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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: 8  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1687-5869 - ISSN (Online) 1687-5877
Published by Hindawi Homepage  [339 journals]
  • Integrated Design of Multimode and Multifrequency Miniaturized Handset
           Antenna at VHF/UHF Bands

    • Abstract: This paper presents an integrated design of a multimode and multifrequency miniaturized handset antenna working at the lower band (0.24–0.7 GHz) with linear polarization and higher band (1.98–2.01 GHz and 2.17–2.20 GHz) with circular polarization simultaneously. At the higher band, the quadrifilar helix antenna (QHA) is utilized with each arm developed into two arms of different lengths and linearly tapered widths to realize double resonance and increase the bandwidth. Moreover, a helical stub behaving as a director is introduced to improve the antenna gain. At the lower band, the outer conductor of the QHA feedline and four QHA arms are designed to constitute a monopole antenna through proper feeding and introducing four quarter-wavelength short-circuit stubs. With this radiator-sharing technique, the QHA not only works at the higher band with a circular polarization pattern but can act as a monopole antenna working at the lower band with a linear polarization pattern simultaneously. As a result, the size of the antenna can be reduced remarkably. Finally, the proposed antenna is fabricated with a total length of 228 mm and a diameter of 15 mm. At the lower band, the measured S11 is below −8 dB, and the gain is larger than 0.5 dBi. At the higher band, the measured S11 and AR are better than −13 dB and 3 dB, respectively, and the gain within the zenith angle range of 0°−35° is greater than 2.5 dBi, which demonstrates better performance.
      PubDate: Fri, 27 Jan 2023 03:35:00 +000
       
  • Analysis of the Function of Schottky Barrier Diode in Microwave Rectifying
           Circuit

    • Abstract: In this paper, a new viewpoint on the function of the Schottky barrier diode (SBD) in microwave rectifying circuit is proposed. In the analog circuit field, it has been formed a relatively mature theoretical system about the rectifying circuit, which constitutes the base of subsequent rectifier design schemes. The researchers take it for granted that the SBD selected as the core component in the microwave rectifying circuit should play the role of rectifying in the same way as the diode in the analog circuit. The fact that the one-directional conductivity of the SBD is not observed in microwave circuit by the means of simulation and experiment is proposed. The basis of the former rectification theory is in doubt here. Due to the interaction of the microstrip line and SBD, the DC component generated at the front end of SBD is the key reason for the DC output power of rectifying circuit. The way of DC generation is completely different from the previous idea. Accurate and in-depth understanding of the function of SBD in microwave rectifying circuit will help the researchers to make use of SBD rightly and design circuit in future applications.
      PubDate: Wed, 25 Jan 2023 07:50:02 +000
       
  • Measurement and Analysis of Local Average Power According to Averaging
           Length Changes of 3, 6, 10, and 17 GHz in an Indoor Corridor Environment
           

    • Abstract: This study measures and analyzes the local average power for line-of-sight (LOS) and non-line-of-sight (NLOS) paths according to the averaging length in an indoor corridor environment. The indoor corridor comprises multiple offices, laboratory spaces, and lecture rooms. We selected 3, 6, 10, and 17 GHz measurement frequency bands. The measurement system consists of a signal generator, a low-noise amplifier, transmission and receiving antenna, and spectrum analyzer. To obtain an accurate prediction model of propagation due to the multipath effect, we determined the measurement method based on the measurement interval and number of measurements according to changes in the averaging length. 2, 4, 6, 8, and 10 lambdas (λ) were selected for the number of measurements by frequency, and 1.5 cm was set as the measurement interval. We used the close-in (CI) path loss model for the analysis according to changes in the averaging length. The coefficient of determination (R-squared) was applied using a linear regression equation to verify the measurement accuracy. Based on parameter n of the CI path loss model, no large differences were observed in the averaging length at each measurement frequency. However, at 2λ, owing to the multipath effect, R-squared was approximately 0.4–0.7 for the LOS path and 0.6–0.8 for the NLOS path. At 10λ, R-squared was approximately 0.7–0.8 for the LOS path and 0.8–0.9 for the NLOS path. This indicated that as the number of measurements increased by increasing the averaging length, the accuracy of the measurement results improved. The study findings will help determine an optimal averaging length, thus ensuring reliable indoor propagation measurement and contributing to the ITU-R standard.
      PubDate: Fri, 20 Jan 2023 03:50:01 +000
       
