Radiation Characteristics Of Antenna Research Articles

Radiation-Based Figure of Merit for Environmental Sensitivity Analysis of Mobile Phone Antennas: A standard tool to evaluate different antenna solutions

The performance of mobile phone antennas is strongly dependent on their environment. However, in the literature, there is no standard criterion to judge this environmental sensitivity. In this work, first, an elaborate figure of merit (FOM) is introduced based on the radiation characteristics of antennas. Then, characteristic modes (CMs) are employed to provide another representation of this FOM. This technique is able to deliver an in-depth understanding of the effect of the environment on the radiating modes of an antenna, which are strongly related to the sensitivity. This perception opens the possibility for designers to achieve less-sensitive antennas. To demonstrate the applicability of the proposed FOM, it is applied to a range of mobile phone antennas available in the literature.

Research on Quasi-isotropic Radiation of Small Circular Arc Antenna

The radiation characteristics of circular arc antennas are studied by applying the method of moments (MoM) to solve the electric field integral equation (EFIE). Based on the triangular current distribution of small circular arc antennas, the analytical expression of radiation fields of circular arc antennas is derived. It is found that the circular arc antenna is equivalent to a superposition of an electric dipole and a magnetic dipole, resulting in near isotropic radiation pattern. Finally, both MoM and CST simulations show that the small arc antenna can realize the near isotropic radiation pattern.

A Simplified Radiation Characteristic Analysis Method for Defocus-Fed Parabolic Antennas in a W-Band Communication System

With increasing interest in the W-band, there is growing focus on parabolic reflector antennas that are known for efficiently inducing high-gain radiation characteristics. There is particular focus on parabolic antennas with diverse defocus-fed applications, including monopulse tracking, multi-beam formation using multiple feeds, and aperture-shared antennas for multi-band operation. Thus, a new simplified method is presented in this paper to analyze the radiation characteristics of defocus-fed parabolic antennas. The presented method is based on the discrete division of a parabolic reflector surface and considers only simplified wave propagation theory and the effect of the scalar function pattern from the feeder. Additionally, array theory is exclusively applied for the analysis of radiation characteristics. Therefore, the presented method uses a very simplified formula to calculate the radiation characteristics of a defocused parabolic reflector antenna. The performance of the presented method was evaluated by comparing the results with commercial EM tools. The results of the analysis confirm the applicability of the presented method for the analysis of defocus-fed parabolic antennas.

Frequency-adjustable OAM antenna with co-divergent beams for IoT applications

A frequency-tunable Orbital Angular Momentum (OAM)-generating antenna array system is introduced for the first time to provide high-data-rate and secure communication for Internet of Things (IoT) infrastructures and devices. Propagation of simultaneous OAM modes brings about the high-data-rate and frequency tunability leads to interference suppression for secure communication. Regarding the design evolution of the proposed structure, the novel Multiple-Input-Multiple-Output (MIMO) antenna consisting of two input ports creates a 2 × 2 UCA, resulting in two 2 × 2 sub-UCA. Feeding each 2 × 2 sub-array with [0°, 90°, 180°, 270°] phase gradients in clockwise and counterclockwise states gives rise to dual-mode OAM-carrying waves with simultaneous excitation capability. It should be mentioned that each MIMO element owns frequency tunability, resulting in a frequency-adjustable dual-mode OAM antenna array. A prototypes of the suggested MIMO antenna as well as the OAM array are fabricated and measured. Changing the applied DC-voltage to the varactor diodes embedded in capacitive stubs of the antenna elements shifts the operating frequency in the MIMO antenna and consequently in the OAM array. Concerning the unique radiation characteristics of the OAM antenna, vortex beams having helical phase fronts are observed, confirming the generation of expected OAM waves. Therefore, it is asserted that the introduced structure, for the first time, proposes new features of frequency-tunability, and co-divergent simultaneous OAM propagation using the MIMO-UCA technique to provide high-data-rate and secure communication in IoT applications.

Adaptive Antenna Array Control Algorithm in Radiocommunication Systems

An important element of modern telecommunications is wireless radio networks, which enable mobile subscribers to access wireless networks. The cell area is divided into independent sectors served by directional antennas. As the number of mobile network subscribers served by a single base station increases, the problem of interference related to the operation of the radio link increases. To minimize the disadvantages of omnidirectional antennas, base stations use antennas with directional radiation characteristics. This solution allows you to optimize the operating conditions of the mobile network in terms of reducing the impact of interference, better managing the frequency spectrum and improving the energy efficiency of the system. The work presents an adaptive antenna algorithm used in mobile telephony. The principle of operation of adaptive systems, the properties of their elements and the configurations in which they are used in practice are described. On this basis, an algorithm for controlling the radiation characteristics of adaptive antennas is presented. The control is carried out using a microprocessor system. The simulation model is described. An algorithm was developed based on the Mathcad mathematical program, and the simulation results of this algorithm, i.e., changes in radiation characteristics as a result of changing the mobile position of subscribers, were presented in the form of selected radiation characteristics charts.

