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  Subjects -> ELECTRONICS (Total: 207 journals)
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International Journal of Antennas and Propagation
Journal Prestige (SJR): 0.233
Citation Impact (citeScore): 1
Number of Followers: 11  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1687-5869 - ISSN (Online) 1687-5877
Published by Hindawi Homepage  [339 journals]
  • Substrate Dielectric Constant Effects on the Performances of a
           Metasurface-Based Circularly Polarized Microstrip Patch Antenna

    • Abstract: This paper presents the effects of substrate dielectric constants on the performance characteristics of a circularly polarized (CP) metasurface-based patch antenna. The antenna structure is a modified patch with a step-like truncation sandwiched between a metasurface composed of a 4 × 4 lattices of periodic metallic patches and a ground plane. The effects on the performance variations are evaluated for two principal cases that include a uniform dielectric constant and a nonuniform dielectric constant for the upper and lower substrates of the antenna. Through careful computational analysis, the effects of the substrate dielectric constant on the antenna performance in terms of bandwidth and gain were investigated, and the results demonstrate that the antenna performance improves with a decrease in the substrate dielectric constant. For a uniform substrate material with dielectric constants of εr1 = εr2 = 2.2, the fabricated antenna with an overall size of 54 mm × 54 mm × 3.0 mm (0.76λo × 0.76λo × 0.042λo at 4.24 GHz) demonstrates the following measured performance characteristics: a −10 dB impedance bandwidth of 3.75–5.24 GHz (33.14%), a 3 dB axial ratio (AR) bandwidth of 3.85–4.64 GHz (18.61%), a radiation efficiency >93%, and a peak gain of 8.96 dBic within the AR bandwidth.
      PubDate: Fri, 30 Sep 2022 08:20:01 +000
  • Ka-Band Single-Layer High-Efficiency Circular Aperture Microstrip Array

    • Abstract: Based on microstrip antenna technology, a compact single-layer circular aperture array is proposed in this paper. The proposed method is suitable for designing large-scale and high-efficiency patch array in Ka band. By using the high-impedance characteristic of the coupled microstrip line, a novel multi-stage feeding network that can realize large power division ratio is proposed, and its structure is center-symmetrical and is fed through a coaxial probe at the center. The parallel branch of the multi-stage divider is connected to the row array, and the array elements can obtain uniform excitation through the design of the division ratio of each stage. A 256-element patch array operating at 35 GHz is proposed, the length and width of the antenna unit are 2.74 mm and 3 mm, respectively, the horizontal spacing between the array elements is 0.742λ0, the vertical spacing varies from 0.677λ0 to 0.737λ0, and the radius of the proposed array is 60 mm (7λ0 at 35 GHz). At the end, a prototype is fabricated and measured, the measured results show that the maximum gain is 29.5 dBi at 35 GHz, which correspond to the radiation efficiency and aperture efficiency of 61.66% and 46.07%, respectively, and the results show that the proposed antenna achieves high efficiency in Ka band, which verifies the correctness of the design. The proposed array antenna is compact in structure and only needs single-layer design, which can achieve high efficiency and low in manufacture cost, which is an excellent candidate for millimeter-wave large-scale array application.
      PubDate: Thu, 29 Sep 2022 08:05:01 +000
  • SAR Antenna Pattern Measurement by Internal Calibration Method for GF-3

    • Abstract: GF-3 is the first C-band multipolarization synthetic aperture radar (SAR) satellite in China. The SAR system is equipped with an active phased array antenna to electronically generate various antenna beams. The accuracy of SAR antenna patterns is of main importance for precise SAR image processing. The traditional method for antenna pattern measurement is the near-field method but it is unable to satisfy the demand for fast measuring in-orbit. In order to measure the SAR antenna pattern quickly with high accuracy, we propose the internal calibration method. The internal calibration uses calibration signals which are routed along the nominal signal path in SAR systems, thus monitoring the gain and phase variations for each T/R channel is possible. This paper will focus on this method, including its principle, operation steps, and results, compared to the near-field method. The internal calibration method provides a valuable solution for SAR antenna pattern measurement.
      PubDate: Thu, 29 Sep 2022 07:50:02 +000
  • A High-Efficiency Deep-Learning-Based Antivibration Hammer Defect

