Slot Radiator Research Articles

SIW-based dual-beam conical conformal slot array antenna for X-band applications

Abstract A design of substrate integrated waveguide (SIW) based conical conformal slot array antenna is presented for X-band applications. The proposed design consists of two SIW arrays of 1 × 6 slot radiators located at ϕ = 0° and ϕ = 180°. The slotted arrays are fed using a rectangular waveguide (RWG) to SIW 1 × 2 T-junction power divider. The arrays are projected in the longitudinal direction on a conical surface having a lower and upper radius of 1.66λ 0 and 1.33λ 0, respectively. The power divider and SIW arrays are designed and simulated in full-wave EM simulation software. It is observed from the results that the proposed array has two main beams in the H-plane located at θ = ± ${\pm}$ 90°, and have sidelobe levels (SLLs) of −23 dB and −20 dB, respectively. For the validation of simulation results, the proposed array is fabricated and measured, and a reasonable agreement is observed between both results.

Design of Miniature UWB-Based Antenna by Employing a Tri-Sectional SIR Feeder

A novel ultra-wideband (UWB)-based microstrip antenna is presented in this work by using a slotted patch resonator, a tri-sectional stepped impedance resonator (SIR) feeder, as well as a reduced ground plane. The whole structure was realized on an FR4 substrate. The impact of incorporating several cases of ground planes on the input reflection has been thoroughly investigated under the same tri-sectional SIR feeder and by employing a slotted patch radiator. Since the complete ground plane presents an inadequate frequency response, by reducing the ground plane, the induced UWB responses are apparent while the antenna exhibits higher impedance bandwidth. The impact of both the uniform impedance resonator (UIR) as well as the SIR feeder on the input reflection has also been examined by following the same adopted reduced ground technique and using a slotted patch radiator. As a result, the UIR feeder exhibits a dual-band frequency response, when a wide notched band is incorporated in the range from 4.5–6.5 GHz. The dual-band response of the bi-sectional SIR feeder is still apparent with a narrower notched band in the frequency range from 4–5 GHz. As far as the tri-sectional SIR feeder is concerned, the UWB response is discernible without recording the existence of a notched band. Additionally, the antenna displays a higher impedance bandwidth compared with the previously reported steps. Our proposed antenna configuration is designed with highly compact dimensions and an overall size of 14 × 27.2 mm2. Moreover, it operates under the impedance bandwidth of 2.86–10.31 GHz that can be leveraged for numerous applications where wireless systems are used. Our approach presents several advantages compared with the other reported UWB-based antennas in the literature, whereas the measured S11 pattern is in good agreement with the simulated one.

Integrated Slotted Serpentine Waveguide to Enhance Radiation Properties and Efficiency

Slotted waveguides are often used when high-power and high-efficiency antennas must be designed and particularly for millimeter waves applications (automotive radar for example). But it is not easy to choose any distance between radiation slots because of the guided wavelength, to obtain a wide beam in E plane and so to cover a wide angular sector in beam scanning antennas. Moreover, the main beam depends of frequency because it is a progressive wave antenna. In this article, the authors propose an original solution based on a slotted serpentine waveguide with slots on the narrow wall of the waveguide allowing to obtain a very wide radiation pattern in E plane, and this antenna is manufactured, thanks a PCB (printed circuit board) process with empty waveguides to enhance the efficiency for the global structure. Simulations and measurements are given to validate the idea and the technological process in W band, and some different prototypes demonstrate that it could be possible to obtain a wide angular sector in a beam scanning antenna configuration.

Calculation technique of intrinsic and mutual admittance of longitudinal slot radiators on a circular metal cylinder based on their radiation patterns

Calculation technique of intrinsic and mutual admittance of longitudinal slot radiators on a circular metal cylinder based on their radiation patterns

Radiation Pattern Reshaping of a Narrow Slot Antenna for Bandwidth Enhancement and Stable Pattern Using Characteristic Modes Analysis