Study on the Effect of Different Feeding Structures on the Performance of Graphene Strips Reconfigurable LWA

This paper introduces a comparative study on the effect of using different feeding structures on the radiation characteristics of graphene strips leaky wave antenna (GS-LWA) at 2 THz. The effect of different plane wave launchers on the radiation characteristics of GS-LWA is investigated. A planar substrate integrated waveguide (SIW) horn antenna is investigated. It provides a peak gain of 18.2 dBi with a bandwidth of 21.95% and a SLL of 10.6 dB. End-fire radiation from parabolic reflector is employed to launch plane-wave in the GS-LWA. A matching BW of 0.82 THz is achieved with peak gain of 18 dBi. A coplanar fed Yagi-Uda like structure element is studied using a single element and two elements array. The two elements provided the highest matching of -40 dB over BW of 6% and gain of 16.5 dBi. Finally, tapered microstrip line is investigated, it introduces the lowest SLL − 16.1 dB with a gain of 17.5 dBi and BW of 39.57% (1.5–2.24 THz). The selection of proper feeding structure depends on the matching BW, peak radiated gain, and the lowest SLL. A full analysis of the GS-LWA from different feeding methods is presented.

Eight element dual-band MIMO array antenna for modern fifth generation mobile phones

In this paper, an eight-element multiple-input multiple-output (MIMO) antenna with dual-band response is designed for fifth-generation (5G) mobile devices. The proposed MIMO systems’ radiators are placed in the inner side frame of the mobile phone board, which has a size of 150 × 7 mm2, each spanning an area of 21.5 × 5.5 mm2. All eight antenna elements are symmetrical to each other and are fed with a 50Ω feeding line. The proposed MIMO antenna covers two distinct 5G frequency bands, i.e., 3.5 and 5.3 GHz, and offers −6 dB impedance bandwidth in a frequency range of 3.4–3.65 and 4.8–5.8 GHz. It is worth mentioning that an isolation of more than 18 dB is achieved over the bands of interest without the use of a decoupling network. Similarly, the proposed MIMO antenna achieved an efficiency of more than 60% across the bands, an envelope correlation coefficient (ECC) below 0.04, antenna gain better than 5 dBi, a mean effective gain (MEG) between any two radiating elements found to be better than 3 dB, and a channel capacity (CC) above 38.5 bps/Hz, which is three times better compared to a 2 × 2 MIMO antenna system. Upon fabrication and testing of the proposed antenna, it was noted that the measured results are in good agreement with the simulated data. Furthermore, the MIMO antenna response was simulated in the presence of a human user and shows how the user phantom affects the radiation characteristics of the MIMO antenna. These performance parameters showed promising results, making the proposed design a better option to be deployed in modern-day 5G communication application scenarios, specifically cell phones.

Design of VHF Horizontal Polarization Omnidirectional Antenna

Horizontally-polarized antennas are usually used in the system of polarization diversity to improve the performance of communication chain and its reliability. Furthermore, the bandwidth of the antenna openly governs the rates of data communication. In order to meet the engineering requirements of high rates for data transmission and multi-band communication, the antenna bandwidth of the communication system needs to be further increased. In this paper we present the scheme of an omnidirectional loop antenna for horizontally-polarized systems. The research status of the horizontally-polarized omnidirectional antenna, and the working principle and radiation characteristics of the small loop antenna are elaborated in detail. The field expression of the loop antenna is deduced from the wave equation, and the characteristics of the far-field and the near-field of the loop antenna are analyzed. On the basis of theoretical analysis, a practical loop antenna is researched and developed for the demands of wireless communication engineering applications. Moreover, we present the related loop antenna technology and how to implement it. The radiation pattern of the antenna is obtained through computer simulations. Our empirical results show that the small loop antenna based on capacitive loading can realize the radiation characteristics of the horizontal polarization omnidirectional pattern. The small loop antenna has the advantages of small size and easy portability, and the small loop antenna operating in the resonant state has a high Q value, which gives it better frequency selectivity. The design and research of this paper have important reference significance for the engineering design and application of the VHF band horizontally-polarized omnidirectional antenna.

