Antenna Diversity Research Articles

Thirty two port super wideband diversity antenna for indoor communications

This paper introduces a novel design featuring a thirty-two port diversity antenna with an elliptical shape, fed by an asymmetric coplanar waveguide (CPW). The antenna incorporates uneven meander lines, tailored for super-wideband (SWB) applications. The structure of the unit cell is of an elliptical patch with an elliptical slot, and it is connected to a rectangular stub and asymmetric meander line. The size of the single element is 22 mm × 20 mm, and it operates from 3 to 40 GHz. The bandwidth dimension ratio of the unit cell is 3911, bandwidth ratio is 13.33:1, and fractional bandwidth is 172.09%. The single element is developed into a 3-D thirty-two port diverse antenna, composed of a horizontal plane and four planes perpendicular to it. The diverse antenna has a peak gain of 12.5 dBi and an efficiency of 94%. The computed envelope correlation coefficient (ECC), as determined using S-parameters and far-field measurements, is less than 0.1. The attained diversity gains (DGs) of the developed MIMO antenna are above 9.9 dB in terms of both S-parameter and far-field computations. The obtained thirty-two port diverse antenna channel capacity loss (CCL) is below 0.25 bits/s/Hz. The mean effective gain (MEG) of the constructed thirty-two port antenna is below 2. To validate the appropriateness of the developed thirty-two port antenna for wireless indoor environment, an enclosure made of acrylonitrile butadiene styrene (ABS) is crafted and fabricated, and the characteristics of the proposed diverse antenna are investigated.

Security-reliability trade-off analysis for transmit antenna selection in cognitive ambient backscatter communications

Massive deployment of IoT devices raises the need for energy-efficient spectrum-efficient low-cost communications. Ambient backscatter communication (AmBC) technology provides a promising solution to achieve that. Moreover, incorporating AmBC with cognitive radio networks (CRNs) achieves better spectrum efficiency; however, this comes with performance drawbacks. In this work, we investigate the security and reliability performance of an underlay CRN with AmBC, where the backscattering device (BD) exploits the radio frequency (RF) signals of the secondary transmitter (ST), and both the ST and the BD share a common receiver. Different from previous work, we consider an ST with multiple antenna. The ST employs a transmit antenna selection (TAS) scheme to enhance the ST performance and overcome the performance degradation caused by the BD interference. TAS exploits multiple antenna diversity with lower hardware complexity and power consumption. Considering the Nakagami-m fading model, closed-form expressions are derived for the outage probability (OP) and intercept probability (IP) of both the ST and the BD transmissions at the legitimate receiver and the eavesdropper. Moreover, the asymptotic behavior of OPs and IPs is also investigated in the high signal-to-noise ratio regime and the high main-to-eavesdropper ratio regime, respectively. Monte Carlo simulations are performed to validate the derived closed-form expressions. Numerical results show that employing TAS enhances the ST and BD reliability performance by percentages up to 98% and 80%, respectively, at high primary user interference threshold values. Moreover, it results in a better security-reliability trade-off for the ST and the BD.

Machine learning validated compact circularly polarized dual port-MIMO antenna with polarization diversity for ku-band applications

A novel dual Port C-Shape MIMO broadband printed antenna with wide axial ratio bandwidth (ARBW) is modelled and built for Ku band Applications. The unit cell of the proposed antenna has a compact size of 25 × 26 × 0.8 mm3 engraved on RT duriod 5880 material (ε r = 2.2, thickness of 0.8 mm). The proposed model consists of C shaped radiator, plus symbol structure and a modified ground plane. The machine learning concept is used to investigate the dimensional dependency of the plus sign on the CP behaviour. The suggested antenna shows impedance bandwidth (−10 dB) and 3-dB ARBW of 6 GHz (12 GHz to 18 GHz) which is covering the whole Ku band. The diversity performance parameters and antenna parametric investigation is also carried out to justify the MIMO identity of the proposed design. The simulated and measured counterparts are found in harmony. The strength of the proposed antenna is its planar structure, wide ARBW, polarization diversity, and wide operating Ku bandwidth.

