International Journal of Antennas and Propagation

Published by Hindawi
Online ISSN: 1687-5877
Print ISSN: 1687-5869
Discipline: Antennas & Propagation
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Aims and scope

International Journal of Antennas and Propagation publishes papers on the design, analysis, and applications of antennas, along with theoretical and practical studies relating the propagation of electromagnetic waves at all relevant frequencies, through space, air, and other media.

As well as original research, the International Journal of Antennas and Propagation also publishes focused review articles that examine the state of the art, identify emerging trends, and suggest future directions for developing fields.

Recent publications
  • Robert Macharia MainaRobert Macharia Maina
  • Philip Kibet LangatPhilip Kibet Langat
  • Peter Kamita KihatoPeter Kamita Kihato
Null steering is essential in collaborative beamforming (CB) in wireless sensor networks (WSNs) to ensure minimal radiation power and interference in the direction of unintended receivers. Current research in null steering in CB in WSNs is mainly from the perspective of planar arrangements of sensor nodes and sink(s). Furthermore, there is no research dedicated to the formation of multiple wide nulls during CB in 3-dimension WSNs. Wide nulls are ideal in scenarios featuring mobile unintended sink(s). A new multiple and wide null steering scheme applicable to CB in WSNs is presented in this work (from the perspective of a 3-dimensional random arrangement of static sensor nodes). It is assumed that desired nulling directions are implicitly known at a CB cluster head. A particle swarm optimization (PSO) algorithm variant is applied in concurrent node transmit amplitude and phase perturbation with an aim of achieving beam steering alongside multiple and wide null steering. The performance of the proposed null steering scheme is validated against a basic null steering approach (with reference to current literature). Furthermore, a comparative null depth, width, and nulling accuracy analysis are done upon varying the count of collaborating nodes and the collaborating cluster radius. An increase in the number of collaborating nodes is found to increase nulling depth at an exponentially decaying rate. An increase in the collaborating nodes’ cluster radius yields a reduction in null width. The contributions of this work to the existing literature are as follows: (i) the design and investigation of a null steering scheme from the perspective of a 3-dimension random arrangement of sensor nodes; (ii) the design of a concurrent beam steering and multiple wide null steering scheme on the basis of concurrent node transmit amplitude and phase perturbation whilst ensuring null depth uniformity; (iii) a statistical analysis of the impact of a count of collaborating nodes and collaborating cluster radius on nulling performance; (iv) investigation of capacity improvement at unintended receivers upon null steering.
  • K. MalaisamyK. Malaisamy
  • G. HaridossG. Haridoss
  • J. Arun PandianJ. Arun Pandian
  • Samira Kabir RimaSamira Kabir Rima
This work proposes, builds, and manufactures a small, high-gain MIMO antenna for radar applications. Using a Parasitic elements such as director & reflector show a simple method for increasing the gain and bandwidth of a Yagi-Uda Antenna. Using a Parasitic elements such as director and reflector show a simple method for increasing the gain and bandwidth of a Yagi-Uda Antenna. Using a nearby parasitic director and reflector. Also, it shows a simple method for increasing the gain and bandwidth of a Yagi–Uda antenna. A strip with a parasitic director is placed close to the top dipole element to improve the gain as well as bandwidth attributes of the Yagi–Uda antenna. The antenna performance parameters are investigated for 1 × 2 MIMO, cross dipole MIMO antenna (1 × 4), and an array configuration (two 1 × 4). It has high gain and operates in the S-band (2 GHz–4 GHz). This antenna supports three bands and has a highest maximum directive gain of 12.5 dBi at 2.5 GHz and a bandwidth of 0.21 GHz. It is made of FR4 substrate. The suggested structure is 120 mm × 70 mm in size. Due to its high gain and less return loss, this antenna is better suited to radar applications.
This article presents a miniaturized wide-angle scanning phased array for fifth-generation (5G) application. A subarray of two closely packed patch antennas on electromagnetic bandgap structure (EBG) ground with the operating bandwidth of 26–29 GHz is used as the basic module of the linear array, which contains four equally spaced subarrays. The existence of the EBG ground enables the array to be compact in size (3.2 × 0.6 × 0.12λL3), yet the mutual coupling between each element can reach to more than 22 dB within the whole band of interest. The EBG structures also contribute to the wide element radiation pattern of the aperiodic array and consequently the wide scanning angle performance of the array. The range of the main beam scan with EBG structure can reach from −70° to 70° with more than 6 dB side lobe levels (SLLs) at 26.5 GHz with 3 dBi scanning gain loss. This proposed method enabling the array to be compact and wide in scanning angle is very attractive for 5G mobile terminal applications.
In view of the existing literature mainly studying the situation of infinite reinforced concrete structure, the shielding effectiveness of three-dimensional single-layer reinforced concrete cavity is studied by considering the structural parameters of steel and the electromagnetic parameters of the concrete. The influence of structure parameters of steel mesh size, the steel diameter, and electromagnetic parameters of concrete dielectric coefficient, conductivity and moisture content on shielding effectiveness of reinforced concrete are analyzed. The research shows that the shielding effectiveness of the reinforced concrete cavity structure has resonance characteristics, and the increase of concrete conductivity and moisture content weaken the resonance characteristics of it so that the shielding effectiveness of the reinforced structure is improved. The results of this paper have a reference value for the analysis of shielding effectiveness of the single-layer reinforced concrete cavity in different practical situations.
