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A numerical model describing a magnonic active ring oscillator (MARO) based on a microscopic spin-wave delay line is proposed. The model considers excitation, propagation, and reception of the magnetostatic surface waves in a yttrium iron garnet (YIG) magnetic film with a thickness in the nanometer range. The waves are excited and received with a microscopic coplanar antenna. We employed the model to analyze the influence of the YIG-film thickness and the distance between the antennas on the MARO performance characteristics. We showed that an increase in the delay time inserted by the delay line reduces the phase noise of the MARO and increases the auto-oscillation threshold. In addition, we found a relation between the auto-oscillation threshold, the thickness of the YIG film, and the distance between the antennas. The relation helps design miniature MAROs and suggests a way to reduce the phase noise of the device. The model predicts a phase noise level of −115 dBc/Hz at a 10 kHz offset from an oscillation frequency in the vicinity of 5 GHz for the MARO based on a 100 nm-thick YIG film and 56 μm of distance between the coplanar nano-antennas of the YIG-film based delay line. We believe that this is a clear way forward to microminiaturize the time-delay feedback microwave auto-oscillators. A further reduction in the phase noise down to −125 dBc/Hz at a 10 kHz offset is found in a model of cascaded connection of several microscopic spin-wave delay lines. [ABSTRACT FROM AUTHOR]

Electromagnetic metasurfaces can achieve effective control of electromagnetic waves and achieve effects such as blocking, enhancing, reflecting, transmitting, or deflecting electromagnetic waves, possessing electromagnetic properties that go beyond traditional materials. Existing research indicates that the dielectric substrate of metasurfaces has a significant impact on their electromagnetic properties. Increasing the substrate thickness will be beneficial for expanding the impedance bandwidth of the metasurface, and changes in dielectric constant will also have some impact on the operating frequency and bandwidth of the metasurface. A metasurface based on an air substrate was proposed through the research of dielectric materials. In addition, an ultrawideband, miniaturized, and high-gain metasurface antenna based on an air substrate is designed. The overall size of the designed antenna is 0.5λL × 0.5λL (where λL represents the wavelength at the lowest working frequency in free space). The measured results indicate that the proposed antenna exhibits a −10 dB impedance bandwidth of 74.3% (2.53–5.52 GHz) and a peak boresight gain of 10.1 dBi. [ABSTRACT FROM AUTHOR]

Scientific research has shown that the geometric structure of the metasurface has a significant impact on its ability to control the propagation of electromagnetic waves. The control of surface current can be achieved by designing the shape of the metasurface unit cell. In this paper, the traditional metasurface is studied using characteristic mode analysis, and a modified metasurface is proposed, which consists of 4 × 4 hexagonal rings with an asymmetric concave interior. The modified metasurface controls the distribution of surface current by increasing the path of surface current, thus lowering the frequency of modal significance. In addition, due to the special asymmetric concave interior, the frequency difference of different modal currents increases, leading to the expansion of the operating bandwidth of modal currents. A metasurface antenna is fabricated and measured for proof of concept. With a size of 0.69λL × 0.69λL × 0.06λL (λL is the wavelength in free space at the lowest operating frequency), the designed antenna achieves a −10 dB impedance band of 40%, 3 dB axial ratio band of 19.4%, and boresight gain of 8 dBi. [ABSTRACT FROM AUTHOR]

Proposed here is a metastructure based on a micro-perforated panel and an impedance-matching coiled-up cavity with continuously variable cross section, which achieves perfect absorption with a resonant frequency of 496 Hz and an absolute bandwidth (α ≥ 0.5) of 468 Hz. The structure thickness is ca. 1/13 of the operating wavelength λ in the deep subwavelength range. A relative bandwidth of 84.04%–111.67% is achieved through parametric studies. Physically, the continuous variation of the cavity cross section through which sound waves enter weakens the acoustic reflections generated by cross-sectional abruptness and enhances the impedance matching with the air. Furthermore, particle swarm optimization is coupled with a theoretical model to tailor the metastructure to realize the maximum absorption coefficient in the defined frequency range. It is shown theoretically that coherent coupling "weak resonance"—in which each unit individually exhibits imperfect absorption peaks—significantly improves the absorption performance in a broad frequency band through the coherent coupling effect. Finally, a hybrid metastructure using a parallel coupling sample is fabricated, and its acoustic properties are measured in an impedance tube. The average absorption coefficient of this metastructure is 0.934 in the quasi-perfect band (α > 0.9) from 400 to 650 Hz, and the thickness is only ca. λ/15. The unique innovation of a cavity with continuously variable cross section provides new ideas for designing broadband low-frequency sound-absorbing metastructures. [ABSTRACT FROM AUTHOR]

