Slot Loop Research Articles

Novel Low Profile Beam Switchable 5G Sub-6 GHz E-GSM Antenna for Vehicular Communication

ABSTRACT A novel low-profile beam-switchable antenna operating in the Extended Global System for Mobile Communications band of 5G sub-6 GHz for vehicular communication is proposed in this paper. The proposed work has a centre patch that connects with four parasitic radiators and encompasses a tapered patch to R1, R2, R3 and R4 which are slotted loop rectangular patches. The main lobe switching is achieved for Extended GSM by switching between the states of PIN diode circuits, which affects the overall performance of the antenna. With the dimensions of 0.346 λe × 0.346 λe, the presented work exhibits a very-low-profile antenna, having an impedance bandwidth of 14.7% and a peak gain of 1.27 dBi. The proposed beam-switchable antenna incorporates four similar radiators facing different directions affixed to the central square patch director. Each PIN diode is incited eventually to obtain the same resonant frequency at each radiator. The pattern of the proposed antenna can be switched using different states of PIN diodes in the angles of 81°, 171°, 261° and 351°. The prototype is fabricated, and the measured results are in agreement with the simulated results. For the validation of the practicability of the proposed antenna, the far-field analysis is done on the vehicle.

Low-Profile Antenna System for Cognitive Radio in IoST CubeSat Applications

Since the CubeSats have become inherently used for the Internet of space things (IoST) applications, the limited spectral band at the ultra-high frequency (UHF) and very high frequency should be efficiently utilized to be sufficient for different applications of CubeSats. Therefore, cognitive radio (CR) has been used as an enabling technology for efficient, dynamic, and flexible spectrum utilization. So, this paper proposes a low-profile antenna for cognitive radio in IoST CubeSat applications at the UHF band. The proposed antenna comprises a circularly polarized wideband (WB) semi-hexagonal slot and two narrowband (NB) frequency reconfigurable loop slots integrated into a single-layer substrate. The semi-hexagonal-shaped slot antenna is excited by two orthogonal +/−45° tapered feed lines and loaded by a capacitor in order to achieve left/right-handed circular polarization in wide bandwidth from 0.57 GHz to 0.95 GHz. In addition, two NB frequency reconfigurable slot loop-based antennas are tuned over a wide frequency band from 0.6 GHz to 1.05 GH. The antenna tuning is achieved based on a varactor diode integrated into the slot loop antenna. The two NB antennas are designed as meander loops to miniaturize the physical length and point in different directions to achieve pattern diversity. The antenna design is fabricated on FR-4 substrate, and measured results have verified the simulated results.

Reconfigurable Millimeter-Wave Tri-Band Antenna Based on VO2-Films-Embedded Co-Aperture Metasurface Structures

A novel reconfigurable millimeter-wave tri-band antenna using co-aperture metasurface structures embedded with electrically controlling vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) films is proposed. A co-aperture metasurface structure is designed by loading a large square ring surrounded with eight small square patches in the same aperture. By embedding the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film into the large ring, two lower frequencies of 22 and 28 GHz can be excited and switched when the film operates in metallic and insulating states respectively. Meanwhile, an extra higher-mode resonance at 40 GHz is produced by the small patches. Benefit from the reasonable co-aperture layout, the three frequency bands exhibit good independent tunability. Furthermore, the tri-band metasurface structure is used as radiation element to construct a reconfigurable antenna. To realize good feeding coupling at three bands with large frequency ratio for the antenna, a new kind of combined slot is proposed and etched on the transverse surface of the feeding waveguide. The combined slot contains a loop slot, a dumbbell-shaped slot and two U-shaped slots, corresponding to low, medium and high frequencies respectively. In addition, a simple coplanar DC bias circuit with little effect on radiation is designed. As results, when the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film is in insulating state, the antenna can simultaneously cover two bands of 27.7-29.8 GHz and 38.8-40 GHz with the maximum gain of about 8.7 dBi and 9.5 dBi respectively; when the film is activated to metallic state, it can also work in two bands of 21.1-21.6 GHz and 38.6-40 GHz with the maximum gain of about 7.2 dBi and 9.3 dBi. Compared with other reported VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based antennas, the proposed antenna can work in three different bands with adjustable frequency ratio and superior radiation performance.

