Antenna Pattern Research Articles

A compact frequency reconfigurable beam switching antenna based on a single‐layer FSS

AbstractA compact frequency reconfigurable beam switching antenna based on a single‐layer frequency selective face (FSS) is proposed in this paper. The proposed antenna consists of a dual‐band dipole antenna and a single‐layer FSS with hexagonally arrangement. The omnidirectional radiation pattern of the dipole antenna designed as a radiation source and surrounded by the FSS can be converted into directional radiation pattern sweeping along the entire azimuthal plane at two single frequency of 2.4 or 5 GHz. The frequency selection is achieved by controlling the diode state of the FSS unit, and the beam switching is realised by a specific combination of electromagnetic wave reflection or transmission from the hexagonal FSS. The novelty lies in applying the hexagonal arrangement to a dual single‐frequency single‐layer FSS unit. This will not destroy the reflection or transmission characteristics of the FSS unit, but also contribute to reduce the antenna size and achieve a low cost. To validate the design, a prototype is fabricated and measured. The single‐layer FSS antenna with a volume of 57 mm × 57 mm × 58.5 mm can be scanned in 12 steps along the azimuth plane at 2.4 and 5 GHz, respectively.

2 x 1 Rectangular-Patch Antenna Array at 2.4 GHz

In this paper a microstrip antenna array is carried out. The array has two rectangular patches in a linear 2 x 1 array. This work includes the design, simulation, implementation and evaluation of both, a single radiator and the linear two rectangular microstrip antenna array. The antenna array was designed and built for low-cost and noncomplex manufacturing techniques, because the array is dedicated for educational purposes in under-graduate radiocommunication courses at Metropolitan Autonomous University. The mechanical tolerance in the structure dimensions is around 0.2 mm, that is easy to be obtained by an inexpensive CNC or very well-known optical techniques. The simulation and optimization of the array was computed using HFSS and the results of this stage include antenna patterns and the reflection coefficient (S11). Besides, the experimental evaluation of the array is quite similar to the simulations results in both, radiation patterns and the frequency response using the matching interval, for a single radiator and the 2x1 array.

Unraveling the Mechanism of Plasma‐Induced Curing of Particle‐Free Complex Inks for Manufacturing of High‐Performance Flexible Copper Films and Patterns

AbstractAlthough cost‐effective copper inks show great potential in printed flexible electronics, the poor stability and high sintering temperatures have hindered their practical application seriously. Herein, the mechanism of plasma‐induced curing of particle‐free complex copper inks is investigated systematically to realize the low‐temperature fabrication of high‐performance copper films and patterns for advanced flexible electronics. The relationships among the ink formulations, plasma characteristics, microstructures, and the properties of the printed copper patterns are identified; the mechanisms of plasma‐induced curing of copper complex inks are summarized. The fabricated copper films exhibit high conductivity (4.1 µΩ cm), excellent flexibility (bending at a radius of 2 mm), and environmental stability because of the dense microstructures and robust interface adhesion, comparable to that of electroless‐plated films. Moreover, intricate copper antenna patterns on flexible substrates can be obtained rapidly using direct writing and gravure printing methods. These results provide a feasible low‐temperature route to fabricate high‐performance copper films and patterns, promoting the practical application of low‐cost copper inks in printed flexible electronics.

Hybridization of Bayesian Compressive Sensing and Array Dilation Technique for Synthesis of Linear Isophoric Sparse Antenna Arrays

This paper presents a deterministic hybrid algorithm combining the merits of Bayesian Compressive Sensing (BCS) and Array Dilation Technique (ADT) for the synthesis of aperiodic and isophoric (equally-fed) Linear Sparse Array Antennas (LSAA). The hybrid technique overcomes the shortcomings of BCS, i.e., non-uniform amplitude taper which results into a lower taper efficiency, utilizing hybridization with ADT resulting into an isophoric LSAA, thereby improving the taper efficiency. The proposed algorithm can be used to synthesize arbitrary antenna array patterns as per the reference pattern while complementing the constraints on the aperture length and the desired thinning levels. The hybrid algorithm provides a computationally efficient and deterministic technique for synthesizing LSAAs with low SLL and demonstrates a wide angular scanning with minimal loss in directivity and SLL over the scan volume. The results demonstrated are comparable or better than the prior literature on LSAAs.