Integration of compact, tunable, low-cost monolithic microwave integrated circuit-based bandpass filters on a semiconductor substrate has been a persistent requirement in the communication industry. In the present investigation, a compact reconfigurable bandpass filter is fabricated using a double T-transducer based on the phenomena of magnetostatic surface spin waves (MSSWs). The Ce-doped Bi0.1YIG 500 μm thick disks with cerium concentration in the range of 0.2–1.0 provide the path for the propagation of MSSWs. The operating frequency for this device extends from S to X band Rogers RT/duroid® substrate, which is used for planar microstrip filter design, fabrication, and testing for practical applications. The effect of the coupling gap between the two transducers was optimized using appropriate choice of lumped components to improve the performance of the filter. The best coupling was observed for 1.2 mm coupling gap. The simulated and experimental results confirm the lowest insertion loss of −1.24 dB. The operating frequency shows a large tunability of 132.3% with a relatively small bias field of 0.3–2.1 kOe. The promising characteristics of bandpass filters such as low passband insertion loss, narrow bandwidth, high bandpass reflection coefficient, and high band-stop rejection were achieved by varying the Ce concentration in YIG samples. [ABSTRACT FROM AUTHOR]

A design method to extend the operating bandwidth of a low-frequency magnetic microwave absorber is presented. According to the mapped impedance distribution from the design objective, a synthesized reactive ground consisting of a triple-ring array, instead of the perfect electric conductor (PEC), is conveniently placed at the back of a commercially available magnetic sheet to realize impedance matching. Compared with the conventional PEC, the reactive ground extends the operating bandwidth of reflection coefficient being less than −10 dB by introducing four consecutive absorption peaks so that the optimized structure achieves broadband absorption from 2.3 to 4.3 GHz with a thickness of 0.027 times the free-space wavelength at the lowest operating frequency and a 60.6% fractional bandwidth which is nearly two times that of the conventional structure. The physical mechanism is further investigated through the distributions of current flow and power loss. Finally, a prototype is fabricated and measured. The good agreement between the simulated and measured results verifies the effectiveness of the presented design method. [ABSTRACT FROM AUTHOR]

Non-coplanar and discontinuously jointed rock masses are more complex than coplanar and discontinuously jointed rock masses. The mechanical properties and propagation mechanisms of non-coplanar and discontinuous joints were studied via direct shear tests with microscopic numerical simulation experiments. The numerical simulation tests were performed under different normal stresses, joint inclination angles, and shear rates. The numerical experimental results show that the microscale failure of non-coplanar and discontinuously jointed rock masses is mainly caused by tensile cracks. Additionally, when the peak shear stress is reached, the growth rate of cracks increases rapidly, and the number of cracks increases with increasing normal stress. The shear strength of non-coplanar and discontinuously jointed rock masses increases with increasing normal stress. Under the same normal stress, the variation curves of the shear strength of non-coplanar and discontinuously jointed rock masses with respect to the dip angle exhibit an "S"-shaped nonlinear pattern. Rock masses with joint inclination angles of approximately 15° and 65° have minimum and maximum shear strengths, respectively. The joint dip angle has a significant impact on the final failure mode of rock bridges in the rock mass. As the joint dip angle increases, the final failure modes of rock bridges change from "end-to-end" connection to a combination of "head-to-head" and "tail-to-tail" connections. The shear rate has a certain impact on the peak shear stress, but the impact is not significant. The spatial distribution of the tensile force chains changes as shearing progresses, and stress concentration occurs at the tips of the original joints, which is the reason for the development of long tensile cracks in the deeper parts. [ABSTRACT FROM AUTHOR]

The Hamming code or Linear block code is used in communication to identify and repair errors. Redundancy bits are introduced to the Hamming communication network (HCN) for error detection and correction. It can detect two errors and correct one error. Quantum-dot Cellular Automata (QCA) is used for designing circuits with high switching speed and low energy dissipation. This work proposes a cost-effective QCA-based (7, 4) Hamming encoder and decoder design. Hamming encoder is designed using coplanar structure and the error detector used in Hamming decoder uses a multilayer structure. The effort is to optimize the area, cost, and energy dissipation. The work proposes a coplanar (7, 4) Hamming encoder and decoder. Hamming decoder is implemented in two parts a syndrome calculator and an error detector. Proposed (7, 4) Hamming encoder circuit reduces cell count by 49.47% compared to [1] and 9.52% compared to [12]. The proposed (7, 4) syndrome calculator has reduced cell count by 56.54%, an 11.11% reduction in total area compared to [1]. The proposed design reduces the cell area, QCA cost, and also energy dissipation. The designs are realized and QCA parameters are assessed in QCADesigner2.0.3 and energy is analyzed in QCADesigner-E. [ABSTRACT FROM AUTHOR]

