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Editorial

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4 pages, 178 KiB

Open AccessEditorial

Antennas and Propagation: A Sensor Approach

by Razvan D. Tamas

Sensors 2021, 21(14), 4920; https://doi.org/10.3390/s21144920 - 20 Jul 2021

Cited by 1 | Viewed by 1720

Abstract

Antennas are essentially transducers, as they convert electromagnetic fields into signals and vice versa [...] Full article

(This article belongs to the Special Issue Antennas and Propagation)

Research

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12 pages, 9798 KiB

Open AccessCommunication

Compact Antenna in 3D Configuration for Rectenna Wireless Power Transmission Applications

by Alassane Sidibe, Alexandru Takacs, Gaël Loubet and Daniela Dragomirescu

Sensors 2021, 21(9), 3193; https://doi.org/10.3390/s21093193 - 4 May 2021

Cited by 9 | Viewed by 3137

Abstract

This work presents methods for miniaturizing and characterizing a modified dipole antenna dedicated to the implementation of wireless power transmission systems. The antenna size should respect the planar dimensions of 60 mm × 30 mm to be integrated with small IoT devices such [...] Read more.

This work presents methods for miniaturizing and characterizing a modified dipole antenna dedicated to the implementation of wireless power transmission systems. The antenna size should respect the planar dimensions of 60 mm × 30 mm to be integrated with small IoT devices such as a Bluetooth Lower Energy Sensing Node. The provided design is based on a folded short-circuited dipole antenna, also named a T-match antenna. Faced with the difficulty of reducing the physical dimensions of the antenna, we propose a 3D configuration by adding vertical metallic arms on the edges of the antenna. The adopted 3D design has an overall size of 56 mm × 32 mm × 10 mm at 868 MHz. Three antenna-feeding techniques were evaluated to characterize this antenna. They consist of soldering a U.FL connector on the input port; vertically connecting a tapered balun to the antenna; and integrating a microstrip transition to the layer of the antenna. The experimental results of the selected feeding techniques show good agreements and the antenna has a maximum gain of +1.54 dBi in the elevation plane (E-plane). In addition, a final modification was operated to the designed antenna to have a more compact structure with a size of 40 mm × 30 mm × 10 mm at 868 MHz. Such modification reduces the radiation surface of the antenna and so the antenna gain and bandwidth. This antenna can achieve a maximum gain of +1.1 dBi in the E-plane. The two antennas proposed in this paper were then associated with a rectifier to perform energy harvesting for powering Bluetooth Low Energy wireless sensors. The measured RF-DC (radiofrequency to direct current) conversion efficiency is 73.88% (first design) and 60.21% (second design) with an illuminating power density of 3.1 µW/cm² at 868 MHz with a 10 kΩ load resistor. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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11 pages, 4338 KiB

Open AccessCommunication

Horizontal Polarized DC Grounded Omnidirectional Antenna for UAV Ground Control Station

by Muhammad Shahzad Sadiq, Cunjun Ruan, Hamza Nawaz, Shahid Ullah and Wenlong He

Sensors 2021, 21(8), 2763; https://doi.org/10.3390/s21082763 - 14 Apr 2021

Cited by 5 | Viewed by 3370

Abstract

A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial vehicle (UAV) ground control station (GCS) applications is outlined in this paper. The proposed antenna consists of oversize coaxial cylinders, slots, and slot-feed assembly. Each of the four vertical slots, [...] Read more.

A new slot-based antenna design capable of producing horizontal polarization for unmanned aerial vehicle (UAV) ground control station (GCS) applications is outlined in this paper. The proposed antenna consists of oversize coaxial cylinders, slots, and slot-feed assembly. Each of the four vertical slots, arranged periodically around the antenna’s outer cylinder, emits a horizontally polarized broad beam of radiation, in phase, to produce an omnidirectional pattern. The antenna possesses a low-ripple ±0.5 dB in azimuth gain (yaw) due to its symmetric axis shape and an enclosed feed within itself, which does not radiate and interfere with the main azimuth pattern. This is crucial for a UAV GCS to symmetrically extend its coverage range in all directions against yaw planes. Simulation and measurement results reveal that the antenna maintains stable gain in the omnidirectional pattern (+0.5 dB) over the entire operational frequency band (2.55 GHz to 2.80 GHz), where S11 is lower than −10 dB. A further advantage of this configuration is its enhanced polarization purity of −40 dB over the full frequency band. The direct-current (DC) grounding approach used in this antenna is beneficial due to its electrostatic discharge (ESD) and lightning protection. Furthermore, its aerodynamic, self-supporting, and surface-mount structural shape makes this antenna a good and worthy choice for a UAV GCS. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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17 pages, 8142 KiB

