Aiming at the problem of poor identification accuracy in traditional particle swarm optimization algorithms, an adaptive search particle swarm optimization algorithm (ASMDRPSO) method for permanent magnet synchronous wind generator (PMSWG) parameter identification is proposed. Firstly, in order to solve the issue of the under-rank equation, a full-rank state equation and fitness function are established. Then, in ASMDRPSO, a dynamic adjustment strategy is adopted in the inertia weight update process to enrich population diversity. In addition, the average best position strategy is designed to avoid getting stuck in a local optimum. Moreover, an adaptive learning radius is supplemented in ASMDRPSO, and the particle search range is enlarged when the ASMDRPSO evolution is stalled. Finally, the simulated and experimental results are presented to verify the stronger optimization ability, stronger robustness, and higher search accuracy of the proposed control strategy than the traditional PSO.
Partitioning large planar antenna arrays into smaller subarrays reduces the system costs and gives many other advantages. In this article, symmetrical T-shaped tetromino subarrays are suggested to perform the partition process of the large planar arrays. Different structures of T-shaped tetromino subarrays have been obtained by simply rotating its orientation by multiple angles of 90 degrees such that the entire planar array aperture can be filled. Two array architectures based on different T-shaped tetrominoes are constructed. The amplitude weights of the designed subarrays are optimized by means of the genetic algorithm such that the resulting array patterns have low sidelobe level. In the first architecture, all the elements in the original array are divided into several subarrays based on three T-shape structures, while in the second architecture all the elements are combined into eight different T-shapes. To control the sidelobe level in the proposed T-shaped tetromino subarrays, a surface mask boundary function is included in the optimization process to find the optimum weights of the T-shaped subarrays. Simulation results showed that the sidelobes can be reduced to less than -20 dB in the first architecture, and less than -25 dB in the second architecture, in addition to a significant reduction in the complexity of the feeding network for each one. Moreover, detailed connections of the feeding network circuitry of the used T-shaped tetromino subarray structures are given for practical implementation.
Most of the works on sparse array synthesizing via the compressed sensing (CS) approach assume that the active elements exactly lie on the predefined grids. In fact, grid-mismatch error is unavoidable when an array aperture is discretized into grids, and the synthesizing results largely depend on the density of the grids. To overcome this limitation, an innovative off-grid CS approach is proposed for jointly estimating the excitations and positions of array elements. The synthesis problem is specifically formulated using a ridge regression model based on dynamic grids. The candidate positions of elements are treated as variables rather than constants predefined by discretization. Numerical experiments are conducted to validate the effectiveness and flexibility of the proposed method in realizing several maximally sparse arrays meeting the targeted patterns, i.e., the focused and shaped beam patterns of 1-D and 2-D arrays.
Flux reversal machines (FRMs) have a broad application prospect due to its simple structure, high efficiency, and high reliability. However, due to the large magnetic flux leakage between poles, the further improvement of torque density of the FRMsis limited. To reduce magnetic flux leakage and improve torque, a novel consequent pole FRM with asymmetric stator poles is proposed in this paper. The `NS-NS' arrangement order of thepermanent magnets (PMs) of the conventional FRM is changed to the `NSN-S' PMs arrangement order with asymmetric stator poles, and the consequent pole topology is used simultaneously. All the N-poles of PMs are replaced by iron poles. Finally, the topology of the `Fe/S/Fe-S' arrangement order is obtained. A simplified magnetic circuit model is established to explain the principle of reducing magnetic flux leakage. To improve the torque density, the key design parameters are optimized by genetic algorithm, and the optimal parameters of the machine are finally determined. Finally, the finite element model is established. Compared with the conventional FRM, the torque of the proposed machine is increased by 67.18%, and the consumption of PM is reduced by 51.6%. Therefore, the proposed machine has good electromagnetic characteristics and economic benefits.
Microstrip patch antennas are becoming increasingly relevant because of their advantages such as light weight, low costs, and ease of fabrication. To enhance the performance of an antenna, graphene was included into the fabrication of the microstrip patch antenna. Because of its numerous excellent characteristics, graphene has gained attention in recent years as a leading material. In this research, a microstrip patch antenna based on graphene was fabricated and tested at 5 GHz. The fabrication started with the production of graphene paste and was screen printed onto RT duroid 5880 substrates. To verify the binding between the graphene paste and the substrate, an adhesion test was performed on the finished graphene-based patch antenna using the Scotch tape method. The performance of fabricated antenna was measured using vector network analyzer (VNA) which includes return loss and bandwidth. The findings of the measurements were compared with the simulation results that were generated by the High Frequency Structure Simulator (HFSS). The return loss of the graphene-based antenna was measured to be -17.6314 dB, which is a little bit lower than the simulated value of -18.0597 dB that was generated by the HFSS software. The calculated bandwidth for simulated and fabricated graphene-based patch antenna were found at 156 MHz and 297.4 MHz, respectively. Based on the findings, it can be concluded that the return loss result indicates that the fabricated graphene-based patch antenna agrees well with the simulated patch antenna, although the fabricated patch antenna has a greater bandwidth than the simulated antenna.
