The reliability of DC-bus capacitors in six-phase drives is an important issue in multi-phase drive systems, and the influence of symmetrical and asymmetrical motor winding loads on the lifetime of DC-bus capacitors is essential. This article uses the SVPWM modulation algorithm to analyze the current and voltage ripple of DC-bus capacitors in a six phase voltage source inverter. Then, by optimizing the capacitance value when searching for the maximum stress point, the capacitance range of DC-bus capacitors is determined. At a power factor of 0.6 and modulation ratios of 0.4, 0.7, and 0.9, considering the changes in ESR, current, and voltage ripple in the capacitor, taking 80% of the rated lifespan as an example, it is found that the lifespan of the DC-bus capacitors in symmetrical configuration of the motor winding is increased by 0.20%, 1.80%, and 10.08% compared to that in asymmetric configuration, respectively. Finally, the analytical and experimental results were compared with existing methods, and the experimental results verified the effectiveness of the proposed method.
A coaxially pin-fed multiband fractal square antenna is proposed in this paper. The designed antenna resonates in five bands: 5 GHz, 10 GHz, 13.2 GHz, 16 GHz, and 20.5 GHz. This multibands are achieved by using a fractal square antenna. The fractal square is formed from an initial square patch and then optimized with increasing fractal iterations to resonate at these bands. The fractal property of the design also helps in the miniaturisation of the antenna. The proposed antenna has gain ranging from 4.9 dB to 9.7 dB and radiation efficiencies from 70% to 98%. The proposed antenna is simulated using the CST microwave studio. The antenna is then fabricated, and its performance parameters are measured. After finding a match between simulated and measured results, the same antenna and its array are tested in a MATLAB simulation environment for direction of arrival (DOA) and adaptive beam forming (AB) at all five bands. Using different DOA and AB algorithms, the performance of the antenna array is evaluated. The ability to accurately estimate the DOA of all signals delivered to the adaptive array antenna allows it to maximise its performance in terms of recovering the required transmitted signal and suppressing any interference signal. Then, the beam of the antenna is modified using the DOA algorithm to generate a beam in the desired direction and nulls in the unwanted direction for proposed satellite communications.
Circularly polarized gap-coupled designs of corner truncated square microstrip antenna in 2400 MHz frequency spectrum are presented. The gap-coupled design on thinner substrate (~0.036λg) yields axial ratio bandwidth of 113 MHz (4.697%) whereas that on thicker substrate (~0.13λg) yields axial ratio bandwidth of 471 MHz (19.24%). Both the designs exhibit broadside radiation pattern with a peak gain above 7 dBi, thus satisfying the requirements of WLAN and Bluetooth applications. Simulated results have been experimentally verified, which show close agreement.
In this paper, reactive impedance surface metasurface (RIS-MS) and negative refractive index metasurface (NRI-MS) are used to design a wideband, high gain, circularly polarized slot loaded patch antenna (SLPA) for 5 GHz WI-FI applications. The RIS-MS is utilized to improve the antenna's bandwidth. It is composed of 6×6 metallic circular patches that are periodic. To improve bandwidth, the RIS-MS is placed between the SLPA and ground plane of a conventional antenna. A metasurface lens composed of 6×6 periodic NRI metamaterial unit cells enhances the gain of the antenna. The NRI-MS superstrate is positioned at the optimal height above the conventional antenna. A prototype of the proposed antenna has been fabricated and measured experimentally. The prototype has an impedance bandwidth (IBW) of 21.7% (5.12-6.37 GHz), a 3-dB axial ratio bandwidth (ARBW) of 18.2% (5.19-6.23 GHz), and a gain of 13.5 dBic.
A parameter identification method based on an improved hunter prey algorithm is proposed to address the issues of poor accuracy and speed in traditional permanent magnet synchronous motor parameter identification methods. By using the Fuch infinite folding chaotic strategy to evenly distribute the initial individuals to enrich their diversity and using the golden sine algorithm to optimize the population search path, the algorithm's local development ability and global search ability are improved. The reasons for the dead time effect of the inverter are analyzed, and the input voltage is compensated for through the rotation coordinate method. SIMULINK simulation and physical experiment indicate that the improved algorithm has faster rate of convergence and higher recognition accuracy than the unmodified algorithm, and can effectively identify motor parameters. On this basis, adding dead time compensation effectively eliminates partial harmonics of the phase current and suppresses the occurrence of zero current clamping phenomenon. Compared with the situation without dead time compensation, the identification error of the four parameters has decreased from below 4.23% to below 2.21%.