Open AccessArticle

Investigation on Wireless Link for Medical Telemetry Including Impedance Matching of Implanted Antennas

by Ilkyu Kim, Sun-Gyu Lee, Yong-Hyun Nam and Jeong-Hae Lee

Sensors 2021, 21(4), 1431; https://doi.org/10.3390/s21041431 - 18 Feb 2021

Cited by 7 | Viewed by 3466

Abstract

The development of biomedical devices benefits patients by offering real-time healthcare. In particular, pacemakers have gained a great deal of attention because they offer opportunities for monitoring the patient’s vitals and biological statics in real time. One of the important factors in realizing [...] Read more.

The development of biomedical devices benefits patients by offering real-time healthcare. In particular, pacemakers have gained a great deal of attention because they offer opportunities for monitoring the patient’s vitals and biological statics in real time. One of the important factors in realizing real-time body-centric sensing is to establish a robust wireless communication link among the medical devices. In this paper, radio transmission and the optimal characteristics for impedance matching the medical telemetry of an implant are investigated. For radio transmission, an integral coupling formula based on 3D vector far-field patterns was firstly applied to compute the antenna coupling between two antennas placed inside and outside of the body. The formula provides the capability for computing the antenna coupling in the near-field and far-field region. In order to include the effects of human implantation, the far-field pattern was characterized taking into account a sphere enclosing an antenna made of human tissue. Furthermore, the characteristics of impedance matching inside the human body were studied by means of inherent wave impedances of electrical and magnetic dipoles. Here, we demonstrate that the implantation of a magnetic dipole is advantageous because it provides similar impedance characteristics to those of the human body. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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15 pages, 4361 KiB

Open AccessArticle

Calibration to Mitigate Near-Field Antennas Effects for a MIMO Radar Imaging System

by Ha Hoang, Matthias John, Patrick McEvoy and Max J. Ammann

Sensors 2021, 21(2), 514; https://doi.org/10.3390/s21020514 - 13 Jan 2021

Cited by 2 | Viewed by 4229

Abstract

A calibration method for a high-resolution hybrid MIMO turntable radar imaging system is presented. A line of small metal spheres is employed as a test pattern in the calibration process to measure the position shift caused by undesired antenna effects. The unwanted effects [...] Read more.

A calibration method for a high-resolution hybrid MIMO turntable radar imaging system is presented. A line of small metal spheres is employed as a test pattern in the calibration process to measure the position shift caused by undesired antenna effects. The unwanted effects in the antenna near-field responses are analysed, modelled and significantly mitigated based on the symmetry and differences in the responses of the MIMO configuration. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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17 pages, 5648 KiB

Open AccessArticle

Multibeam Reflectarrays in Ka-Band for Efficient Antenna Farms Onboard Broadband Communication Satellites

by Daniel Martinez-de-Rioja, Eduardo Martinez-de-Rioja, Yolanda Rodriguez-Vaqueiro, Jose A. Encinar and Antonio Pino

Sensors 2021, 21(1), 207; https://doi.org/10.3390/s21010207 - 31 Dec 2020

Cited by 8 | Viewed by 3396

Abstract

Broadband communication satellites in Ka-band commonly use four reflector antennas to generate a multispot coverage. In this paper, four different multibeam antenna farms are proposed to generate the complete multispot coverage using only two multibeam reflectarrays, making it possible to halve the number [...] Read more.