This paper presents a design of a compact wide slot circularly polarized antenna which is being fed by a microstrip feed line. The designed antenna covers an area of size 25 mmx25 mm with a substrate thickness of 1.6 mm. The 3 dB axial ratio (AR) band can be produced by projecting a circular stub in the ground plane and feeding the slot through an asymmetry-fed microstrip feedline. The AR bandwidth of the antenna is further improved by adding truncation in the ground plane. Measured results show that the graph attains an impedance matching bandwidth of 124.3% centered at 7.4 GHz (2.8-12 GHz) and a 3 dB AR bandwidth of is 52.42% centered at 5.15 GHz (3.8-6.5 GHz). The proposed antenna is suitable for the use in C-band application.
A network optimization approach based on Neural Architecture Search (NAS) and network pruning is suggested to solve the issue of poor recognition performance of missile-borne radar active jamming under the condition of short sample sizes. The approach realized the ideal network design under severely constrained technical indications by combining the benefits of several methods, including NAS, convolutional light-weighting, and network pruning. The recognition network's convolution kernel size parameters were first optimized using NAS. The number of model parameters were then decreased via convolutional substitution. Finally, the structured pruning algorithm further screened the redundant network based on the technical indicators. The WideResNet28_2 wide residual network's recognition accuracy is only 84.38% when there are only 1000 training samples for each type of signal, according to the simulation results. After optimization, the number of new model parameters was increased 2.55M, 2.26M, and 1.78M, respectively, and their respective recognition accuracy was increased to 85.7%, 85.61%, and 85.37%. According to the simulation results, the technique offers a wide range of possible applications in the optimized design of radar active jamming identification networks for small sample sizes.
In this study, an adjustable reflectionless diplexer is designed and fabricated for the L-band based on microstrip transmission lines. The proposed diplexer can separate and combine different frequencies within the L-band frequency range. The equations and theoretical process of the structure can be proved from coupling matrix and even/odd mode circuit analysis. In this design, our aim is that the proposed diplexer not only has low insertion loss and proper return loss in the channels' stopband but also can change the channels' frequency. The physical specifications are calculated proportionally to the central frequency based on the coupling coefficients and diagram. Also, frequency adjustability is achieved by connecting the varactor diode to the structure's resonator. The proposed structure can be used in the frequency range of 1.6-2.2 GHz. Furthermore, the measured return losses in the stopband and passband are 8 dB and 13 dB, respectively. In this paper, all simulations are performed by ADS software.
An analytical multi-rays path loss model with low complexity and high accuracy is proposed to realize the ubiquitous communication links with solid stability and full coverage. The closed-form formulas are derived to describe the path loss above 6 GHz under regularly-structured indoor environments, ensuring a clear propagation mechanism and low computational complexity. In this model, the construction and destruction of the dominant rays, i.e., the direct, reflected, diffracted, diffracted reflected, and reflected-reflected rays, on the path loss, are considered according to variation of the transmitting antenna position and propagation condition. The proposed model contains information on the sizes, structures, and materials of the environments and eliminates the influences of small scale fading by averaging the path loss over a circle with radius of ten wavelengths. Based on the measurements under the ``L-shaped'' corridor and office environments at 8 GHz band, the accuracy and extensibility of the proposed path model are verified. This work can help analyze the propagation mechanisms and construct the solver for calculating the attenuation of electromagnetic waves under indoor environments. It can also provide vital information for the link budget and node deployment for future wireless communication systems above 6 GHz.
This study describes the development of a low-profile, omnidirectional, CPW fed Ultra-Wide Band (UWB) MIMO antenna. The antenna is designed on a flexible FR4 substrate with thickness 0.07 mm, making it suitable for wearable applications. The fractional bandwidth obtained is more than 100% (3.1-9.3 GHz) which spans the wireless communication bands such as ISM (5.15-5.35 GHz), ISM (5.725-5.825 GHz), Wi-Fi (5 GHz), Wi-Max (3.4-3.6 GHz), Sub 6 GHz 5G (3.3-4.2 GHz), and WLAN (5.15-5.825 GHz). The antenna also provides safe SAR value, low envelope correlation coefficient, good antenna gain, acceptable radiation efficiency, optimum Total Active Reflection Coefficient (TARC) value, low Channel Capacity Loss (CCL), good gain, and acceptable radiation efficiency across the frequency ranges. Simulated and measured performances of the antenna in the entire band are presented.
