Slotted Square Research Articles

Design a metamaterial based applicator for hyperthermia cancer treatment

This research describes a metamaterial-based applicator with and without water bolus for cancer treatment. The metamaterial based applicator consists of a double spiral antenna and a slotted square shape artificial magnetic conductor (SSA) structure. The antenna is designed on a low-cost FR4 substrate with dimensions of 32 × 32 × 3.27 mm3, and the SSA unit cell which behaves as a metamaterial, is designed on an RT-duroid substrate with dimensions of 15 × 15 × 0.76 mm3 (size of the unit cell). The 4 × 4 unit cells of the SSA structure are optimized to direct the maximum field toward the cancer tissue. The proposed applicator (antenna + SSA structure) is tested for hyperthermia treatment using a heterogeneous phantom (skin, fat, and muscle layers) and the human-mimicked model with an air medium and a water bolus layer. The applicator’s performance is evaluated in terms of specific absorption rate (SAR), penetration depth (PD), and effective field size (EFS). Further, thermal analysis is performed, with 1.5 W of input power at the antenna port, and the maximum temperature rise of 44 0C is obtained. The cancer tissue (tumor) temperature ranges between 41 °C to 45 °C, sufficient for effective hyperthermia therapy. Finally, the suggested metamaterial based applicator is built and tested in the presence of a phantom and head tissue simulating liquid.

A bilayer angular selective surface with transmission at non-zero incident angle based on odd resonance of square ring slot FSS

In this paper, a bilayer angular selective surface (AGSS) is proposed and designed based on the first odd mode resonance of frequency selective surface (FSS). It can realize angular selective transmission (AST) at non-zero incident angles whereas reflection occurs at other angles. Based on the band pass FSS with square ring slot (SRS) structure, we cascade two uniform SRS structures with air space to form the quarter-wave stack. It can realize AST at 30° or 60° for TE or TM polarization, respectively. In addition, a bilayer FSS with maximum transmission at 30° under TE polarization is fabricated and measured. The measurement result shows good agreement with the simulation one, with -3 dB transmitted angular width of 10° The proposed angular selective surface can be applied in high efficient energy harvesting system and radar system with increased signal-to-noise ratio (SNR) level.

Compact metamaterial-based single/double-negative/near-zero index resonator for 5G sub-6 GHz wireless applications

The concept, performance, and analyses of distinctive, miniaturized metamaterial (MTM) unit cell addressing the forthcoming Sub 6 GHz 5G applications are presented in this paper. Two circular split-ring resonators (CSRR) with two parallel rectangular copper elements in front of the design and a slotted square element in the background make up the suggested metamaterial. It has a line segment with tunable features that is positioned in the center of the little ring copper structure. The suggested design offers a significant operating frequency band of 220 MHz together with a resonance of transmission coefficient S21 at 3.5 GHz. Furthermore, in two (z & x) principal axes of wave propagation, wide-range achievement, single/double-negative (S/DNG) refractive index, negative permittivity, and near-zero permeability properties were demonstrated. Through varying central slotted-strip line length, resonance frequencies can be selectively altered. Moreover, the metamaterial has overall dimensions of 9 × 9 mm2 and is composed on a Rogers 5880 RT substrate. In order to create the suggested MTM's equivalent circuit, which shows similar coefficient of transmission (S21), a proposed design’s numerical simulation is carried out in the CST micro-wave studio. This simulation is after that put to comparison with manufacturing of the design.

A Metasurface Based High Gain Patch Antenna for Future Multiband Wireless Communication

This paper presents a novel, compact, and high gain metasurface (MS) patch antenna. The antenna structure consists of a slotted square patch in a fractal shape, integrated with a metasurface layer stacked on Taconic RF-30 dielectric material. The individual cells are arranged periodically, creating a 5 x 5-layer configuration. The proposed antenna is designed with physical dimensions of 290 x 290 mm² and achieves a maximum gain of 13.3 dBi at a frequency of 2.2 GHz. Moreover, it achieves a satisfactory minimum reflection coefficient of -10.9 dB. The design process and analysis were performed using the CST MWS simulation software. Based on the performance results obtained from this study, the suggested antenna can be considered suitable for applications in 5G communication.