A novel design concept to reshape radiated fields of a slot antenna for improved bandwidth and stable radiation pattern is proposed. Initially, the radiated fields of the traditional slot antenna are theoretically studied using characteristic modes (CMs). The results demonstrate that its CM1, CM2, and CM3 are resonated around 2.39, 4.78, and 7.17 GHz, respectively. Both CM1 and CM3 maintain the bidirectional radiation patterns, whereas CM2 generates a radiation null in the broadside direction. Then, in order to utilize the nearby CM1 and CM2 for wide bandwidth, the linear slot is properly folded so as to transform the nonbidirectional pattern of CM2 into the bidirectional one. After that, the narrow slot is reformed as the stepped scheme, thus reallocating these dual modes in proximity to each other. With these arrangements, the impedance bandwidth of the antenna is dramatically widened with two attenuation poles, while keeping a compact size and stable radiation pattern. Finally, the proposed antenna is fabricated and tested. Measured results show that the antenna without any extra feeding network has gained a wide bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert &lt; -10$ </tex-math></inline-formula> dB) of around 31.4% ranging from 3.22 to 4.42 GHz, which is about 2.24 times wider than its traditional counterpart (14%). Besides, the overall size of the slot radiator is kept as small as about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.42\lambda _{0} \times 0.06\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength). Particularly, the bidirectional radiation pattern, stable gain of around 5 dBi, and low cross-polarization of below −12.3 dB are all satisfactorily generated during the operating band.

C-SRR loaded CBCPW fed H-shaped slot radiator for ECG monitoring

C-SRR loaded CBCPW fed H-shaped slot radiator for ECG monitoring

C-SRR loaded CBCPW fed H-shaped slot radiator for ECG monitoring

C-SRR loaded CBCPW fed H-shaped slot radiator for ECG monitoring

Orthogonally polarized meandered fed multiple input multiple output antenna array for C‐band sub‐6GHz 5G and unlicensed Wi‐Fi smart‐phone applications

An eight-element meandered fed concentric annular ring slot resonator MIMO (multiple input multiple output) antenna array with dual-band operation is presented for sub-6 GHz 5G and unlicensed C-band Wi-Fi applications. The annular slot radiators are fed by meandered elements designed for operation at 3.15–3.9 and 6.27–6.6 GHz frequency bandwidth with enhanced isolation of more than 20 and 15 dB in the respective bands. The resonator rings are placed on the four corners of the smart-phone PCB with orthogonal meandered elements. The double-band operation is because of two rings and the isolation has been improved by meandered feed elements. The performances of the proposed MIMO antenna was analyzed and validated experimentally. The design offers sufficient gain of more than 5 dBi and efficiencies of upto 75% with better radiation coverages. The measured results of the MIMO antenna are found to be in good agreement with the simulated results. Further, the antenna has been studied for SAR effects as well as radiation coverages in the proximity of users head and hand-head. The antenna housed on 130 × 70 mm 2 1.47 λ 0 × 0.79 λ 0 common ground plane has provided good characteristics making it a potential candidate for sub-6 GHz C-Band 5G and unlicensed Wi-Fi smart-phone applications.

Optic disc cupping after circumpapillary Pd-103 slotted plaque radiation therapy

ObjectifExaminer les effets vasculaires et morphologiques sur le disque optique après une radiothérapie par plaque fendue dans le traitement d'un mélanome choroïdien touchant le disque optique. NatureÉtude transversale rétrospective. ParticipantsTrente-neuf patients atteints d'un mélanome choroïdien touchant le nerf optique. MéthodesChaque mélanome a été traité au moyen d'une plaque radioactive fendue (palladium-103) incluant et/ou entourant la gaine du nerf optique entre 2005 et 2019. Les images du nerf optique avant et après la radiothérapie ont permis de documenter et d’évaluer les changements au chapitre de la pâleur du nerf optique et du rapport cupule/disque (C/D). On a mesuré le rapport C/D à la tomographie par cohérence optique (OCT) de même que la pression intraoculaire (PIO) avant le traitement et pendant le suivi, et 22 patients ont également fait l'objet d'une angiographie-tomographie par cohérence optique (OCT-A) dont la qualité des images permettait l’évaluation de la densité et de la longueur des vaisseaux sanguins. On a noté une corrélation entre les différences quant aux mesures du rapport C/D et les modifications de la densité et de la longueur des vaisseaux sanguins visibles à l'OCT-A. RésultatsSuivant une radiothérapie par plaque fendue, on n'a pas observé de hausse significative de la PIO ni d'augmentation de la pâleur du nerf optique. Les images OCT et les photographies couleur ont mis au jour une augmentation significative (p < 0,001 pour les 2 techniques) du rapport C/D à la fin du suivi, comparativement à ce qui avait été mesuré avant le traitement. On notait une corrélation significative entre la hausse du rapport C/D selon l'OCT et les variations de la longueur des vaisseaux sanguins mesurées à l'OCT-A (p = 0,027). De même, on a établi une corrélation significative entre une augmentation du rapport C/D dans les photographies du fond d’œil et les variations de la densité (p = 0,043) et de la longueur (p = 0,019) des vaisseaux sanguins mesurées à l'OCT-A. ConclusionLes photographies du fond d’œil et les images OCT ont mis en lumière une augmentation du phénomène d'excavation du disque optique au décours d'une radiothérapie par plaque fendue. L'excavation était associée à une occlusion et à une atténuation vasculaires progressives synchrones de la zone péripapillaire, visibles à l'OCT-A. On en conclut que l'ischémie péripapillaire et papillaire due à la radiothérapie par plaque fendue s'accompagne d'une hausse du rapport C/D et d'une aggravation de l'excavation du disque optique.