The discrete Fourier transform (DFT)-based codebook is currently among the mostly commonly adopted codebooks for beamforming using arrays of different shapes and sizes, including the large-scale two-dimensional uniform planar array (UPA). DFT-based codevectors can be easily generated in arbitrary angle resolutions and apply well to millimeter-wave (mmWave) channels due to their directive nature of resulting beams. However, a fixed set of codevectors is applied regardless of the user distributions and the propagation environment, which may exhibit limited beamforming performance under certain transmission scenarios. In this paper, we propose a new way of generating a set of beamforming vectors for multiple-input multiple-output (MIMO) transmission using massive arrays under the limited feedback of the channel state information (CSI). Precoder matrix indicator (PMI) and channel quality indicator (CQI) reports from the users have become the sources for the generation of a new set of codevectors, which are autonomously determined by the deep learning (DL) module at the base station (BS). The process is operated in an iterative fashion to produce updated versions of the codebook with the reduced return of the loss function at the deep neural network (DNN). The time-varying codebook for each BS automatically reflects the characteristics of a given wireless environment to adapt to its channel and traffic conditions. The reference signal (RS) at the BS is periodically transmitted in the form of beamformed CSI-RS, thus the operation is transparent to the users of the system and no significant specification changes are necessary. A simple plug-and-play type of BS installation suffices to achieve the potential gain of the proposal, which is demonstrated by the implementation details of the DL engine and the corresponding performance simulation results.
In this study, a new stacked microstrip slot antenna (MSA) with wideband circular polarization (CP) characteristics is proposed. The antenna consists of a square-loop feed configuration, four parasitic square patches, four parasitic vertical planes, and a square ground plane etched with four parasitic square slots. The corner-cut square-loop can excite a stable 270° phase difference by loading an arc-shaped strip into the square-loop. Square-patches, vertical planes, and square slots as parasitic elements are placed together at the side of the square-loop to stimulate two CP resonant points. Simulation and measurement are performed on the designed antenna prototype to demonstrate the design’s rationality. The measured results depict that the measured impedance bandwidth (IBW) for |S11| < −10 dB is 36.4% (4.65 to 6.70 GHz) and the measured axial ratio bandwidth (ARBW) for AR < 3 dB is 25.1% (5.01 to 6.45 GHz). Compared with other reported stacked CP antennas, the proposed antenna has significant advantages in CP bandwidth, which could occupy the wireless local area network ITS (5.8 GHz), (5.725–5.85 GHz), and WIFI (5.85–5.925 GHz) bands.
Radio astronomy is a discipline of dynamics and wonders. The vast universe has many secrets to unravel. As one of the important facilities in this discipline, radio telescopes play a key role in collecting astronomical data and unraveling mysteries. With the demand of radio astronomy for a higher frequency, wider bandwidth, higher gain, and higher pointing accuracy, the aperture of the radio telescope is gradually increasing, and its electrical performance and structure have become tightly coupled. Therefore, how to ensure the stable and efficient operation of the telescope for the long-term operation has become the urgent demand for large aperture high-performance radio telescopes. Therefore, this paper firstly makes a comparison of the overall condition of large radio telescopes in nearly a decade that are both constructed and operated, including the progress of radio telescopes that are being constructed and the planning for construction. Then, systematically summarized the latest research progress of electromechanical coupling technology from 3 aspects of connotation and application of electromechanical coupling, and performance guarantee under slowly varying load and performance guarantee under rapidly varying load from the perspectives of design, manufacturing, and observation operating. Lastly, the future research direction of electromechanical coupling technology is pointed out according to the development trend of radio astronomy.
In this paper, a low profile and high-efficiency decoupling antenna pair for multiunit smartphones is proposed using a similar π-shaped feed structure that can excite the dipole radiation mode of microstrip antenna. Ordinarily, symmetrical single-port T-shaped microstrip antennas can only excite monopole modes of bilateral radiation. This paper changes the vertical feeding microstrip structure into two oblique, similar π-shaped feeding structures. This oblique feeding structure can excite the dipole mode of unilateral radiation of the microstrip antenna. Using this method, the antenna design can be simplified, and the low-coupling independent radiation on both sides of the microstrip antenna can be freely controlled without the need for additional structures. Considering the ultra-thin characteristics of 5G smartphone devices, the parameters of the antenna are further optimized: the optimized antenna profile is only 3.7 mm. The measured results show that the 2 × 2 microstrip antenna pairs can effectively cover the 3.5 GHz band (3.4–3.6 GHz), with a coupling that varies from −16.14 dB to −11.01 dB and an efficiency that varies from 80% to 94.1%. The 8 × 8 MIMO smartphone antenna results show that the coupling varies from −20.1 dB to −12.17 dB, the efficiency varies from 79.72% to 93.7%, and the envelope correlation coefficient (ECC) is lower than 0.05. The microstrip antenna decoupling pair with a similar π-shaped feed structure proposed in this paper has high efficiency and low-profile characteristics have important application value in the decoupling design of 3.5 GHz 5G ultra-thin smartphone antennas.