This article presents a meticulously engineered MIMO antenna system tailored specifically for 26 GHz millimeter-wave applications. It integrates a compact planar-patterned metamaterial (MTM) structure, carefully designed with split square and hexagonal unit cells to realize an effective near-zero index (NZI) range for both permeability and permittivity. Comprehensive wave propagation analysis along the y-axis rigorously examines the MTM's characteristics. The antenna system showcases impressive technical attributes, including an extensive 8.7 GHz bandwidth, notably highlighting mu-near-zero (MNZ) characteristics spanning over 8.7 GHz wide frequency spectrum, and epsilon near zero (ENZ) properties covering 8 GHz (26–34 GHz). Notably, a 4-ports MIMO antenna design is adopted with each element meticulously crafted using a 4-unit cell array configuration. The designed 4 × 4 MIMO antenna is fabricated using Rogers RT/duroid 5880 substrate and it occupies a compact dimension of 45.5 × 45.5 × 0.8 mm3. Experimental validation reveals compelling performance metrics, including a bandwidth spanning from 24.3 to 30.9 GHz, isolation levels below − 25 dB, and a maximum peak gain of 15.48 dBi. Additionally, the antenna exhibits circular polarization characteristics, maintaining an axial ratio below 3 dB within the frequency bands of 25.35 to 28.05 GHz and 28.10 to 29.83 GHz. Furthermore, the fabricated MIMO antenna demonstrates outstanding diversity parameters, exemplified by a high diversity gain (DG > 9.99), low envelope correlation coefficient (ECC < 0.0001), minimal channel capacity loss (CCL < 0.5), and total active reflection coefficient (TARC < − 8 dB). The suggested MTM-based MIMO antenna system with sophisticated design and exceptional performance could be an exemplary choice for seamless integration into the evolving landscape of 5G NR networks, particularly those operating within the n257/n258/n261 bands. [ABSTRACT FROM AUTHOR]

This work presents a novel design of a low-profile broadband circularly polarized (CP) metasurface (MS) antenna based on characteristic mode analysis (CMA) technique for potential use in C-band satellite communications. The proposed antenna is composed of a 4 × 4 array of truncated patch unit cells and incorporates an enhanced slot coupling feeding structure. CMA technique is employed to analyse and modify to improved CP performance. The proposed design exhibits good radiation characteristics including measured − 10 dB impedance bandwidth of 22.72% (4.8–6.05 GHz), a 3 dB axial ratio bandwidth (ARBW) of 16.3% (5.1–5.95 GHz), and a peak gain of 8 dBi within its operational frequency range. Furthermore, the antenna's metasurface design contributes to scattering suppression over a wide frequency span (4–18 GHz), with a notable peak reduction of 9.1 dB at 8 GHz. This characteristic holds potential significance for radar cross-section (RCS) reduction. [ABSTRACT FROM AUTHOR]

Using the fluorescence method, the study quantifies the cleaning efficiency of flat surfaces of selected materials (steel, polymethyl methacrylate, glass) compared to the usual cleaning methods: cleaning using ultrasound and cleaning using solutions (ethanol/isopropyl alcohol – isopropanol). Cleaning using ethanol/isopropanol solutions was carried out in such a way as to simulate common procedures: rubbing, rinsing and a combination of application of the solution and ultrasound. Based on the prepared and evaluated (following the average at several places on the surface) values of fluorescence maps of material surfaces, the resulting values of fluorescence before/after cleaning or at the selected moment of degreasing/cleaning of surfaces (applies to steel) were determined. The application of diffuse coplanar surface barrier discharge plasma discharge to the surfaces of flat materials can provide: a reduction in the environmental burden (no chemicals are needed to clean the surfaces) and an improvement in the efficiency of surface cleaning in industrial/manufacturing conditions (plasma cleaning usually takes a few seconds). diffuse coplanar surface barrier discharge plasma can clean and simultaneously activate the surfaces of flat materials. [ABSTRACT FROM AUTHOR]