Broadband communication satellites in Ka-band commonly use four reflector antennas to generate a multispot coverage. In this paper, four different multibeam antenna farms are proposed to generate the complete multispot coverage using only two multibeam reflectarrays, making it possible to halve the number of required antennas onboard the satellite. The proposed solutions include flat and curved reflectarrays with single or dual band operation, the operating principles of which have been experimentally validated. The designed multibeam reflectarrays for each antenna farm have been analyzed to evaluate their agreement with the antenna requirements for real satellite scenarios in Ka-band. The results show that the proposed configurations have the potential to reduce the number of antennas and feed-chains onboard the satellite, from four reflectors to two reflectarrays, enabling a significant reduction in cost, mass, and volume of the payload, which provides a considerable benefit for satellite operators. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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23 pages, 6869 KiB

Open AccessArticle

Numerical and Experimental Investigation of the Opposite Influence of Dielectric Anisotropy and Substrate Bending on Planar Radiators and Sensors

by Plamen I. Dankov, Praveen K. Sharma and Navneet Gupta

Sensors 2021, 21(1), 16; https://doi.org/10.3390/s21010016 - 22 Dec 2020

Cited by 6 | Viewed by 2841

Abstract

The simultaneous influences of the substrate anisotropy and substrate bending are numerically and experimentally investigated in this paper for planar resonators on flexible textile and polymer substrates. The pure bending effect has been examined by the help of well-selected flexible isotropic substrates. The [...] Read more.

The simultaneous influences of the substrate anisotropy and substrate bending are numerically and experimentally investigated in this paper for planar resonators on flexible textile and polymer substrates. The pure bending effect has been examined by the help of well-selected flexible isotropic substrates. The origin of the anisotropy (direction-depended dielectric constant) of the woven textile fabrics has been numerically and then experimentally verified by two authorship methods described in the paper. The effect of the anisotropy has been numerically divided from the effect of bending and for the first time it was shown that both effects have almost comparable but opposite influences on the resonance characteristics of planar resonators. After the selection of several anisotropic textile fabrics, polymers, and flexible reinforced substrates with measured anisotropy, the opposite influence of both effects, anisotropy and bending, has been experimentally demonstrated for rectangular resonators. The separated impacts of the considered effects are numerically investigated for more sophisticated resonance structures—with different types of slots, with defected grounds and in fractal resonators for the first three fractal iterations. The bending effect is stronger for the slotted structures, while the effect of anisotropy predominates in the fractal structures. Finally, useful conclusions are formulated and the needs for future research are discussed considering effects in metamaterial wearable patches and antennas. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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13 pages, 2183 KiB

Open AccessArticle

Near-Field to Far-Field RCS Prediction on Arbitrary Scanning Surfaces Based on Spherical Wave Expansion

by Woobin Kim, Hyeong-Rae Im, Yeong-Hoon Noh, Ic-Pyo Hong, Hyun-Sung Tae, Jeong-Kyu Kim and Jong-Gwan Yook

Sensors 2020, 20(24), 7199; https://doi.org/10.3390/s20247199 - 16 Dec 2020

Cited by 4 | Viewed by 4142

Abstract

Near-field to far-field transformation (NFFFT) is a frequently-used method in antenna and radar cross section (RCS) measurements for various applications. For weapon systems, most measurements are captured in the near-field area in an anechoic chamber, considering the security requirements for the design process [...] Read more.

Near-field to far-field transformation (NFFFT) is a frequently-used method in antenna and radar cross section (RCS) measurements for various applications. For weapon systems, most measurements are captured in the near-field area in an anechoic chamber, considering the security requirements for the design process and high spatial costs of far-field measurements. As the theoretical RCS value is the power ratio of the scattered wave to the incident wave in the far-field region, a scattered wave measured in the near-field region needs to be converted into field values in the far-field region. Therefore, this paper proposes a near-field to far-field transformation algorithm based on spherical wave expansion for application in near-field RCS measurement systems. If the distance and angular coordinates of each measurement point are known, the spherical wave functions in an orthogonal relationship can be calculated. If each weight is assumed to be unknown, a system of linear equations as numerous as the number of samples measured in the near electric field can be generated. In this system of linear equations, each weight value can be calculated using the iterative least squares QR-factorization method. Based on this theory, the validity of the proposed NFFFT is verified for several scatterer types, frequencies and measurement distances. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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16 pages, 4448 KiB

Open AccessArticle

Glide-Symmetric Holey Structures Applied to Waveguide Technology: Design Considerations

by Zvonimir Sipus, Katarina Cavar, Marko Bosiljevac and Eva Rajo-Iglesias

Sensors 2020, 20(23), 6871; https://doi.org/10.3390/s20236871 - 1 Dec 2020

Cited by 11 | Viewed by 3384

Abstract

Recently, there has been an increased interest in exploring periodic structures with higher symmetry due to various possibilities of utilizing them in novel electromagnetic applications. The aim of this paper is to discuss design issues related to the implementation of holey glide-symmetric periodic [...] Read more.