Stand spatial structural diversity: Developing and validating a novel index

Numerous studies related to the diversity-productivity relationships have mainly focused on the effects of species diversity, function diversity, and nonspatial structural diversity (e.g., variations of diameter), but have overlooked the significant roles of spatial structural diversity. Therefore, the motivation of the present study was to develop a comprehensive index of stand spatial structural diversity (H′) by integrating the strengths of the Shannon-Wiener index and the quaternion joint probability distribution of commonly used neighborhood-based parameters, namely the uniform angle index (W), mingling index (M), diameter dominance index (U) and crowdedness index (C). The application abilities of the index were tested using ten 100 m ×100 m sample plots that were distributed in three different climate zones [4 plots in Greater Khingan Mountains (GKM), 2 plots in Lesser Khingan Mountains (LKM), 4 plots in Changbai Mountains (CBM)] in Heilongjiang Province, northeast China. Meanwhile, the potential driving factors on stand spatial structural diversity were also detected using stepwise regression and hierarchical partitioning techniques based on 3000 simulated stands. The results indicated that the average values of H′ at GKM, LKM, and CBM were 0.8436, 0.8079, and 0.8098, suggesting that the stand spatial structural diversities of the forests in GKM were notably higher than those in LKM and CBM. The characteristics of M, C, and W emerged as the three most influential factors driving stand spatial structural diversity. This study contributes significantly not only by providing an effective index for measuring stand spatial structural diversity, but also by streamlining the complex decision processes associated with optimizing stand spatial structure.

A slotted frustum-shaped 4 × 4 MIMO dielectric resonator antenna with enhanced isolation for 5G Wi-Fi applications

In this paper, a slotted frustum-shaped 4 × 4 multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) is designed and developed for portable 5G Wi-Fi ( 5.15 − 5.85 GHz ) applications. The DRA is excited by HE M 11 δ and HE M 21 δ modes. A slotted right-angle frustum-shaped (SRFS) structure of alumina material as a dielectric resonator (DR) is positioned on the ground plane of the FR4 substrate to design a DRA. Based on the designed DRA, a compact ( 2.57 λ g × 2.57 λ g , where λ g is guided wavelength and calculated at a lower cut-off frequency, 5.0 GHz , for ϵ f of 4.4 ) 4 × 4 MIMO antenna with high isolation of greater than 27.13 dB (from 5.0 to 6.1 GHz ) and 24.3 dB (from 6.1 to 6.25 GHz ) is proposed. The developed MIMO antenna's measured working frequency ranges from 5.0 to 6.25 GHz , with an impedance bandwidth, B W i of 22.22 % , peak gain, G P of 5.85 dBi and an average peak gain, G av of 5.25 dBi . The calculated MIMO antenna's diversity performance parameters, channel capacity loss ( C CL ij ) , diversity gain ( D G ij ) , envelop correlation coefficient ( E CC ij ) , mean effective gain ( M EG i ) , total active reflection coefficient ( T ARC ) , and channel capacity ( C C ) are obtained as < 0.17 bits / sec / Hz , > 9.99 dB , < 0.0301 , < − 6.06 dB , < − 12.5 dB , and < 21.6 bits / sec / Hz , respectively. The agreement between the simulation and measurement results is found to be remarkably consistent.