  • Design and Measurement of a Vibrating Intrinsic Reverberation Chamber
           Working in Tuned Mode

    • Abstract: In this letter, a vibrating intrinsic reverberation chamber (VIRC) working in mode tuning is designed and fabricated; the designed RC is made of a highly electrically conductive silver fabric. A stepper motor is used to tune the cavity surface step by step along its normal direction, and an RC with vibrating wall is realized. The corresponding relationship between the vibrating amplitude and frequency of use is calculated. A test system is developed and the performance of VIRC is experimentally verified. Measurement results show that the measured E-field samples follow a Rician distribution, and the standard deviation of the space E-field is less than 3 dB, which meets the requirements of statistical uniformity tolerance in IEC 61000-4-21.
      PubDate: Mon, 16 Jan 2023 08:35:01 +000
       
  • Practical Noise Model of an Active Electronically Scanning Array

    • Abstract: Active electronically scanning arrays are now widely used in radar and communication systems. The noise characteristics are critical to the system signal-to-noise ratio, thus modeling of the antenna array noise is useful. In this paper, a two-port noise model of an active electronically scanning array is presented, which is more practical than the model in previous publications. In this model, an antenna array with a multistage combiner network is equivalent to a one-stage combiner network, thus the calculation of the noise figure is greatly simplified. Since the model is based on measurable parameters, it can be applied directly to the design of electronically scanning arrays. The noise model of a spaceborne synthetic aperture radar antenna system is displayed for example. Some useful conclusions are got about the noise figure for tapered antenna arrays. For a weighted antenna array with taper efficiency εT, if the gain of low noise amplifiers is sufficiently large, the noise figure of the antenna array is increased by 1/εT, compared to a uniformly weighted array. Besides, the deterioration of the signal-to-noise ratio for a tapered antenna array system originates from the increase of antenna noise temperature, rather than the decrease of antenna aperture gain.
      PubDate: Mon, 16 Jan 2023 05:05:01 +000
       
  • Polarization Stable Triband Thin Square-Shaped Metamaterial Absorber

    • Abstract: An efficient triband metamaterial absorber is presented for X- and K-band applications. The unit cell is of simple shape. The absorber is fabricated on a thin polyamide, which makes it flexible. The parameters of the designed absorber are optimized. The simulated results show that it has good absorption rate and polarization stability. The stability is exhibited over a wide range in both TE and TE modes of the incident waves. The measured results are on par with the simulated results. The measurement is carried out with the waveguide measurement method.
      PubDate: Sat, 14 Jan 2023 05:35:00 +000
       
  • A Single-Layer Circularly Polarized Reflectarray Antenna with High
           Aperture Efficiency for Microwave Power Transmission

    • Abstract: In this article, a single-layer circularly polarized reflectarray antenna (RA) with a linearly polarized feed is proposed for microwave power transmission. The unit cell of the reflectarray is composed of a rectangular patch surrounded by four groups of E-shaped structures, which feature a very low level of cross-polarization. Simulation results demonstrate that the phase of its reflection coefficient can be tuned continuously in a range of 500° by adjusting the lengths of the E-shaped structures. In response to a normally incident plane wave, the phase values of the reflection coefficient associated with two orthogonal linear polarization directions of the reflected wave can be tuned independently, which makes it possible to convert a linearly polarized incident wave to a circularly polarized beam. A reflectarray with 15 × 15 unit cells is fabricated and tested. The measurement results demonstrate a 3-dB axial ratio bandwidth of more than 2 GHz around the center frequency of 5.8 GHz. The measured gain value of the fabricated reflectarray is 25.4 dBi, corresponding to an aperture efficiency of 52.5%.
      PubDate: Thu, 12 Jan 2023 07:35:00 +000
       
