The deep flux weakening (FW) switching point of the interior permanent magnet synchronous motor (IPMSM) is difficult to track accurately. After entering the deep FW region, the current regulator is easily saturated, and the current following capability is poor. Aiming at these problems, a deep FW control of the IPMSM based on thed-axis current error integral regulator (DCEIR) is proposed. Firstly, the deep FW switching point is accurately calculated by using the maximum torque per volt (MPTV) as the limit of the d-axis current. Secondly, through the study of the voltage deviation, it is found that the q-axis regulating current is related to the DCEIR. On this basis, a new transformation relationship between d-axis current and q-axis current in the deep FW region is obtained. Finally, the simulation and experiment results are compared with the conventional negative d-axis current compensation method (NDCCM). It is verified that the proposed method can successfully restrain the saturation of the current regulator and enhance the current following capability in the deep FW region.
To meet 5G requirements, designing an optimal antenna is challenging due to numerous design factors. Conventional electromagnetic modeling simulators require excessive time and processing power during the antenna design process. Machine learning (ML), an innovative technology, can be used in the domain of antenna design with favorable performance and can resolve problems that the previous conventional methods cannot. The main goal of this work is to create an antenna that operates at 28 GHz, which is a significant 5G band for the 5G futuristic infrastructure revolution, and to predict the return loss of an antenna using some machine learning models like K-Nearest Neighbor (KNN), Extreme Gradient Boosting (XG-Boost), Decision Tree (DT) and Random Forest (RF). On comparing results, all models perform well with over 83% accuracy. However, the Random Forest model predicts return loss with higher accuracy at 90% and lower MSE and MAE values of 1.99 and 0.827, respectively. Moreover, this antenna holds potential for 5G applications and can be efficiently optimized using a machine learning approach, saving valuable time.
Quartz-enhanced photothermal spectroscopy (QEPTS) technique is suitable for simultaneous measurement of multi-gas in near-infrared (NIR) and mid-infrared (MIR) bands with advantages of wide spectral response and high sensitivity. Here, we report a multi-gas sensing system based on QEPTS using NIR and MIR Lasers. A quartz tuning fork (QTF) with a resonant frequency f0 of 32.742 kHz was employed as a photothermal detector. A continuous wave distributed feedback (CW-DFB) fiber-coupled diode laser with a center wavelength of 1.58 µm and an interband cascade laser (ICL) with a center wavelength of 4.47 μm were used as the light sources to simultaneously irradiate on different surfaces of QTF for scanning the absorption lines of carbon dioxide (CO2) and nitrous oxide (N2O). A multi-pass cell with an effective optical path of 40 m and a 40 cm absorption cell were selected for the measurements of CO2 and NO2, respectively. The developed sensor was validated by the detection of mixtures containing 3000 ppm CO2 and 20 ppm N2O. The relationships between the second harmonic (2f) amplitude of the QEPTS signal and the CO2 and N2O concentrations were investigated. Allan deviation analysis shows that this sensor had excellent stability and high sensitivity with a minimum detection limit (MDL) of 2.729 ppm for CO2 in an integration time of 195 s and 0.038 ppb for N2O in an integration time of 90 s, respectively.
A brand-new four-channel mux system built entirely out of multicore photonic crystal fiber (PCF) structures, which permit wavelength multiplexing at 0.85, 1.19, 1.1, and 1.35 µm, has been confirmed. The multiplexer is a device that sends multiple messages or signals simultaneously via one communication channel. PCF is a category of optical fiber primarily according to the characteristics of photonic crystals, and it is an effective waveguide based on the interaction of microstructured materials with various refractive indices. Silica substance was used to fill up a few air-hole places to optimize the PCF mux structure along with coupling light between more nearby ports (cores) over the PCF axis. The low-index portions are air holes that may be found anywhere along the length of the fiber, and the background material is often natural silica.