Penta-band rectangular slot antenna for multi-function wireless communication with linear and circular polarizations

AbstractThis paper presents a multi-band rectangular slot antenna, which can be used in Beidou navigation system, 4G, WLAN and 5G system. The proposed antenna adopts a single feeding line, generating circular polarization for satellite navigation, and linear polarization for mobile communication systems. The proposed antenna consists of three c-type resonators and three rectangular loop slots. A c-type resonator and a rectangular loop slot work together to produce a usable frequency band. Multiple frequency bands can be generated by increasing the number of c-type resonator and rectangular loop slots. It is found that the c-type resonator changes the current distribution on the antenna surface, making the axial ratio less than 3 dB in the low frequency bands. Eventually, five operation frequency bands are realized. Experimentally, it is verified that the impedance bandwidths of each frequency band are 11.8% (1.12–1.26 GHz), 15.4% (1.5–1.75 GHz), 11.9% (2.36–2.66 GHz), 19.7% (3.15–3.84 GHz) and 2.6% (4.47–4.59 GHz), respectively. The measured 3 dB axial ratio bandwidths are 20 MHz at 1.2 and 1.56 GHz, fully covering BDS B1 and B2 bands. The measured gains are 3, 3.59, 4.07, 4.2 and 4.35 dBi, respectively.

Power Handling of Slot Loop Frequency Selective Surface Based on Approximate Analytical Method

Power Handling of Slot Loop Frequency Selective Surface Based on Approximate Analytical Method

Optically Transparent Antenna for Smart Glasses

The optically transparent antenna technology has been gaining attention in consumer electronic industry owing to its potential to release the antenna volume constraints in compact mobile devices. Earlier studies have been heavily focused on the transparent antenna integration to the display for smartphone applications, for example, to improve its spatial coverage of 5G mm-wave at the forehead side. To our knowledge, the application of the transparent antenna technology to smart glasses and augmented reality glasses, especially considering the constraints from the coexistence with optical features in the lens stack-up, has remained unexplored. Thus, for the first time, we suggest a feasible existence solution between antennas and the RF lossy layers in the lens stack-up, to reduce the negative impacts on antenna performances. A slot loop antenna formed by metal-mesh based transparent antenna film and metallic glass frame has been investigated. Experimental results of such an antenna on human head phantom shows a total efficiency better than −4.5 dB in 2.4 GHz band. Even though it is demonstrated through a 2.4 GHz antenna example, the same principle can be applied to any other sub-6 GHz antenna applications, i.e., LTE, WiFi, GNSS, etc.

Millimeter‐wave frequency reconfigurable antenna using simple VO 2 ‐based paired metasurface

In this article, a millimeter-wave frequency-reconfigurable metasurface antenna by electrically controlling vanadium dioxide (VO2) is proposed and studied. As a phase change material, VO2 is an insulator at room temperature but can turn into high conductivity metallic state when activated by continuous direct current (DC) voltage. By integrating the VO2 film between two simple rectangle metasurface cells, a frequency-reconfigurable paired metasurface structure (FRPMS) is achieved. The FRPMS can be considered as one unit when VO2 film is activated to metallic state while as two independent cells when VO2 film is in insulating state. In this way, the FRPMS can operate, respectively at 28 and 38 GHz with independent tunability. Moreover, a coplanar and staggered DC bias circuit with little effect on radiation is designed to switch the operating modes of VO2 easily. The antenna is fed by a stepped waveguide with ridges through a loop slot, which is suitable for dual-band feeding with large frequency ratio. One prototype is fabricated and measured for demonstration. When the VO2 film is in metallic state, the measured working band covers from 28.5 to 29.6 GHz with the maximum gain of about 7.1 dBi. When cooled down to insulating state, the antenna can work in a higher band from 36.7 to 38.3 GHz with the maximum gain of about 7.9 dBi. Due to the advantages of simple structure, high gain and easy tuning, the antenna can be expected to use in mmW wireless communication.

A Novel Low-Profile 5G MIMO Antenna for Vehicular Communication

The proposed work is a novel low-profile 5G MIMO antenna configuration to exhibit dual-band frequencies for 5G NR-n2 band (1.9 GHz) and safety band (ITS-5.9 GHz) in vehicular communication. In the proposed antenna, it is quite difficult to achieve the lowest resonance frequency in a comparatively miniaturized dimension concerning its operating wavelength. The designed antenna is a modified square patch with the dual-band resonance achieved by the incorporation of slots for increasing the electrical length within the dimension. Hence, the design comprises ring and loop slots exhibiting resonance at 1.9 GHz and the loop U, and modified-W slots for 5.9 GHz. The antenna achieves 1.9% and 0.64% impedance bandwidth and a peak gain of 1.944dBi and 6.06dBi at the resonant frequencies of 1.9 GHz and 5.9 GHz, respectively, with dimensions of 0.114λo × 0.114λo × 0.0016λo, where λo is the wavelength of the lowest operating frequency. The MIMO configuration is presented to assess the antenna’s suitability for large-scale applications. The MIMO antenna presented here is deployed with the edge-to-edge distance between the single element radiators being 0.01λo by parametric sweep. The presented MIMO antenna provides an isolation value greater than 19 dB because of reduced mutual coupling between the single element radiators in that MIMO structure due to the presence of a ground slot. The ECC values are 1.659 × 10−9 and 0.000601 for frequencies of 1.9 GHz and 5.9 GHz, respectively, and the diversity gain is relatively near 10 dB, which is the acceptable value for MIMO antennas. This modified square single-element and MIMO antenna provides a relatively higher gain and better performance in vehicular communication for GSM and safety applications. The MIMO configurations’ on-vehicle analysis is performed to check the reliability of the designed antenna in a vehicular environment.