To improve the work efficiency of on-site inspection personnel in diagnosing faults of power transmission lines, in this paper we propose an infrared image segmentation method based on DeepLabV3+ for identifying key components of transmission line. We collected 556 infrared images of transmission lines in our own power supply system, and expanded the original data by data augmentation method. Based on the comparison of the DeepLabV3+ model with three different backbone networks, MobileNetV2 with the best performance is selected as the main backbone network. Compared with FCN, U-Net and SegNet, the test results show that DeepLabV3+ using MobileNetV2 (compared with ResNet50 and Xception) can segment the five types of key components in power transmission lines from infrared images more accurately and faster. The MIoU on the test set is 0.8624, which is better than the performance of FCN, U-Net and SegNet. This lays a foundation for improving the work efficiency of on-site inspection personnel and improving the continuous power supply capacity, stability and safe operation level of the power grid.
In this article, a new design approach for an unequal coupled transmission line dual-band Wilkinson power divider is presented. A parallel short or open circuit stub is considered at the input port for dual frequency response, and two resistors are connected in order to isolate the outputs. The method is based on an even-odd mode procedure. The main objective of this paper is to fabricate a dual band Wilkinson power divider in order to achieve higher dividing ratio, simple structure, and easier fabrication. First, the desired power divider is divided to two parts known as even and odd mode equivalent circuits. Then by analyzing the circuits, the characteristic impedances are calculated. Next, the coupled transmission lines dimensions are extracted. Afterward by using the calculated characteristic impedances, an error function is formulated, and by minimizing, the isolating resistors are obtained. To clarify the applicability of this method, several microstrip power dividers which operate at both 1 GHz and 2.3 GHz with dividing ratio equal to 1.2589 are designed and simulated with the assumption that relative permittivity is equal to 2.56. In order to demonstration the advantage of using coupled lines tow dividers, one by separated-lines and the other one by coupled-lines are designed and compared with each other. The results illustrate that while the coupled-line dividers have simpler structure, they have significantly similar frequency operation to separated-line ones. Then the designed structure fabricated on an FR4 substrate and S parameters are measured. The results show excellent agreement with simulation.
A novel miniatured reconfigurable antenna for wireless applicationsusing defective ground structure is proposed and studied. This proposed antenna generates eight different frequencies, operating at 2 GHz (IMT), 2.3 GHz (UMTS), 2.5 GHz (Wi-Fi), 2.7 GHz (Radio astronomy), 2.9 GHz (Weather radar), 4.2 GHz (Radio altimeter), 4.4 GHz (Radio determination) and 5.5 GHz (Wi-MAX) while maintaining overall compact size of 24×33×1.6 mm3 using an FR-4 substrate having a permittivity of εr = 4.4. The proposed reconfigurable antenna consists of three switches in the slots of the patch along with rectangular defects on ground surface and a microstrip feed line. The lumped elements are used in place of three switches in the simulation to get tunable capacitance, which is responsible for frequency reconfigurability. It makes the antenna operate at eight useful bands. The structure shows the impedance bandwidths of 6.86%, 6.04%, 2.51%, and 2.73% with gains 5 dB, 4.8 dB, 6 dB, and 6.8 dB, respectively. The designed antenna can be easily integrated on the modern communication devices. A prototype of the designed antenna is fabricated, and simulation results are compared with measured values using PIN diode switches.
Three-dimension (3-D) images provide additional information of targets for automatic target recognition (ATR) and 3D scattering model generation. Methods based on sparse representations can reconstruct extreme resolution 3D images from sparse measurements, but suffer from the huge dimension of separable dictionaries. This paper presents a time-domain sparse representation method for 3-D target imaging from multi-view synthetic aperture radar (SAR) data, including a basic method and two improved ones. The time-domain framework uses time-domain responses to build a separable dictionary and a sparse representation model. In the time-domain framework, the basic approach is to transform the dictionary into a rather sparse matrix via a low-energy threshold that shrinks the spatial region of the 3D imaging based on multi-aspect 2D images. By exploiting the properties of multi-aspect SAR data in the time domain, one modification makes the sparse representation model more compact, leading to a reduction in dimension, and another additional modification splits a high-dimensional large-scale model into a set of very low-dimensional small-scale models. They overcome the curse of dimensionality and improve the efficiency of sparse representation-based 3D imaging to varying degrees. Experimental results show the effectiveness and great efficiency of the proposed method.