    • Abstract: Automated inspection using unmanned aerial vehicles (UAVs) is an essential means to ensure safe operations of the power grid. Defect detection for antivibration hammers on transmission lines in inspection imagery is one of the critical tasks for automated UAV inspection. It needs a machine interpretation system to automatically detect numerous inspection images. In this paper, a high-efficiency model based on Cascade RCNN (region-convolutional neural network) is proposed to detect antivibration hammer defects with reduced costs and speedier response, which applies in energy-efficient transmission line inspection systems. Firstly, to reduce computational costs, this study modifies the Cascade RCNN with a probabilistic interpretation to achieve the best trade-off between the inference time and average precision. Secondly, an antivibration hammer defect detector (AVHDD) model is proposed that uses a deep layer aggregation-based feature extraction network and a highly effective weighted bidirectional feature fusion network to replace the original ResNet and FPN on the modified Cascade RCNN to further enhance the model performance. Finally, a fine classification (FC) scheme for the types of antivibration hammer defects is proposed based on defect features to rationalize the model. The AVHDD reached an experimental mAP of 97.24% when IoU = 0.75, which is 2.93% higher than the original Cascade RCNN, and the defect recall was 98.9% while also significantly improving the inference speed. Moreover, the experimental results indicate that the overall performance of the proposed model is superior to typical models, confirming its suitability for energy-efficient transmission line inspection systems.
      PubDate: Wed, 28 Sep 2022 09:05:02 +000
  • Fast Tensor-Based Joint Estimation for Time Delay and Angle of Arrival in
           OFDM System

    • Abstract: Nowadays, the joint estimation of time delay (TD) and angle of arrival (AOA) using conventional vector structure suffers from the considerable complexity of multidimensional spectrum search. Therefore, a fast estimation method using orthogonal frequency division multiplexing (OFDM) technology and uniform planar array (UPA) is proposed in this paper, which adopts low-complexity tensor-based operations and spatial-frequency features to reconfigure the channel frequency response. To begin with, the array response is integrated with the OFDM signal characteristics to build an extended array in tensor form. Afterwards, we process the covariance matrix of the tensor structure by CANDECOMP/PARAFAC decomposition (CPD) to separate the respective signal subspaces of TD and AOA estimates. Finally, we conduct a one-dimensional (1-D) spectrum search to locate the TD estimates and a two-dimensional (2-D) spectrum search to locate the AOA estimates. The simulated performance demonstrates that the proposed algorithm offers precise estimates at low signal-to-noise ratios in a multipath environment and outperforms traditional vector-based algorithms with respect to computational complexity.
      PubDate: Tue, 27 Sep 2022 11:50:03 +000
  • On the Design and Performance Analysis of Flexible Planar Monopole
           Ultra-Wideband Antennas for Wearable Wireless Applications

    • Abstract: With the promising developments in wearable communication technology, attention towards flexible electronics is increasing day-by-day. This study presents flexible low-profile ultra-wideband (UWB) antennas for wearable applications. The antenna comprised of a modified dewdrop-inspired radiator and a defected ground plane and has an impedance bandwidth of 3.1–10.6 GHz. The antenna flexibility is investigated using four different substrates (polyester, polyamide, denim, and Teslin) and tested on a cotton shirt and a high-end Res-Q jacket to evaluate their performance stability for body-worn applications. The fabricated planar dewdrop-shaped radiator (PDSR) antennas have a radiation efficiency of >90%, a gain of >4 dBi, and a group delay variation of fewer than 0.5 ns. The antenna conformability is measured by placing the fabricated antennas on various curved and nonplanar parts of the human body. The aforementioned antennas offer better flexibility for different bent conditions. The specific absorption rate (SAR) of the designed antennas is investigated to determine their wearability, and values are found to be less than 0.2 W/Kg. Also, the received signal strength (RSS) is discussed in order to analyze signal attenuation, and the performance analysis of the antennas is compared.
      PubDate: Mon, 26 Sep 2022 17:35:03 +000
  • Design of Dual-Band, 4-Ports MIMO Antenna-Diplexer Based on Quarter-Mode
           Substrate Integrated Waveguide

    • Abstract: Here, a compact, dual band, 4-elements multi-input and multi-output (MIMO) antenna diplexer is designed to use in wireless local area network (WLAN) applications. The antenna is accomplished in a planar profile by employing Substrate Integrated Waveguide (SIW) technology. To reduce the size of a single element by 75%, a quarter-mode substrate integrated waveguide (QMSIW) technology is introduced. The QMSIW is realized by bisecting the full-mode SIW along the two magnetic walls and considering the quarter-mode for the operation. Initially, two-QMSIW cavities of distinct dimensions are designed to operate in two frequency bands, 5.2 GHz and 5.8 GHz, respectively. Later, two more radiating elements operating at the same frequencies are integrated with a 2-elements antenna. For better polarization decoupling, the identical elements are placed perpendicular to each other, and a parasitic metallic strip loaded with shorting vias is placed between two identical frequency antenna elements; hence, the port isolation is improved up to −25 dB. The antenna covers a bandwidth of 1.8% in the lower frequency band while 2.2% in the upper frequency band. The antenna prototype is fabricated, and its results are verified with experimental data. It is observed that the measured results are closely following the simulated results.
      PubDate: Mon, 26 Sep 2022 12:35:03 +000
  • Metamaterial-Loaded 16-Printed Log Periodic Antenna Array for Microwave
           Imaging of Breast Tumor Detection

