields, Faraday's law of electromagnetic induction, magnetic field circulation theorem, theorems on the flux and circulation of vector potential, which are valid in curved spacetime, are presented in a covariant form. Covariant formulas for magnetic and electric fluxes, for electromotive force and circulation of the vector potential are provided. In particular, the electromotive force is expressed by a line integral over a closed curve, while in the integral, in addition to the vortex electric field strength, a determinant of the metric tensor also appears. Similarly, the magnetic flux is expressed by a surface integral from the product of magnetic field induction by the determinant of the metric tensor. A new physical quantity is introduced - the integral scalar potential, the rate of change of which over time determines the flux of vector potential through a closed surface. It is shown that the commonly used four-dimensional Kelvin-Stokes theorem does not allow one to deduce fully the integral laws of the electromagnetic field and in the covariant notation requires the addition of determinant of the metric tensor, besides the fact that the validity of the Kelvin-Stokes theorem is limited to the cases when determinant of metric tensor and the contour area are independent from time. This disadvantage is not present in the approach that uses the divergence theorem and equation for the dual electromagnetic field tensor. The problem of interpreting the law of electromagnetic induction and magnetic field circulation theorem cannot be solved on the basis of the Lorentz force in the absence of charges, and therefore requires a more general approach, when transformation of the field components from the reference frame at rest into the moving reference frame is taken into account. A new effect is predicted, according to which the circulation of magnetic field can appear even in the absence of electric current and with a constant electric field through the contour, if the area of this contour would change. By analogy with electromagnetic induction, for the magnetic field circulation to appear it is important that electric field flux passing through the area of the contour would change over time.
A reconfigurable antenna with on-demand single-band or dual-band rejection capability for ultra-wideband (UWB) applications is presented. A modified monopole structure is integrated with a U-shaped slot and an open-ended slot to realize band-rejection. The antenna operates in four modes: a full UWB (3.1-10.6 GHz) coverage antenna, a UWB antenna with a single-band WiMax or wide local area network (WLAN) rejection, and a UWB antenna with dual-band WiMax/WLAN rejection. On-demand single and dual-band rejections are implemented by controlling two slots using two PIN diodes. Thus, the adopted control technique is quite easy and requires low operating power. Details of the design process and reconfiguration mechanism are presented. The band-rejection performance is explained by return loss and surface current distribution at single-band mode. A prototype is built on a Rogers substrate and tested to validate the performances. The antenna exhibits stable radiation characteristics and almost flat gain responses across the whole band, while significantly gain reduction is achieved at the rejected bands. Therefore, this antenna is suitable for high-performance UWB systems in WiMax/WLAN dense environments with the aim to improve signal quality, system capacity, and communication efficiency.
In this paper the design of asymmetric wideband printed dipole antenna is presented along with measured results. The wide bandwidth covering 0.8-4 GHz is achieved using inset feeding technique. This paper also presents the techniques for achieving good omni-directional radiation patterns over the wide frequency band with deviation from omni-directionality within ±2.5 dB. This design offers more than 5:1 impedance bandwidth (for VSWR≤2.2:1), with good radiation efficiency and omni-directionality. The comparison study of symmetrical and asymmetrical printed dipole antennas with and without inset feed is presented in this paper. Thus, the proposed antenna finds a wide range of applications in trans-receive modes in today's wireless devices.
Wireless technology has significant improvement in features enhancement of device applications. It is highly desirable to operate multiple applications from a single device. A compact size antenna is presented for a variety of IoT based applications, such as home automation, surveillance, satellite communication, vehicle tracking, and medical instruments. This article explores an analytical solution of ultra-large band frequency characteristics of a compact size, trident shape, fractal patch antenna. The overall structure has dimension 18x12x1.6 mm3. This antenna exhibits the multi-edge radiating effects of fractal structure with the help of ground optimization technique. The design evolution consists of a performance measure of the antenna with varying characteristics of the EBG patterns with respect to fractal structure. The design is validated by fabricating the antenna on an FR4 (4.2) substrate, and the return loss & radiation characteristics are measured. The measured |S11| has the impedance bandwidth of 1.59-13.31 GHz and sustainable radiation characteristics. This miniaturized antenna is compatible with the GSM, GPS, Bluetooth, Wi-Fi, WLAN, Wi-MAX, ISM, and other UWB spectrums. The gain of the antenna is 2.52 dBi for the complete operating range. Therefore, the proposed antenna is highly compatible with various wireless devices associated with IoT applications.