In this paper, a wideband eight-element multiple-input multiple-output (MIMO) antenna array for 5G smartphone applications is presented. Each antenna is composed of a dual-arm tortuous monopole radiating element with a double-stub tuner and an open slot on the ground plane. Tuning stub microstrip lines are utilized to improve impedance matching. The operating bandwidth of the single antenna element is from 3200 to 6000 MHz with three resonant frequencies. The operating bandwidth covers the 5G new radio (NR) bands (n77/n78/n79) and the WLAN-5GHz band. The isolation of the proposed MIMO antenna array is above 10 dB in the entire operating band without any isolation elements. Furthermore, the proposed MIMO array was manufactured and measured. The measured results validate that the MIMO antenna array has a wide 6-dB impedance bandwidth from 3.2 to 6 GHz and the isolations are all more than 10 dB. The total efficiency ranges from 38% to 83%. The above results show that this MIMO antenna array can support 5G applications in smartphones.
In antenna array design, low dynamic range ratio (DRR) of excitation coefficients is important because it simplifies array’s feeding network and enables better control of mutual coupling. Optimization-based synthesis of pencil beams allows explicit control of DRR. However, incorporating DRR into an optimization problem leads to nonconvex constraints, making its solving challenging. In this paper, a framework for global optimization of linear pencil beams with constrained DRR is presented. By using this framework, the methods for synthesis of pencil beams with minimum sidelobe level and minimum sidelobe power are developed. Both methods utilize convex problems suitable for the synthesis of pencil beams whose coefficients’ signs are known in advance. By incorporating these problems into a branch and bound algorithm, the procedures for global optimizations are formed which systematically search the space of all coefficient signs. The method for minimization of sidelobe power is further analyzed in the context of beam efficiency. It is shown that this method can be utilized in an approximate and at the same time global design of pencil beam arrays with maximum beam efficiency and constrained DRR. Based on this approach, a method for the design of pencil beam arrays with minimum DRR and specified beam efficiency is proposed.
In this paper, a novel design approach with universal applicability is proposed for realizing a low cross-polarized terahertz tri-reflector compact antenna test range (CATR). This approach not only enables the radiation direction of the feed relative to the main reflector to be designed arbitrarily but also enables the designed CATR systems corresponding to different feed rotation angles while still maintaining a low cross-polarization. By using the beam mode analysis method and cross-polarization elimination conditions, the geometric configurations of the tri-reflector CATR can be designed for feeds in any different rotation angles, and then according to the kinematic and dynamic ray-tracing method with frequency independence in geometric optics, shaped subreflectors can also be synthesized. Through the above design procedure, four tri-reflector CATRs corresponding to four different feed rotation angles have been achieved, respectively. Numerical simulation results show that the cross-polarizations of four tri-reflector CATRs are all less than –38 dB and the peak-to-peak amplitude (phase) ripples of the quiet zone (QZ) are all within 1 dB (10°) in the frequency range of 100–500 GHz. This demonstrates the effectiveness and universal applicability of the proposed design method in realizing the design of low cross-polarization and good QZ performance for tri-reflector CATRs with different feed rotation angles.
In this paper, a W band (75–110 GHz) phase shifter based on the liquid crystal of continuous tunability and the three-electrode bias network of excellent electrical manipulation is designed. Taking Rexolite 1422 as the transmission dielectric, in which slots are dug and filled with liquid crystal. The voltage is regulated by the electrode bias network, and then the liquid crystal dielectric constant is changed to realize phase shift. The measured results show that the phase shift of the liquid crystal dielectric phase shifter can be up to 440° through the electrical control of the bias electrode network, which surpasses many designed phase shifters. In the whole W band, the insert loss is about 3 dB and the return loss is almost over 10 dB, emerging excellent matching.
In this paper, a compact dual-band filtering power divider (FPD) combined by conventional Wilkinson power divider and dual-mode resonators is proposed. The resonators submitting the quarter wavelength transmission line can act as a filter. The proposed resonator is composed of two cascading symmetrical ring branches connected to the ground in the middle. The inter-digital coupling structure constitutes the feed lines of the band-pass filter (BPF) operating at 2.45/5.8 G. The resonator with symmetrical structure is analyzed by the odd-even mode method in detail. The two resonant frequencies can be adjusted by the length of the stub separately. In addition, two isolation resistors are placed at proper position for ensuring the isolation effect. The proposed FPD is fabricated for verifying simulation results, and good agreements between the simulated and measured results are achieved here.