Cross-Coupling Mitigation in Polarimetric PAR via Antenna Tilt

Abstract The existence of significant cross-polar antenna patterns, as well as the scan-dependent measurement biases, inherent to the polarimetric phased array radar (PPAR), are among the most important risk factors for using this technology in weather observations. The cross-polar patterns on receive induce cross coupling between returns from the two orthogonal fields causing biases in polarimetric variable estimates. Furthermore, the electromagnetic coupling in hardware may exacerbate the cross-coupling effects. To address this problem, a pulse-to-pulse phase coding in either the horizontal or vertical ports of the transmission elements has been proposed. However, it does not affect the scan-dependent system biases in PPAR estimates, which require corrections via calibration mechanisms. Further, the cross-coupling signals are proportional to the cross-polar pattern power levels, rendering mitigation effective only at steering angles where these levels are sufficiently low (e.g., approximately less than −25 dB). In that regard, any approach that augments the number of such steering angles benefits the cross-coupling mitigation effectiveness. Herein, a simple approach that has a potential to achieve this via antenna tilt is presented. Significance Statement The issue of biases caused by cross coupling (due to significant cross-polar patterns in PPARs) is one of the biggest challenges for their weather observation applications. Numerous approaches have been proposed to address this issue, but none has been comprehensive. This suggests that the solution to the cross-coupling issue should be a combination of various mitigation approaches. In that regard, it is suggested in this work that a small antenna tilt can aid in the mitigation of the cross-coupling issue.

Downlink Interference Analysis of UAV-Based mmWave Fronthaul for Small Cell Networks

In this paper, an unmanned aerial vehicles (UAV)-based heterogeneous network is studied to solve the problem of transferring massive traffic of distributed small cells to the core network. First, a detailed three-dimensional (3D) model of the downlink channel is characterized by taking into account the real antenna pattern, UAVs' vibrations, random distribution of small cell base stations (SBSs), and the position of UAVs in 3D space. Then, a rigorous analysis of interference is performed for two types of interference: intra-cell interference and inter-cell interference. The interference analysis results are then used to derive an upper bound of outage probability on the considered system. Using numerical results show that the analytical and simulation results match one another. The results show that, in the presence of UAV's fluctuations, optimizing radiation pattern shape requires balancing an inherent tradeoff between increasing pattern gain to reduce the interference as well as to compensate large path loss at mmWave frequencies and decreasing it to alleviate the adverse effect of a UAV's vibrations.

Holographic phase-retrieval method of near-field antenna pattern measurement for bolometer-array-equipped millimeter-wave telescopes

Wide field-of-view millimeter-wave telescopes with a bolometric detector array have been developed for cosmic microwave background radiation observations. For the purpose of laboratory verification of these telescopes, several studies have demonstrated near-field antenna measurements using a phase-sensitive detector that replaces a few representative pixels of the focal-plane detector array. We present a holographic phase-retrieval method that enables near-field measurements with the bolometric detector array as it is. We place a reference emitter at a fixed position and scan a signal emitter at the telescope aperture. These two emitters are phase-locked and generate interference patterns (holograms) on the focal plane, from which the amplitude and phase of the aperture field can be retrieved. We experimentally demonstrated this method with a crossed-Dragone telescope with a field-of-view that is 18 deg × 9 deg. In the demonstration, we placed a phase-sensitive detector at three detector positions on the focal plane. The antenna patterns calculated from the hologram, neglecting the directly measured phase information, were consistent with those calculated from both intensity and phase measurements at the −60-dB level at 180 GHz. Applying this method, the antenna patterns for all of the bolometric detectors on the focal plane can theoretically be measured simultaneously.