In this Article, the antenna is designed by using different shapes of patch structures on 8.468×9.741 mm2 ground plane. Different shapes like A, H, F, T, and U are simulated by using HFSS Software. For gain enhancement, various techniques on the different shape patches have been applied. The maximum gain achieved in the case of A shape patch with MTM structure and circular reflector with superstates is 14.2 dBi, and the band covered is (36.248-38.764) GHz and (33.384-34.503) GHz. Other shapes like H, F, T, and U are designed by modification in A shape patch, and by applying various techniques like MTM and reflector surface with superstates interesting results have been achieved. The designed antenna is an mm-wave antenna and a novel structure for 5G communications.
In order to further reduce the computational complexity as well as the average switching frequency of the inverter for model predictive torque control (MPTC), an improved MPTC control strategy for a three-vector low switching frequency based permanent magnet synchronous motor is proposed. Firstly, an analysis is conducted on the combined effect of the torque and magnetic chain based on the three voltage vectors, based on which the vector combinations are matched to form an offline optimized switching table, and then the three voltage vector combinations are selected from the offline optimized switching table according to the torque control requirements in order to reduce the amount of system calculations. Then, on this basis, a hysteresis loop technique for direct torque control is introduced to reduce the average switching frequency of the inverter. An improved MPTC control strategy with fuzzy variable hysteresis loop width is further proposed to fuzzy control the dynamic output hysteresis loop width scaling factor according to the motor operating state. Experimental results show that the improved MPTC control strategy with fuzzy variable hysteresis loop width results in optimal combined average switching frequency and current harmonics with reduced computational effort.
In this paper, a miniaturized Ultra-Wideband (UWB) flower-shaped radiator antenna is designed and simulated for 2.9 GHz to 14.8 GHz applications in Wireless Body Area Networks (WBAN). To achieve wideband, two alterations have been incorporated into the proposed design i.e. by adopting a flower-shaped patch to enhance bandwidth and by using the defective ground plane, which reduces capacitive effects, increasing impedance matching within the operating band. This innovative antenna has a footprint of 15 mm x 20 mm x 1.6 mm and uses textile material denim as its substrate, making it compatible with portable UWB devices. Aside from these characteristics, the device also has omnidirectional radiation patterns, a peak gain up to 5 dB, and a fidelity factor over 85%. It is found that the simulation and measurement results are in good agreement. In comparison with existing structures, the antennas obtained show wide operating ranges and compact dimensions.
Modern wireless communication systems require low profile, high gain and wideband antennas. To meet these requirements a low profile Cylindrical Dielectric Resonator Antenna (CDRA) is proposed with wide bandwidth and high gain for ISM and C-Band applications. The CDRA is excited with a 50 ohm microstrip feed line with HEM12δ, HEM21δ and HEM13δ modes being observed at 5.6 GHz, 7.4 GHz and 8.6 GHz resonant frequencies respectively. The perturbation on the basic CDRA leads to the excitation of higher order modes and also decrease the effective permittivity of the CDRA by a factor of 13.4%, thereby reducing the antenna's Q factor, which helps to broaden the antenna's operating frequency range. The proposed structure offers wide impedance bandwidth of 69.4% from 4.8 GHz to 9.9 GHz. A peak gain of 8.9 dBi at 9.4 GHz and 95% radiation efficiency at 5.6 GHz are observed. Additionally, the proposed CDRA has a small footprint of 1.12λ0 x 1.12λ0 with a low profile of 0.16λ0 where λ0 is the wavelength of the lower cut-off frequency. The proposed antenna is fabricated and measured, and a close agreement is found between the simulated and measured results.
A 2 bit reconfigurable beam-steering antenna array using phase compensation is proposed, which consists of a 1 bit reconfigurable antenna and 90˚ digital phase shifter. The p-i-n diodes are soldered in the 2 bit element to realize 2 bit phase shift. Due to the 2 bit phase quantization error, a fixed compensation phase is added to each array element to reduce sidelobe level. A 2 bit reconfigurable antenna array with 1×8 elements shows that the sidelobe levels of the scanning-beams are less than -6.2 dB. At the same time, simulated results also show that the antenna can steer beam direction from -48˚ to 50˚, and the beam gain fluctuation is less than 2.2 dB. A prototype is fabricated and tested. The proposed antenna can provide a novel idea to design a 2 bit reconfigurable beam-steering antenna array with a better beam-scanning performance in various applications.