High Data Capacity Chipless RFID Tag Based on Time-Domain Scattering Modulation

In this communication, we present a low-cost chipless radio frequency identification (RFID) tag with a high data capacity and a wide reading range based on time-domain scattering modulation. The proposed tag consists of a slotted square patch antenna with a switchable resistor and a mechanically driven slider etched with a barcode-like metallic wire array. Encoding is achieved by the presence and absence of the metallic wire on the slider, and tag identification is obtained by sequential bit reading. A special encoding strategy is applied to improve its insensitivity to the motion velocity of the slider. For a proof-of-concept demonstration, a prototype designed to operate at 2.1 GHz was fabricated and measured, and the experimental results verified the effectiveness. Compared with the methods based on time-domain reflectometry, spectral signature, and resonator-based sequential encoding, the proposed approach provides a substantially enhanced data capacity within a narrow spectrum without sacrificing its reading range and tag size, due to the design of nonresonant code cell. Such a mechanically triggered chipless RFID tag exhibits promising potentials in some practical applications, such as personal ID and credit cards.

Octagonal Shaped Annular Ring Pattern Reconfigurable Antenna Designs for Cognitive Radio Application

An Octagonal shaped Annular Ring pattern reconfigurable antenna is proposed for cognitive radio applications which gives Omni-directional and directional pattern at 1.3 GHz. The antenna has the frequency switching capability at 1.5 GHz, 3.2 GHz, 4.8 GHz and 6.8 GHz with the use of a single PIN diode. Further, the antenna is modified by inserting a slotted square shape in an octagonal ring. With the use of two diodes, the proposed antenna shows the pattern diversity at 3.2 GHz and 4.6 GHz with the gain of 6.23 dBi. Also, the antenna shows the frequency switching for 1.5 GHz, 3.1 GHz, 4 GHz, 4.3 GHz, 4.8 GHz and 6.8 GHz with the different states of the PIN diode. The proposed antennas can be used for RFID, S and C band applications.

Dual-Band Millimeter-Wave Beam Scanning Slotted Square Patch Antenna Based on Active Frequency Selective Surfaces for 5G Applications

This paper is concerned with dual-band electronically beam-scanning for millimeter-wave (mm-wave). A design encompassing slotted square patch antenna with an Active Frequency Selective Surface (AFSS) screen is presented. Each unit cell of AFSS is constructed of spiral arms endorsed with four varactors to enhance a wide tuning range over dual modes. Among many other features, the design supports dual operation bands at 48.5 and 68.5 GHz which is considered without any 90° phase shifter and is excited by a single-feed microstrip line. The overall size of the proposed antenna is only 3.9(3.9(0.1 mm3, which is smaller than some mm-wave antenna modules released recently. The whole structure is an ideal option for wireless applications due to its ability to scan its primary beam in dual-band throughout the whole azimuth plane with a resolution of 60°. The proposed structure can sweep beams throughout the whole 360° angular range and is capable of both dual-band and single-band beam sweeping with high gain, making it an excellent choice for 5G mm-wave applications.

Compact dual-mode microstrip bandpass filter based on slotted square patch resonator

PurposeThe purpose of this paper is to present the design of a compact microstrip bandpass filter (BPF) in dual-mode configuration loaded with cross-loop and square ring slots on a square patch resonator for C-band applications.Design/methodology/approachIn the proposed design, the dual-mode response for the filter is realized with two transmission zeros (TZs) by the insertion of a perturbation element at the diagonal corner of the square patch resonator with orthogonal feed lines. Such TZs at the edges of the passband result in better selectivity for the proposed BPF. Moreover, the cross-loop and square ring slots are etched on a square patch resonator to obtain a miniaturized BPF.FindingsThe proposed dual-mode microstrip filter fabricated in RT/duroid 6010 substrate using PCB technology has a measured minimum insertion loss of 1.8 dB and return loss better than 24.5 dB with a fractional bandwidth (FBW) of 6.9%. A compact size of 7.35 × 7.35 mm2 is achieved for the slotted patch resonator-based dual-mode BPF at the center frequency of 4.76 GHz. As compared with the conventional square patch resonator, a size reduction of 61% is achieved with the proposed slotted design. The feasibility of the filter design is confirmed by the good agreement between the measured and simulated responses. The performance of the proposed filter structure is compared with other dual-mode filter works.Originality/valueIn the proposed work, a compact dual-mode BPF is reported with slotted structures. The conventional square patch resonator is deployed with cross-loop and square ring slots to design a dual-mode filter with a square perturbation element at its diagonal corner. The proposed filter exhibits compact size and favorable performance compared to other dual-mode filter works reported in literature. The aforementioned design of the dual-mode BPF at 4.76 GHz is suitable for applications in the lower part of the C-band.