The reradiation interference from power transmission lines (PTL) on the adjacent wireless stations is directly caused by the induced current on metal parts, which means the interference could be suppressed by reducing the induced current. In order to effectively analyze the induced current of PTL, a method for analyzing induced current on PTL based on characteristic modes is proposed combining MoM with intrinsic modes. This method breaks through the traditional antenna resonance theory proposed by IEEE and could effectively avoid model equivalent defects and frequency limitations of traditional methods. Firstly, a generalized characteristic equation about the characteristic mode currents of PTL is constructed, and the numerical solutions of the characteristic mode currents are obtained by the idea of a discrete solution. Then, through the weighted orthogonal relationship between different characteristic mode currents, the expansion coefficients of the characteristic mode currents are obtained; finally, combined with the Poynting theorem, the physical meaning of the expansion coefficients and their related quantities are explained from the perspective of energy and the analysis of the induced current is realized from the physical level. The results of the example analysis show that the error between the peak frequencies of the induced current calculated by the method in this paper and the peak frequencies calculated by MoM does not exceed 2.46% and the method in this paper can well explain the disappearance of the “double wavelength loop resonance frequency” under the excitation of a vertically polarized plane wave.
In this paper, a new beamforming algorithm for phased array antennas is proposed, the plant growth gene algorithm. The algorithm consists of three steps. Firstly, according to the excitation relation of the array unit before and after the local fine-tuning of the antenna radiation pattern, the model for solving the array unit excitation difference is established. Secondly, the Taylor series expansion is used to solve the model, and the growth model is established based on this, and the beam tuning network is designed to realize the growth model. Finally, based on the growth gene obtained by the neural network algorithm, the growth model is called multiple times for high-precision beamforming. This algorithm converts the complex optimization process of array antenna excitation by the classical optimization algorithm into a simple process of fine-tuning the gain at any angle on the beam to make it grow and approach the target pattern. The growth gene is used to weigh the target angle and gain to achieve beamforming, which greatly reduces the complexity of the algorithm and improves its accuracy of the algorithm. Taking a 1 × 16 linear array as an example, a cosecant square beam pattern with a coverage range of −31° to 31° and a maximum gain direction of 17° is designed using the algorithm proposed in this paper. The experimental results show that the proposed algorithm can easily fine-tune the gain of any angle to achieve precise beamforming. Importantly, the growth genes trained by the algorithm are universal to the phased array antenna with the same topology.
In this paper, a Millimeter Wave antenna is designed which has a compact, lightweight and planar configuration. The frequency band is 27–29.5 GHz as a candidate band for 5G/millimeter Wave (mmW) systems. The antenna structure is similar to Quasi Yagi antenna which has driver, director, feeding part, and reflector. Substrate Integrated Waveguide used for feeding part of single element antenna and Wilkinson power divider used for antenna array feeding network. The proposed antenna has been simulated, fabricated, and measured (S11, E, and H pattern). The simulation and measurement values showed good similarity. The switched line phase shifter used to consider the beam steering (rotation) ability of the designed antenna which is important in (mmW) systems such as RADARs and mobile handsets. To evaluate this ability, for 0°, 30°, 45°, and 90° phase differences, the beam steering angle (θ) simulated and also for −90° and 90° implemented. The results showed that the efficiency, S11, and E patterns in the rotated beam is suitable and without degradation in antenna operation. To simulate and evaluate the designed antenna HFSS and CST Software are used.
In this article, high-gain ultra-wideband (UWB) monopole antenna is presented. The UWB monopole antenna is a semicircular-shaped antenna with a semicircular slot at the top side. The bottom plane consists of partial ground with triangular and rectangular slotted structures to improve the impedance bandwidth of the proposed antenna. In order to enhance gain, a 6×6 metallic reflector (FSS) is placed below the antenna. The performance of the offered design is validated experimentally. The simulated results show resemblance with the measured results. The antenna resonates for the UWB ranging from 3 to 11 GHz. Moreover, the integration of FSS improves the average gain by 4 dB, where peak gain obtained is 8.3 dB across the UWB. In addition, the reported unit cell having dimension of 0.11λ×0.11λ gives wide bandwidth (7.2 GHz) from 3.3 GHz to 10.5 GHz. The performance of the proposed antenna determines its suitability for the modern day wireless UWB and GPR applications.
Interrupted-sampling repeater jamming (ISRJ) is a new kind of coherent jamming for linear frequency modulation (LFM) signals. Based on digital radio frequency memory (DRFM), ISRJ can generate multiple false target groups by intercepting, storing, and retransmitting radar signal fragments, which significantly affects the postprocessing results of radar systems. Furthermore, due to the fragment interception of ISRJ, ISRJ false targets present a regular and discontinuous time-frequency (TF) distribution in contrast with real targets. Considering this intrinsic property and the coherent nature of ISRJ, this study proposes a new method based on TF analysis and target sparse reconstruction to address the ISRJ suppression issue. In this method, the echo signal is first sparsely represented to obtain both the real and false target positions. Then, according to the acquired target positions, information entropy features of targets are extracted in TF data for subsequent target identification. Finally, guided by the identification result, the real targets can be retained and reconstructed by adaptive filtering in the sparse domain to realize ISRJ suppression. Simulations have validated the effectiveness of the proposed method under various situations.