    • Abstract: This article presents printed log periodic antennas with metamaterials for use in microwave imaging. A single layer of epsilon negative (ENG) metamaterial (MTM) array (1 × 6) of the unit cell is on the radiating patch. Adding a single negative metamaterial structure enhances the properties of far-field antennas, such as radiation pattern and gain, both of which are vital for breast imaging. Two frequency bands exhibit negative permittivity: 3–3.3 GHz and 3.6–4.5 GHz. In the operating band, the proposed antennas have achieved a maximum gain of 5.5 dBi and impedance bandwidth of 3 GHz (2–5 GHz) with a reflection coefficient less than −10 dB. At the lowest operating frequency of 2 GHz, the electrical dimensions of this designed antenna are 0.34λ × 0.26λ × 0.01λ. All 16 transceiver antennas are arranged vertically in a circular pattern around the phantom, each acting as a transmitter and the rest as receivers. The system design is carried out with the electromagnetic simulators CST and HFSS. After receiving the extracted data, the data are postprocessed using the MATLAB software and the delay multiply and sum (DMAS) imaging algorithm. Based on the reconstructed image, it is evident that the MTM-loaded antenna-based imaging system can detect many undesired tumors inside the breast phantom.
      PubDate: Mon, 26 Sep 2022 11:35:01 +000
  • Optimization Method of RFID Reader Antenna Deployment in Obstacle
           Environment Based on Improved FA

    • Abstract: The aim of this study is to solve the problem of RFID reader antenna deployment when an obstacle in the environment or the material itself is an obstacle. The article establishes a new reader antenna constraint model based on the rectangular obstacle RFID antenna deployment optimization environment model and the reader antenna sensing model containing Gaussian distribution noise probability and applies the improved firefly algorithm to find the optimum with coverage rate, interference degree, and load balance function as multiobjective functions. First, to obtain a uniform traversal of the target space, and a cube mapping is applied for chaos initialization. Second, a weighting model is proposed to control the speed of firefly variation and combine the variable step strategy of elite individuals to expand the movement step of elite individuals and reduce the movement step of nonelite individuals to improve population diversity. Finally, to improve the algorithm’s continuous optimality-seeking ability, a Gaussian variation operation strategy based on elite fireflies is introduced to ensure the algorithm’s optimality-seeking throughout the process.
      PubDate: Sat, 24 Sep 2022 09:50:00 +000
  • Highly Robust Synthetic Aperture Radar Target Recognition Method Based on
           Simulation Data Training

    • Abstract: Sufficient synthetic aperture radar (SAR) data is the key element in achieving excellent target recognition performance for most deep learning algorithms. It is unrealistic to obtain sufficient SAR data from the actual measurements, so SAR simulation based on electromagnetic scattering modeling has become an effective way to obtain sufficient samples. Simulated and measured SAR images are nonhomologous data. Due to the fact that the target geometric model of SAR simulation is not inevitably consistent with the real object, the SAR sensor model in SAR simulation may be different from the actual sensor, the background environment of the object is also inevitably different from that of SAR simulation, the error of electromagnetic modeling method itself, and so on. There are inevitable differences between the simulated and measured SAR images, which will affect the recognition performance. To address this problem, an SAR simulation method based on a high-frequency asymptotic technique and a discrete ray tracing technique is proposed in this paper to obtain SAR simulation images of ground vehicle targets. Next, various convolutional neural networks (CNNs) and AugMix data augmentation methods are proposed to train only on simulated data, and then target recognition on MSTAR measured data is performed. The experiments show that all the CNNs can achieve incredible recognition performance on the nonhomologous SAR data, and the RegNetX-3.2GF achieves state-of-the-art performance, up to 84.81%.
      PubDate: Wed, 21 Sep 2022 10:05:01 +000
  • Fast TDOA and FDOA Estimation for Coherent Pulse Signals