Optimization Design for Sparse Planar Array in Satellite Communications

The antenna is one of the key components of satellite communication load. To address the evolving requirements of future satellite communication systems, the sparse planar array has become an important device for transmitting and receiving electromagnetic waves in emerging antenna systems. The advantages of this technology include low cost, low system complexity, and robust anti-interference ability, which have attracted widespread attention within the industry. In this paper, we investigate an optimization design of sparse planar arrays in satellite communication scenarios. Firstly, we introduce the mathematical foundation of the array antennas and establish the optimization design model of the sparse planar array. Secondly, we analyze and compare the impact of different array layout methods on the sparse planar array antenna pattern, and then introduce the latest design trend of array material design. Thirdly, we review some classical optimization methods for optimizing sparse planar arrays and the recent research advancements in promising and novel methods. Lastly, on the basis of the present research status, we propose three future research directions and two critical challenges for optimal design of sparse planar arrays in satellite communication scenarios, which can facilitate the development and realization of array technology under future B5G and 6G wireless networks.

Analysis of fluctuations of antenna pattern in U-V2X communications

The third-generation partnership project (3GPP) defined several scenarios of vehicle-to-everything (V2X) networks such as vehicle-to-vehicle, vehicle-to-pedestrian, and vehicle-to-infrastructure. Unmanned aerial vehicles (UAVs) exploiting such scenarios for vehicular applications like vehicular-platooning, autonomous driving, and traffic management have shown improved networks’ performance in UAV-V2X (U-V2X) communications. This promising performance is typically obtained by considering high directional UAV antennas. However, the UAV vibration makes UAV antennas’ beam-width sensitive to UAV fluctuations which results in degrading the networks’ performance. Thus, in this paper, the performance of a U-V2X network in the presence of UAV fluctuations is investigated. The UAVs are modeled using an independent homogeneous Poisson Point Process and the vehicular-nodes are modeled using an independent Poisson Line Process. To this end, the association probability and success probability of various links such as vehicular-node connected to a UAV link, vehicular-node connected to a near-by vehicular-node link, and the overall U-V2X link are derived. In addition, the effect of different network settings such as the number of vehicular-nodes, UAVs, roads, and antennas is quantified. Moreover, the spectral efficiency of a U-V2X network is evaluated. Extensive simulations revealed that V2X networks facilitate UAVs and that for less dense areas with fewer roads, buildings, and crowds; UAVs provide more reliable links for connectivity than vehicular-nodes. Furthermore, it is also revealed that UAVs provide less reliable connection for V2X networks with larger UAV antenna fluctuations.

Design of NULLMAC Protocol for Mobile Ad Hoc Network Using Adaptive Antenna Array

Usually, omnidirectional radiation pattern antenna is used in the mobile ad hoc network (MANET) which causes neighbor node interference, consumes more power, and supports only limited range of transmission. To overcome these problems, smart antennas are used. A lot of medium access control (MAC) protocols are proposed using smart antennas. Existing works addressed various problems such as hidden terminal problem, hidden beam problem, deafness of nodes, and head of line blocking problem. However, certain factors including determination of weight vector and conveying it to the neighbor nodes for distortion-free transmission are not considered. In this study, nullifying MAC (NULLMAC) framework is proposed using an adaptive antenna array (AAA) for improving network performance in MANET. NULLMAC framework uses channel information for achieving high throughput and spatial reuse through integrated physical and MAC layer. Before the transfer of data packets, the receiver initially determines its weight vector and conveys it to the transmitter through control packets. Then, the transmitter computes its weight to nullify the dynamic receivers present in the neighborhood region to find the desired receiver. Beamformer weights are determined through channel coefficients between a transmitter-receiver pair to establish distortion-free transmission. Extensive simulations are performed using OPNET integrated with MATLAB. NULLMAC framework achieves 27.22% more throughput and 40.46% increase in signal-to-noise ratio.