Recently, there has been an increased interest in exploring periodic structures with higher symmetry due to various possibilities of utilizing them in novel electromagnetic applications. The aim of this paper is to discuss design issues related to the implementation of holey glide-symmetric periodic structures in waveguide-based components. In particular, one can implement periodic structures with glide symmetry in one or two directions, which we differentiate as 1D and 2D glide symmetry, respectively. The key differences in the dispersion and bandgap properties of these two realizations are presented and design guidelines are indicated, with special care devoted to practical issues. Focusing on the design of gap waveguide-based components, we demonstrate using simulated and measured results that in practice it is often sufficient to use 1D glide symmetry, which is also simpler to mechanically realize, and if larger attenuation of lateral waves is needed, a diagonally directed 2D glide symmetric structure should be implemented. Finally, an analysis of realistic holes with conical endings is performed using a developed effective hole depth method, which combined with the presented analysis and results can serve as a valuable tool in the process of designing novel electrically-large waveguide-based components. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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17 pages, 2526 KiB

Open AccessArticle

Modified Split Ring Resonators Sensor for Accurate Complex Permittivity Measurements of Solid Dielectrics

by Amer Abbood al-Behadili, Iulia Andreea Mocanu, Norocel Codreanu and Mihaela Pantazica

Sensors 2020, 20(23), 6855; https://doi.org/10.3390/s20236855 - 30 Nov 2020

Cited by 25 | Viewed by 4025

Abstract

In this paper, a sensor using modified Split Ring Resonators (SRRs) is designed, simulated, fabricated, and used for advanced investigation and precise measurements of the real part and imaginary part solid dielectrics’ permittivity. Adding vertical strips tightly coupled to the outer ring of [...] Read more.

In this paper, a sensor using modified Split Ring Resonators (SRRs) is designed, simulated, fabricated, and used for advanced investigation and precise measurements of the real part and imaginary part solid dielectrics’ permittivity. Adding vertical strips tightly coupled to the outer ring of the SRR leads to the appearance of two resonant frequencies at 1.24 GHz and 2.08 GHz. This modified geometry also assures an improved sensitivity. Using the full wave electromagnetic solver, both the unloaded and loaded sensors are investigated. The numerical simulations are used to develop a mathematical model based on a curve fitting tool for both resonant frequencies, allowing to obtain analytical relations for real and imaginary parts of permittivity as a function of the sample’s thickness and quality factor. The sensor is designed and fabricated on 1.6 mm thick FR-4 substrate. The measurements of different samples, such as transparent glass, acrylic glass, plexiglass, and Teflon, confirm that the modified SRR sensor is easy to implement and gives accurate results for all cases, with measurement errors smaller than 4.5%. In addition, the measurements highlight the importance of the second resonant frequency in the cases in which numerical limitations do not allow the usage of the first resonant frequency (1 mm thick sample). Full article

(This article belongs to the Special Issue Antennas and Propagation)

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16 pages, 5193 KiB

Open AccessArticle

Compact N-Band Tree-Shaped Multiplexer-Based Antenna Structures for 5G/IoT Mobile Devices

by Amélia Ramos, Tiago Varum and João N. Matos

Sensors 2020, 20(21), 6366; https://doi.org/10.3390/s20216366 - 8 Nov 2020

Cited by 3 | Viewed by 2524

Abstract

This paper presents a simple, compact and low-cost design method that allows one to obtain low-profile multi-band antennas for the overcrowded future generation networks, which are widely versatile and very heterogeneous in the K/Ka bands. The proposed antennas comprise n radiating monopoles, one [...] Read more.