Composite materials are being widely used in the automotive industry where they are progressively replacing metallic materials as structural parts for being robust and lightweight. Their complexity, often leading to lots of unknown behavioral effects when placed near the electronic systems present in vehicles, should be studied and treated. In the automotive industry, the shielding effectiveness of these materials should be considered as the most important parameter to be known in advance. Faurecia, one of the world's largest leading automotive suppliers, sought to assess the shielding effectiveness of their product such as dashboards and door trims. Their objective was to enhance the shielding effectiveness, thereby ensuring superior isolation and protection of electronic systems against electromagnetic interferences (EMI). Thus, this paper presents a novel method for characterizing the shielding effectiveness of various composites using two electromagnetic methods to cover a wide frequency range, starting from 10 Hz up to 8 GHz. The first method, based on loop antennas, was used to cover the low frequency range starting from 10 Hz up to 120 MHz. Frequencies between 100 KHz and 1.5 GHz were not discussed in this paper because of the many studies that already exist at this frequency range, using the coaxial transmission cell. The second method used for frequencies higher than 1.5 GHz, consists of ultra-wide band antennas (Vivaldi).
In this paper, a pioneering and innovative approach for multiple-band ridge gap waveguide (MB-RGW) based narrowband bandpass filter for satellite applications is presented. The MB-RGW represents a significant and emerging technological advancement within the domain of microwave and millimeter-wave engineering. It comprises a periodic structure that enables the propagation of electromagnetic waves along its axis. We have provided a detailed analysis of the MB-RGW, which includes its design, simulation, and experimental results. A prototype filter, designed according to specifications, was successfully produced with a fabricated circuit area measuring 42.25 mm × 76.25 mm × 8.8 mm. We demonstrate that the MB-RGW can achieve multiple bands with a single structure, making it a versatile and efficient device for a wide range of applications. We also present a detailed analysis of the factors that affect the performance of the MB-RGW, including the geometry of the ridge and the spacing between ridges. Our experimental results show that the MB-RGW can achieve high levels of attenuation and isolation, making it a promising candidate for use in microwave and millimeter-wave circuits and systems. The experimental results show S11 smaller than -20 dB over relative bandwidths, and S21 has a maximum of -0.6 dB. The proposed filter demonstrates four resonances at frequencies of 10.6 GHz, 12.6 GHz, 14.7 GHz, and 17.1 GHz, catering to mobile and fixed radio locations as well as satellite applications. It exhibits a fractional bandwidth of 0.44% at 3 dB in the X-Band and approximately 0.57% to 0.61% at 3 dB bandwidth in the Ku-band. The filter offers a compact, cost-effective, and easily implementable solution for satellite communication systems, including space operations, earth exploration, satellite TV broadcasting, and fixed satellite services (FSS). Overall, this paper provides a comprehensive overview of the MB-RGW and its potential for the use in a range of applications.
Orbital angular momentum (OAM) is a fundamental characteristic of electromagnetic waves and has gained significant attention in recent years because of its potential applications in various fields of radio and optics. Furthermore, the OAM has been proposed as a means to increase the spectral efficiency of wireless communication systems. By encoding multiple independent data streams on different OAM modes of electromagnetic waves, OAM communication systems can increase the amount of information that can be transmitted over a single radio frequency channel. In this paper, we developed a new method for steering the OAM wave using an intelligent reflective surface (IRS) that is suitable for the far field. Specifically, we designed the IRS coefficients to reflect and steer different multiplexed orders between different users based on OAM waves by controlling the IRS impedance, which can be fluctuated depending on the beam steering direction. Moreover, we investigated the physical limitations of the IRS by noting the relations between the number of transmitted modes, the IRS size, and the impedance values in the IRS. Each impedance element in the IRS consists of real and imaginary values, and the negative values in the real part are used as an indication for reaching the physical limit. One suggestion to decrease the negative real values is by using windowing to decrease the beam waist. The proposed method may enable the extended coverage of OAM wireless communication.