Sum-rate maximization for a distributed space-time block code-aided cooperative NOMA with energy harvesting

AbstractIn this paper, we exploit the spatial and transmission diversities in cooperative non-orthogonal multiple access (C-NOMA) networks to improve the system sum-rate. To achieve this, we propose a user-pairing scheme where near-field user pairs serve as relays for user pairs in the far-field region. Based on this pairing scheme, we incorporate a space-time block code transmission technique at the near-field user pairs to maximize the transmission diversity in the cooperative phase. Moreover, we consider a non-linear energy harvesting model at the near-field user pair to alleviate the problem of energy consumption during the cooperative transmission phase. Further to this, we formulate a sum-rate maximization problem that is addressed from the viewpoint of joint power allocation factor and power splitting ratio optimization. We develop a low-computational iterative algorithm based on the concepts of the Stackelberg game and the Nash bargaining solution. We benchmark our findings with different scenarios, such as energy harvesting C-NOMA with a fixed power allocation factor and power splitting ratio, energy harvesting C-NOMA without STBC, non-cooperative NOMA, and orthogonal multiple access. The results obtained via simulations outperform the benchmark schemes.

Frequency selective asymmetric coupled-fed (ACS) antenna using additive manufacturing

In this study, the development of diverse antenna designs using additive manufacturing processes, specifically spanning from L-band to K-band is proposed. All designs are implemented on a flexible FR4 substrate to make them suitable for wearable sensors and biomedical applications. The fabrication process involves the utilization of aerosol jet printing with nanoparticle silver ink, followed by curing in a vacuum chamber. Additionally, screen printing with copper paste is employed as another method, with subsequent curing in a laminator. The reflection coefficient (S11) and radiation patterns for the simulated design and fabricated samples were found to align closely. The achieved return loss consistently reaching −10 dB across fairly large operating frequency range underscores the efficacy of the proposed antennas and their associated additive manufacturing mechanisms. The design and simulation were performed using Ansys high frequency structural simulator (HFSS), and the parameters under test for the fabricated antennas were validated using a vector network analyzer (VNA) to assess overall performance.

Secure authentication in MIMO systems: exploring physical limits

Multiple-input multiple-output (MIMO) technology is employed to improve the reliability and capacity of wireless communication systems. However, the wireless communication environment creates vulnerabilities to spoofing attacks. Furthermore, the authentication challenges posed by the heterogeneous characteristics of wireless applications increase as diverse technologies facilitate the growing number of Internet of Things (IoT) devices. To address these challenges, adaptive physical-layer authentication (PLA) leveraging the inherent antenna diversity in MIMO systems is examined, and an information-theoretic perspective on PLA in MIMO systems is given. The real and imaginary components of the received reference signals are used as attributes with a single-class classification support vector machine (SCC-SVM). It is shown that the authentication performance improves with the number of antennas, and the proposed scheme provides robust authentication.

Design of a Circular Micro-strip Patch Antenna for Improved Directivity and Gain of Mobile Communication Base Station

This study presents the design of Circular Micro-strip Patch Antenna (CMPA) for improved directivity and gain of mobile communication base station. The design incorporates a Rogger/5880 substrate material with a permittivity of 2.2, tangent angle of 0.00009 and a substrate height (thickness) of 0.98μm at a frequency of 1.65THz. Diversity Antenna Array Processing (DAAP) and Chebyshev Antenna Array (CAA) methods were used in the design. AutoCAD software and 2D data plotter were used for the diagrams and charts while Maple software was used for simulation. For angles of 0o, 30o, 60o, 90o, 120o, 150o and 180o, the array factors are 7.84dB, 7.85dB, 7.87dB, 7.88dB, 7.87dB, 7.85dB and 7.84db respectively. The results from the design demonstrated a remarkably low side lobe level of 0.01dB, indicating excellent suppression of unwanted radiation in undesired directions. Additionally, the antenna exhibits a Voltage Standing Wave Ratio (VSWR) of unity, ensuring maximum power transfer efficiency from the source to the load. Furthermore, the antenna shows a high directivity and gain of approximately 9dB, which enhances the signal strength and coverage range. The Half Power Beam-width (HPBW) and First Null Beam-width (FNBW) was measured as 300 and 600 respectively. These parameters depict the angular width of the main radiation beam and the sharpness of the beam pattern’s nulls. In all, the designed CMPA with its CAA based antenna array holds great potential for communication networks and for mobile communication base station, offering enhanced performance in terms of radiation characteristics and signal quality.