A Simple Polarization-Insensitive and Wide Angular Stable Circular Ring Based Undeca-Band Absorber for EMI/EMC Applications

In this article, a closed ring resonator-based absorber with eleven consecutive absorption peaks is proposed over <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> bands with an average absorption rate of 96.29%. The proposed design consists of circular ring resonators embedded in the circularly slotted square patch printed on the top of the grounded FR-4 substrate. The surface current distributions well illustrates the reason behind the electromagnetic (EM) wave absorption. The design is polarization insensitive for normal incidence and wide angular stable up to 45° for TE (60° for TM) polarization. The structure is fabricated on a single-layered FR-4 dielectric substrate with a periodicity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$</tex-math></inline-formula> /2.32 and thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$</tex-math></inline-formula> /16.74, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$</tex-math></inline-formula> is the free-space wavelength at the lowest resonant frequency. A transmission line-based equivalent circuit model has been illustrated and good agreement is observed with full-wave simulations. This article's novelty lies in the absorption mechanism of eleven consecutive absorption peaks, demonstrating the controllability of the absorptivity peaks and resonant frequency. To the best of the authors’ knowledge, the proposed absorber demonstrates the highest number of near-unity successive absorption bands with better angular stability. The proposed structure was checked for radar cross section reduction application with an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band antenna and results show 19.7-dBsm reduction at normal incidence.

Using a simple rope-pulley system that mechanically couples the arms, legs, and treadmill reduces the metabolic cost of walking

BackgroundEmphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject’s wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing.MethodsTo test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8).ResultsWith our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001).ConclusionsThese findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability.Trial registration: Study registered on 09/29/2018 in ClinicalTrials.gov (ID—NCT03689647).

Circularly polarized MIMO antenna utilizing parasitic elements for simultaneous improvements in isolation, bandwidth and gain

A circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with wideband operation and high isolation characteristics is presented. The proposed antenna is first designed with two diagonal slotted square patches and then, four parasitic elements are utilized to significantly improve the antenna performances. Notably, besides enhancing the operating bandwidth and the gain radiation, the parasitic elements also contribute to reduce the mutual coupling between the MIMO elements. The measurements demonstrate that the proposed two-element MIMO antenna with edge-to-edge spacing of 0.09λo and profile of 0.05λo at the center operating frequency has operating bandwidth of 12.8% (5.1–5.8 GHz) and high isolation of better than 22 dB. The antenna also achieves high gain of better than 7.5 dBic and good diversity performances. Compared to other CP MIMO antennas reported in literature, our design possesses several exclusive features including wideband operation, high gain, very small edge-to-edge element spacing as well as low-profile configuration.

A wideband four‐port multiple‐input‐multiple‐output slot antenna for WLAN / WiFi / 5G below 6 GHz applications

In this article, a four-port wideband multiple-input-multiple-output (MIMO) antenna consisting of moon-shaped slot radiators positioned at the ground plane corners is presented. Slotted square ring metamaterial structures as parasitic element have been loaded on the substrate adjacent to the feed lines to enhance the operating bandwidth and miniaturize the antenna. The proposed MIMO antenna has a measured bandwidth of 3.11 to 6.6 GHz (71.88%) with more than 18 dB isolation between antenna elements. Furthermore, simulated diversity parameters such as envelope correlation coefficient, diversity gain, mean effective gain, and channel capability loss are validated with the measured values and found within the acceptable limits over the operating frequency. The proposed antenna can be applied in 5G below 6 GHz (3.3-5.0 GHz), WLAN (4.9-5.725 GHz), and WiFi (5.15-5.85 GHz) bands.

