An efficient field-to-circuit hybrid method is presented for the electromagnetic interference (EMI) analysis of penetrated wire of an electronic device excited by ambient wave, which consists of finite-difference time-domain (FDTD) method, transmission line (TL) equations, Thevenin's theorem, and circuit analysis method. The significant feature of this method is that it can avoid modelling the structures of penetrated wire and terminal circuit directly on the premise of guaranteeing sufficient accuracy. At first, the whole model of penetrated wire of an electronic device is decomposed into external and internal regions according to the shielded enclosure of the device. Then, the FDTD method combined with TL equations is applied to build the coupling model of external transmission line with the shielded enclosure and extract the equivalent circuit model of an external region based on Thevenin's theorem, which is further imported into the internal region as excitation source. Finally, the EMI analysis of internal region is executed by constructing the transmission parameter matrices of the two-port cascade network, which is contributed by the penetration node, internal transmission line and terminal circuit. Then the interference response on terminal circuit can be obtained. Numerical simulations have been taken into account to verify the the accuracy and efficiency of this field-to-circuit hybrid method by comparing with the traditional FDTD method.
A novel optically-switched antenna is proposed, in which a photodiode is embedded into an antenna radiator. In order to avoid the high loss problem in series structures for the integration of photodiodes and patch antenna, a photodiode parallel structure with sensitive radio frequency response is selected for the design. The status of the antenna while at work can be effectively adjusted by illumination. Its reflection coefficient and radiation gain vary with the exposure of photodiode to light illumination and non-illumination state. The simulation and experiment of this design at 1.52 GHz produce an obvious effect on light control with a maximum 6.6 dB gain variation on omnidirectional pattern. It is thus deemed suitable for speed measurement and occlusion detection in remote wireless sensor networks and other applications.
In order to overcome the problem of high voltage loss rate caused by the increase of current harmonics due to dead-time effect and the decrease of average potential output of inverter in the control process of the interior permanent magnet synchronous motor (IPMSM) for electric vehicles, a dead-time compensation control method based on an extended Kalman filter (EKF) and a neural network bandpass filter (NNBPF) is proposed. Firstly, from the mechanism of dead-time effect, the problems and causes of dead-time effect are analyzed. Secondly, the extended Kalman filter combining feedback and prediction function is used to filter the d- and q-axis currents of the motor, so as to solve the problem that zero current polarity is difficult to judge in the traditional dead-time compensation process. Thirdly, the high-order harmonics due to dead-time effect in the d- and q-axis currents are extracted by using the neural network band-pass filter, and the dead-zone compensation is carried out after the amplitude phase adjustment. Finally, the effectiveness of the proposed dead zone compensation method is proved by comparing no dead-time compensation with the dead-time compensation strategy proposed in this paper. The experimental results show that the proposed dead-time compensation method can effectively suppress the current harmonics, reduce the current distortion, reduce the voltage loss rate to 0.04%, improve the voltage utilization ratio, and effectively improve the operating performance and endurance of electric vehicles.
In practice, the amplitude and phase excitations of array elements undergo random errors that lead to unexpected variations in the array radiation patterns. In this paper, the technique of the clustered array elements with discretized amplitude excitations is used to minimize the effect of random amplitude excitation errors and restore the desired array patterns. The most important feature of the proposed technique is its implementation in the design stage which may instantly count for any errors in the amplitude excitations. The cost function of the used optimizer is constrained to prevent any undesirable increase in the sidelobe levels due to unexpected excitation errors. Moreover, the error occurrences on the element amplitude excitations are considered to be either randomly over the whole array aperture or regionally (i.e., error affecting only a part of the array elements that located in a particular quadrant of the array aperture). Simulation results fully verify the effectiveness of the proposed technique.
The (6k±1)th harmonics exist in the extended electromotive force estimates due to the influence of the inverter nonlinearities and the flux spatial harmonics in the process of sensorless control of permanent magnet synchronous motor (PMSM), which give rise to the (6k)th harmonic in the rotor position estimate. A method of rotor position observation based on the time delay signal cancellation-frequency locked loop (DSC-FLL) is proposed to improve the sensorless control system of PMSM. The equivalent back EMF information is obtained by using the sliding mode observer, and the harmonic component in the specified back EMF observation value is filtered by using the delay signal elimination operator in the two-phase static coordinate system. The frequency locking loop is designed to track the rotor position information online, so as to improve the observation accuracy of the rotor position information. The model of sensorless control system of PMSM based on DSC-FLL is established, and compared with the model of sensorless control system of PMSM based on arctangent function. The results show that after adopting the method of rotor position observation based on DSC-FLL, the high harmonic in back EMF is suppressed, the error of rotor position fluctuation observation reduced, and the error of rotation speed observation reduced. The observation accuracy of rotor position information is significantly improved.