High‐Speed Wide‐Angle Sensing and Imaging by WideBand Metasurfaces with Joint Frequency, Polarization, and Spatial Diversities

AbstractHigh‐speed wide‐angle radio detection is crucial for intelligent wireless systems, autonomous vehicles, rescue operations in urgent situations, and security in various fields. This can be achieved through diverse controls of electromagnetic waves. Currently, multidimensional manipulations of electromagnetic waves are determined by dynamic antennas like phased arrays, mechanical beam‐steering radars, and programmable metasurface imagers. However, these methods face challenges in achieving rapid responses and large data collection intervals for high‐speed sensing and imaging, due to limitations in the speedy explication of analog‐to‐digital (AD) converters, electronic switches, phase shifters, and stepped motors for radiation beam reconfigurations. To address these challenges, advanced microwave‐to‐millimeter‐wave metasurfaces are introduced, designed to offer joint frequency, polarization, and spatial diversities. The metasurface with a disordered atom permutation enables wide‐angle sensing for accurate trajectory tracking of moving objects. On the other hand, a dispersion‐engineered atom arrangement allows the metasurfaces to facilitate wide‐angle through‐wall imaging, effective in detecting objects of varied shapes and positions. The experiments reveal that these metasurfaces can reconstruct objects at 100 frames per second (fps) from a single‐shot measurement, allowing 0.3x speed playback for detailed analysis. This demonstrates their potential in high‐speed sensing and imaging. Such a breakthrough is pivotal in unveiling new modalities and expanding possibilities in real‐time radio applications, including smart transportation, all‐condition surveillance, perspective radio, and integrated sensing and communication (ISAC) systems, especially relevant to technologies of 6G and beyond.

A compact UWB MIMO antenna augmented with isolation improvement structures in situ with ground stubs and slots

Abstract An orthogonally oriented microstrip-fed bi-element ultra-wideband (UWB) diversity antenna possessing a super-wide bandwidth, high isolation, and band rejection attributes is proposed. The intended diversity antenna uses a 2nd-order Cayley fractal tree-shaped neutralization line among a pair of radiating square monopoles along with additional components like extended ground stubs, hybrid Koch fractal parasitic elements, and an L-shaped defected ground structure to attain high isolation of &lt;−20 dB over 3.1–18 GHz. To nullify the intervention from the existent wireless local area network band, a hybrid Koch–Minkowski slot is carved out from the radiators. A minimal inter-element spacing of 8 mm is attained with the suggested layout measuring 28 mm (L) × 42 mm (W) in extent. The numerical as well as experimental investigations of vital diversity attributes like the envelope correlation coefficient, mean effective gain, total active reflection coefficient, and multiplexing efficiency depict high diversity actualization. The consistency amidst the simulation as well as the empirical results recommends the worthiness of the intended antenna for handy UWB and UWB multiple-input multiple-output systems.

Combined Shark-Fin Rooftop Antenna for LTE, WLAN and BeiDou Applications

This paper presents rooftop automobile antennas designed for Long-Term Evolution (LTE), Wireless Local Area Network (WLAN) and navigation system applications. The proposed antennas are housed within a shark-fin structure on the car’s roof, and comprise a main antenna and a diversity antenna. The main antenna and diversity antenna combine for spatial diversity, receiving and processing the same signal to optimize signal quality. To accommodate the limited space within the shark-fin housing, various miniaturization and multiband techniques are utilized. The hexagonal substrate is more closely fitted to the shape of the shark fin, thus making full use of the space of the shark-fin shell. The main antenna and the diversity antenna are perpendicular to each other, which saves the space of the overall antenna and improves the utilization rate of the overall antenna space. The proposed main antenna, compactly sized at 50 mm × 20 mm × 1.59 mm, maintains a VSWR value below 2 across the frequency range of 1.19–2.8 GHz, enabling support for LTE bands 1, 2, 3, 4, 7, 11, 15, 16, 34, 39, 40, and 41, as well as WLAN 2400 bands. The diversity antenna maintains a VSWR value below 2 across the frequency range of 1.5–2.6 GHz, which can cover BeiDou B1-1, LTE 1, 2, 3, 4, 7, 11, 15, 16, 34, 39, and 40, and WLAN 2400 bands. The main antenna and the diversity antenna both demonstrate favorable radiation patterns on the azimuth plane. Simulation and measurement results exhibit a high level of agreement.