Wideband circularly polarized array antenna based on sequential phase feeding metasurfaces for 5G (sub-6G) applications

In this paper, a broadband circularly polarized array antenna is presented, which consists of four loop slot antennas based on metasurfaces. The antenna element is a loop slot antenna fed by a microstrip line. Cross slots are added to the loop slot to improve the antenna bandwidth, and four corner-cut square metasurfaces are loaded above it, thus generating circularly polarized radiation. The antenna adopts a sequential phase (SP) feed network to realize broadband characteristics. The antenna has been fabricated and experimented. The overall size of the antenna is 78 × 78 × 10.1 mm3 (approximately 1.22 λ0 × 1.22 λ0 × 0.15 λ0), the antenna array has a measured |S11| < −10 dB bandwidth of 3.6–6.2 GHz (53.1%) and a 3-dB axial ratio bandwidth of 3.7–4.8 GHz (28.32%). Furthermore, the antenna also has radiation with a peak gain of 5.5 dBi.

Modeling and Design of a Large Segmented Loop Antenna With a Coplanar Parasitic Slot Loop for NF UHF RFID Readers

This work proposes an improved electrically large antenna based on segmented loops for near-field radio frequency identification readers. The paper applies dispersion analysis of an equivalent circuit model to optimize the segmented loop geometric dimensions and enlarge the tag detection perimeter of the antenna. The novel application of a coplanar parasitic slot loop is shown to improve the dispersion properties of the segmented loop and expand the read perimeter to more than 3.5 times the free-space wavelength at the operating frequency. Furthermore, using the proposed circuit model, a loop antenna with perimeter equivalent to 3.54 times the free-space wavelength is designed and tested for both bidirectional and unidirectional detection. The fabricated prototype demonstrated an improved read range reaching <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~mm$ </tex-math></inline-formula> for the bidirectional range and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$35\,\,mm {-}55\,\,mm$ </tex-math></inline-formula> for the unidirectional operation setup as well as impedance matching at the design frequency (0.915 GHz) located in the North American RFID band from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.902 {-}0.928\,\,GHz$ </tex-math></inline-formula> .

UWB-Mimo antenna of high isolation two elements with wlan single band-notched behavior using roger material

A highly isolated MIMO antenna is proposed for Ultra-wide band (UWB) applications. The proposed MIMO antenna structure consists of two rectangular shaped monopole antennas placed alongside each other on the same substrate. The structure of the identical radiators shaped as simple four open loop cutting at the end of the patch. The proposed antenna is designed to operate at the UWB frequency range from 2.5 GHz to 13.5 GHz. Moreover, a single band notched feature has the spectrum range from 5 GHz to 6 GHz for IEEE802.11 (WLAN) and it is realized by loading an open loop slot in the radiator to minimize the interference. The reflection and transmission coefficient values are below than −10 dB and −25 dB respectively within the UWB frequency range. Furthermore, by embedding a simple rectangular stub between two monopole patch antenna elements, reduce mutual coupling and thus its control the utilization of bandwidth and radiation. Radiation can also be reduced by using roger semiconductor materials. As well as, designed MIMO-UWB antenna has a good impedance matching between measured and simulation results which enhance the isolation to achieve a high signal strength.

Directive Multiband Antenna Based on Rectangular Loop Array and Dumbbell-Shaped Slot Radiator.

In this article, a combination of rectangular loop array and slot radiator for multiband applications is presented. The antenna is configured by arranging, concentrically, a set of rectangular loop radiators excited by electromagnetic coupling provided by a dumbbell slot. The size of the loops is calculated to obtain the desired resonant frequencies, which are almost independent of the adjacent rings. The exciting slot is designed to operate in a wideband frequency range to cover the upper desired resonance. In addition, to obtain directive radiation patterns, a reflector shaped like a box is introduced, giving a stable gain, radiation pattern shape, and port matching at the selected frequencies. The configuration presents great results, since to the authors’ knowledge, even a similar configuration given in the open literature presents some disadvantages compared to this one; moreover, not just any structure can be employed as the resonating elements, obtaining multiband behavior at the same time.