In the forward modeling of the transient electromagnetic (TEM) method, a frequency-domain solution is usually obtained first, and the solution in the time domain is then calculated by a frequency-time transformation. At present, the three main fast frequency-time transformation methods are the Guptasarma algorithm, the sine and cosine numerical filtering algorithms, and the Gaver-Stehfest (G-S) algorithm. In recent years, with the increasing demand for fine detection at shallow depths, the small-loop TEM method has undergone rapid development. It is therefore important to evaluate whether the traditional forward modeling approaches can be directly applied to the small-loop method. In this paper, the principles of the three forward modeling methods and their limitations when being applied to the small-loop TEM method are discussed. Through a comparison with the analytical solution for a uniform half-space, we demonstrate that the accuracy of forward numerical calculation is affected by loop size and earth resistivity. When the Guptasarma, G-S, and cosine numerical filtering algorithms are used for small-loop TEM forward calculation, the overall calculation error becomes non-negligible, whereas the sine numerical filtering algorithm retains a high calculation accuracy. By studying the response of the frequency-domain solution, we analyze the cause of the error in the forward calculation. Generally, the sine numerical filtering algorithm is the most suitable method for fast and high-precision small-loop TEM forward modeling. The results obtained here should provide a foundation for high-precision forward modeling and inversion of the small-loop TEM method.
A pattern reconfigurable patch antenna with dual band characteristic is investigated in this paper. Two substrates with an air layer of 2 mm is used to design the antenna. Two radiators are respectively printed on the top surfaces of the two substrates. The first radiator, which is the circular patch, is printed on the top surface of the upper substrate. Eight rectangular slots are also introduced to obtain directional radiation pattern with reconfigurable characteristic in low band by changing the current distribution, and no metal layer is printed on the bottom surface of the upper substrate. The second radiator, which is composed of a cross branch and four arc-shaped branches, is printed on the top surface of the lower substrate to provide weak coupling effect with the circular patch. A round ground plane and four symmetrical rectangular slots are printed on the bottom surface of the lower substrate to generate additional resonance point in high band with the characteristic of pattern reconfiguration. A total of 12 PIN diodes are installed in the rectangular slots to verify the accuracy of dual-band and pattern reconfigurable features. The measured result exhibits that the designed antenna has dual band characteristic, in which the low band f1 is from 2.43 to 2.50 GHz with an average gain of 3.2 dBi and an average radiation efficiency of 73.5%, and the high band f2 is from 4.83 to 5.03 GHz with an average gain of 5.24 dBi and an average radiation efficiency of 73.9%. Moreover, the measured radiation patterns show that the patterns can be reconfigured at 90-degree intervals simultaneously in two bands.
Bearingless switched reluctance motor can be used in aerospace and flywheel energy storage industry. Taking a 6/4/4 hybrid excitation double stator bearingless switched reluctance motor as an example, the motor adopts an E-block structure on the outer stator and is excited by permanent magnet and current. The loss calculation and thermal analysis of the motor is carried out by using finite element method. The result shows temperature distributions of the motor under natural air-cooling condition. The temperature change under different operating status is analyzed. Finally, the temperature change and transient temperature curve of each part of the motor are obtained through simulation, and the motor can run stably.
Conformal low profile antenna array has been widely used towards reduced radar cross section and good radiation characteristics. Being conformal, it has a number of advantages over planar antenna structure. This paper presents the radiation and scattering characteristics of a planar and conformal patch array with conventional and hybrid HIS-based ground plane on a low loss dielectric substrate. The use of a hybrid HIS layer instead of conventional metallic ground plane contributes to achieving wideband RCS reduction over 8 GHz-50 GHz, without degrading the radiation performance in terms of antenna gain, return loss and VSWR. The measurement results of the fabricated antennas are found in good agreement with the simulated ones. The radiation mode RCS of the conformal patch array has been analytically estimated and shown to be controlled in the operating frequency range. Such a low profile low RCS antenna array can be used as a subarray of phased arrays in fire control radars.
This paper presents the resonant properties of a new Asymmetric Single Split Resonator (ASSR) structure for metamaterial applications. The compact uniplanar structure is an asymmetric single split ring resonator with two non-concentric rings. The prototype is fabricated on a substrate of dielectric constant 4.4, loss tangent 0.025, and thickness 1.6 mm and analyzed based on reflection and transmission coefficients and unit cell simulations. The fabricated unit cell of miniaturized ASSR has a footprint area of 0.163ƛ0 x 0.163ƛ0 where ƛ0 is the measured free-space wavelength corresponding to 1.63 GHz. The negative permeability meta-particle is best suited for high-performance multiband bandstop filters, sensors, and RFID applications in advanced communication systems. The paper presents the electric and magnetic responses of ASSR with its constitutive parameters for different field orientations in normal incidence.