This paper presents a simple, compact and low-cost design method that allows one to obtain low-profile multi-band antennas for the overcrowded future generation networks, which are widely versatile and very heterogeneous in the K/Ka bands. The proposed antennas comprise n radiating monopoles, one for each of the desired operating frequencies, along with a frequency selective feeding network fed at a single point. This concept enables a single antenna to be shared with different radio-frequency (RF) frontends, potentially saving space. Typically, with n-band structures the biggest challenge is to make them highly efficient and here this is assured by multiplexing the frequency, and thus isolating each of the monopoles, allowing the design of scalable structures which fit the 5G applications. Based on the vision proposed here, a dual-band and a tri-band structures were built and characterized by their main parameters. Both prototypes achieved peak efficiencies around 80%, with adequate bandwidths and gains, as well as great compactness. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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21 pages, 6993 KiB

Open AccessArticle

Small Antennas for Wearable Sensor Networks: Impact of the Electromagnetic Properties of the Textiles on Antenna Performance

by Gabriela Atanasova and Nikolay Atanasov

Sensors 2020, 20(18), 5157; https://doi.org/10.3390/s20185157 - 10 Sep 2020

Cited by 35 | Viewed by 4983

Abstract

The rapid development of wearable wireless sensor networks (W-WSNs) has created high demand for small and flexible antennas. In this paper, we present small, flexible, low-profile, light-weight all-textile antennas for application in W-WSNs and investigate the impact of the textile materials on the [...] Read more.

The rapid development of wearable wireless sensor networks (W-WSNs) has created high demand for small and flexible antennas. In this paper, we present small, flexible, low-profile, light-weight all-textile antennas for application in W-WSNs and investigate the impact of the textile materials on the antenna performance. A step-by-step procedure for design, fabrication and measurement of small wearable backed antennas for application in W-WSNs is also suggested. Based on the procedure, an antenna on a denim substrate is designed as a benchmark. It demonstrates very small dimensions and a low-profile, all while achieving a bandwidth (|S₁₁| < −6 dB) of 285 MHz from 2.266 to 2.551 GHz, radiation efficiency more than 12% in free space and more than 6% on the phantom. Also, the peak 10 g average SAR is 0.15 W/kg. The performance of the prototype of the proposed antenna was also evaluated using an active test. To investigate the impact of the textile materials on the antenna performance, the antenna geometry was studied on cotton, polyamide-elastane and polyester substrates. It has been observed that the lower the loss tangent of the substrate material, the narrower the bandwidth. Moreover, the higher the loss tangent of the substrate, the lower the radiation efficiency and SAR. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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19 pages, 5137 KiB

Open AccessArticle

A Fully-Printed CRLH Dual-Band Dipole Antenna Fed by a Compact CRLH Dual-Band Balun

by Muhammad Kamran Khattak, Changhyeong Lee, Heejun Park and Sungtek Kahng

Sensors 2020, 20(17), 4991; https://doi.org/10.3390/s20174991 - 3 Sep 2020

Cited by 7 | Viewed by 4580

Abstract

In this paper, a new design method is proposed for a planar and compact dual-band dipole antenna. The dipole antenna has arms as a hybrid CRLH (Composite right- and left-handed) transmission-line comprising distributed and lumped elements for the dual-band function. The two arms [...] Read more.

In this paper, a new design method is proposed for a planar and compact dual-band dipole antenna. The dipole antenna has arms as a hybrid CRLH (Composite right- and left-handed) transmission-line comprising distributed and lumped elements for the dual-band function. The two arms are fed by the outputs of a compact and printed CRLH dual-band balun which consists of a CRLH hybrid coupler and an additional CRLH phase-shifter. Its operational frequencies are 2.4 and 5.2 GHz as popular mobile applications. Verifying the method, the circuit approach, EM (Electromagnetics) simulation and measurement are conducted and their results turn out to agree well with each other. Additionally, the CRLH property is shown with the dispersion diagram and the effective size-reduction is mentioned. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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12 pages, 2368 KiB

Open AccessArticle

RF Channel-Selectivity Sensing by a Small Antenna of Metamaterial Channel Filters for 5G Sub-6-GHz Bands

by Muhammad Kamran Khattak, Changhyeong Lee, Heejun Park and Sungtek Kahng

Sensors 2020, 20(7), 1989; https://doi.org/10.3390/s20071989 - 2 Apr 2020

Cited by 5 | Viewed by 4468

Abstract

In this paper, a new small antenna is suggested for 5G Sub-6-GHz band mobile communication. It can change the channel among the three given bands (called the 3.5-GHz area), as a wide-band antenna is connected to a small multiplexer comprising three metamaterial channel [...] Read more.