A multibeam slot antenna using dual-layer metasurface

ABSTRACT A novel multibeam slot antenna using metasurface is presented in this communication. This antenna is fed by a coupling aperture and its radiating element consists of dual-layer metasurfaces formed by different units. By employing the rectangular loop slot as the coupling aperture, a wide impedance bandwidth is obtained. Meantime, a dual-layer cross-placed checkerboard metasurface is utilized to generate four beams and expand the operation bandwidth. The experimental results demonstrate that the antenna has a bandwidth of 1.37 GHz (2.18–3.55 GHz). Moreover, the four beams point at (φ, θ) = (180°, 23°), (270°, 23°), (0°, 23°), and (90°, 23°) and the maximum gain reaches 7.63 dBi.

Textile Electromagnetic Brace for Knee Imaging.

A wearable textile brace is introduced as an electromagnetic imaging system that breaks hospital boundaries to real-time onsite scanning for knee injuries. The proposed brace consists of a 12-element textile slot loop antenna array, which is designed to match the human knee for enhanced electromagnetic wave penetration. Wool felt and conductive fabric are used to fabricate the antenna array thanks to their flexibility and proper dielectric properties. Each antenna element has a compact footprint of 42 ×24 ×3.22 mm3 and achieves unidirectional radiation, high front-to-back ratio of 14 dB, wide bandwidth of 81% at 0.7-1.7 GHz, and safe SAR levels. A modified double-stage delay, multiply, and sum (DS-DMAS) algorithm is used to process the collected signals from the antenna array based on differential left/right knee imaging. The reconstructed images numerically and experimentally on realistic phantoms demonstrate the potential of the brace system for onsite detection of different types of ligaments/tendon tears.

A circularly polarized Fabry‐Perot resonant cavity antenna using frequency selective surface ‐based partial reflecting surface

This paper designed a circularly polarized (CP) Fabry-Perot (F-P) resonant cavity antenna which utilized a frequency selective surface (FSS)-based partial reflecting surface (PRS). The loading thin single-layer FSS-based PRS is composed of patches on the top layer of the substrate and square loop slots on the bottom. With the obtained positive slope for the reflection coefficient phase of the loading PRS, the operating bandwidth of the F-P resonant cavity antenna is expanded. In order to further expand the bandwidth, we introduced a sequentially rotating feeding network to excite a 2 × 2 CP patch array, which is used as a feed source for the resonant cavity antenna. By experiment, the actual measured |S11| < −10 dB impedance bandwidth is 26.9%, while the 3-dB axial ratio (AR) bandwidth is approximately 17%. A maximum gain of 15.4 dBic and a radiation efficiency is 86.8% are achieved, which indicate that the proposed antenna is a promising candidate for CP communication applications.

A Conceptual Investigation at the Interface between Wireless Power Devices and CMOS Neuron IC for Retinal Image Acquisition

In this paper, a conceptual investigation of the interface between wireless power devices and a retina complementary metal oxide semiconductor (CMOS) neuron integrated circuit (IC) have been presented. The proposed investigation consists of three designs: design-I, design-II, and design-III. Design-I involves a slotted loop monopole antenna as per American National Standards Institute (ANSI) guidelines, which achieve an ultra-wide band ranging from 3.1 GHz to 10.6 GHz. The biocompatible antenna is made on silicon-nitride substrate using on-wafer packaging technology and it is used as a receiver device. The performance of antenna provides a wideband, sufficient power to receive, and low losses due to the avoidance of printed circuit board (PCB) fabrication. A CMOS based multi-stack power harvesting circuit achieves the output power ranging from 4 mW to 2.7 W and corresponds from the selected Radio Frequency (RF) bands of loop antenna is exhibited in design-II. The power efficiency of 40% to 82%, with respect to output powers of 4 mW to 2.7 W, is achieved. Design-III includes a CMOS based retina neuron circuit that employs a dynamic feedback technique and support to achieve the number of read-out spikes. At the end of the interface between wireless power devices and a CMOS retina neuron IC, 50 mV read-out spikes are achieved, with varying light intensity, from 0 mW/cm2 to 2 mW/cm2. The proposed design-II and design-III are implemented and fabricated using commercial CMOS 0.065 µm, Samsung process. The antenna and RF power harvesting IC could be placed on a contact lens platform while retina neuron IC can be implanted after ganglions cells inside the eye. The antenna and harvesting IC are physically connected to the retina circuit in the form of light. This conceptual investigation could support medical professionals in achieving an interfacing approach to restore the image visualization.