  • The Research on Application of Resistance Compression Network (RCN) in
           Microwave Rectifying Circuit

    • Abstract: Resistance compression networks (RCNs) have attracted special attention in the field of wireless power transmission (WPT) since they were put forward. A lot of research work has been done in rectifier basing on RCN for the purpose of increasing conversion efficiency. It is reported that many kinds of rectifiers containing RCN which operate in various circuit and physical forms are proposed. RCN and all kinds of modified versions are studied deeply in this paper, the rectifiers related to which are analyzed also. The results show that RCN only plays the role of bandpass filter (BPF) in the rectifying circuit, which does not reach the original idea of the first proposer. We have different understandings of the rectifying circuits presented in other papers.
      PubDate: Thu, 05 Jan 2023 04:50:01 +000
       
  • Composite Scattering from a PEC Object above Two-Layered Rough Soil
           Surfaces Based on an Efficient Bi-Iterative Model

    • Abstract: In the study, an efficient bi-iterative physical optics (PO) electromagnetic model is used to analyze the composite scattering from a PEC object above two-layered rough soil surfaces for the first time. The PO method is applied to calculate the direct scattered fields from the object and the upper layer rough surface and to deal with the mutual coupling effect between the object and the two-layered rough surfaces. During the mutual coupling process, a bi-iterative strategy is considered to solve the coupling interaction between the object and the upper rough surface and the coupling interaction between the upper and lower rough surfaces. We assume a 2-D scattering problem. The result is validated by comparing it with that obtained from the conventional method of moments (MoM). Comparison results from different object types show that the scattered curves calculated using the proposed method resemble the ones obtained from MoM. The comparison of computer resources also shows the efficiency of our method. Meanwhile, the normalized radar cross-section of the composite model is analyzed under different parameters.
      PubDate: Sat, 31 Dec 2022 14:05:00 +000
       
  • A Compact Penta-Band Low-SAR Antenna Loaded with Split-Ring Resonator for
           Mobile Applications

    • Abstract: A compact rectangular patch with dual-ring SRR (split-ring resonator) is presented in this article. An antenna is designed on FR4 substrate with an overall footprint size of 26 mm × 30 mm × 1.6 mm. The antenna presented operates in five bands from 2.95 to 3.06 GHz, 3.79 to 3.87 GHz, 4.11 to 4.19 GHz, 5.39 to 5.51 GHz, and 5.97 to 6.11 GHz. Mobile and fixed voice communication, WiMAX (Worldwide Interoperability for Microwave Access), 5G (5th generation), WLAN (Wireless Local Area Network), and ISM (Industrial Scientific and Medical) are some applications that utilized the above resonating bands. The penta-band operation is due to the inclusion of dual-ring SRR. The optimum values of the critical parameter of the SRR are identified using parametric analysis, and the results are presented. The antenna is also analyzed for the SAR (specific absorption rate) values, and it was found to be less than 2 W/kg for 10 g volume of tissue. The designed antenna is fabricated and tested, and the presented results show that there is good agreement between the simulated and measured results. Penta-band operation with simple structure, stable radiation pattern, and low SAR makes this antenna more intelligent and suitable for the mobile application.
      PubDate: Fri, 30 Dec 2022 11:05:01 +000
       
  • Simultaneous Estimation of Wall and Object Parameters in TWR Using Deep
           Neural Network