In this paper, a new small antenna is suggested for 5G Sub-6-GHz band mobile communication. It can change the channel among the three given bands (called the 3.5-GHz area), as a wide-band antenna is connected to a small multiplexer comprising three metamaterial channel filters. The function of channel selection of this antenna system is experimentally demonstrated to prove the validity of the presented scheme. The channel selection for 5G mobile communication is conducted from f₁ (channel 1) through f₂ (channel 2) to f₃ (channel 3), when TX and RX antennas with gains over 0 dBi and S₁₁ less than −10 dB are located far-field apart (R_Far ≫ 2.1 cm), and result in the transmission coefficient (S₂₁) being the greatest at the selected channel, which is detected by a vector network analyzer. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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Other

Jump to: Editorial, Research

13 pages, 7531 KiB

Open AccessLetter

An Efficient Photomixer Based Slot Fed Terahertz Dielectric Resonator Antenna

by Xiaohang Li, Wenfei Yin and Salam Khamas

Sensors 2021, 21(3), 876; https://doi.org/10.3390/s21030876 - 28 Jan 2021

Cited by 9 | Viewed by 2407

Abstract

A slot fed terahertz dielectric resonator antenna driven by an optimized photomixer is proposed, and the interaction of the laser and photomixer is studied. It is demonstrated that in a continuous wave terahertz photomixing scheme, the generated THz power is proportional to the [...] Read more.

A slot fed terahertz dielectric resonator antenna driven by an optimized photomixer is proposed, and the interaction of the laser and photomixer is studied. It is demonstrated that in a continuous wave terahertz photomixing scheme, the generated THz power is proportional to the 4th power of the surface electric field of photocondutive layer. Consequently, the optical to THz conversion efficiency of the proposed photomixer has an enhancement factor of 487. This is due to the fact that the surface electric field of the proposed photomixer with a 2D-Photonic Crystal (PhC) superstrate has been improved from 2.1 to 9.9 V/m, which represents a substantial improvement. Moreover, the electrically thick Gallium-Arsenide (GaAs) supporting substrate of the device has been truncated to create a dielectric resonator antenna (DRA) that offers a typical radiation efficiency of more than 90%. By employing a traditional coplanar strip (CPS) biasing network, the matching efficiency has been improved to 24.4%. Therefore, the total efficiency has been considerably improved due to the enhancements in the laser-to-THz conversion, as well as radiation and matching efficiencies. Further, the antenna gain has been improved to 9dBi at the presence of GaAs superstrate. Numerical comparisons show that the proposed antenna can achieve a high gain with relatively smaller dimensions compared with traditional THz antenna with Si lens. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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13 pages, 4477 KiB

Open AccessLetter

A Wide Frequency Scanning Printed Bruce Array Antenna with Bowtie and Semi-Circular Elements

by Zeeshan Ahmed, Patrick McEvoy and Max J. Ammann

Sensors 2020, 20(23), 6796; https://doi.org/10.3390/s20236796 - 27 Nov 2020

Cited by 4 | Viewed by 2985

Abstract

A printed edge-fed counterpart of the wire Bruce array antenna, for frequency scanning applications, is presented in this paper. The unit-cell of the proposed antenna consists of bowtie and semi-circular elements to achieve wide bandwidth from below 22 GHz to above 38 GHz [...] Read more.

A printed edge-fed counterpart of the wire Bruce array antenna, for frequency scanning applications, is presented in this paper. The unit-cell of the proposed antenna consists of bowtie and semi-circular elements to achieve wide bandwidth from below 22 GHz to above 38 GHz with open-stopband suppression. The open-stopband suppression enables a wide seamless scanning range from backward, through broadside, to forward endfire. A sidelobe threshold level of −10 dB is maintained to evaluate efficient scanning performance of the antenna. The antenna peak realized gain is 15.30 dBi, and, due to its compact size, has the ability to scan from −64° to 76°. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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13 pages, 4715 KiB

Open AccessLetter

A Single-Fed Multiband Antenna for WLAN and 5G Applications

by Zakir Khan, Muhammad Hunain Memon, Saeed Ur Rahman, Muhammad Sajjad, Fujiang Lin and Liguo Sun

Sensors 2020, 20(21), 6332; https://doi.org/10.3390/s20216332 - 6 Nov 2020

Cited by 43 | Viewed by 4049

Abstract

In this paper, a slotted conical patch connected to a small triangular patch multiband antenna for both microwave and millimeter-wave applications is presented. The designed antenna has three characteristics. The proposed antenna is a multiband, having a compact size of 0.35λ₀ [...] Read more.