The field of wearable computing technology describes the future of electronic systems being an integral part of our everyday clothing with various enhanced functionalities. The present work is aimed at making closer steps towards the real wearability of electronics using textiles. We designed a fully-textile meander line Z–shaped monopole antenna for radio-frequency (RF) harvesting and for short-range communication purposes in the body-area network for various wearable applications. The target antenna was designed in the Ansys HFSS software tool and fabricated on a single-layer cotton textile using silver conductive threads and an embroidery technique. The antenna was characterized using a vector network analyzer (VNA), and the selected design was found to be nearly invariant under different deployment conditions. Antenna performance was studied by measuring the return loss while the antenna was in close proximity to the human body, or under various bending scenarios and/or wet conditions with sweat. The simulated return loss was −20.36 dB at an operating frequency of 1.62 GHz, and the measured return loss for the fabricated antenna was −19.45 dB at 1.6275 GHz with a −10 dB bandwidth of 100 MHz (i.e., 1.58 GHz to 1.68 GHz), and a fractional bandwidth of 6.17%. The results of this study are very important for the design of future wearable antennas in the new concept of the Internet of bodies.
The aim of this study is to efficiently excite the radiation of phase gradient metasurface (PGM), a novel coplanar discontinuous transmission line feed is proposed for reduction of the profile, where 12 uniform discontinuous rectangular rings form the feeding structure. The unit cells of PGM are symmetrically placed on both sides of this feed structure at the same layer, and they are close enough. The measurements agree well with those of simulations in the range of 10.48–11.18 GHz.
In order to master the law of the pseudo-signal interference effect of dual-frequency electromagnetic radiation in typical radar equipment, a certain type of Ku-band swept-frequency ranging radar was used as the test object to carry out single-frequency continuous wave and dual-frequency continuous wave pseudo-signal interference effect experiments. Through experiments, it is found that dual-frequency electromagnetic radiation will cause “hill” and “spike” type pseudo-signal interference to the swept-frequency radar. Based on the frequency analysis of the radar receiving circuit, the interference mechanism of the dual-frequency pseudo-signal is revealed, and the morphological characteristics and distance law of the pseudo-signal are explained. The variation law of the pseudo-signal level with interference field strength is obtained. The results show that the in-band dual-frequency nonintermodulation interference is similar to the single-frequency interference, and the only difference is that the number of pseudo-signals increases; when the interference frequency difference is about 400∼600 MHz, the out-of-band dual-frequency second-order intermodulation signal will cause “hill” type pseudo-signal interference, and the pseudo-signal distance is random; when the interference frequency difference is less than 5 MHz, both the dual-frequency second-order intermodulation signal and the third-order intermodulation signal will cause “spike” pseudo-signal interference inside and outside the radar operating frequency band; the pseudo-signal distance is fixed.
This paper presents accurate empirical path loss models with route classification for the high band frequency of 5 G wireless. Propagation path routes are mainly classified into line of sight (LOS) and non-line-of-sight (NLOS). The NLOS routes are classified into 2 separate routes, namely, Hard_NLOS and Soft_NLOS. Their path loss models include free-space loss (Lfs) and multiscreen diffraction loss (Lmsd) together with the reflection from the building blocks. However, these NLOS routes can be combined into a single formula. The path loss models were fitted with measured path loss data at frequencies of 28 GHz and 73 GHz. These models are compared with four 5G empirical models, namely 5GCM, 3GPP, METIS, and mmMAGIC. The results show that the separated route models provide good agreement, especially for the hard routes compared with those models and provide the minimum MAE of 4.45 dB, 4.34 dB, and 6.72 dB for the hard route, soft route, and an all-NLOS route, respectively, for the dual-band frequency.
Open dielectric waveguide structures such as circular dielectric rods can be used as antennas by leaking energy in the transverse direction or as guiding structures with low loss in integrated circuits at different frequency ranges. It is essential to understand electromagnetic wave behavior in different frequency regions such as reactive mode region, leaky-wave or antenna mode region, and guided mode region. In this study, it is aimed to assimilate the electromagnetic phenomenon for open dielectric structure by showing the overlapping between the analytic solutions and the simulation results of the TM01 mode of the circular dielectric rod. The analytic solutions for leaky-wave modes have been obtained using the coefficients matrix of the system of characteristic equations of the structure and Davidenko’s method. The field distributions and the scattering parameters have been obtained in CST microwave studio software. The outcomes obtained in the study presented the overlapping between the analytical results and the simulations. The simulation results show the leakage starts end of the reactive mode region where the electromagnetic energy reflects to the feed line, and the electromagnetic energy leaks at the leaky-wave/antenna mode region, and the leakage decreases at the guided mode region as much as it can be neglected while the frequency increases.