In order to improve the efficiency and safety of emergency rescue operations, a wearable circularly polarized (CP) antenna suitable for GPS applications has been designed. It adopts a coplanar waveguide (CPW) feed structure, where the ground plane and radiation patch form an annular gap. The impedance bandwidth and axial ratio performance are enhanced by adjusting the amplitude and phase difference of the current distribution through two pairs of notches and open-circuit branches. When the single antenna is more than 20 millimeters away from the human body model, its CP radiation performance is acceptable, and the peak Specific Absorption Rate (SAR) also meets the required standards. To minimize the separation distance between the antenna and the human body, a 2×2 Artificial Magnetic Conductor (AMC) with in-phase reflection characteristics is integrated at the antenna's bottom as a reflector, which increases the antenna gain and reduces the SAR. Simulation and test results indicate that in the GPS L1 frequency band, the antenna achieves a gain greater than 7 dBi, an axial ratio less than 2 dB, a front-to-back ratio of 24 dB, and a peak SAR of 0.53 W/Kg, which is well below the standard limit of 1.6 W/Kg set by the Federal Communications Commission (FCC). Compared with other relevant antennas, this antenna features compact size, wide impedance bandwidth, and robust anti-interference capability, effectively improving the flexibility and compatibility of the wearable antenna, thereby meeting the demand for efficient and reliable positioning of rescuers.
This article introduces a planar monopole antenna specially designed for NB-IoT module devices. The preferred choice for Internet of Things (IoT) technology is the Narrow-Band Internet of Things (NB-IoT) due to its extensive coverage and low power consumption. NB-IoT is specifically designed for IoT applications. A circular patch antenna with dimensions of 30 mm×60 mm is fabricated, which is specifically tailored for the NB-IoT module. The antenna dimensions are meticulously chosen to ensure compatibility with the device module, considering the NB-IoT B1 (2100) and B3 (1800) frequency bands. Among various patch shapes, the circular design is preferred for its advantages over hexagon and square patches. The desired antenna configuration combines a square-slotted patch with a monopole ground plane, and it offers several advantages in terms of design simplicity, compact size, and characteristics such as broad bandwidth, acceptable gain, and high radiation efficiency. The design process employs HFSS Software and utilizes an FR4 substrate of 1.6 mm thickness. Operating at resonance frequencies of 2.1 GHz and 1.8 GHz, the antenna covers a broad frequency spectrum of 1100 MHz (1.5 to 2.6 GHz) with a fractional bandwidth of 53.65%. The suggested antenna achieves a peak gain of 3.3 dB and maximum radiation efficiency of 96% within its operating band. It exhibits an omnidirectional radiation pattern, meeting the specific requirements of NB-IoT technologies. Experimental measurements of the fabricated antenna validate the results achieved from the simulated data.
Micro Deformation Monitoring Radar has been widely used in the field of surface deformation and displacement monitoring. However, limited by radar imaging geometry, the deformation measurement by existing radar technology can only extract the deformation and displacement of the target line of sight (LoS), which cannot directly reflect the actual deformation and displacement of the landslide direction and easily results in misjudgment or omission of the surface deformation monitoring information. In this paper, the relationship model and mapping between radar data and three-dimensional coordinate system were analyzed to perform three-dimensional analysis of the LoS displacement. Combined with the landslide displacement direction, the mapping angle between the LoS direction at any point in the observation area and the landslide direction was solved, and then the deformation displacement in the landslide direction was obtained by solving the LoS direction displacement. Finally, taking the measured data of one slope as the research object, the feasibility and accuracy of the method were analyzed and verified. The conclusion shows that the method proposed in this paper can be effectively applied to calculate the true value of landslide deformation.
A miniaturized and closely packed eight element annular ring multiple-input multiple-output (MIMO) antenna array is designed to operate from 3 to 6 GHz band for 5G smartphone applications. In MIMO, the orthogonally placed antenna pairs maintain high isolation. The proposed decoupling structures placed between two adjacent antenna pairs improve the isolation. The decoupling structure consists of a rectangular metallic strip with metallic vias that reduces the mutual coupling and excites the additional modes to extend the bandwidth from 3 to 6 GHz. The MIMO structure offers isolation of more than 24 dB, ECC of less than 0.1, TARC of less than 7 dB over the complete operation band, DG of 10 dB, and more than 95% efficiency. The specific absorption rates (SARs) of the antenna placed in the human head and hand models are 0.41 W/Kg and 0.66 W/Kg, respectively. The performance obtained with the fabricated prototype offers excellent matching with that of the simulated ones.