In this paper, the performance analysis of a reconfigurable intelligent surface (RIS) assisted underwater optical communication (UWOC) system with a decode-and-forward (DF) relaying protocol is presented. The radio frequency (RF)-RIS link is subjected to Rayleigh fading while the optical UWOC link experiences mixture Exponential-Gamma distributions subject to heterodyne detection and intensity modulation with direct detection (IMDD). In order to obtain a traceable closed-form expression, the statistical distribution of the RF-RIS link is derived in terms of Meijer-G function. Thus, the exact closed-form expressions for system end-to-end outage probability and average bit error rate (ABER) for different modulation schemes are then derived. To gain further insight about the derived analytical expressions, asymptotic expressions for the system are derived at high signal-to-noise ratio (SNR) through which the diversity gain is obtained. The findings show the significant impact of the number of RIS elements, detection technique, and the UWOC optical turbulence on the system performance. Finally, Monte-Carlo simulation is used to justify the accuracy of the derived analytical results.
According to the orthogonality of each sub-carrier in the multi-carrier phase-coded (MCPC) signal, this paper focuses on anti-interrupted sampling repeater jamming (ISRJ) and creatively proposes a novel radar signal based on time-frequency random coded (TFRC) method, namely TFRC-MCPC signal. Based on the perspective of waveform design, the TFRC-MCPC signal adopts a chaotic sequence with good pseudo-random to code each chip in time-domain and each subcarrier in frequency-domain. The TFRC method increases the pseudo-randomness of radar waveform pulses and reduces the correlation between radar echo and ISRJ, thereby effectively suppressing the interference of false targets. The TFRC-MCPC method and common filter design methods do not conflict with each other and can be used in combination. The simulation experiment results show that under the typical parameters described in the paper, compared with the traditional MCPC signal and LFM signal, the signal-jamming ratio (SJR) improvement factor of the TFRC-MCPC signal is optimized by 1-2dB after pulse compression, which verifies its feasibility and effectiveness.
A new metasurface (MS) structure for wideband low radar cross section (RCS) and its performance as an antenna has been analyzed and proposed in this paper. The MS has been designed with two different AMC unit cells, and the novel AMCs scatter the incident waves diffusively. The parameters and dimensions of the AMCs are optimized to get the best performance of the antenna. Furthermore, the unit cell structure of metasurface is designed and positioned to improve the directivity of the antenna. The reflected electromagnetic waves scatter in a manner of 180⁰ out of phase with the incident waves, and the antenna's scattering and radiation performance has also been examined. Full-wave simulations and measurements confirm that the proposed antenna achieves 10 dB RCS reduction over a wide bandwidth of 3-12 GHz (61.2%). A monostatic peak RCS reduction of 45 dB is accomplished at 5 GHz, 7 GHz, and 11.5 GHz. Besides, the radiation characteristics of the antenna are appropriate in the boresight direction, and the antenna exhibits good performance in $E$-, $H$-planes and ensures adequate directivity.
In the iterative solution of the matrix equation arising from the multilevel fast multipole algorithm (MLFMA), sparse approximate inverse (SAI) preconditioner is widely employed to improve convergence property. In this paper, based on the geometric information of nearby basis functions pairs and finer octree grouping scheme, a new sparse pattern selecting strategy for SAI is proposed to enhance robustness and efficiency. Compared to the conventional selecting strategies, the proposed strategy has only one variable parameter instructing the constructing time and memory usage, which is more user friendly. Numerical results show that the proposed strategy can make use of the non-zero entries of near-field matrix in MLFMA more effectively and elaborately without compromising the numerical accuracy and the natural parallelization of SAI.
This paper presents a novel compact printed antenna exploitable for Dedicated Short-Range Communication at 5.8 GHz. The design of the proposed device is based on the concentric arrangement of two contemporary fed patches operating with different modes. The resulting antenna exhibits a fan-beam pattern, with a wide lobe in one plane and narrow lobe in the plane perpendicular to the former, while retaining exceptionally small dimensions. The actual width of the beam makes the antenna suitable to cover a single road lane, as prescribed by the Intelligent Transportation System framework requirements. Furthermore, it natively operates in Circular Polarization, as prescribed by the ETSI EN 302 663 normative. Experimental validations demonstrate that the proposed antenna presents a Left-Hand gain of 4.1 dB at center frequency, with HPBWx and HPBWy equal to 160˚ and 45˚, respectively, showing good agreement with the simulations. This measured performance confirms that the device is adequate to cover a single road-lane, according to the European framework for Dedicated Short-Range Communication for traffic monitoring.