Liquid Crystal Polymer-Based Flexible Trap Ultra-Wideband Antenna Design

The wearable ultra-wideband antenna that is appropriate for body area networks is designed and implemented in this article. Stepped circular radiation patches, microstrip feeders, and trapezoidal floors make up the majority of the antenna. Good bending qualities have been attained by using liquid crystal polymer, a flexible material, as a dielectric substrate. An antenna measuring 30 mm × 35 mm × 0.1 mm was designed with two C-shaped slots etched on it to achieve notch function in the 3.20–4.10 GHz and 5.19–5.98 GHz frequency bands. Its working frequency range was 1.96–11.61 GHz, and its specific absorption rate for the human body was less than 2 W/kg. The test findings demonstrate that ultra-wideband body area network systems can be implemented using the antenna impedance and radiation characteristics.

Shielded HMSIW-based frequency-tunable self-quadruplexing antenna using different solid/liquid dielectrics

This article proposes a frequency-tunable self-quadruplexing antenna based on a shielded half-mode substrate integrated waveguide (S-HMSIW). In order to reduce the size of the HMSIW cavity resonator and to obtain quad-band characteristics, a modified E-shaped slot is engraved on the top of the metal. The experimental validation is carried out after analyzing the data using a circuit model. Flexibility of each resonant frequency is enabled by integrating solid and liquid dielectrics of different permittivities within the designated etched region of the proposed antenna. With a broad tuning range of 3-8.5 GHz, the operating frequencies can be tuned individually according to the application-driven demands. Furthermore, the port isolation is better than 23.5 dB in all four bands. The proposed antenna, with distilled water-filled pockets, exhibits realized gain of 3.82, 4.1, 4.3, and 5.6 dBi at 5.17, 5.76, 3.55, and 7.03 GHz, respectively. The antenna features stable radiation characteristics in all bands and throughout the entire tuning ranges. Owing to its compact size, broad tuning capability, consistent radiation patterns, and competitive isolation levels, the presented design can be considered a suitable solution for compact tunable devices required by the existing and emerging application areas, especially multi-standard wireless communications.

Effect of the Dielectric Container on the UWB Antenna Radiation Characteristics

Effect of the Dielectric Container on the UWB Antenna Radiation Characteristics

Dual nanocomposite materials that enhance the radiation characteristics of flexible circular antenna

A novel dual nanocomposite filled circular shaped flexible slot antenna is introduced for WLAN/WiMAX/5G/Wi-Fi applications. The circular radiating patch is given two slots that are filled with nanocomposite materials PANI/CCo and PDMS/AgNW, which enhances antenna radiation properties in both lower and upper band independently. The antenna is fabricated deploying a coplanar waveguide (CPW) fed system that encompasses a patch featuring a circular shape and CPW ground combined with a circular ring shape. The dual band is formed by introducing a narrow rectangular slot on the circular radiating patch and is designed for a mid-frequency 3.85 GHz, of two resonance frequencies. Different bending radii are used to evaluate antenna flexibility, and findings are in good match for a flat antenna. With good radiating qualities over the whole dual band, the suggested fabricated antenna covers the 2.4/5.2/5.8 GHz WLAN, 2.5/5.5 GHz WiMAX, 2.3/2.6 GHz 5G, 2.4/4.9/5.2/5.5/5.8 GHz Wi-Fi, and 5G SUB 6 GHz bands.

Parametric study of a dual-band quasi-Yagi antenna for LTE application

Due to small size and lightweight properties, the development of microstrip (MS) patch antennas for wireless communication has become one of the mobile application devices in demand in recent years. This has helped to reduce reliance on wired cables. In this paper, a study has been performed on MS antenna by developing a quasi-Yagi structure on a fire retardant-4 (FR-4) substrate with a MS to coplanar strip line (CPS) transition feeding technique. The antenna is designed by using computer simulation technology (CST) to achieve the desired resonant frequency and bandwidth. The proposed dual band quasi-Yagi antenna has impedance bandwidths of approximately 0.3 GHz and 0.22 GHz resonating at 1.80 GHz and 2.60 GHz, respectively, which makes it suitable for long-term evolution (LTE) applications. Eight-director elements in four pairs are constructed to achieve directivity with magnitudes of 6 dB and 8.3 dBi at both resonant frequencies, 1.80 GHz and 2.60 GHz, respectively. Different parametric studies have also been performed to characterize the antenna radiation characteristics. The return loss, voltage standing wave ratio (VSWR), front to back (F/B) ratio and far-field radiation are analyzed and discussed.