    • Abstract: The purpose of this paper is to present a deep learning model that simultaneously estimates targets and wall parameters in through-the-wall radar (TWR). As a result of the complexity of the environments in which through-the-wall radars operate, TWR faces many challenges. The propagation of radar signals through walls is further delayed and attenuated than in free space. Therefore, the targets are less able to be detected and the images of the targets are distorted and defocused as a consequence. To address the above challenges, two modes are considered in this work: single targets and two targets. In both cases, permittivity and wall thickness are considered, along with the target’s center in two dimensions and the permittivity of targets. Therefore, in the case of a single target, we estimate five values, whereas in the case of two targets, we estimate eight values simultaneously, each representing the mentioned parameters. As a result of using deep neural networks to solve the task of target locating problem in TWR, the model has a better chance of learning and increased accuracy if it involves more parameters (such as wall parameters and permittivity of the wall) in the target location problem. In this way, the accuracy of target locating improved when two wall parameters were considered in problem. A deep neural network model was used to estimate wall permittivity and thickness, as well as two-dimensional coordinates and permittivity of targets with 99% accuracy in single-target and two-target modes.
      PubDate: Wed, 28 Dec 2022 04:05:03 +000
       
  • SPECTRUMNET: Cooperative Spectrum Monitoring Using Deep Neural Networks

    • Abstract: Spectrum monitoring is one of the significant tasks required during the spectrum sharing process in cognitive radio networks (CRNs). Although spectrum monitoring is widely used to monitor the usage of allocated spectrum resources, this work focuses on detecting a primary user (PU) in the presence of secondary user (SU) signals. For signal classification, existing methods, including cooperative, noncooperative, and neural network-based models, are frequently used, but they are still inconsistent because they lack sensitivity and accuracy. A deep neural network model for intelligent wireless signal identification to perform spectrum monitoring is proposed to perform efficient sensing at low SNR (signal to noise ratio) and preserve hyperspectral image features. A hybrid deep learning model called SPECTRUMNET (spectrum sensing using deep neural network) is presented. It can quickly and accurately monitor the spectrum from spectrogram images by utilizing cyclostationary features and convolutional neural networks (CNN). The class imbalance issue is solved by uniformly spreading the samples throughout the classes using the oversampling method known as SMOTE (Synthetic Minority Oversampling Technique). The proposed model achieves a classification accuracy of 94.46% at a low SNR of −15 dB, which is an improvement over existing CNN models with minor trainable parameters.
      PubDate: Thu, 22 Dec 2022 07:35:00 +000
       
  • Design and Analysis of UWB MIMO Antenna for Smart Fabric Communications

    • Abstract: This paper presents a flexible multiple-input, multiple-output (MIMO) antenna with ultrawideband (UWB) performance for smart clothing applications. The MIMO antenna is comprised of four octagonal-shaped radiators with several slots loaded into them, and it offers a frequency range of 2.9–12 GHz. The unit cell has a size of 0.26λ0 × 0.164λ0 × 0.014λ0 and the MIMO antenna has a size of 0.48λ0 × 0.48λ0 × 0.014λ0, where λ0 corresponds to the lowest operating frequency. The radiation and diversity performances of the antenna are evaluated, and the obtained metrics are envelope correlation coefficient (ECC) 9.9 dB, total active reflection coefficient (TARC)
      PubDate: Wed, 21 Dec 2022 07:50:02 +000
       
  • Design and Analysis of a Dual-Band Semitransparent MIMO Antenna for
           Automotive Applications

    • Abstract: This paper presents the design and development of a semitransparent antenna that can be used in automotive applications to support multiple wireless services. The proposed quad-port multiple input multiple output (MIMO) antenna is comprised of four orthogonally arranged identical semitransparent antenna elements on a transparent substrate. The MIMO antenna covers the 2.4 GHz band and 3.2–15 GHz band, supporting automotive/wireless applications such as Bluetooth, Wi-Fi, intelligent transport system (ITS), advanced driver assistance systems (ADASs), vehicle to infrastructure (V2I), vehicle to vehicle (V2V), vehicle to network (V2N), and vehicle to device (V2D). The parameters such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity loss (CCL) are studied to evaluate antenna diversity performance. The antenna has an ECC of less than 0.15, DG of more than 9.85 dB, TARC of less than −10 dB, and CCL of less than 0.2 bits/s/Hz. The developed antenna can be easily installed on the mirror and windshield of the vehicles. Also, the housing effect and on-vehicle performance of the antenna at various positions in a car are investigated.
      PubDate: Wed, 21 Dec 2022 07:50:02 +000
       