A New Generation of Fast and Low-Memory Smart Digital/Geometrical Beamforming MIMO Antenna

Smart multiple-input multiple-output (MIMO) antennas with advanced signal processing algorithms are necessary in future wireless networks, such as 6G and beyond, for accurate space division multiplexing and beamforming. Such a MIMO antenna will yield better network coverage and tracking. This paper presents a smart MIMO antenna configuration with a highly innovative beamforming technique using several nonlinear configurations of dipole arrays. Phase delay factors are optimized at the transmitter to form a single beam and then to steer the beam towards a particular direction. A number of phase shifters are added in order to obtain maximum directional gain. This configuration also significantly increases the power gain of the MIMO antenna at a low cost and with operational simplicity. The paper also demonstrates how the beam width and beamsteering can be effectively controlled. Wolfram Mathematica software was used to generate the three-dimensional radiated beam patterns of the transmitter antenna. There are two approaches to configure the receiver antenna. In the first approach, the received signal magnitude is maximized by aligning the contribution of all elements of the receiver antenna to the same phase. With this approach, the field gain of the proposed system is 25.52 (14.07 dBi). The signal processing gain at the receiver is 64 (18.06 dBi). Therefore, the overall power gain for this proposed new digital/geometrical smart MIMO system is 32.13 dBi. In the second approach, the receiver beam is directed towards the transmitter by optimizing the phase delay coefficients of the receiver. Here, the overall gain of the system is found to be 134.56 (21.28 dBi). Even though the system gain in the second approach is lower, it has the advantage of low interference at the receiver side.

Design and measurements of 6 x 6 m collimator reflector with rounded edges

Compact antenna test range (CATR) is designed to form a plane wave at a small distance from the aperture of the collimator reflector, which allows measurements to be made under far field conditions in a compact anechoic chamber. Currently, collimators are in demand due to the technical re-equipment of the industry for the production of 4G, 5G and Internet of Things stuff. The typical size of a quiet zone for these needs is 1–1.5 m. Along with antenna pattern measurements, collimators are widely used for RCS measurements. In the latter case, the measured objects may have dimensions several times larger than the average size of the quiet zone. Manufacturing, installation and adjustment of collimator reflector of several meters in size is a non-trivial task that requires separate study for each project. An incorrect choice of the reflector geometry can lead to an increase in mass and size, which entails an increase in production costs and the anechoic chamber designed for the CATR. In addition, increase in mass imposes additional requirements on the rigidity of the rack to which the reflector is attached, and the foundation under the collimator. As a rule, large-sized reflectors consist of a dozen fragments, which leads to the need to have special adjustment mechanisms for precision tuning of the reflector fragments. These and other problems need to be solved when developing large CATR. The article presents the issues faced by the LLC «RadioLine» in the process of manufacturing and setting up a collimator stand with a 6 x 6 m reflector. The issues of choosing the geometry of the reflector, its focal length have been highlighted. It has been shown how the agreement of the results of three-dimensional modeling of the reflector and production capabilities has been carried out. The features of the design of the reflector rack are touched upon, in particular, the appropriateness of using two materials: one for the base, and the second for the truss, which is connected to the reflector. After discussing the design features, a scheme for measuring the electromagnetic field distribution in a quiet zone, approaches to improving the quality of the RF characteristics of the CATR have been presented. It is noted that in the process of setting up the collimator, in order to determine the directions to the sources of diffraction, it is useful to apply the recalculation of the measured electromagnetic field in the quiet zone into the plane wave spectrum. At the end of the article, quiet zone cuts have been shown at frequencies of 0.75 GHz, 8.2 GHz and 50 GHz. Average peak-to-peak ripple of the amplitude-phase distribution in the operating frequency range of the CATR is 1 dB in amplitude and 10 degrees in phase.

Cell Phone Radiation Exposure Limits and Engineering Solutions

In the 1990s, the Institute of Electrical and Electronics Engineers (IEEE) restricted its risk assessment for human exposure to radiofrequency radiation (RFR) in seven ways: (1) Inappropriate focus on heat, ignoring sub-thermal effects. (2) Reliance on exposure experiments performed over very short times. (3) Overlooking time/amplitude characteristics of RFR signals. (4) Ignoring carcinogenicity, hypersensitivity, and other health conditions connected with RFR. (5) Measuring cellphone Specific Absorption Rates (SAR) at arbitrary distances from the head. (6) Averaging SAR doses at volumetric/mass scales irrelevant to health. (7) Using unrealistic simulations for cell phone SAR estimations. Low-cost software and hardware modifications are proposed here for cellular phone RFR exposure mitigation: (1) inhibiting RFR emissions in contact with the body, (2) use of antenna patterns reducing the Percent of Power absorbed in the Head (PPHead) and body and increasing the Percent of Power Radiated for communications (PPR), and (3) automated protocol-based reductions of the number of RFR emissions, their duration, or integrated dose. These inexpensive measures do not fundamentally alter cell phone functions or communications quality. A health threat is scientifically documented at many levels and acknowledged by industries. Yet mitigation of RFR exposures to users does not appear as a priority with most cell phone manufacturers.