Development and Research of a Medium Vertical Dipole Electromagnetic Pulse Simulator

In this paper, the design of a self-developed EMP simulator with a 5 m height and an inverted conducting mono-cone antenna with a cone half-angle of 32° is introduced. The experimental region of the simulator is a circular area of 25 m in diameter around the cone vertex. Two feeding modes, feed-in over the ground and feed-in under the ground, are realized by two different high-voltage pulse sources. It can be concluded through radiation field testing that the radiation field waveform generated by the simulator has a rise time of 2–3 ns and a half-width of about 25 ns, meeting the specifications of the EMP experimental waveform in the IEC61000-2-9 standard. Meanwhile, the differences between the engineering implementation of the simulator and its ideal structure during the design process can lead to some distortion issues in the antenna radiation characteristics and the electromagnetic radiation field it generates. The radiation field waveform and the distribution of the EMP field generated by the simulator under different feeding methods, antenna wire quantities, antenna end processing methods, and different antenna resistive loading were studied, and the changes in the radiation field waveform and field distribution with different angles and distances of the monitoring point were analyzed. Based on the measurement results, the radiation characteristics of the antenna and the factors that affect the waveform of the field were studied and analyzed. Through the aforementioned work, a comprehensive understanding of the performance, radiation characteristics, and engineering factors affecting the electromagnetic environment generated by the simulator has been obtained. On this basis, the parameters of the antenna wire quantity, antenna end processing method, and test point position of the designed simulator were reconfirmed and optimized. In summary, this work has important reference significance for mastering the development technology of such simulators, understanding their antenna radiation characteristics, and conducting EMP-related assessments and effect experiments in the future.

A reconfigurable graphene patch antenna inverse design at terahertz frequencies

This article investigates the inverse design of a reconfigurable multi-band patch antenna based on graphene for terahertz applications to operate frequency range (2–5THz). In the first step, this article evaluates the dependence of the antenna radiation characteristics on its geometric parameters and the graphene properties. The simulation results show that it is possible to achieve up to 8.8 dB gain, 13 frequency bands, and 360^circ beam steering. Then and due to the complexity of the design of graphene antenna, a deep neural network (DNN) is used to predict the antenna parameters by given inputs like desired realized gain, main lobe direction, half power beam width, and return loss in each resonance frequency. The trained DNN model predicts almost with 93% accuracy and 3% mean square error in the shortest time. Then, this network was used to design five-band and three-band antennas, and it has been shown that the desired antenna parameters are achieved with negligible errors. Therefore, the proposed antenna finds many potential applications in the THz frequency band.

Practical approach of measuring of angular bearing errors for radiotransparent radomes with complex shape in the “antenna – radome” system in the entire possible scanning ar-ea of the airborne radar antenna system

A nose radiotransparent radome (RTR) plays the role of a dielectric lens of a complex shape, which can significantly affect the radiation characteristics of the airborne radar antenna of an aircraft located under it. Modern radars, as a rule, are built on the basis of antenna systems with electronic beam control – phased antenna arrays. The phasing of the array is carried out in the most different (available for a given phased array) spatial directions. One of the parameters that define the operation of the radar under the RTR is the error in determining the angular position of the targets found by the radar. With complex forms (with one plane of symmetry) of the nose RTR, the resulting angular bearing errors (ABE) depend significantly on the spatial position in which the radar antenna is currently phased. In some cases, bearing errors must be taken into account when operating the radar. This becomes especially important in direction finding and tracking of targets remote to the limit for radar aircraft. In this case, the data on the values of the ABE depending on the current coordinates of the array phasing become relevant. The aim of the article is to present a simple technique that makes it possible to practically measure the ABE in the system “antenna – RTR” in a significant area of electronic scanning by the antenna beam. The technique for measuring the ABE has been developed, which was tested on the basis of an antenna-measuring collimator complex (“compact test site”). Mathematical expressions have been given for calculating both components of ABE (in the phased antenna array angular coordinate system) based on the measured data. At the initial stage, the technique has been tested on the basis of a specially made quick-detachable model-simulator of the radome, which has the ability to introduce arbitrary ABE. With the help of this model, a comparison of the results of measurements obtained on the basis of the proposed method and the method associated with the measurement of dynamic spatial radiation patterns (RP) has been performed. A good correlation of data has been noted for different methods, but on one physical model-simulator of the RTR, which allows us to speak about the correctness of the chosen approach. Subsequently, the correctness of the proposed method has been confirmed by the data collected when working with the system “phased antenna array – RTR” (teardrop shape). In this case, the calculated components of the ABE have been compared with the results of direct measurements by the difference method, when each of the orthogonal components is calculated by measuring the angle of displacement of the minimum of the corresponding difference pattern, obtained before and after the installation of the RTR. The developed technique of preliminary measurement of angular bearing errors over a significant part of the surface of a real RTR makes it possible, if necessary, to compensate the measured ABE in aircraft radar computers, thereby increasing the accuracy of determining the spatial coordinates of targets in space.