Research Status and Progress of Multi-antenna Technology

With the continuous upgrading of wireless communication technology, the types of mobile service businesses continue to increase, and the number of communication terminal equipment has also increased sharply, greatly increasing people's demand for wireless data traffic and network coverage. As one of the research hotspots of wireless transmission, multi-antenna technology can improve system transmission rate, improve spectrum utilization and expand network coverage. According to the different implementation methods, this paper discusses the research status of three typical multi-antenna technologies, such as antenna diversity technology, beamforming technology and spatial multiplexing technology, and looks forward to the potential research direction of multi-antenna technology in the future.

On the design of ideal pattern diversity antennas with low mutual coupling using the golden angle concept

AbstractIn this paper, we come up with a unique technique to generate the ideal pattern diversity with the help of 24 Vivaldi antennas. With the help of a mathematical concept called golden angle, the 24 antenna elements are arranged in such a way that the radiation patterns will never overlap and the mutual coupling will be very low. It is also verified from the simulations and the measured results that the envelope correlation coefficient is less than 0.01 in the 3–4.2 GHz which is a sub‐6 GHz band for 5G. This same concept can be extended to a greater number of antennas also.

New developments and trends in 5G technologies: applications and concepts

Fifth-generation (5G) wireless technology is the most up-to-date iteration of mobile data networks. This research analyzes the effectiveness of next-generation mobile networks in tandem with mobile communication technologies. Various difficulties encountered at each stage are discussed. With the advent of 5G networks, users may connect to the internet at lightning speeds from almost any location. 5G is one of a kind because of its new characteristics, which allow it to link people and enable them to operate gadgets, machines, and things. 5G mobile technology’s varying speed and capabilities will allow for new user experiences and link new businesses. Companies must know where they can best put 5G to use. This research paper examines and analyzes various topics in great detail, demonstrating how mmWave, massive multiple-input and multiple-output (massive MIMO), microcells, mobile edge computing (MEC), beamforming, diverse antenna technologies, and so on can all work together to improve cellular networks. The primary goals of this article are to demonstrate some of the most recent technical developments and to analyze potential future research directions for the 5G mobile system.

CSI-F: A Human Motion Recognition Method Based on Channel-State-Information Signal Feature Fusion.

The recognition of human activity is crucial as the Internet of Things (IoT) progresses toward future smart homes. Wi-Fi-based motion-recognition stands out due to its non-contact nature and widespread applicability. However, the channel state information (CSI) related to human movement in indoor environments changes with the direction of movement, which poses challenges for existing Wi-Fi movement-recognition methods. These challenges include limited directions of movement that can be detected, short detection distances, and inaccurate feature extraction, all of which significantly constrain the wide-scale application of Wi-Fi action-recognition. To address this issue, we propose a direction-independent CSI fusion and sharing model named CSI-F, one which combines Convolutional Neural Networks (CNN) and Gated Recurrent Units (GRU). Specifically, we have introduced a series of signal-processing techniques that utilize antenna diversity to eliminate random phase shifts, thereby removing noise influences unrelated to motion information. Later, by amplifying the Doppler frequency shift effect through cyclic actions and generating a spectrogram, we further enhance the impact of actions on CSI. To demonstrate the effectiveness of this method, we conducted experiments on datasets collected in natural environments. We confirmed that the superposition of periodic actions on CSI can improve the accuracy of the process. CSI-F can achieve higher recognition accuracy compared with other methods and a monitoring coverage of up to 6 m.