The loss of magnetic bearing in the process of operation will lead to the temperature rise of the bearing and affect its performance. A permanent magnet is used to provide bias magnetic flux for hybrid magnetic bearing, which can reduce the loss and temperature rise of the magnetic bearing. In this paper, the loss of radial 2-DOF hybrid magnetic bearing (HMB) is analyzed. On this basis, the 3D thermal analysis model of HMB is constructed by using ANSYS Workbench finite element software. The loss is introduced into the temperature field as a heat source, and the temperature distribution of magnetic bearing is calculated. Combined with the results of loss and temperature analysis, the structural parameters were optimized by using genetic particle swarm optimization algorithm (GAPSO). The results show that the loss and temperature rise of the optimized magnetic bearing are significantly reduced.
Synthetic aperture interferometric radiometer (SAIR) is a high-resolution passive imager by sparsely arranging a number of small aperture antennas to synthesize a large aperture. However, the SAIR requires as many receivers as antennas needed, which results in high system complexity and hardware cost and limits the application of the SAIR. Aiming to reduce the system complexity of SAIR, a new passive coding imaging method is proposed in this paper. By using a new aperture coded measurement approach, the proposed method can significantly reduce the number of RF chains while keeping the image fidelity. The effectiveness of the proposed imaging method has been varified by simulations. The results reveal that the proposed method can be an efficient alternative for simplifying the architectures of SAIR.
High Impedance Textured Substrate is presented for suppression of Surface Waves in Microstrip Antennas. Surface wave propagation limits the radiation efficiency, bandwidth, gain, alters the main beam radiation pattern and increases side lobe levels as well as the back lobes. A novel technique to suppress the surface waves with periodic arrangement of metallic cylindrical pins embedded in the substrate except the area underneath the radiating microstrip patch is presented here. Two structures with solid as well as hollow cylindrical pins are analysed with Spectral Domain Analysis. The textured pin bed structure creates negative permittivity and high capacitive impedance and thus suppresses the propagation of TM-surface waves. The gain of 11.83 dB with an enhancement of 6dB over normal microstrip patch antenna is achieved. Further an increase of 1.61 dB gain with 12.27% improvement in radiation bandwidth is observed in the antenna structure with hollow cylindrical pins as compared to that of solid cylindrical pins. A uniform gain of more than 11 dB is achieved with a percentage bandwidth of 17.43%.
In this paper, a dual-band Multiple Input Multiple Output (MIMO) antenna for fifth-generation (5G) band (3.3-3.6 GHz and 4.8-5.0 GHz) is presented. The proposed MIMO antenna fed by coplanar waveguide (CPW) contains two symmetric antenna elements with two inverted L-shaped stubs. High isolation is successfully acquired by adopting a double-Y-shaped stub and partial ground plane. To obtain compactness, the antenna printed on an FR4 substrate has two triangle corners cut off. To study the performance, the antenna is simulated by Ansoft HFSS 13.0, and then fabricated and tested. The measurement results demonstrate that the antenna has achieved impedance bandwidths (S11 < -10 dB) of 790 MHz (3.08-3.87 GHz) and 880 MHz (4.7-5.58 GHz) with fractional bandwidths of 22.7% and 15.8% respectively, which covers 3.45/4.9 GHz 5G bands. Meanwhile, the measurement results exhibit an enhanced isolation more than 20 dB, a low envelope correlation coefficient (ECC) below 0.001, an average gain better than 2 dB and a stable radiation pattern within operation bands. In addition, the parameters including efficiency, DG, CCL, MEG and TARC are also analysed. The simulated and measured results indicate that the proposed MIMO antenna can be applied to 5G communication system.
The paper aims at studying the shielding effectiveness of a closed cylindrical surface simulated by N dielectric coated conducting strips. The far fields of an electric line source in the presence of the simulated surface and in the absence of the surface were calculated, and the ratio between them represents the shielding effectiveness produced around the surface. The solution of the problem was developed based on full wave analysis. In which all fields are represented in terms of infinite series of Mathieu functions. The addition theorem of Mathieu function was employed to facilitate the application of boundary condition. Computer program was developed based on the resulting formulations to produce numerical values. Numerical results are presented for circular and square cross-sectional cylindrical surfaces. Comparison with the published data for the radiation from slotted circular cylinder showed excellent agreement. Other useful results for shielding effectiveness are furnished.