This study aimed to investigate the structural design of a cantenna with Woodpile shaped electromagnetic band gap (EBG) for gain enhancement and to increase the efficiency of signal transmission for measuring the moisture content and the bulk density of goat manure, which can help farmers reduce the cost of buying chemical fertilizers. From the test of operating frequency ranges from 2 to 3 GHz, it was found that the frequency band that responds to humidity the best is 2.60 GHz, increasing the efficiency of the gain with the 6x6 cm2 Woodpile shaped EBG. It was arranged in transverse electric (TE) and placed parallel to the end of the cantenna. This allows the gain to be increased to 9.31 dBi, in which the cantenna structure without EBG has the gain of 7.32 dBi. When the cantenna is used to determine the moisture content (MC) and bulk density, the transmission distance between the cantenna Tx/Rx is 3 cm with an average power rating of 0.0001-0.5 mW. This cantenna can measure humidity in the unit of wet basis (wb.) as low as 0.14% wb., at an average power of 0.5 mW.
A novel miniature antenna is proposed for wireless communications in the K-band and Ka-band of the electromagnetic spectrum. The frequency band of this antenna extends from 18 to 40 GHz. The proposed antenna is a planar monopole printed on a thin dielectric substrate of 0.25 mm thickness. To enhance the frequency bandwidth of this antenna it is constructed as five circular sectors placed with sequential rotations and merged to form a multi-leaf shaped monopole patch antenna. To enhance the antenna performance, the monopole patch is fed through a coplanar waveguide (CPW) structure. This enables the overall antenna structure and the feeding CPW to be printed on only one side of the dielectric substrate leaving the other side blank, which reduces the dielectric loss and enhances the radiation efficiency. The assessment of the antenna performance is achieved through simulation as well as experimental work. A prototype of the antenna is fabricated for this purpose. The experimental results show excellent agreement with the simulation ones. The antenna is printed on a Rogers' RO3003 substrate of 0.25 mm thickness. It is shown, through both results, that the antenna has 2.2:1 ratio bandwidth, 76% percentage bandwidth, and 278 bandwidth-dimension ratio. The radiation efficiency is maintained above 99% over the entire bandwidth (18-40 GHz).
The design and analysis of a compact printed Archimedean spiral electromagnetic bandgap (EBG) structure are presented for frequency shielding in microwave circuits, including antenna and bandpass filters. The EBG characterization resonating at 7.7 GHz is done through a performance matrix such as transmission and reflection coefficients and equivalent circuit modeling, which demonstrates excellent resonance stability. The EBG unit cell is investigated for achieving frequency rejection in the printed monopole-based ultra-wideband (UWB) antenna and bandpass filter circuits. By introducing the Archimedean EBG unit cell on the UWB antenna ground plane, dual-frequency rejection, at 7.4, and 7.7 GHz, was realized. Further, such structure is utilized in a multi-mode resonator (MMR) based UWB bandpass filter to attain band-notched functionality at 7.6 and 7.8 GHz with a maximum attenuation of -16.5, and -15.6 dB, respectively. The prototypes of the EBG-loaded UWB antenna and EBG-Loaded UWB filter are fabricated and characterized. Excellent agreement is achieved between simulated and measured results of both prototypes.
A concentric circular array consisting of two rings is proposed to focus the radiated field at a point in the near-field zone. In the proposed two-ring array, the radius of the outer ring was chosen so that the radiated fields from all elements on the two rings add constructively at the focal point, thus no phase shifter is needed in this design. The N elements of the inner ring are uniformly excited in amplitude and phase, while the M elements on the outer ring are excited uniformly in phase, and given uniform magnitude excitations of N/M of that given to the inner. Therefore, two deep nulls are achieved on both sides of the focusto enhance the focal width. The focusing properties are investigated by exploring the array parameters, such as variation of the focused field along the normal to the array, field distribution on the focalplane, and depth of field (size of the focal spot). Computer simulations using the MATLAB environment are performed by point source radiators. For verification, the array was simulated using the CST microwave studio, and the obtained results showed good agreement. The array is useful for hyperthermia and imaging applications.
In this paper, the electromagnetic vibration characteristics of hybrid excitation double-stator Bearingless Switched Reluctance Motor (HEDSBSRM) used in flywheel battery are analyzed when the rotor is eccentric. Firstly, the influence of rotor eccentricity on motor vibration is theoretically analyzed. Then the finite element method is adopted to study the radial electromagnetic force of the motor in the two-dimensional air-gap region. In addition, the three dimensional equivalent vibration model of the motor outerstator is established, and the mode shapes and natural frequencies of the motor stator are obtained by the modal analysis. The vibration characteristics of the outer stator under eccentric motion are analyzed by the coupling calculation of electromagnetic field and mechanical field. Finally, the modal combination principle is used to analyze the vibration characteristics of the motor running at multiple speeds under eccentric condition. The results show that the vibration of HEDSBSRM is closely related to eccentricity, which affects the motor performance and lays the foundation for the optimization design of HEDSBSRM application in flywheel battery.