Design of Frequency-Reconfigurable Antenna on Dielectric and Magnetic Metamaterial Composite Substrate

Reconfigurable planar antennas are essential in multifunctional wireless communication devices. This letter presents the design of a frequency-reconfigurable patch antenna printed on a composite substrate made of a dielectric and a magnetic metamaterial (MMM). The MMM comprises magnetized ferrite slabs with embedded split-ring resonators (SRR). The constructive coupling between the resonances of the magnetized ferrites and SRR is optimized to achieve promising reconfigurable properties. The proposed frequency-reconfigurable antenna demonstrates a 158% increase in the frequency tuning range. Furthermore, the simulated results are experimentally verified, and the composite substrate shows slight effects on the antenna radiation characteristics.

High-Efficiency Diagnosis of Antenna Radiation Characteristics Based on Scanning Optic-Induced Plasma Scattering Technology

This article presents an innovative quasi-real-time antenna near-field diagnosis method, by scanning a laser-induced plasma on a silicon wafer and imaging the field with the synchronously produced scattered signals. Several approaches have been devised to adapt to the antenna diagnosis scenarios. By using the multilayer matching approach, the issue of multiple reflection disturbance between the aperture and silicon wafer is avoided, especially for large aperture antennae at high frequencies. The accuracy of near-field distribution is improved, and far-field patterns can be transformed directly. The experimental results of a Ka-band 20 dB standard antenna agree well with the simulation results. Diagnosis of radiation states in the reactive near-field region is demonstrated, and the resonate modes of a 2.4 GHz Wi-Fi patch antenna at different frequencies are clearly observed. The experiments of a TM01 mode antenna verify the full polarization diagnosis ability of the method, and the linear polarization component is measured with the help of a polarization grid. The demonstrated diagnosis method has the advantages of high efficiency, ultraclose measurement distance, and superresolution and provides a highly promising and widely available method for antenna diagnosis.

A Novel Compact Ultra-Wideband Frequency-Selective Surface-Based Antenna for Gain Enhancement Applications

This article presents a compact ultra-wideband (UWB) circular monopole antenna with a frequency-selective surface (FSS) for gain enhancement. The proposed antenna has a circular patch with circular cuts at the edges and is excited by a microstrip feed. The bottom plane is truncated and further modified by two triangular cuts at the sides and one rectangular cut in the middle to improve the radiation characteristics of the UWB antenna. The antenna is designed on an FR-4 substrate with a thickness of 1.6 mm, a relative permittivity of 4.3, and planner dimensions of 30 mm × 30 mm. To improve the proposed antenna’s gain, an FSS is designed that consists of periodic unit cells of metal printed on the upper layer of an FR-4 substrate with dimensions of 0.11λ × 0.11λ at the lowest operating frequency of 3.3 GHz. The FSS shows a very low transmission coefficient and linearly reducing reflection phase with increasing frequency over a frequency range of 3.3–10.8 GHz. The gain of the proposed antenna is increased from 3 dB to 8.1 dB at 9 GHz by placing the antenna on the FSS. Moreover, the prototype of the proposed antenna is fabricated, and the experimental results are measured, which show close agreements with simulated results. The FSS-based antenna has directional radiation patterns, making it a potential candidate for ground-penetrating radar and UWB applications.

A Novel Compact Filtering Antenna for 5.0-GHz WLAN Communication System

The proposed antenna presents a microstrip filter antenna with both filter out-of-band rejection characteristics and antenna radiation characteristics for WLAN communication system. The antenna consists of four U-shaped microstrip resonators, one Γ-shaped antenna, and one parallel coupling line. The Γ-shaped antenna has the filtering function as the last order resonator, and the parallel coupling line integrates the filter and antenna as the conductance converter. After simulation and test, the results show that the center frequency of the filter antenna is 5.25 GHz, the fractional bandwidthis 8.0% (5.0 − 5.42 GHz), the in-band gain changes smoothly, the maximum in-band gain is 3.059 dBi, the gain at 150 MHz outside the passband rapidly decreases to 10.0 dBi, and the overall out-of-band gain drops to below −24 dBi. The filter antenna has a simple structure and thin substrate, which optimizes the overall size of the filter and antenna, reduces the transmission loss between them, and is applicable to the RF front-end of wireless communication systems.