Design of an applied method with graphite structure for suppression of surface electromagnetic waves between array antennas

In this study, a method of combining graphite structure and electromagnetic bandgap to reduce the mutual coupling of electromagnetic waves in array antennas is proposed. This structure is designed according to the special physical properties of graphite for the emission of electromagnetic waves, transmission theory, as well as the inductance and capacitive properties of the electromagnetic bandgap structure to dissipate surface currents. The proposed multi-input and multi-output (MIMO) antenna was designed and measured with two radiating elements on a substrate. The results show that the effects of mutual coupling between radiating elements are reduced by 30 dB at the operating frequency of 3.34 GHz. By placing this structure, all antenna components, including gain, patterns, and radiation efficiency, are improved. Calculations showed that antenna components: gain and antenna radiation efficiency increased by 1.2 dB and nearly 24%, respectively. To confirm the good performance of the graphite structure, all components of the MIMO antenna, including the envelope correlation coefficient, diversity gain, mean effective gain, channel capacity loss, and total active reflection coefficient, were investigated. The results showed the desired values, which indicate the very good performance of the graphite structure on all the basic characteristics of the antenna.

Performance Analysis of Uncoordinated Interference Mitigation for Automotive Radar

As a key sensor for Advanced Driving Assistance System (ADAS), millimeter automotive radar has been a promising candidate for fulfilling tasks including adaptive cruise control and collision avoidance. However, the widely deployment of millimeter automotive radars may cause serious mutual interference among vehicles, thus degrading radar ranging performance severely. In this article, we analyze the mutual interference among multiple Frequency Modulated Continuous Wave (FMCW) radars. On one hand, we model the interference precisely by employing Matern Hard-Core Process (MHCP) model to characterize the distribution of vehicle nodes in practical bidirectional two-lane and multi-lane scenarios. Besides, the interference is analyzed in terms of the channel fading, the directional antenna pattern and the fluctuation of the target Radar Cross-Section (RCS) in two-lane and multi-lane scenarios. Besides, we analyze the reflected interference in detail. On the other hand, we evaluate the interference mitigation performance of the Random Frequency Division Multiplexing (RFDM) and Frequency Hopping (FH) approaches in terms of the probability of false detection and miss detection, effective detectable density and maximum number of interference-free radar. Finally, a novel AFH-PM mitigation approach is proposed to further improve the interference mitigation performance, which combines the adaptive FH technology with the binary phase modulation. Simulation results verify the proposed framework for interference analysis by employing Monte Carlo method, and the performance improvement of RFDM, FH and AFH-PM is 6.7 dB, 7.6 dB and 8.2 dB, respectively.

A Proposed Analytical Inter-Cell Interference Model for Mobile Cellular Systems with Isotropic Antenna

4G and beyond cellular systems intend to use a frequency reuse factor of one with three sectors per BS site. This configuration leads to an increase in inter-cell interference (ICI). Thus, ICI modeling is very necessary to design and analyze any cellular system. The impact of ICI is modeled analytically in this paper. The effect of six interfering BS sites surrounding the serving BS is examined. The ICI is first mathematically modeled as a function of BS-UE distance for several environments based on pathloss exponent and then validated using an explicit simulation model. Secondly, the results obtained from the proposed model and the explicit simulation model are compared. The comparisons showed good agreement between the results of the proposed model and the simulation model. The mathematical model is convenient to the standardized ITU-R model and has the flexibility to apply any antenna patterns that is compatible with these international models. Furthermore, this model enables ICI estimation by deploying the serving BS cell only without the need to deploy the surrounding nine interfering cell. This has positive impact on reducing the time required for system level simulation.