This study focuses on the utilization of a slotted patch MIMO antenna to enhance isolation and gain. The MIMO antenna configuration includes two radiators integrated with an array of Frequency Selective Surfaces (FSSs). These antenna components are implemented on an FR-4 substrate and encompassed by FSS units that are optimized for X-band frequencies. The proposed MIMO antenna possesses dimensions of 65 mm (width) × 45 mm (length) × 1.6 mm (height). The primary objective of incorporating FSSs is to not only enhance isolation but also achieve high gain. The proposed FSS design features a circular ring structure with a rectangular loop at its center. The FSS unit cells exhibit excellent stability across various polarization incidence angles and operate within the frequency range of 7 to 9 GHz. The FSS loaded antenna offers a bandwidth ranging from 8.0 to 8.55 GHz, with a peak gain of 6.5 dB and isolation exceeding -20 dB among the MIMO elements. Furthermore, the study explores the MIMO antenna's performance in terms of diversity gain (DG), efficiency, and Envelope Correlation Coefficient (ECC), demonstrating superior results compared to existing state-of-the-art approaches. The proposed findings are validated by fabricating a sample prototype and conducting a comprehensive comparison between simulated and measured results.
Enhancing the capacity of wireless communications systems is necessary to manage growing networks. Thus, this work presents an analytical model for describing the deterioration in orbital angular momentum (OAM). The proposed model is based on a uniform circular array, which can be applied in OAM generation to obtain the desired beam properties. First, the side-lobe problem in OAM applications is examined and resolved by optimizing the beam synthetization. Then, comparisons between the two window techniques are used to evaluate their impacts. Finally, the effects of selecting the optimal window technique and width on the solutions are investigated. Numerical results and the comparisons between derived formulas and those obtained via full-wave numerical simulations are shown.
An efficient time domain hybrid method, consisting of the finite-difference time-domain (FDTD) method, Norton's theorem, transmission line (TL) equations, and some interpolation techniques, is presented to realize the fast coupling simulation of branched lines (BLs) radiated by ambient wave. Firstly, the branched lines are decomposed into multiple independent multi-conductor transmission lines (MTLs) according to the branched nodes. Then the TL equations with interpolation techniques are employed to build the coupling model of each MTL. The transient responses on these MTLs are solved by the FDTD method, which are employed to extract the Norton circuits of these MTLs acting on the branched nodes according to the Norton's theorem. Finally, the correlation matrix of the voltages and currents at the ports of the branched nodes is derived and solved. Meanwhile, these voltages are fed back to the corresponding MTLs as boundaries to realize the interference signal transmission among the BLs. Numerical examples about the coupling of branched lines contributed by five wires in free space and complex environment are simulated and compared with that of traditional FDTD to verify the correctness and efficiency of this proposed method.
At present, numerical methods suitable for the electromagnetic interference (EMI) analysis of the transmission line (TL) excited by the leakage electromagnetic (EM) fields generated by the integrated circuit (IC) of the electronic device are still rare. An efficient time domain hybrid method, consisting of the dynamic differential evolution (DDE) algorithm, transmission line equations, finite difference time domain (FDTD) method and non-uniform grid technique, is presented to realize the fast simulation of the leakage EM fields to the TL. Firstly, a source reconstruction method based on the DDE algorithm is employed to extract the equivalent dipole array to represent the leakage EM radiation from the IC of the device. Then, the coupling model of the TL excited by the leakage EM fields is constructed by the TL equations and non-uniform grid technique, and solved by the FDTD method to realize the synchronous calculation of the leakage EM field radiation and the transient responses on the TL. Finally, the correctness of the source reconstruction method has been tested, and the accuracy and efficiency of the proposed method have been verified via two simulation cases of the transmission line excited by leakage EM fields arising from IC in free space and shielded enclosure by comparing with that of the MOM method.