A low-profile dual-band directional antenna operating at both 2.4 and 5 GHz for wireless local area networks (WLANs) for unmanned aerial vehicles (UAVs) applications is proposed in the paper. Two pairs of dipole antenna arrays with different electrical lengths are utilized to achieve dual-band directional radiation performance, which is desirable for a remote-control unit of the UAVs. Note that the directional radiation characteristic is obtained according to the double-dipole antennas driven by antiphase signals (W8JK), provided the distances between different dipole antennas are properly optimized. Note that the distance between the two longer dipoles, as well as the two shorter dipoles, can be calculated by equations. For each pair of dipoles with equal electrical lengths, an antiphase along the two dipoles can be obtained, and directional radiation characteristics can be achieved in the dual band. Coplanar strips (CPS) are employed as feeding networks, which lie on the same substrate layer as the antenna arrays, resulting in a low profile of merely 0.762 mm. Also, the overall size of the antenna together with the feeding network is 58.42 × 32.58 × 0.762 mm³. To verify the performance of the proposed antenna, a prototype is fabricated and measured. The measured gain is 5.2 and 7.0 dBi, respectively, in the 2.4 and 5.8 GHz bands. The measured reflection coefficients as well as radiation patterns are consistent with those of the simulated results. The proposed antenna scheme can be a good candidate for UAV applications with the advantages of a lower profile, dual-band characteristics, directional radiation characteristics, and a simple assembly. Since the remote-control unit operates at 2.4 GHz and 5.8 GHz to control the UAV unit, the low-profile dual-band directional radiation antenna has extensive application prospects when integrated into the space-limited unit.
In the era of the Internet of Things (IoT) and the Industrial Internet of Things (IIoT), elements along the supply chain can be connected to one another to offer tracking capabilities. The information obtained from an always connected and working supply chain is then incorporated into the simulations of the virtual world (digital twin). This allows for an instantaneous simulation of the environment at any point in time and better, more optimized, and quicker decisions are made based on the results. This translates into more performance and a stronger competitive advantage. This paper will examine the main concepts surrounding the supply chain from the perspective of digitalization. In this paper, we will take a closer look at the main concepts related to the supply chain in light of digitalization.
This work provides a new approach for computing the impedance of a proposed multiband printed fractal antenna for wireless applications. Galerkin’s method is applied to deduce the impedance relationship of the proposed structure and then compute the return loss verses frequency by converting the impedance matrix of the proposed antenna [Z] to the scattering matrix [S]. This model is developed in order to study the impedance of the proposed antenna after adding a metamaterial structure in the antenna substrate. The obtained model is able to determine the resonant frequencies and the return loss of the proposed antenna. The model is also able to define the changes in these values when the dimensions of the proposed structure change. The proposed antenna provides multiband wireless applications in the (1–10) GHz frequency band, and the return loss of the proposed fractal antenna has been improved using negative permittivity and negative permeability metamaterial structure.
This letter presents a wideband antenna for high-precision Global Navigation Satellite System (GNSS) applications. The antenna consists of a pair of improved orthogonal dipoles that are fed by a feed network with Composite Right/Left-Handed Transmission Lines (CRLH-TLs), a polygonal patch, and a reflector. By using improved orthogonal dipole, the beamwidth of the antenna is broadened. The CRLH-TLs is adopted in feed network to obtain outputs with stable phase difference. Experiment results indicate that the antenna has a less than 10-dB return-loss bandwidth in the range of 1.1 to 1.7 GHz, a 3-dB axial-ratio bandwidth from 1.2 to 1.6 GHz, and a larger than 6.37 dBi gain in the whole operating band. The measured results show that the proposed antenna has stable performance in the whole operating band, which means that it is a suitable antenna used for GNSS applications.
This study proposes a multiband printed planar antenna with cloud-like grooves. The outer contour of the antenna is shaped like a cloud, and the groove-like pattern is similar to the cloud-like pattern in ancient China. It can support 3G, 4G, 5G, WLAN, Bluetooth, WiMAX, and other applications. Based on the traditional monopole antenna, the antenna combines the advantages of a coplanar waveguide. The antenna uses an Archimedes helix to create grooves that resemble ancient Chinese cloud structures. Three effective frequency bands are obtained. The relative bandwidth of the first frequency band (1.8–2.6 GHz) is 32.7%, covering 5G band n2 (1.85 GHz–1.99 GHz), WCDMA (1.9–2.17 GHz), LTE33-41 (1.9–2.69 GHz), Bluetooth (2.4–2.48 GHz), WLAN (2.4–2.48 GHz), LTE Band40 (2.3–2.4 GHz), ISM Band (2.42–2.4835 GHz), WiMAX (2.3 GHz), and SCDMA (1.88–2.025 GHz and 2.3–2.4 GHz). The second frequency band (3.35–4.1 GHz) has a relative bandwidth of 20.5%, covering LTE42/43 (3.4–3.8 GHz) and 5G band n78 (3.4 GHz–3.8 GHz). The relative bandwidth of the third band (5.5–7.9 GHz) is 40.3%, covering Emergency and Public Protection (5.85 GHz–5.925 GHz) (WRC03). The antenna is printed on a G10/FR4 dielectric board with a size of 1.6∗45∗40 mm3, the dielectric constant is 4.4, and the omnidirectional radiation pattern gain is 0.59–4.14 dBi. The measurement results are in good agreement with the simulation results. The proposed design method is verified to meet the requirements of various wireless applications.