  • Direction-of-Arrival Estimation in Time-Modulated Linear Arrays Based on
           the MT-BCS Approach

    • Abstract: This article proposes a novel approach for the estimation of the direction-of-arrival (DoA) of multiple signals impinging on time-modulated arrays (TMAs). The algorithm transforms DoA estimation into compressive sensing (BCS) formulation to tackle the sparse signal problem. Based on the voltage outputs of the TMAs at multiple times instants, a strategy using multitasks BCS (MT-BCS) is applied to recover the DoA and improve the accuracy. The comparison with the existing algorithms of DoA estimation in TMAs verifies the effectiveness and feasibility of the proposed method.
      PubDate: Tue, 20 Dec 2022 06:20:01 +000
       
  • An Effective Method for Electromagnetic Parameter Measurement of Flexible
           Materials Based on Air Coaxial Line

    • Abstract: When measuring the electromagnetic parameters of flexible material with an air coaxial line, the specimen is prone to bend and deform in the fixture, which results in erroneous results. In order to solve this problem, this paper proposes a new measurement method. Firstly, a rigid material is selected and loaded into the air coaxial line for two-port S parameters measurement. Then, the flexible material is attached to one end of the rigid material and loaded into the air coaxial line together for repeated two-port S parameter measurement. According to the S parameters measured and the two-port network cascading theory, the S parameters of the flexible material separately loaded in the fixture can be deduced. Finally, the electromagnetic parameters of the flexible material can be calculated by the Nicolson−Ross−Weir (NRW) method. Experimental results show that the method proposed is effective and reliable.
      PubDate: Sat, 17 Dec 2022 02:05:01 +000
       
  • Remote Calibration Technology in Target RCS Time Domain Outfield
           Measurement

    • Abstract: In this paper, a new method of remote calibration in time domain measurement of outfield RCS is proposed. Based on the basic principle of RCS time domain measurement and the characteristics of time domain system, the difference in time and frequency domain measurement is analyzed. The frequency domain remote calibration formula is extended to the time domain by time-frequency transform. Through the analysis of the time domain echo signal of the calibration body in the correction formula and the experimental verification of the calibration sphere echo signal, the influence of the calibration body size and measurement distance on the time domain echo signal and spectrum of the calibration body is given. The typical targets are measured by using the time domain system, and the results of time domain remote calibration, theoretical simulation, and frequency domain measurement are compared. The results show that the error between the time domain remote calibration results and the theoretical simulation results is not more than 1 dB at the −25 dB level. In the outfield measurement, this scheme can fully reflect the advantages of time domain measurement of wide frequency bands and low environmental requirements.
      PubDate: Wed, 14 Dec 2022 07:50:00 +000
       
  • Fractional-Order Active Disturbance Rejection Controller Design for Large
           Radio Telescope Antenna

    • Abstract: large radio telescope antennas are required in current astronomical research and deep space communication applications. The wind disturbance becomes a serious problem with an increase in the size of the antennas. Based on the typical antenna model, this work aims to design a fractional-order active disturbance rejection controller (FOADRC) for improving the accuracy of the antenna pointing mechanism in wind disturbance. First, the fractional-order active disturbance rejection control scheme is chosen to estimate and compensate both the wind disturbance and other uncertain mechanical dynamics. Afterwards, the relationship between the parameters of fractional-order extended state observer and the performance of disturbance suppression and noise immunity is revealed. The stability of fractional-order extended state observer is proved under similar assumptions as an integer order extended state observer. In addition, a stability region boundary calculation method is presented to simplify the parameter setting procedure. Finally, we perform simulations to verify the superiority of FOADRC in the antenna control system under wind disturbance. The results demonstrate that FOADRC has a good capability of resisting wind disturbance; at the same time, it limits the response overshoot and converges faster compared to other industrial controllers.
      PubDate: Fri, 09 Dec 2022 08:05:01 +000
       
  • A Semiblind Receiver for a Two-Way UAV-Aided PIC System Based on the
           PARAFAC Model