    • Abstract: Time difference of arrival (TDOA) and frequency difference of arrival (FDOA) have been widely used for localizing temporally continuous signals passively. Temporal sparsity of pulse signals makes their TDOA and FDOA estimation processes much different, and computational complexity is a major concern in this area. This paper addresses the problem of fast TDOA and FDOA estimation of pulse signals and focuses mainly on narrowband coherent pulses. By decoupling the effects of TDOA and FDOA in the cost function of localization approximately, we propose a fast coarse TDOA and FDOA estimation method. The estimates are then refined with the cross-ambiguity function (CAF) algorithm within a small TDOA and FDOA neighborhood. In the simulations, the proposed method is demonstrated to have satisfying TDOA and FDOA estimation precisions, and it exceeds existing counterparts largely in computational efficiency.
      PubDate: Tue, 20 Sep 2022 11:05:01 +000
  • Study on Numerical Simulation and Electromagnetic Scattering of
           Time-Invariant Freak Waves

    • Abstract: The occurrence probability of freak waves is related to the sea wave spectrum. In this paper, different wave spectrums are used to simulate time-invariant three-dimensional freak waves. Freak waves that meet the international standards are generated at fixed time and location by adjusting the energy of the wavelets. We studied the occurrence probability of freak waves under the conditions of different wave spectrums, different wind speeds, and different modulation ratios and optimized the calculation speed of the model. Simulation data show that the difference in the shape of the wave spectrum affects the probability of freak waves occurrence. The model conforms to the Benjamin–Feir index (BFI), and the ratio of wave steepness to spectrum bandwidth is the key. In this paper, the Kirchhoff approximation theory is used to study the electromagnetic scattering (EM scattering) properties of freak waves on the large scale. We ideally calculate the Normalized Radar Cross-Section (NRCS) from the sea surface with freak waves, under different wind speeds and different grazing angles. The NRCS of freak waves is extremely low, and the increase of wind speed and the decrease of the grazing angle will make the detection of freak waves more difficult. The possibility of detection of freak waves is higher at high grazing angles (low incidence angles). The numerical simulations provide reference for engineering.
      PubDate: Tue, 20 Sep 2022 09:20:01 +000
  • Research on the Integration Method of Character Costume Culture in
           Dunhuang Murals Based on Deep Learning Algorithm

    • Abstract: Objective. As one of the world’s cultural heritages, Dunhuang murals contain profound cultural, historical, social, and artistic values. In this paper, the evolution and progress of character costumes are analyzed and the development process of Chinese costumes is studied. Methods. This paper compares the characteristics of the costumes in different times; the progress and changes in graphics, styles, and textures; and the different characteristics from the costumes in the modern society. It also compares the coupling degree data of clothing culture in the two periods. Through analysis and research it is found that, compared with traditional algorithms, the integration of clothing culture using deep learning algorithms is more coupling. Through the calculation and analysis of clothing evolution in Dunhuang murals, more design inspiration can be provided for Chinese clothing designers, and more strength and research materials can be contributed to future design and clothing development in combination with ancient and modern clothing culture.
      PubDate: Wed, 14 Sep 2022 06:05:01 +000
  • Analysis of Network Information Retrieval Method Based on Metadata

    • Abstract: In order to solve the problem that people can accurately search for the network information they need, the research on network information retrieval methods becomes more important. This article is mainly about the research of network information retrieval methods based on metadata ontology calculations. This article constructs an LDA three-layer Bayesian model with a three-layer structure of document, topic, and single order. The three-layer structure obeys a random polynomial distribution and can be calculated the joint distribution probability of all variables in the LDA model greatly increases the calculation efficiency. Using a cross-modal information retrieval method, it can mine the common data features between different modal data and analyze the semantic correlation between different modal data, improve the accuracy of search, and solve the existence of different modal data. There is a gap in the expression semantics between heterogeneous and different modal data. The experimental results in this paper show that the text feature extraction of the network information retrieval method based on the metadata ontology calculation has a good performance in terms of accuracy, and the accuracy of the extraction and clustering results is as high as about 90%. The improved CCA algorithm used is better than the traditional CCA and the accuracy is improved by 23%, which is 12% higher than the LDA-CCA algorithm.
      PubDate: Mon, 12 Sep 2022 06:35:00 +000
  • A Wideband Feed Network for Vivaldi Antenna Arrays