C-Shaped Open Slot Antenna Array for Millimeter-Wave Applications

In this article, we present a novel slot radiator to achieve a broadband and high-gain antenna array for millimeter-wave (mmW) applications. The slot radiator consists of two C-shaped apertures to generate a pair of folded magnetic dipole radiations. From the obtained results, this slot radiator can produce a broadside radiation and have a wide impedance bandwidth of 39.8% with a reflection coefficient less than −10 dB from 21.7 to 32.5 GHz. Based on the promising result from the antenna element, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> antenna array with a 1-to-64 full-corporate feed network is designed and constructed. The measured results prove that the proposed array achieves a wide impedance bandwidth of 37.1% from 21.3 to 31 GHz. Meanwhile, the gain of the array is from 26.4 to 28.3 dBi across the operating bandwidth, with an average radiation efficiency of 70.1%. This proposed antenna array has a wide bandwidth and a high directive gain, which is a good candidate for long-distance mmW communications and related applications.

Wideband Gain Enhancement of High-Isolation Fabry–Pérot Antenna Array With Tandem Circular Parasitic Patches and Radial Gradient PRS

A high-isolation Fabry–Pérot (FP) antenna array with wide bandwidth and high gain is proposed for <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</b> -band vehicle satellite communications. Each antenna element consists of a pair of tandem circular parasitic patches (TCPPs), a radial gradient partially reflective surface (PRS), and a reflector, respectively, separated from the ground plane with a double-dumbbell-shaped slot (DDSS) by air layer and foam dielectric. The slot radiator steers the TCPPs to create multiple resonant frequencies and then the impedance bandwidth is widened. The impedance matching could be improved by adjusting four circular slot diameters of the DDSS. The gain is raised by TCPPs and radial gradient PRS, which function to guide the electromagnetic field and uniformize the aperture near-field, successively. The reflector with several resonator elements is used to reduce the backside radiation. As proof of concept, the FP antenna array prototype with a height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.613\lambda _{0}$ </tex-math></inline-formula> has been fabricated and measurements confirming simulations are provided. Experimental results show that the impedance bandwidth ranges from 13.48 to 16.95 GHz [22.8% fractional bandwidth (FBW)], and the realized gain is up to 21.59 dBi. A decoupling metallic strip could achieve over 40.8 dB isolation. The proposed antenna element is easily extended for the multiple-input multiple-output (MIMO) and beamforming antennas, further improving the directivity.

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.

Saturn's Inner Magnetospheric Convection in the View of Zebra Stripe Patterns in Energetic Electron Spectra

AbstractBanded structures observed in energetic particle spectrograms in the Earth's inner radiation belt and slot region, that is, “zebra stripes,” have been resolved in the Saturnian magnetosphere with Cassini. This study implements a large‐scale statistical analysis of Saturnian zebra stripe properties in association with the noon‐to‐midnight electric field of the inner magnetosphere to which the stripes' origin was recently established. Cassini has detected zebra stripes extending between L‐shells (L) of 5–9 for more than half of the orbits that crossed inward of L = 9. The amplitude of the stripes is on average above the background differential energy flux, and their age is estimated to be 20–60 hr. The regular observation of zebra stripes suggests that their regeneration and the corresponding electric field enhancements develop over timescales comparable to their estimated lifetime (days), revealing that internal processes contribute to the electric field dynamics, in addition to a solar wind‐induced variability indicated by previous investigations. The flux‐enhanced stripes are traced back to the dayside, preferentially from postnoon, indicating an electric field orientation from postnoon to postmidnight. Our results further suggest that the electric field's offset from the noon‐midnight line is subject to both L‐shell and temporal dependencies, confirming the previous inferred variability.