A compact square patch band-pass filter is proposed in this paper. The dual-mode filter is designed based on a square patch resonator with a complementary split ring resonator (CSRR) split to be used as a perturbation element. The CSRR split is properly embedded in the square patch resonator to perturb electric current distribution on this patch and thus to simultaneously excite a pair of degenerate modes. Using the proposed CSRR elements, the band-pass filter is designed with miniaturized size, and two transmission zeros in stopbands are achieved to improve the selectivity of the filter. The influence of the CSRR elements on the band-pass filter is analyzed in detail. The proposed dual-mode filter is then fabricated and measured. Good agreement over a wide frequency range is achieved between the simulated and measured results. Moreover, in order to further investigate the characteristic of the dual-mode patch filters with CSRR perturbation, a dual-mode filter with a rectangular ring slot is presented for comparative study.
Distributed beamforming (DBF) is an efficient technique for reliable communications in wireless sensor networks (WSNs). In DBF based networks, the randomly distributed nodes cooperate together to form a randomly distributed antenna array (RAA) which has a main beam directed towards the intended receiver. Due to the nodes randomness, the DBF results in poor pattern characteristics such as high side lobe level (SLL) and pattern asymmetry around the main beam sides. In this paper, a fast deterministic algorithm for SLL reduction of open loop distributed antenna arrays is introduced. Unlike the existing state of the art optimization techniques for SLL reduction, the proposed algorithm provides a fast deterministic solution for energy transmission or the weight of each node without changing its location. Consequently, the exhaustive search burden of the optimization based techniques for the optimum weights is avoided. The simulation results reveal that the proposed algorithm has superior performance to the optimization techniques in terms of execution time, synthesized SLL, and half power beam width (HPBW).
A ridged horn antenna with metallic grid sidewalls is proposed and quantitatively analyzed. Simulated and measured results indicate that the operating band is from 1.0 to 20.0 GHz with the reflection coefficient less than -10 dB, and the relative bandwidth is as high as 180.95%. The gains are greater than 10 dBi in the frequency band of 2.6-20 GHz, greater than 16 dBi in the frequency band of 10-20 GHz with the gains fluctuation less than 1 dB. In the whole operating band, the radiation patterns radiate directionally along the normal direction of the horn aperture and do not split. In this paper, the ridged horn antenna with metallic girds is analyzed quantitatively. A modified equivalent traveling wave current model of the ridged horn antenna is proposed, which matches better to the patterns of the ridged horn antenna in high frequency band. The working mechanism of metallic grid sidewalls is also analyzed quantitatively, and the reason that metal strips can improve the matching performance of ridged horn antenna in low frequency band, restrain the patterns splitting in high frequency band and improve the antenna gains is explained. The proposed antenna has the characteristics of ultra-wideband, stable gains, miniaturization, and directional radiation patterns with no splitting main lobe in ultra-wideband. The proposed ridged horn antenna can be used for the measurement in a microwave anechoic chamber.
This paper presents a novel reconfigurable filtering antenna with three tunable states used for IoT applications. The frequency reconfigurability is achieved using the combination of a hairpin filter and an open loop filter in the structure with the switching of p-i-n diodes. The open-loop filter structure provides two narrow band states at 2.4 GHz and 7.8 GHz, and the hairpin filter provides a single narrow band state at 10.4 GHz. The frequency reconfiguration is obtained without compromising the compact size of the designed circuit along with the targeted frequency bands at lower WLAN (2.47 GHz), WiMAX (3.42 GHz), INSAT C-band (7.18 GHz), fixed/mobile satellite service in X-band (8.4 GHz), direct broadcast service in Ku-band (12.14 GHz) applications. The prototype is constructed on an FR4 substrate and tested for validation in an anechoic chamber. The designed antenna provides excellent radiation characteristics and considerable gain at resonant frequencies. The proposed reconfigurable antenna is also tested using the CDAC Cmote device in the real-time environment and found more suitable for the IoT based communication applications.
The estimation of the direction of arrival (DOA) and the estimation of the number of signal sources are very important techniques in modern communications. The effect of mutual coupling can degrade the performance of the estimation algorithms. Mutual coupling compensation is used to mitigate this effect. However, errors remain when the compensation is carried out with such methods as minimum description length (MDL) to estimate the number of signal sources. This work presents a new method based on threshold decision to estimate the number of signal sources in presence of mutual coupling. The results of computer simulations demonstrate that the proposed method outperforms the MDL method.