    • Abstract: A wideband feed network for a Vivaldi antenna array is presented. A limitation of current wideband antenna arrays is the bandwidth of either the feed network or the antenna element. The proposed antenna array consists of four wideband Vivaldi antennas fed with an improved wideband feed network to extend the useable bandwidth of the array. The proposed feed network consists of coplanar waveguide-to-slotline-to-microstrip line transitions. The feed network has a single coplanar waveguide input and four microstrip line output ports. The feed network achieved uniform amplitude and phase balance and an impedance bandwidth of 160% from 1 GHz to 9 GHz. The feed network was used in a uniform linear antenna array to feed four Vivaldi antenna elements. The Vivaldi antenna array achieved stable radiation patterns from 1.3 GHz to 8 GHz, resulting in a useable bandwidth of 144%. The antenna array has a minimum gain of 8 dBi and a maximum of 13.8 dBi within the frequency band. Results for a prototype Vivaldi antenna array, measured in a compact antenna test range, are presented and compared to simulated results from CST Studio Suite.
      PubDate: Sat, 10 Sep 2022 08:50:02 +000
  • Near-Field Electromagnetic Scatterings and Imaging of a Ship Based on
           High-Frequency Techniques

    • Abstract: In radar detection, it is important to investigate the near-field scattering characteristics since the far-field condition is not easily satisfied for the distance between the radar and the electrically large ship on the sea surface. A high-frequency techniques of the physical optics (PO) and shooting and bouncing rays (SBR) with local expansions based on the facets of the target are proposed to take the electromagnetic scatterings in the near zone. Therefore, it is a more straightforward method to modify the computation from traditional far-field problem to near-field problem with the singularity-free characteristic. Simulation results show that it has high accuracy but requires very little increase in computational costs in the near-field problem. Moreover, the 1-D high-resolution range profile (HRRP) demonstrates that the near-field scattering mechanism is much different from the cases in the traditional far-field problem.
      PubDate: Sat, 10 Sep 2022 06:35:01 +000
  • Prediction Method of Electromagnetic Wave Propagation on High Sea State
           Based on P-M Wave Spectrum

    • Abstract: In order to realize the near sea surface communication under high sea states, a link-peak diffraction model is proposed. A P-M sea wave model is established based on the bilinear superposition method. The simple single-peak diffraction model is modified and the theoretical calculation is carried out. The steps to correct the simple single-edge peak diffraction model are multi-edge diffraction model, multi-circular peak diffraction model, and link-peak diffraction model. Simulation experiments are carried out on the applicable frequencies of the link-peak diffraction model, and the attenuation of electromagnetic waves at the round peak diffraction is calculated. The link-peak diffraction model not only simplifies the calculation process in the applicable frequency but also shows good agreement with the results of the multi-peak diffraction model, which provides a theoretical basis for the calculation of electromagnetic wave propagation attenuation in high sea states.
      PubDate: Thu, 08 Sep 2022 12:20:01 +000
  • Optimization of Self-Media Film and Television Content Production and
           Dissemination Paths under the Background of Artificial Intelligence

    • Abstract: The development of Internet technology and cloud computing has promoted the rapid development of self-media technology. The self-media technology has better people-friendliness compared to the traditional media communication mode, so it has gained more popularity compared to the traditional media mode. For professional self-media teams, the popularity and clicks of self-media content are very critical. It needs to make corresponding predictions and judgments according to the content and transmission path of the self-media. However, self-media is transmitted in the form of video, which involves a huge amount of data. This team of self-media staff is a more difficult and tedious task. This study uses the atrous convolution and long short-term memory neural network to predict the video content, sound features, and propagation path of self-media technology. Atrous convolution is more suitable for research objects with more data. The research results show that the atrous convolution and LSTM methods have better feasibility and credibility in predicting three special characteristics of self-media. Compared with a single atrous convolution, the feature prediction errors of the three kinds of self-media are smaller by using the atrous convolution and LSTM hybrid method. The largest prediction error is 2.39%, and this part of the error is mainly due to the sound characteristics of self-media technology.
      PubDate: Thu, 08 Sep 2022 10:20:02 +000
  • Wavelet Transform-Based 3D Landscape Design and Optimization for Digital