    • Abstract: In this paper, we consider a two-way communication system using the unmanned aerial vehicle (UAV) as a relay (UAV-aided). This system eliminates impulse interference through an adaptive filter based on the least mean square (LMS) and uses the received signal transmitted by the UAVs to construct a parallel factor (PARAFAC) model. Based on the identifiability condition of the PARAFAC model, a pulse interference cancellation orthogonal pilot tensor (PIC-OPT) receiver without iteration is proposed. Our algorithm is also used in millimeter-wave to achieve the acquisition of channel information. Compared with the least squares method, the simulation results demonstrate the superiority of the proposed semiblind receiver in terms of the relative mean square error and bit error rate.
      PubDate: Fri, 09 Dec 2022 08:05:01 +000
       
  • Field Deviation in Radiated Emission Measurement in Anechoic Chamber for
           Frequencies up to 60 GHz and Deep Learning-Based Correction

    • Abstract: The measurement of radiated emission (RE) in an anechoic chamber becomes very challenging at high frequencies, up to 60 GHz, because the scanning plane of the receiver is in measurement standard deviation from the actual wavefront. As a result, the RE intensity of the devices may be underestimated, resulting in electromagnetic interference. The deviation between the electric field at the far-field vertical scanning point and the actual wavefront is researched. Then, in an anechoic chamber, a hybrid deep learning amendment model of convolutional neural network (CNN) and transformer is proposed to correct the RE measurement at a 3 m distance. The results indicate that the correction is reliable, with an average error of 6.35% for a 3 m distance in a semianechoic chamber and less than 4.83% for other test scenarios. The proposed method provides a promising solution for RE measurement at a millimeter wave band in an anechoic chamber.
      PubDate: Fri, 09 Dec 2022 08:05:00 +000
       
  • Design and Analysis of a Multiple and Wide Nulling Collaborative
           Beamforming Scheme in the Domain of 3-Dimensional Wireless Sensor Networks
           

    • Abstract: 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.
      PubDate: Tue, 06 Dec 2022 07:35:01 +000
       
  • Design of Crossed Dipole Yagi–Uda MIMO Antenna for Radar
           Applications

    • Abstract: 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.
      PubDate: Tue, 06 Dec 2022 02:35:01 +000
       
  • Miniaturized Wide Scanning Angle Phased Array Using EBG Structure for 5G
           Applications

    • Abstract: 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.
      PubDate: Fri, 02 Dec 2022 01:50:01 +000
       
  • Analysis of Shielding Effectiveness of the Cavity Built with Single-Layer
           Reinforced Concrete

    • Abstract: 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.
      PubDate: Thu, 01 Dec 2022 05:20:01 +000
       
  • A Next-Generation Codebook Evolution Strategy for Massive Arrays Using
           Deep Neurals Networks

    • Abstract: 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.
      PubDate: Fri, 25 Nov 2022 08:05:00 +000
       
  • Wideband Circularly Polarized Microstrip-Slot Antenna with Parasitic
           Ground Planes

    • Abstract: 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| 
      PubDate: Wed, 23 Nov 2022 08:05:04 +000
       
  • Progress and Challenges in Electromechanical Coupling of Radio Telescopes

    • Abstract: 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.
      PubDate: Tue, 22 Nov 2022 08:05:01 +000
       
  • A High-Efficiency Microstrip Antenna Pair with Similar Pi-Shaped
           Decoupling Structure for 3.5 GHz 5G Ultrathin Smartphones

    • Abstract: 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.
      PubDate: Mon, 21 Nov 2022 07:20:02 +000
       
  • Optimum Synthesis of Pencil Beams with Constrained Dynamic Range Ratio

    • Abstract: 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.
      PubDate: Wed, 16 Nov 2022 11:05:04 +000
       
  • A Wideband Eight-Element MIMO Antenna Array in 5G NR n77/78/79 and
           WLAN-5GHz Bands for 5G Smartphone Applications

    • Abstract: 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.
      PubDate: Wed, 16 Nov 2022 10:50:02 +000
       
 
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