In this paper, a slotted conical patch connected to a small triangular patch multiband antenna for both microwave and millimeter-wave applications is presented. The designed antenna has three characteristics. The proposed antenna is a multiband, having a compact size of 0.35λ₀ × 0.35λ₀ × 0.004λ₀ at its lowest operational frequency, i.e., 2.4 GHz, and more importantly, it can cover both the microwave and millimeter-wave bands with a single feeding. According to the −10 dB matching bandwidth, experimental results show that the antenna operates at (2.450–2.495) GHz, (5.0–6.3) GHz, and (23–28) GHz. The reduced size, simple design, and multiband large bandwidth are some of the advantages over the reported designs in the latest literature. Both simulated and experimental results show a good agreement, and the proposed antenna can be used for wireless local area network (WLAN) applications and fifth-generation (5G) wireless communication devices. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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13 pages, 17434 KiB

Open AccessLetter

Integration of Microstrip Slot Array Antenna with Dye-Sensitized Solar Cells

by Bowen Bai, Zheng Zhang, Xiaoping Li, Chao Sun and Yanming Liu

Sensors 2020, 20(21), 6257; https://doi.org/10.3390/s20216257 - 2 Nov 2020

Cited by 11 | Viewed by 2336

Abstract

This paper describes the integration of microstrip slot array antennas with dye-sensitized solar cells that can power array antennas at 5.8 GHz, ensuring normal communications. To appraise the antennas, a 2 × 2 circularly polarized microstrip slot array antenna integrated with dye-sensitized solar [...] Read more.

This paper describes the integration of microstrip slot array antennas with dye-sensitized solar cells that can power array antennas at 5.8 GHz, ensuring normal communications. To appraise the antennas, a 2 × 2 circularly polarized microstrip slot array antenna integrated with dye-sensitized solar cells using a stacked design method was analyzed, fabricated and measured. The size of the entire array is 140 mm × 140 mm, where the size of each solar cell is 35 mm × 35 mm. The results show that the effect of the antenna has a slight influence on the output performance of the solar cells, and the interference of the output current of the solar cells to the antenna feeding system is negligible. The gain of the array antenna increases by 0.12 dB and the axial ratio is reduced to 1.50 dB after the integration of dye-sensitized solar cells. The integration saves a lot of space, and has the ability of self-sustaining power generation, thus providing reliable and long-term communication for various communication systems. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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15 pages, 3270 KiB

Open AccessLetter

Timestamp Estimation in P802.15.4z Amendment

by Ioan Domuta, Tudor Petru Palade, Emanuel Puschita and Andra Pastrav

Sensors 2020, 20(18), 5422; https://doi.org/10.3390/s20185422 - 22 Sep 2020

Cited by 7 | Viewed by 3637

Abstract

Due to the known issue that the ranging in the 802.15.4™-2015 standard is prone to external attacks, the enhanced impulse radio (EiR), a new amendment still under development, advances the secure ranging protocol by encryption of physical layer (PHY) timestamp sequence using the [...] Read more.

Due to the known issue that the ranging in the 802.15.4™-2015 standard is prone to external attacks, the enhanced impulse radio (EiR), a new amendment still under development, advances the secure ranging protocol by encryption of physical layer (PHY) timestamp sequence using the AES-128 encryption algorithm. This new amendment brings many changes and enhancements which affect the impulse-radio ultra-wideband (IR-UWB) ranging procedures. The timestamp detection is the base factor in the accuracy of range estimation and inherently in the localization precision. This paper analyses the key parts of PHY which have a great contribution in timestamp estimation precision, particularly: UWB pulse, channel sounding and timestamp estimation using ciphered sequence and frequency selective fading. Unlike EiR, where the UWB pulse is defined in the time domain, in this article, the UWB pulse is synthesized from the power spectral density mask, and it is shown that the use of the entire allocated spectrum results in a decrease in risetime, an increase in pulse amplitude, and an attenuation of lateral lobes. The paper proposes a random spreading of the scrambled timestamp sequence (STS), resulting in an improvement in timestamp estimation by the attenuation lateral lobes of the correlation. The timestamp estimation in the noisy channels with non-line-of-sight and multipath propagation is achieved by cross-correlation of the received STS with the locally generated replica of STS. The propagation in the UWB channel with frequency selective fading results in small errors in the timestamp detection. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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14 pages, 4086 KiB