A Compact Single-Layer Four-Port Orthogonally Polarized Yagi-Like MIMO Antenna System

A wideband compact Yagi-like directional multiple-input- multiple-output (MIMO) antenna system is presented based on a slot loop excitation. Four orthogonally polarized beams are generated by orthogonally feeding the slot loop elements using microstrip lines. The proposed design is based on a single-layer geometry with an overall size of 35 × 90 × 0.76 mm3, which is suitable for compact wireless handheld devices. The conventional vertically polarized omnidirectional beams from each slot loop element are made directional and horizontally polarized by using two passive complementary slot reflector (CSR) elements. The antenna system has a wide measured bandwidth of 620 MHz (3.26-3.88 GHz) targeting the 3.6 GHz WiMAX band. It has a maximum realized gain of 4 dBi and front to back ratio (FBR) of more than 7 dB within the band of operation. The proposed antenna system shows good MIMO performance with a minimum measured isolation of 10 dB between the adjacent ports and more than 20 dB between other ports. The orthogonal beams of the antenna system help in achieving low envelope correlation coefficient (ECC) values of less than 0.1. The measured total efficiency of the antenna system is more than 75% for all the ports of the antenna system.

Wideband and Wide-Angle FSS Using Loop Slotted Hybrid Quarter-Mode Substrate Integrated Cavity With Two Independently Controllable Poles

A wideband and wide-angle frequency selective surface (FSS) is proposed in this communication. The periodic element consists of a quarter-mode substrate integrated waveguide (QMSIW) cavity surrounded by two identical loop slots located on the top and bottom layers of the cavity. Two transmission poles and one transmission zero are caused by the fundamental mode in the QMSIW cavity, the slot mode, and the coupling between them, respectively. By precisely tuning the dual-mode configuration, the proposed FSS shows a wide passband with a good transmission efficiency and a rapid roll-off at the high side of the operation band due to the transmission zero. With the QMSIW-based miniaturized elements, the FSS is also insensitive to a large angle of incidence. Thanks to the novel structure, several higher order modes close to the target band are suppressed, making the parasitic passband far away from both sides of the designed band. To verify the advantages, a prototype operated at 10 GHz is fabricated and tested. The measured results show a wide passband performance with the 1/3 dB relative bandwidths of 34%/49% for normal incidence, which agree well with the simulated results. Besides, the 3 dB bandwidth still remains 23% for the incident angle of 60°.

Frequency reconfigurable Yagi‐like MIMO antenna system with a wideband reflector

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based on a single-layer geometry unlike complex multi-layer reflectors used in the literature. It improves the front-to-back ratio between 5 and 17 dB in the entire frequency range covering 2.5–4.5 GHz. The proposed reconfigurable MIMO antenna system covers the LTE and WiMAX bands with a minimum measured bandwidth of 200 MHz per covered bands. The frequency reconfigurability is achieved by reactively loading the slot loop with varactor diodes. The overall size of the proposed antenna system is 40 × 100 × 0.76 mm 3 , making it suitable for tablet handheld devices and access points. It has a maximum measured peak gain of 5 dBi and total measured radiation efficiency of 78%. The proposed MIMO antenna system has port isolation of > 10 dB within the entire band of operation. The radiation patterns are isolated in space from each other and ensure very low envelope correlation coefficient.

A Wideband Dual Polarized Dual-Mode Antenna with Simple Differential Feeding

A wideband differentially fed dual-polarized dual-mode antenna is presented in this letter. Four slots are placed a square shape to construct the slot loop antenna, and the outer ground of the slot loop is bended to achieve a compact size. A simple out-of-phase power splitter with a wide bandwidth and accurate 180° phase difference is integrated with the radiator to feed the slot loop. The 1 and 2 λ modes of the slot loop antenna are excited with the differential feeding for a wide impedance bandwidth (IMBW). By loading the distributed inductors at the ends of each slot, a radiator size of 106 × 106 mm2 is obtained to cover LTE700/GSM850/GSM900 bands. Measured results show that the antenna has the IMBWs of 0.63–1.09 GHz (0.46 GHz, 53.5%) and 0.63–1.08 GHz (0.45 GHz, 52.6%) for the two input ports, isolation of more than 31.5 dB, and stable gain of around 7.15 ± 0.35 dBi for Port 1.