A CPW THz-MIMO antenna with reduced mutual coupling using Frequency Selective Surface for future wireless applications

In this article, we propose a novel THz-MIMO antenna system for future wireless applications. The performance of THz systems is prominently influenced by the MIMO configuration of the antenna. Increased signal attenuation and bit error rate (BER) are major hurdles to system performance at THz frequencies. MIMO antenna diversity techniques at the RF front end can significantly improve system performance. Toward this aim, this work attempts to develop a new THz-MIMO antenna system for future wireless applications. The proposed antenna uses a modified version of a traditional rectangular patch as the radiating element. The combination of a co-planar waveguide (CPW) feed structure and a modified stair-case radiator with an inverted L-shaped arch achieves excellent impedance matching between the feed line and the radiator, resulting in a broad bandwidth in the THz range. To evaluate the diversity performance of the antenna, both spatial and orthogonal 2-port antenna systems are designed and analyzed. Furthermore, isolation is enhanced by placing a frequency-selective surface (FSS) between the radiators of the proposed 4-port antenna. This design offers dual bandwidth, covering the ranges of 2.3–2.7 THz and 5.5–8.9 THz. The proposed antenna achieves very low mutual coupling (less than −30 dB), an extremely low envelope correlation coefficient (ECC) of 0.00001, and a low channel capacity loss (CCL) of 0.1 bps/Hz.

A New Method of Lung Nodule Detection in CT Scans using 3D U-Net Convolutional Neural Network

Automatic detection of lung nodules in CT scans has attracted significant research interest in computer-aided diagnosis (CAD) system because it can help improve the early and accurate diagnosis, therefore reducing lung cancer mortality. The aim of this paper is to propose a new method of lung nodule detection in CT scans by using 3D U-Net convolutional neural networks (CNNs) which can successfully reflect the 3D characteristics of CT scans. We use 3D U-Net architecture for CNNs in order to accurately and automatically detect the lung nodules in CT scans. We employ the masked Lung Image Database Consortium (LIDC) dataset containing 400000 CT images of over 1000 patients for training the 3D U-Net model. We introduce an integrated loss function in order to detect lung nodules with different sizes and prepare 3D input data by the use of 2D CT images fixing the hyper parameters of CNNs. Our method successfully detects the lung nodules with different sizes ranging from 3mm to 30 mm exhibiting higher sensitivity of 93.2, 94.5 and 94.8% at 1.0, 2.0 and 3.0 FPs per patient, respectively than the state-of-the-art methods. The proposed method of using 3D U-Net CNNs and integrated loss function is effective for early diagnosis of lung nodules in different sizes with improved sensitivity

Pattern Diversity Antenna with Odd and Even Modes for Intelligent Wi-Fi Applications

Pattern Diversity Antenna with Odd and Even Modes for Intelligent Wi-Fi Applications

Blockage loss and shadow fading behavior of millimeter‐wave signals due to human bodies at 28 GHz

AbstractAs the millimeter‐wave (mm‐Wave) spectrum is considered to be an essential enabler to the fifth generation (5G) wireless communication systems. Human movements are one of the most significant factors that cause transient blockage in indoor mm‐wave channels. In this letter, human blockage measurements and shadow fading statistics due to human body movements in an indoor office environment are reported for the 28 GHz band. The effect of human bodies on the channel is measured for several scenarios including a variety of population and using diverse antenna heights. The reported shadow fading statistics include both the duration and the depth of the blockage fade, and accordingly, we propose several empirical models that cater for such blockage events. The findings reported in this letter could improve the modeling of indoor radio channels at 28 GHz bands by considering the presence of humans, as well as their movements.