    • Abstract: As a hot concept, the digital city has developed rapidly in recent years. The digital city uses information technology to realize all the contents of the past, present, and future of the city on the network, and can build a three-dimensional visual landscape. However, the traditional information fusion model has the problems of noise susceptibility and low efficiency in landscape design. In order to solve the above problems, this article proposes a wavelet transform-based 3D landscape design and optimization method for digital cities, which removes the noise influenced by wavelet change and builds an information fusion model based on neural network to complete the design optimization of the three-dimensional landscape of the digital city. Firstly, for the wavelet change denoising problem, an effective denoising algorithm for natural noise and abnormal noise is proposed by combining convolutional neural network and wavelet transform. The algorithm extracts mixed feature information of local long path and local short path based on the information retention module, and decomposes the information by combining wavelet transform, inputs the different components obtained from the decomposition into the network for training, and removes the noise by subsequent feature screening of the network structure. Then, aiming at the optimization of 3D landscape design, an information fusion model based on long-short time memory network and radial basis backpropagation network is proposed for fusing multiple sources of information in the digital city to evaluate the landscape. The method collects digital city feature information at the information layer and preprocesses the feature information by a rate detection algorithm. Then, LSTM and RBF-BP neural networks in deep learning are used in the feature layer for adaptive learning of multiple feature signals, and finally, fuzzy logic is used to control the system decision output to improve the efficiency of 3D landscape design. Finally, the simulation experimental results show that the proposed denoising method in this article can better retain the texture details in the images and the denoised images have better visual effects; the proposed information fusion model has higher accuracy compared with the traditional methods. Combining this method to design and optimize 3D landscapes in digital cities can improve the efficiency of landscape design.
      PubDate: Wed, 07 Sep 2022 06:05:00 +000
  • Conjoined, Two-Monopole Antenna Pair with Decoupling Inductor for Wi-Fi 6E
           Notebook Applications

    • Abstract: A low-profile, conjoined and yet decoupled two-monopole design for Wi-Fi 6E notebook applications is presented. The single monopole antenna has a small size of 4 mm × 18.7 mm. The antenna is composed of a two-branched monopole with two shorting inductors for producing the 5 GHz (5150–5825 MHz) and 6 GHz (5925–7125 MHz) bands, and an inductor loaded at one branch end and connecting to a tuning portion for 2.4 GHz (2400–2484 MHz) operation. Two symmetrical monopoles are further conjoined by a chip inductor that connects the open ends of the tuning portions, forming a compact footprint of 4 mm × 38.4 mm for the two-notebook antenna design. With the use of the decoupling inductor and a proper two-monopole arrangement, acceptable isolation and a low envelop correlation coefficient (ECC) can be attained.
      PubDate: Mon, 05 Sep 2022 10:50:02 +000
  • Planar High-Gain Millimeter-Wave Slotted SIW Cavity Antenna Array with Low
           Sidelobe and Grating Lobe Levels

    • Abstract: In this paper, a planar high-gain millimeter-wave (mmW) slotted substrate integrated waveguide (SIW) cavity antenna array with low sidelobe and grating lobe levels is proposed. The antenna consists of a slotted SIW resonator and an SIW transmission line (TL). To achieve a high gain and simplify the structure of the antenna element, the slotted SIW cavity is resonated in high-order mode. Then, a high-gain antenna array is implemented with only four such elements. By analyzing the pattern multiplication principle of the antenna array and accurately adjusting the element spacing, the high grating lobe level caused by the large spacing of the high-order mode resonator is considerably reduced. In addition, a one-four unequal amplitude power divider is introduced to further reduce the antenna array’s sidelobe levels (SLLs). Finally, the proposed antenna array is fabricated for verification. The measured peak gain is 21.4 dBi at 27.3 GHz. The measured grating lobe level in the E-plane is reduced to −17.9 dB, and the measured SLLs are lower than −19.1 dB.
      PubDate: Tue, 30 Aug 2022 11:05:06 +000
  • Analysis, Optimization, and Hardware Implementation of Dipole Antenna
           Array for Wireless Applications

    • Abstract: The antenna pattern synthesis is one of the significant problems in the phased array antenna. Pattern synthesis refers to the optimized weight excitation of each antenna element in order to steer the beam electronically without mechanically rotating the antenna. It can be achieved by using a combination of phase shifters and attenuator circuits. In this paper, a 2 by 2 dipole antennas with an RF beamforming circuit has been designed to steer the main beam along the azimuth plane. The main beam coverage from 100° to 140° with a step size of 10° has been successfully optimized using a hybrid of the induced EMF method and a genetic algorithm. The optimization results were compared to the full-wave simulation technique implemented in Empire XCCel. The design is realistically implemented at 2.45 GHz, with both simulation and measurement results shown. The measured reflection coefficient of the phased array antenna is −48 dB at 2.56 GHz. The feasibility of the beam synthesis has been validated successfully with the main beam being steered at 110°. The possibility of a fabrication discrepancy resulting in minor radiation degradation is also discussed in this research. The dipole antenna system with RF beamformer circuit can be applied to indoor positioning systems such as Wi-Fi, wireless local area network (WLAN), and fifth-generation.
      PubDate: Tue, 30 Aug 2022 11:05:05 +000
  • Aperture-Fed Quad-Port Dual-Band Dielectric Resonator-MIMO Antenna for
           Sub-6 GHz 5G and WLAN Application