Design of miniaturized FSS structure using Optimization Technique based on Machine Learning

This work presents the design of a miniaturized FSS structure characterized by three resonant frequencies for S and C-band applications. When an incident normalized plane wave is illuminated, the miniaturized FSS shows three rejecting bands at 2.42 GHz, 7.2 GHz, and 9 GHz simultaneously with the wide bandwidth of 2.3 GHz from 5.8 GHz to 8.1 GHz. The Frequency Selective Surface is designed by creating some rectangular slots within the square patch. The resultant slotted square patch can achieve a size reduction of 93.2%, 47.8%, and 18.98%. The measured results show great acceptance for the simulated ones. The theoretical investigation has been done by the Ansoft HFSS EM simulation tool. An experimental investigation has been performed and analytical results are achieved. A machine learning technique is implemented which also validates the experimental resonant frequency values.

Broadband single-layer reflectarray antenna loaded with meander-delay-lines for X-band applications

In this work, delay-lines loaded broadband reflectarray antenna is proposed for X-band applications. The array cells contain slotted square patch and quad meander delay-lines. The slotted square patch elements are combined with delay-lines to increase the reflection phase range. A smooth linear phase variation of 650° is realized through varying the length of delay-lines. The reflectarray unit element resonant behavior is observed through an equivalent circuit model approach. The reflectarray antenna is simulated and measured on a low-cost FR-4 substrate. A 23 × 23 elements reflectarray antenna is designed and simulated using a hybrid finite element boundary integral (FEBI) method. The proposed reflectarray antenna offers a measured gain of 25 dBi and 52.8% aperture efficiency for 10 GHz frequency band. The cross-polarization levels and side-lobe-levels and in E and H-plane are less than −35 dB and −22 dB respectively. Moreover, a measured 3-dB gain bandwidth of 29% and 1-dB gain of 19.5% is realized for the proposed reflectarray antenna.

Multiband Printed Koch Antenna Unified with Hilbert Split-Ring Structure for Better Front-to-Back Ratio

A multiband printed Koch antenna integrated with multi-band high-impedance surface (HIS) is proposed. The antenna can operate at three frequencies like 11.725 GHz, 26.155 GHz and 39.22 GHz which covers application in frequency bands namely X-band (8-12 GHz), K-band (18-27 GHz), and Ka-band (26.5-40 GHz). In order to achieve a modest design with better front-to-back ratio (FBR), gain, directivity and radiation efficiency a multi-band Hilbert split-ring HIS is presented as a reflector. The proposed HIS has an array of slotted square patches based on Hilbert curve. This arrangement provides in-phase reflection at the operating frequencies and can be presented as an artificial magnetic conductor (AMC). The antenna when integrated with HIS has an incorporated uniform profile thickness of 2 mm for different frequencies of operation. The printed Koch antenna is simulated, analyzed for various substrate thickness and is finally integrated with Hilbert split-ring HIS to obtain good FBR and radiation efficiency in all the three bands.

A Broadband Circularly Polarized Cross-slotted Patch Antenna with Horizontal Meandered Strip (HMS)

AbstractA broadband circularly polarized slotted square patch antenna with horizontal meandered strip (HMS) is presented and studied. The HMS feeding technique provides the good impedance matching and broadside symmetrical radiation patterns. A set of cross asymmetrical slots are etched on the radiating patch to realize the circular polarization. An electrically small stub is added on the edge of the antenna for further improvement in performance. Measured 10-dB impedance bandwidth (IBW) and 3-dB axial ratio bandwidth (ARBW) of the proposed antenna are 32.31 % (3.14–4.35 GHz) and 20.91 % (3.34–4.12 GHz), respectively. The gain of the antenna is varied from 3.5 to 4.86dBi within 3-dB ARBW. Measured results matched well with the simulated results.