The dual band notched features of an ultra-wideband (UWB) antenna are presented. The radiator element is a rectangular one with several slots. The planned antenna's operational frequency ranges from 2.8 to 10.6 GHz. By embedding a rectangular slot on the radiator and a folding stepped resonator in the ground plane, it is possible to create dual notched bands that are 3.76-5.9 GHz with a central frequency of 5.2 GHz (WLAN) and 2.85-3.32 GHz with a centre frequency of 3.2 GHz (WiMAX). The antenna measures 32 × 32 mm2 across the board. In terms of VSWR, group delay, efficiency, and radiation pattern, the antenna's performance is confirmed. Results from simulation and testing of the stated antenna are closely matched.
A Mushroom-Cloud-shaped wide slot Microstrip patch antenna (MC-MSPA) was discovered and proved to be a viable option for Wideband applications in this research study. The given antenna has a high radiation and wideband reflection coefficient of 134.47% from 1.15 GigaHz to 5.87 GigaHz for |S11|<-10 dB. This antenna has a peak gain of 6.47 dBi at 4.6 GigaHz and 6.1 dBi at 5 GigaHz, as well as an return loss of 47.37 dB at 1.88 GHz. MC-MSPA has optimised dimensions of 0.73λg×0.72λg×0.02λg. Furthermore, a reflecting surface of a 7×7 square-shaped array beneath the ground plane has been included to provide even higher gain and directivity. The proposed MC-MSPA+RP antenna has a fractional bandwidth of 63% with dual bands from 1.438 to 2.782 GigaHz and 38.89% from 3.964 to 5.878 GigaHz, with a peak gain of 9.657 dBi, maximum directivity of 10.44 dBi at 5 GigaHz, and maximum return loss of 54 dB at 4.9 GigaHz. Reflector plate electrical dimensions have been enhanced to 0.87λg×0.87λg×0.24λg. The proposed design improves gain and directivity, both of which are important for WLAN and Wi-MAX applications.
In this paper, several multiband patch antennas with sinc-shaped edges were analyzed, designed, simulated and implemented for modern sub-6 GHz applications. The aim is to use the sinc function parameters such as amplitude and number of maxima (frequency) to control the antenna performance such as resonance and radiation characteristics. It is shown that changing the sinc pattern parameters has a significant impact on the resonance of the antenna, and hence these parameters can be used to directly control the multiband behavior of the antenna. The proposed antenna designs were manufactured, and their performance was tested experimentally in the lab and compared to simulation results. An acceptable agreement between experimental and simulated results was achieved.
The performance of the Vertical Cavity Surface Emitting Laser (VCSEL) for hybrid optical links SMF/FSO based on different data rates and MIMO configuration techniques was obtained using OptiSystemTM which is close to the results of the experimental system. The developed system was tested with various transmission distances: 20, 30, 40, and 50 km, and in the existence of many configuration kinds and modulations. In addition to that the hybrid system was estimated with different weather cases: clear, rain, and snow. The results state that the performance of the OOK-NRZ system reveals better performance than OOK-RZ system under the same conditions. Also, the performance of the free space link is better than the fiber link formost of the link ranges considered and configurations. For OOK-NRZ of the fiber link, it was found that the MIMO 8×8 technique has better system performance than other configurations, and the Q-factor = 11.39 and BER = 5.4×10-30 for a length of 50 Km while for the FSO link, it was found that MIMO 8×8 indicates a high performance for Q-factor = 12.7 and BER = 1.8×10-37. The maximum FSO link distances under different weather conditions and coupling ratios were found. For BER≤10−9, in NRZ format for SMF 50 km utilizing MISO8×1 technology in clear weather for 10 Gbps, 15 Gbps, and 20 Gbps for FSO links, the maximum accessible lengths are 0.6 Km, 0.51 Km, and 0.43 Km, respectively. The process is expanded to include snow conditions for data rates of 10 Gbps, 15 Gbps, and 20 Gbps for FSO links with lengths of 0.4 Km, 0.3 Km, and 0.26 Km, respectively.