    • Abstract: A four-port dielectric resonator-based connected ground multiple-input multiple-output (MIMO) antenna is designed. The presented antenna was excited through the aperture feeding technique. The dual bands are achieved by optimally feeding the rectangular dielectric resonator through engineered triangular slots. The antenna has operating modes of and at 4.5 GHz and 5 GHz, respectively. It presents a 2 : 1 VSWR bandwidth of 2.64% (4.48 GHz–4.60 GHz) and 1.2% (4.96 GHz–5.04 GHz) in the lower and upper bands, respectively. The edge-to-edge distance between array elements is around 7.5 mm. The single antenna dimension is 30 mm × 30 mm, whereas the four-port antenna dimension is 60 mm × 60 mm. The optimum isolation was achieved by carefully placing the antenna elements on the substrate through multiple iterations. The antenna provides port isolation better than 20 dB at both resonances with full ground profile. The advantage of the antenna is that it provides fair antenna and MIMO parameters without additional isolation techniques. The antenna has efficiency in order of 88.02% and 86.31%. The peak gain is 7.67 dBi and 8.32 dBi at 4.5 GHz and 5 GHz, respectively. The optimum envelope correlation coefficient (ECC) is 0.037, channel capacity coss (CCL) is 0.2 bits/sec/Hz, diversity gain (DG) is 9.99 dB, and total active reflection coefficient (TARC) is −18.87. The antenna elements are orthogonally placed with adequate separation to achieve polarization diversity and spatial diversity. The antenna provides the utilization in Sub-6 GHz 5G and WLAN communication applications.
      PubDate: Sun, 28 Aug 2022 11:20:03 +000
  • Low-Cost Lens Antenna Design for Microwave Moisture Detection

    • Abstract: In this study, a novel Vivaldi antenna with dimensions of 100 mm × 85 mm × 1.6 mm, designed for a moisture measurement system, is built to enhance the gain of conventional Vivaldi antennas in the low-frequency band to suit the needs of moisture detection. The fence structure and choke slot are modified to enhance the antenna’s radiation properties in the low-frequency band, and simulation is performed to determine how different structural parameters affect the antenna’s performance. The results show that in the frequency band of 5-6 GHz, the voltage standing-wave ratio (VSWR) of the antenna is less than 2, and the gain at 5.8 GHz reaches 16.2 dBi after installing the lens. Compared with conventional unmodified Vivaldi antennas, the gain at 5.8 GHz increases by approximately 6.11 dBi. The antenna is then processed and measured, and the measured results are in good agreement with the simulated results; hence, the antenna can be widely used in the field of moisture detection.
      PubDate: Sun, 28 Aug 2022 11:20:02 +000
  • Broadband Compact MIMO Antenna Employing CRLH Transmission Lines with High

    • Abstract: A broadband and planar multiple-input multiple-output (MIMO) antenna with pattern diversity is presented in this letter. The four-port MIMO antenna is designed by using a novel metamaterial structure with small dimensions of 60 × 60 × 1.6 mm3. Each radiating element of the MIMO antenna is comprised of composite right/left-hand (CRLH) transmission lines (TLs). Between its four elements, there are four open L-shaped slot loading on the ground plane of the patch antenna system. The antenna obtains the wide frequency range of 2.31–4.99 GHz. In addition, The proposed antenna has an isolation greater than 20 dB between its four elements. The MIMO antenna has excellent bandwidth performance and good diversity properties between elements.
      PubDate: Sat, 27 Aug 2022 13:50:01 +000
  • Navigation Control Method of Indoor Mobile Robot Based on Visual Servo

    • Abstract: In order to improve the navigation control effect of indoor mobile robot, this paper studies the navigation control method of indoor mobile robot combined with visual servo technology. For the problem that the target may be out of the camera’s field of view during the servo process, a control algorithm with field-of-view constraints is proposed, which assigns a certain weight to the image feature error at each moment. Moreover, this paper realizes the servo process that the image features are always located in the field of view by setting the variable values involved in the weight value calculation method. Through the simulation test, it is verified that the indoor mobile robot navigation control method based on visual servo has certain effects.
      PubDate: Sat, 27 Aug 2022 09:20:01 +000
  • Implementation of DOA Estimation System Based on HackRF One