Performance improvement of a slotted square patch antenna using FSS superstrate for wireless application

This paper presents a wideband planar antenna integrated with a frequency selective surface (FSS). Initially, the FSS array screen is investigated using a basic square ring to construct a unit cell of the FSS periodical structure with a (12x12) array. FR4 with a permittivity of 4.7 and a thickness of 1.6 mm is used as the substrate material for both FSS structure and antenna. Then, the antenna is placed closely parallel over the FSS configuration at a distance of 28 mm. After analyzing the performance of the antenna in terms of return loss, directivity and antenna gain, the design is integrated with the FSS structure in order to achieve a stable frequency response. Directivity and gain improvement of 6.5 dB and 5.1 dB respectively are observed along broadside direction.

Twenty‐eight‐gigahertz beam‐switching ridge gap dielectric resonator antenna based on FSS for 5G applications

A new design of the double dielectric resonator antenna (DRA) fed by a printed ridge gap waveguide for beam-switching applications based on frequency selective surfaces (FSSs) is presented here. The dual-sided printed FSS element works in its reflection mode and comprises a slotted square C-shaped patch on the top layer and a square strip on the back plane. Therefore, the beam switching can be implemented by loading the proposed FSS array over and in the middle of DRAs. Loading the antenna with two layers of 3 × 3 FSS unit cells results in ±77° beam switching and a 3.16 dBi gain enhancement at 28 GHz. Simulation and measurements confirm the operation of the proposed antenna, with good matching and gain observed.

A substrate integrated cavity‐fed dual‐polarized filtering patch antenna with high isolation

This article presents a dual-polarized filtering patch antenna, which uses two orthogonal modes (TE210/TE120) of the substrate integrated cavity (SIC) to couple with two orthogonal modes (TM10/TM01) of the patch by the cross slot, respectively. The second-order filtering response on dual polarizations can be achieved by using just one SIC resonator and one slotted square patch, which display simple structure of the proposed antenna. The slotted square patch provides a new way to obtain same external quality factor of the radiator on dual polarization, which makes the performances on two polarizations agree well with each other when changing the bandwidth. High isolation can be achieved by controlling the space of the vias of the SIC. Radiation nulls can be produced by connecting the coupled lines with the feeding lines in parallel. A prototype with the entire height of 0.019 λ0 (λ0 is the free-space wavelength at center frequency) achieves a 10-dB bandwidth of 1.6%, the gain of 4.9 dBi at the center frequency, the port isolation of 43 dB, and the out-of-band rejection level of 25 dB.

Multi-Band MIMO Antenna Design with User-Impact Investigation for 4G and 5G Mobile Terminals.

In this study, we propose a design of a multi-band slot antenna array applicable for fourth-generation (4G) and fifth-generation (5G) smartphones. The design is composed of double-element square-ring slot radiators fed by microstrip-line structures for easy integration with radio frequency (RF)/microwave circuitry. The slot radiators are located on the corners of the smartphone printed circuit board (PCB) with an overall dimension of 75 × 150 mm2. The proposed multiple-input multiple-output (MIMO) antenna is designed to meet the requirements of 4G and 5G mobile terminals with essential bandwidth for higher data rate applications. For −10 dB impedance bandwidth, each single-element of the proposed MIMO design can cover the frequency ranges of 2.5–2.7 GHz (long-term evolution (LTE) 2600), 3.45–3.8 GHz (LTE bands 42/43), and 5.00–5.45 GHz (LTE band 46). However, for −6 dB impedance bandwidth, the radiation elements cover the frequency ranges of 2.45–2.82 GHz, 3.35–4.00 GHz, and 4.93–5.73 GHz. By employing the microstrip feed lines at the four different sides of smartphone PCB, the isolation of the radiators has been enhanced and shows better than 17 dB isolation levels over all operational bands. The MIMO antenna is implemented on an FR-4 dielectric and provides good properties including S-parameters, efficiency, and radiation pattern coverage. The performance of the antenna is validated by measurements of the prototype. The simulation results for user-hand/user-head impacts and specific absorption rate (SAR) levels of the antenna are discussed, and good results are achieved. In addition, the antenna elements have the potential to be used as 8-element/dual-polarized resonators.