OCT-A evaluation of radiation vasculopathy following slotted plaque brachytherapy.

To determine a reliable diagnostic method to reveal and monitor subclinical progression of neural and perineural radiation vasculopathy. A retrospective cross-sectional study, where optical coherence tomography angiography (OCT-A) imaging data was collected and analyzed from 22 consecutive patients that had been treated with circumneural slotted plaque brachytherapy for peripapillary, juxtapapillary, or circumpapillary choroidal melanomas. Pre-operative dosimetry of palladium-103 radiation dose to the optic nerve and fovea were collected. Quantified differences in OCT-A-measured vessel density and length in treated verses untreated contralateral control eyes were collected. Vessel density and length were correlated to radiation dose, plaque slot depth, visual acuity outcomes, and circumpapillary retinal nerve fiber layer thickness. Patients had post-irradiation follow-up of median 39 months, interquartile range 62 months). The mean optic disc radiation dose was 89.9 Gy ± 39.2 (86.5, 30.8-189.0). In comparison to controls, OCT-A imaging revealed significant differences in radial peripapillary capillary vessel density (18 μm2 in case eyes, 34 μm2 in control eyes; p < 0.001) and length (10 μm in case eyes, 14 μm in control eyes; p < 0.001). Change in vessel density did not show a significant correlation to radiation dose, slot depth, or visual acuity. However, change in vessel length was significantly correlated to radiation dose (p = 0.049) and change in visual acuity (p < 0.001). OCT-A imaging revealed that radial peripapillary capillary vessel density and length were significantly reduced after circumneural irradiation for choroidal melanoma. Therefore, OCT-A imaging can be used to monitor progression of papillary vasculopathy associated with radiation optic neuropathy.

Enhanced Pencil-Beam Scanning CTS Leaky-Wave Antenna Based on Meander Delay Line

This letter presents a millimeter-wave (mmW) continuous transverse stub (CTS) leaky-wave antenna (LWA) with pencil-beam broadside radiation, high scanning-rate, and low sidelobe levels (SLLs) characteristics. A parallel-plate waveguide (PPW) meander delay line is employed to control the phase constant of the proposed LWA. By adjusting the length of the transverse electromagnetic TEM-mode PPW delay line, the phase difference between adjacent radiating elements can be altered, achieving flexible control of scanning-rate. Match stubs close to the radiation slots are utilized to suppress the open stopband, which help enlarge the beam scanning range. A linear source generator excited by multiple ports with amplitude tapering is employed to generate the quasi-TEM wave. Combined with additional amplitude tapering among the CTS radiation slots, low SLLs at both principal planes are realized. Experimental results show that the LWA with 12 radiation elements has a scanning range of -68° to 42° over the frequency range of 26-34 GHz (a scanning-rate of 13.75°/GHz) with SLLs lower than 13.5 dB/16.6 dB and a peak gain of over 22.5 dBi.

Wideband miniaturized patch radiator for Sub-6 GHz 5G devices

In this article, the compact wideband elliptically slotted semi-circular patch radiator with the defected ground structure for sub-6 GHz applications is designed and developed. The proposed miniaturized patch radiator offers flexibility in adjusting the band of operation by varying the slot dimensions. The effective size reduction is achieved by comparing different iterations in the process of designing and the size of the regular circular-shaped radiator is reduced into the semi-circular radiating patch. The impact of the variation of effective radius of the semi-circular patch, major-axis radius of the elliptical slot, ground plane length, and feed line width is investigated. The size of the proposed radiator is 23.885 × 23.885 × 1.405 mm3. This compact structure manifests the wide bandwidth of 2140 MHz (3.2 GHz–5.34 GHz) with 50% of fractional bandwidth (FBW). The measured results show good agreement with the simulated results. The various parameters validate the utility of the radiator in the C band of super-high frequency (SHF) spectrum and n77 (3.3 GHz–4.2 GHz), n78 (3.3 GHz–3.8 GHz), and n79 (4.4 GHz–5 GHz) bands of the frequency range 1 (FR1) of the sub-6 GHz 5G spectrum.