An anti-multipath antenna is an antenna that can effectively suppress multipath signals from the source of signal reception. There are many problems in the traditional choke design, such as excessive volume and low elevation gain damage. In this paper, the conventional choke ring is improved by using the complementary trapezoidal structure, and the detailed design process is given. The measured results show that the choke has good resistance to a multipath effect in the navigation frequency band (1.1–1.7 GHz) and can significantly improve the front-to-back ratio of the antenna.
Artificial intelligence and the IoT-based structure diagram of multilayer perceptron.
Artificial intelligence and the IoT-based seq2seq learning of neural network.
Artificial intelligence and the IoT-based Long Short-Term Memory Networks translation principle.
Artificial intelligence and IoT-based process of English translation.
Artificial intelligence and IoT-based closed-loop flow chart of teaching and self-study.
In recent years, with the development of artificial intelligence, the Internet of Things (IoT) has become a research hotspot in industry and academia. At the same time, as a derivative tool of artificial intelligence, machine translation based on the IoT is constantly being applied to English translation and its teaching. In teaching, helping students learn English translation has been the focus of machine translation in recent years. Compared with human translation, machine translation is more efficient and convenient. However, machine translation also has some problems. Compared with traditional human translation, it cannot meet the requirements of faithfulness, expressiveness, and elegance of translation. In many fields, neural network translation is comparable to human translation. In the field of English translation teaching, neural network translation has broad prospects. With the gradual maturity of neural network translation, we should think about how to use neural network translation to make it a powerful English translation teaching tool instead of sticking to traditional teaching and cultivating students who are completely unable to compare it with neural network translation. Therefore, in the context of rapid AI iteration, college English translation teaching should also keep pace with the times. With the help of tools such as neural network translation, English translation talents who can skillfully use AI technology can be trained quickly and efficiently so that they can keep pace with the times and master the power of AI. The research in this paper provides important guidance for the application of artificial intelligence and the Internet of Things, especially for intelligent relaying.
For robust adaptive beamforming (RAB), the variable loading (VL) technique can provide a better trade-off between robustness and adaptivity than diagonal loading (DL). Despite its importance, few research efforts have explored the loading factor for VL to ensure robustness in various environments. Moreover, the performance of VL is restricted by the sample covariance matrix in snapshot deficiency situations. This paper proposes a modified variable loading (VL) method for robust adaptive beamforming, considering imprecise steering vector effects and finite sample size impairments. First, a novel subsampling method is used to construct the calibrated covariance matrix to improve the robustness of the VL in sample-starving scenarios. Then, a parameter-free method for the VL factor is proposed to further enhance the insensitivity to the steering vector mismatches of the antenna array. Simulation results verify the effectiveness and robustness of the proposed method as compared to the traditional VL and other widely used robust techniques.
Comparison of the proposed antenna with existing antennas in literature.
The proposed work is a novel low-profile 5G MIMO antenna configuration to exhibit dual-band frequencies for 5G NR-n2 band (1.9 GHz) and safety band (ITS-5.9 GHz) in vehicular communication. In the proposed antenna, it is quite difficult to achieve the lowest resonance frequency in a comparatively miniaturized dimension concerning its operating wavelength. The designed antenna is a modified square patch with the dual-band resonance achieved by the incorporation of slots for increasing the electrical length within the dimension. Hence, the design comprises ring and loop slots exhibiting resonance at 1.9 GHz and the loop U, and modified-W slots for 5.9 GHz. The antenna achieves 1.9% and 0.64% impedance bandwidth and a peak gain of 1.944dBi and 6.06dBi at the resonant frequencies of 1.9 GHz and 5.9 GHz, respectively, with dimensions of 0.114λo × 0.114λo × 0.0016λo, where λo is the wavelength of the lowest operating frequency. The MIMO configuration is presented to assess the antenna’s suitability for large-scale applications. The MIMO antenna presented here is deployed with the edge-to-edge distance between the single element radiators being 0.01λo by parametric sweep. The presented MIMO antenna provides an isolation value greater than 19 dB because of reduced mutual coupling between the single element radiators in that MIMO structure due to the presence of a ground slot. The ECC values are 1.659 × 10−9 and 0.000601 for frequencies of 1.9 GHz and 5.9 GHz, respectively, and the diversity gain is relatively near 10 dB, which is the acceptable value for MIMO antennas. This modified square single-element and MIMO antenna provides a relatively higher gain and better performance in vehicular communication for GSM and safety applications. The MIMO configurations’ on-vehicle analysis is performed to check the reliability of the designed antenna in a vehicular environment.