This paper presents a novel design of Compact Notched Wide Band Antenna that has dual notches in the band of Wireless Local Area Network (5.15 GHz-5.825 GHz) and X-band Satellite Communication (8 GHz-12 GHz). The proposed antenna has a defective ground structure (DGS) to operate the antenna for wide band applications. Notch bands are achieved by inserting slots on the radiating patch and feed line. A horizontal S-shaped slot on patch is responsible for the notch in the band of wireless local area network, and an inverted U slot is used in feed line to get a notch in the band of Satellite Communication. The proposed antenna is fabricated using FR4 substrate of size 26 x 26 x 1.6 mm3 and tested using Vector Network Analyzer MS2037C. Although the measured results are slightly changed in comparison with simulated, they agree reasonably well. The measured result also reveals that the prototype antenna is in compact size and resonated from 4.24 GHz-12.59 GHz with two notch bands centered at 5.8 GHz and 10.3 GHz.
In order to reduce the cogging torque and improve the back electromotive force (EMF) performance of the motor, a three-phase permanent magnet (PM) synchronous motor with magnetic pole eccentricity and slotting design is proposed in this paper. Firstly, the analytical expression for the cogging torque of the motor is derived based on the energy method, and the factors influencing cogging torque are analyzed. Subsequently, taking the cogging torque and the amplitude of the back EMF as the optimization objectives, the response surface method (RSM) and multi-objective genetic algorithm (MOGA) are combined to obtain the optimal values for the eccentricity distance of the PMs, slotting radius, and slot position. Finally, a finite element model is established for simulation comparison. The results show that compared with the traditional model, the optimized model effectively reduces the cogging torque while slightly sacrificing the back-EMF amplitude, and improves the sine degree of the no-load back-EMF.
The rapid advancement of communication technology has led to an increase in electromagnetic interference (EMI), or electromagnetic (EM) pollution. This is a cause for concern, as EMI can disrupt communication services, damage electronic equipment, and pose health risks. Regulatory bodies are working to develop standards for the safe use of wireless devices, but the problem of EMI is likely to continue to grow as the number of Internet of Thing (IoT) devices continues to increase. To address this issue, this study investigated the effectiveness of carbon-coated cobalt ferrite nanoparticles as a potential material for electromagnetic shielding. The synthesis of cobalt ferrite (CoFe2O4) nanoparticles was successfully achieved using the co-precipitation method. Subsequently, a carbon coating was applied to the nanoparticles through a hydrothermal process using a 200 mL autoclave made of teflon-lined stainless steel. This process was carried out at a temperature of 180˚C for a duration of 12 hours, with a heating rate of 8˚C per minute. This study examined both uncoated and carbon-coated CoFe2O4 nanoparticles at various ratios of glucose to CoFe2O4 (1:1, 2:1, and 3:1) using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and higher resolution transmission electron microscopy (HRTEM) analysis. The XRD analysis revealed distinct and well-defined peaks corresponding to CoFe2O4, indicating the successful synthesis of the nanoparticles. The crystallite size of the uncoated CoFe2O4 nanoparticles was measured to be 11.47 nm, while for the carbon-coated CoFe2O4, the average crystallite size was determined to be 14.15 nm through XRD analysis. The results obtained from the FTIR analysis were consistent with previous reports and confirmed the formation of spinel CoFe2O4 nanoparticles, as suggested by published data. The morphological and structural properties of the prepared samples were further characterized using FESEM and HRTEM analysis, which demonstrated uniformity in both particle size distribution and morphology. Overall, the research findings indicated that the structure and properties of CoFe2O4 nanoparticles were significantly influenced by the carbon coating process. Notably, the optimum ratio of carbon to CoFe2O4 was found to be 2:1, which resulted in the highest carbon thickness. The electromagnetic properties of the samples were evaluated using a vector network analyzer (VNA) and measured S-parameters in the frequency range of 8.2 to 12.4 GHz, known as the x-band region, suitable for radar applications. The sample with a carbon ratio of 2:1 exhibited the highest total shielding effectiveness (SE) of -17 dB at approximately 10 GHz. As a conclusion, the carbon-coated CoFe2O4 nanoparticles showed promising potential as an effective material for shielding against electromagnetic wave pollution, particularly when the carbon coating and filler composition reached an optimal point. Additionally, the shielding effectiveness performance of the sample could be further enhanced by incorporating a conductive polymer as an auxiliary material.