Open AccessLetter

An Ultra-Wide Band Antenna System for Pulsed Sources Direction Finding

by Razvan D. Tamas and Stefania Bucuci

Sensors 2020, 20(17), 4695; https://doi.org/10.3390/s20174695 - 20 Aug 2020

Cited by 1 | Viewed by 3161

Abstract

Electric discharges in high-voltage power distribution systems can be localized through their electromagnetic signature in the radio-frequency range. Since discharges produce series of short pulses, the corresponding spectrum usually covers wide frequency ranges, typically up to 1 GHz. In this paper, we propose [...] Read more.

Electric discharges in high-voltage power distribution systems can be localized through their electromagnetic signature in the radio-frequency range. Since discharges produce series of short pulses, the corresponding spectrum usually covers wide frequency ranges, typically up to 1 GHz. In this paper, we propose an ultra-wide band (UWB) antenna system and a direction-finding (DF) approach based on using energy-based descriptors, instead of classical frequency-domain parameters. As an antenna system, we propose a dual-padlock configuration with a suitable pulse-matched response, featuring two unbalanced outputs. The proposed antenna system was successfully validated, both by simulations and measurements. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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10 pages, 5530 KiB

Open AccessLetter

Wideband Dual-Polarized VHF Antenna for Space Observation Applications

by Alexandru Tatomirescu and Alina Badescu

Sensors 2020, 20(15), 4351; https://doi.org/10.3390/s20154351 - 4 Aug 2020

Cited by 4 | Viewed by 5665

Abstract

This work presents the design for an antenna element that can be used in radio arrays for the monitoring and detecting of radio emissions from cosmic particles’ interactions in the atmosphere. For these applications, the pattern stability over frequency is the primary design [...] Read more.

This work presents the design for an antenna element that can be used in radio arrays for the monitoring and detecting of radio emissions from cosmic particles’ interactions in the atmosphere. For these applications, the pattern stability over frequency is the primary design goal. The proposed antenna has a high gain over a relative bandwidth of 88%, a beamwidth of 2.13 steradians, a small group delay variation and a very stable radiation pattern across the frequency bandwidth of 110 to 190 MHz. It is dual polarized and has a simple mechanical structure which is easy and inexpensive to manufacture. The measurements show that the ground has insignificant impact on the overall radiation pattern. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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15 pages, 8325 KiB

Open AccessLetter

Evaluation and Impact Reduction of Common Mode Currents on Antenna Feeders in Radiation Measurements

by Andreea Constantin and Razvan D. Tamas

Sensors 2020, 20(14), 3893; https://doi.org/10.3390/s20143893 - 13 Jul 2020

Cited by 9 | Viewed by 3013

Abstract

Common mode currents on antenna feeders usually occur when feeding a symmetric radiator through an asymmetric line, or when the ground plane is electrically small. Such currents may have magnitudes comparable to the feed currents and therefore have a major impact on the [...] Read more.

Common mode currents on antenna feeders usually occur when feeding a symmetric radiator through an asymmetric line, or when the ground plane is electrically small. Such currents may have magnitudes comparable to the feed currents and therefore have a major impact on the total radiated field. For antenna radiation measurements, both assessment and reduction of the common mode currents on antenna feeders are crucial. Techniques to discriminate antenna and feeder radiation are mainly needed for design and optimization purposes. Antenna gain measurements in a multipath site can be performed by using the distance averaging method. In this paper, we show that the distance averaging technique can be applied to reduce the effect of common mode currents for measuring the field radiated by symmetrical antennas. Two measuring configurations are proposed depending on the number of symmetry degrees of the antenna under test, and a differential approach for extracting the field created by the common mode currents was also developed. The experimental validation was performed by measuring a simple wire dipole and a log-periodic dipole array (LPDA) with a small square loop as a probe, both on the feeder side and on the feeder free side. Full article

(This article belongs to the Special Issue Antennas and Propagation)

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