Current spatial resolutions achieved by mesoscale weather forecast models allow them to be used to generate the state of the lowest layers of the atmosphere over areas as small as a few square kilometers which corresponds to the typical size of the tropospheric area crossed by Earth-space links. Furthermore, they allow the evolution of the troposphere to be predicted with a time stamp of five minutes instead of every hour with large-scale weather forecast models which makes them attractive for radio propagation predictions for satellite communication applications. This paper aims at studying the capability of the Weather Research and Forecast (WRF) model coupled with an electromagnetic physical model to reproduce rain attenuation statistics for Earth-space paths at Ka-band. To this purpose, one year of propagation measurements collected at 20 GHz in different places at midlatitudes in Toulouse and Salon de Provence (France), Spino d’Adda (Italy), Aveiro (Portugal), and Madrid (Spain), at high latitudes in Svalbard (Norway) and at low latitudes in Kourou are used to make comparisons between simulations and measurements. Comparisons between the simulated and the experimental annual statistics considered in this paper provide encouraging results, with a similar accuracy as Recommendation ITU-R P.618–13 for midlatitude European locations and with better accuracy for a high latitude area in Svalbard and for an equatorial location in French Guiana.
This paper proposed a new radar echo simulation method for ultra-low altitude targets in far-field conditions. Based on the electromagnetic (EM) scattering calculation of target and environment, combined with the weighted four-path model, the scattering data of target, environment, and multipath are obtained. The Range-Doppler ring partitioning method is used to determine the size of the minimum resolution units, and then the environment is divided into several scattering elements. By using the method of temporal decomposition, the wide-time pulse is decomposed into a plurality of narrow pulse signals, and the narrow pulses act on scattering elements with different distances and orientations in space. The total echo is obtained by a linear superposition of the responses of each scattering unit. In addition, the numerical results with different parameters, including signal bandwidths, target types, and target height, are simulated and analysed. The simulation results demonstrate that the proposed method can provide a better description of the scattering characteristics of sea-skimming targets in complex scenes in far-field conditions. Meanwhile, it can be applied to the detection and recognition of ultra-low altitude targets above the sea surface.
Since 2012, green bond markets have boomed worldwide, particularly in the European Union, the United States, and China. Under this background, the researchers use the methods of literature research, qualitative analysis, and descriptive research to compare the structure of Chinese and American green bond markets and analyze their differences from the perspective of historical evolution, issuance standards, and market operation characteristics. The researchers believe that China’s bank-oriented financial structure and America’s market-oriented financial structure are the main reasons for the difference between the two countries. The researchers then discuss the strengths and weaknesses of China’s green bond market and conclude that the advantages of China’s green bond market structure lie in low risk and close relationships between banks and enterprises, while the disadvantages lie in low financial efficiency and give relevant suggestions. This article makes up for the lack of cross-country comparison in the existing research on the green bond market and provides a qualitative research perspective. The suggestions put forward have specific policy significance for developing the green bond market in China and other developing countries.
An omni-directional inset fed wideband microstrip patch antenna (MPA) for Sub-6 GHz applications has been presented. Initially, a slotted small patch antenna with a full ground plane is designed and then partial ground plane and electromagnetically coupled parasitic elements have been incorporated and optimized to get desired performance. The volume of the studied antenna is 40 × 40 × 1.575 mm3 having a partial ground plane. Rogers RT 5880 is used as the dielectric substrate tier. The simulated operating band of the MPA ranges from 2.67 GHz to 4.20 GHz, covering the N77 and N78 bands with a centre operating frequency of 3.29 GHz. The antenna can also be used for WiMAX rel 2 (3.4–3.6 GHz) applications. After fabrication and testing, the antenna also shows almost the same working band extending from 2.67 GHz to 4.15 GHz. The use of a partial ground plane plays a vital role in making it an omni-directional antenna, and the existence of a rectangular parasitic element in the ground plane influences the improvement of gain and directivity of the antenna. The designed MPA allows it to run as a wide band antenna with a good reflection coefficient profile, high average efficiency, and 1 < VSWR < 2. At a resonant tip of 3.29 GHz, the simulated gain and directivity are 3.16 dB and 3.38 dBi, respectively. The measured gain is slightly higher than the simulated gain. The computer simulation technology (CST) is used for modelling and exploring all the performance matrices of the antenna. The results of the fabricated prototype present very good similarity with the simulated results and both simulated and measured results also support the Sub-6 GHz band. The antenna prototype shows a very well balanced set of radiation characteristics with a miniaturized volume and high efficiency. Therefore, the inset fed MPA can be contemplated as a candid model for Sub-6 GHz band applications.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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%.
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.
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.
Comparative analysis of characters’ costumes in Dunhuang murals in different periods.
Analysis of the background value of the Dunhuang murals.
Visual analysis of the Dunhuang murals and modern costumes under different algorithms.
Visual analysis of the impact of clothing and culture in different periods.
Comparison of the influence of clothing and culture in different periods.
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.
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.
Journal metrics
Article Processing Charges (APC)
Acceptance rate
21 days
Submission to first decision
79 days
Submission to final decision
19 days
Acceptance to publication
1.244 (2021)
Journal Impact Factor™
2.8 (2021)
Top-cited authors
Diego Caratelli
  • Eindhoven University of Technology
Binod Kumar Kanaujia
  • Dr B R Ambedkar NIT Jalandhar Punjab
Yingsong Li
  • Anhui University
Dr K P Ray
  • Defence Institute of Advanced Technology (DIAT)
Dong-You Choi
  • Chosun University