    • Abstract: In the practical direction of arrival (DOA) estimation applications, it is required that the multichannel signal acquisition equipment can synchronously collect the signals received by the array antenna. In addition, the signal phase relationships between channels are supposed to be stable. However, this kind of equipment is usually complex and expensive to manufacture. Since some SDR devices are reconfigurable and open source, this paper adopts HackRF Ones as the signal sampling devices to design the DOA estimation system. The clocks line is used to synchronize the clock frequencies between HackRF Ones. Besides, an external pulse is introduced to control the sampling devices to start sampling simultaneously. In this case, the stable phase difference between channels can be obtained. The experimental results show that the synchronization error between channels of the system is less than one sampling period. The system can be used to estimate the incident angles of single carrier signals or modulated signals. The RMS errors of the system when estimating one source and two sources are 1.94° and 2.85°, respectively.
      PubDate: Sat, 27 Aug 2022 08:35:01 +000
  • Modelling of Metal Removal Rate in Copper Alloy Milling Using MATLAB

    • Abstract: The copper found in Earth’s soil ranks fourth in abundance among structural metals. Copper alloys are composed of copper and other elements. Most commonly, these alloys are used in aerospace, medical, and energy applications, but they are also used in many other areas. The amount of the stabilizing agents and the temperature determine which phase copper alloys exist in, including α, α + β, and β. The temperature in the cutting zone is one of the most important factors to control when machining copper alloys. Copper alloys have low thermal conductivity and high heat capacity, meaning that they have low heat conduction from the cutting zone, which leads to the built-up heat in the cutting edge. As the workpiece and cutting tool moves at different speeds, the temperature is strongly affected by the cutting speed. The physical and chemical properties of tool wear progression have been used in several studies and research projects to model tool life and metal removal as a result of this fact. The focus of this article is on establishing a model connecting cutting parameters and measured responses in terms of tool life, using the design of experiments and metamodeling to establish a model that can be used to predict tool life from milling experiments. In order to secure reliable machining operations, these models were designed for customer recommendation and cutting data optimization. The study focused on copper alloys 6Al-4V, the most common being α + β alloy. In conclusion, the two models developed in this study are able to predict the tool life based on the cutting speed and radial width of cuts. As long as certain parameters are met, the models will ensure the highest possible metal removal rate.
      PubDate: Thu, 25 Aug 2022 17:35:05 +000
  • Analysis of Transmission Characteristics on an MSK-Based Rotating
           Magnet-Based Mechanical Antenna

    • Abstract: A rotating magnet-based mechanical antenna (RMBMA) is a new promising paradigm which can significantly reduce both the size and the power consumption of the super-low frequency electromagnetic transmitter. To further reveal the effects of the rotational motion on transmission, this paper investigates the performance analysis of MSK (Minimum Shift Keying)-based RMBMA for the first time. Initially, based on the framework of MSK-based RMBMA, both the information loading of RMBMA and the control strategies of the motor are proposed, such that the impacts of the step response induced by the motor on the information loading are characterized. Then, the transmission capacity of the MSK-based RMBMA is derived in the closed form. The results indicate that increasing output torque or decreasing inertia load can enhance the transmission capacity. Finally, numerical simulations using a realistic system model demonstrate the validity of the proposed performance analysis. The simulation results show that when the inertia is less than 0.0128 kg∙m2 and the symbol rate is less than 4 bit/s, the bit error rate is less than 10%, thereby improving the transmission capacity. The proposed comprehensive design principles of RMBMA provide guidance for system design and practical implementation.
      PubDate: Thu, 25 Aug 2022 17:35:05 +000
  • Search-Free Angle, Range, and Velocity Estimation for Monostatic FDA-MIMO

    • Abstract: The monostatic frequency diverse array multiple-input multiple-output (FDA-MIMO) has attracted much attention recently. However, much research is concentrated on the estimation of angle-range parameters based on the FDA-MIMO radar, and the velocity has not been considered. In this study, we propose a search-free method to estimate these parameters. To overcome the problem of the high computational complexity associated with the searching estimation algorithms, the parallel factor (PARAFAC) decomposition is introduced to estimate the space-time steering vector. Next, we can utilize the least square method to solve the angle, range, and velocity of each target. In addition, the Cramér–Rao bounds (CRBs) of angle, range, and velocity are derived. Besides, the other performance analysis consists of the root mean square error, and complexity is derived. We compare the PARAFAC decomposition algorithm with the estimation of signal parameters via the rotational invariance techniques (ESPRIT) algorithm, and our method owns a superior performance. Finally, the proposed method is verified by simulations and has the ability to achieve greater estimation accuracy than existing algorithms.
      PubDate: Wed, 24 Aug 2022 17:20:02 +000
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