Radar cross section reduction and gain enhancement of slot antenna using polarization conversion metasurface for X‐band applications

A compact metasurface loaded slot antenna with wide impedance and radar cross section (RCS) bandwidths and a high gain is reported in this communication. The proposed polarization conversion metasurface (PCMS) and its mirror image is arranged into four quadrants and placed atop the slot antenna. A 10-dB monostatic RCS reduction from 7.85 to 12.25 GHz is achieved due to the 180° phase difference of the reflected waves from the PCMS and its mirror image. The gain of the proposed structure gets enhanced by almost 3 dB compared to the radiator alone, throughout the operating band, by partially removing the PCMS just above the slot radiator. The antenna is suitable for use in stealth applications in X-band communication. The antenna structure is fabricated and measured and a good agreement is observed between the simulated and measured results.

Design and packaging of polarization diversity 3D-UWB MIMO antenna with dual band notch characteristics for vehicular communication applications

In this article, the design, fabrication, testing, and packaging of a Substrate Integrated Waveguide(SIW) based polarization diversity 3D eight-port Ultra-Wideband (UWB) MIMO antenna introduced with dual-band notch characteristics for vehicular communication applications. In this proposed UWB MIMO design, we employed a SIW technique to achieve UWB bandwidth with a compact size of 60 × 60 mm3. The SIW based metallic via integrated with L-shaped parasitic slot stub and radiator to notch the WLAN and L-shaped stub connected at the ground plane to notch the X-band. The SIW based radiators are placed in the vertical and horizontal plane to realize the polarization diversity. In addition to providing polarization diversity, the antenna’s direction also contributes a reliable link with communication equipment. The antenna performance metrics such as reflection coefficient(Sii), mutual coupling(Sij), the peak gain, radiation pattern, radiation efficiency, Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Total Active Reflection Coefficient (TARC), Channel Capacity Loss (CCL) and Mean Effective Gain(MEG). The proposed 3D antenna performance analyzed when mounted inside the different types of housing. Hence, the proposed polarization diversity antenna is suitable for vehicular communication applications.

Integration of dual function array with nested slot radiator for MIMO applications

In this communication, a compact dual-element MIMO antenna with decoupling structure has been proposed for handheld devices. The proposed decoupling structure acts as a resonator and as a decoupling structure. The proposed antenna consists of nested slots in the radiator and it supports the application such as LTE, WLAN, Wi-Fi, and WiMAX. The total size of the antenna is 30 mm × 10 mm. The impedance bandwidth of the antenna is 300/400/700 MHz, respectively. The decoupling structure consists of a feed line printed on one side of the substrate and swastika-shaped array on another side. The power fed to the feed line coupled to the swastika-shaped array for achieving the operating bands at 0.9 GHz and (8-10) GHz. Meanwhile, the decoupling array provides isolation more than 20 dB at (2.3-2.6) GHz, (3.4-3.8) GHz, and (5.15-5.85) GHz. The edge to edge spacing between the antennas is 10 mm. The percentage bandwidth of the antenna is 12.2/11.1/12.7/22.2%. The MIMO performance metrics such as envelope correlation coefficient, effective diversity gain, apparent diversity gain, and mean effective gain are evaluated. The proposed antenna is fabricated and tested. The measured results correlate with the simulated results.

A foldedhigher‐modeslot antenna with enhanced bandwidth and radiation pattern reshaping

In this article, an approach to reshape the radiation pattern of the 1.5λ-mode of the slot antenna is proposed. Unlike previous works on slot antenna operating at the fundamental mode with a broadside radiation performance, the proposed slot antenna holds four symmetric radiation beams by resonating at its radiative λ- and 1.5λ-mode. Initially, by folding the straight slot radiator at one short-ended terminal, radiation patterns in H-plane of the 1.5λ-mode could be significantly reshaped from the broadside beam into four symmetric radiation beams, while that of the λ-mode almost remains unchanged. Then, a pair of slot stubs is symmetrically introduced to further improve the bandwidth of multibeam radiation performance. An antenna prototype is finally fabricated and measured to validate the predicted performance. Good agreement between the simulated and measured results is observed. The antenna operates in a frequency range of 3.64 to 3.96 GHz with S11 lower than − 10 dB under dual-mode resonance. And four symmetric beams for radiation have been successfully obtained at the directions of 40°, − 40°, 140°, and − 140° with respect to the broadside direction across the whole operating bandwidth.