Optically transparent antennas have attracted increasing interest in recent years. However, the inherent ohmic loss of transparent conductor used in antennas will always introduce degradation of radiation efficiency. It is of most importance to find the optimization between the material loss and radiation efficiency. In this paper, we design and experimentally demonstrate a high-performance optically transparent dual-polarized cross dipole antenna over 3.4-3.8 GHz for 5G wireless communication based on the characteristic analysis of surface current distribution. By making current distribution uniform on the radiators and reducing the current on the ground, the mutual coupling between the elements is alleviated, and the radiation efficiency can be optimized. The proposed antenna is fabricated with 0.118-Ohm/sq meshed metal, and the optical transparency of antenna is 81%. The proposed antenna achieves a voltage standing wave ratio (VSWR) of less than 1.3, radiation efficiency of 72% (84% of pure copper) and a peak gain of 4.5 dBi (5.1 dBi of pure copper). Compared to current state-of-arts, the proposed antenna exhibits better performance of the figure of merit (FOM) in terms of the bandwidth, optical transparency and radiation efficiency. Our work paves the way to diverse application of beyond-5G wireless communication.
The response of a uniformly moving metallic slab to an electromagnetic plane wave, at normal incidence, is studied. The analysis is based on the application of boundary conditions to Maxwell's equations as a function of time. The Doppler effect and amplitude of the obtained reflected wave agree with the literature. Moreover, a transferred wave which has not been analyzed in the literature is demonstrated. The frequency shift and the amplitude of this wave are studied analytically with the same technique used for the reflected wave. The transfer of electromagnetic wave through the metallic slab is made possible by the presence of a static magnetic field inside the moving metallic slab, if the motion of the slab is opposite to the direction of propagation of the incident wave. The amplitude of the transferred wave is approximately 2v/c times the amplitude of the incidence wave, with v being the speed of motion and c the speed of light in vacuum. This amplitude is thus very small for non-relativistic speeds. The analytical results are validated by full-wave simulations based on the Finite Difference Time Domain method, where both reflected and transferred waves are demonstrated. Furthermore, numerical electric field and magnetic field distributions are presented at different time instants.
A four-port ultra-wideband (UWB) multi-input multi-output (MIMO) Vivaldi antenna loaded with resistance and rectangular radiation patch is designed and fabricated. The compact antenna consists of an improved ground and four microstrip feeders, with an overall size of 26 mm × 52 mm × 0.8 mm. The antenna adopts the resistance loading technology to absorb the excess electromagnetic waves in the low-frequency band and broaden the low-frequency bandwidth of the antenna. The rectangular radiation patch loading technique optimizes the main radiation direction and broadens the high-frequency bandwidth of the antenna. Meanwhile, T-slots and fence-type structures are etched on the ground plane, and I-stubs are added between microstrip feeders to reduce the antenna coupling and increase the isolation degree between the antenna ports. Simulation and experiments show that the impedance bandwidth of the MIMO antenna is 3.0~12.3 GHz; the isolation degree of the whole working bandwidth is higher than 15 dB; the envelope correlation coefficient (ECC) is smaller than 0.0125; and the increased diversity gain (DG) is more significant than 9.98 dBi. The antenna has good radiation performance and stable gain, which is suitable for applying the UWB MIMO system. This antenna has a particular reference significance for the research of the MIMO Vivaldi antenna.
To solve the problem of single working frequency of traditional reflective focused metasurface, a dual-band reflective focused metasurface is proposed, which can realize independent focusing characteristics at 7.25 GHz and 20.5 GHz. The metasurface unit is composed of metal elements combined by a split-ring resonant structure working at 7.25 GHz and an elliptical resonant structure working at 20.5 GHz in the same plane, dielectric substrate and ground. Dual-band independent control and 360° phase coverage are achieved by adjusting the dimensions of unit. The surface current distribution also verifies the rationality of the designed metasurface element. Based on the principle of quasi-optical path, a dual-band reflective focused metasurface with independent focusing characteristics is designed. Through full-wave simulation, the focusing efficiency at 7.25 GHz and 20.5 GHz is calculated by Poynting theorem, which are 56.9% and 57.5%, respectively. The proposed dual-band metasurface has the characteristics of simple structure and low profile without multi-layer stacking and metal through-holes.