High Gain and Wideband Antenna-in-Package Solution Using Fan-Out Technology

AbstractThe technology of fan-out wafer level packaging (FOWLP) has been widely adopted for millimeter wave antenna-in-package (AiP) system integration with low interconnection parasitic parameters. Present AiP solutions using FOWLP technology generally form antenna pattern on redistribution layer, which brings design inconvenience. In our work, a low-cost printed circuit board RO4350B laminate for substrate-integrated waveguide (SIW) antenna with a relatively large size is integrated, forms a three-dimensional stacked structure. The AiP employs a right-angle transition board embedded in epoxy molding compound (EMC), which transmits millimeter-wave signal to the SIW antenna stacked on the backside of EMC. The SIW antenna consists of 4 × 4 radiation slots with modified magneto-electric dipole for bandwidth enhancement. The measured gain is 14dBi at 60 GHz with bandwidth beyond 55–65 GHz. The three-dimensional AiP structure improves heat dissipation, no extra thermal design is needed for applications under 0.5 W mm-wave chip power consumption. The AiP module is manufactured and measured on the test board. The proposed approach is a convenient solution for wide band and high gain millimeter wave AiP system integration.

Study of the Radiation Pattern and Frequency Response of a Short Linear Antenna Surrounded by Discharge Tubes for the Development of Rapidly Adjustable Wideband Antenna Systems

Plasma antenna systems consisting of discharge elements have great practical application prospects due to their ability to quickly adjust parameters over a wide range. In this work, the radiation patterns of a 30 mm long linear antenna surrounded by 16 standard T8 fluorescent lamps were measured by using a spectrum analyzer with a tracking generator. The radiation pattern of the system is measured by connecting the output of the spectrum analyzer tracking generator to a linear antenna and connecting the input of the spectrum analyzer to the receiving broadband horn antenna. The work features experimental measurements over a wide frequency range of 0.5 to 1.5 GHz and a wide discharge with current values from 35 to 200 mA. The specific frequency band and uniquely selected geometry allowed for the investigation of both the in-phase and out-of-phase antenna modes, while some modes were found to have a narrow directional radiation pattern, within 50 degrees, with a beam width of −3 dB. The parameters of the gas-discharge plasma were also evaluated using drift theory, as well as using the microwave transmission of the 20 GHz signal. The electron density value corresponding to the used discharge currents was approximately from 4 × 1011 to 7 × 1010 cm−3.

Employment of Self-Adaptive Bayesian Neural Network for Systematic Antenna Design: Improving Wireless Networks Functionalities

The performance of wireless networks is related to the optimized structure of the antenna. Therefore, in this paper, a Machine Learning (ML)-assisted new methodology named Self-Adaptive Bayesian Neural Network (SABNN) is proposed, aiming to optimize the antenna pattern for next-generation wireless networks. In addition, the statistical analysis for the presented SABNN is evaluated in this paper and compared with the current Gaussian Process (GP). The training cost and convergence speed are also discussed in this paper. In the final stage, the proposed model's measured results are demonstrated, showing that the system has optimized outcomes with less calculation time.

Microstrip patch antennas for various applications: a review

<span lang="EN-US">This paper aims to review microstrip antennas for various applications. The design of microstrip patch antennas is a new research field developed for use in 5th generation communication applications. An antenna is a collection of multiple devices connected together that function as a single antenna to send or receive radio waves. Antennas can be of different shapes and sizes. The microstrip patch is an antenna pattern that is light in weight, low profile, and focuses on producing results. In the future, microstrip patch antennas may be used for some 6G communication systems applications. In addition, 6G communication applications can be created on other devices, including biomedical, autonomous vehicles, vehicle-to-vehicle (V2V) communication, internet of things (IoT), machine learning, Artificial Neural Network Algorithms, radar, and wireless communication. In the past, the multiple input, multiple output (MIMO) pattern was a standard geometry used in 4G wireless applications. This paper discusses the geometric structures of antennas, various analysis methods for antenna characteristics, antenna dimensions, and many different types of antennas. Also, it will discuss the previous papers' substrate materials, loss tangent, thickness, return loss, bandwidth, voltage-standing-wave-ratio (VSWR), gain, and directivity.</span>