An all-in-one self-sustained integrated system composed of a Si film solar cell, spray-printed a micro-supercapacitor and a gas sensor, exhibits excellent flexibility and durability. [Display omitted] Printable micro-supercapacitors (MSCs) with remarkable versatility, customizability, high power density and long cycling lifespan, are regarded as a promising class of miniaturized power source for wearable and portable microelectronics. Herein, we demonstrate a novel Fe-based zeolitic imidazolate framework (Fe-ZIF)/graphene (FZG) heterostructure with high specific surface area and outstanding electrical conductivity for planar MSCs (FZG-MSCs) worked in a high-voltage ionic liquid gel electrolyte via a spray-printed strategy. The fully printed FZG-MSCs deliver a high areal energy density of 9.5 μWh/cm2, extraordinary cyclability, and tailored voltage/capacitance output. Furthermore, using a fully printed FZG-MSC, we seamlessly integrate a monolithically planar all-flexible self-sustained sensor system with a mounted solar cell and a printable NH 3 gas sensor on the same side of single flexible substrate. The self-sustained sensor system exhibits high-sensitivity NH 3 detection with a good response of 18.3% at 20 ppm and linear sensibility exposed to 2–20 ppm. Such a fully integrated system can utilize the converted solar energy stored in the MSC, and offer efficient electricity to power microelectronics whenever needed. Therefore, this contribution of printable planar device and integrated system paves a new avenue for constructing flexible microelectronics. [ABSTRACT FROM AUTHOR]

Breast cancer is the most prevalent cancer in females in a large number of countries around the world. One in every twenty females gets confirmed to have breast cancer during their lifetime, though the number varies significantly by country. There are various conventional methods to spot the breast cancer cells, such as magnetic resonance imaging, X-ray mammography, biopsies, and ultrasound. The early identification of cancer cells helps to save many human lives. This paper investigates tumor detection in a breast phantom using a Photonic crystal (PhC) based hourglass terahertz patch antenna. This paper designed four different antenna structures: conventional hourglass patch antenna (with and without breast phantom) and PhC-based hourglass patch antenna (with and without breast phantom). The proposed PhC antenna models and the breast phantom are designed using the CST studio suite and analyzed the various antenna parameters. The observed S11 parameter for the proposed structures is − 21.50, − 25.34, − 33.78 and − 50.32 dB. The proposed antenna resonated in THz frequency, which does not affect human health and is safer due to non-ionizing characteristics. The suggested PhC structure is tiny, less expensive, lightweight, environmentally benign, and can be utilized as a primary screening technique for people with breast cancer, especially in resource-limited areas. [ABSTRACT FROM AUTHOR]

This manuscript presents a simple and compact, high gain & highly efficient wideband circularly polarised slotted waveguide antenna array based on WR-3 waveguide. The proposed geometry is based on a cross-slot-based element capable of providing a wide circular polarisation bandwidth. These slots are connected to each other through horizontal slots. Hexagonal slots of finite circumradii are cut at the center of the cross slots along with a series feed across the WR-3 waveguide, which results in a gain of up to 14.4 dBi and a fractional bandwidth of 27.2%. Furthermore, a grooved metal cabin flared at 45 ∘ is used as an enclosure, which enhances the gain. The grooved metal cabin provides a state-of-the-art gain, efficiency, and fractional bandwidth of 17.8dBi, 98.6%, and 34.5%, respectively. It also facilitates beam scanning over a span from ±34 ∘ to ± 60 ∘ . [ABSTRACT FROM AUTHOR]

A compact series‐fed high‐quality linear array antenna for 5G maritime communication is proposed. Building upon the wideband high‐efficiency electromagnetic radiation structure (WHEMS), a linear integrated series‐fed method is proposed, enhancing applicability in maritime environments. A self‐decoupling structure without the parasitic elements is introduced, resulting in a 7 dB increase in isolation while achieving array spacing of less than half the wavelength. The antenna has an impedance bandwidth of 19.9% (676–825 MHz) to cover the maritime 700 MHz application band, a high gain of 13–14.2 dBi, and a smaller volume compared to classical Yagi arrays with the same gain level. Furthermore, it exhibits characteristics such as low wind load, cost‐effectiveness, and high voltage resistance. The proposed antenna will play a vital role in the construction of the current 5G maritime communication network. [ABSTRACT FROM AUTHOR]

In this article, we present new design techniques to improve the gain and impedance bandwidth of short backfire antennas. For the gain enhancement procedure, our approach was to flare the rim of the antenna, which simultaneously led to an increase in the impedance bandwidth of the antenna. Parametric studies were carried out to obtain the optimal flaring angle. The peak realized gain was obtained as 17.2 dBi with an impedance bandwidth of 55% (2.4 dB and 28.6% increase in gain and bandwidth, respectively, compared to the unflared antenna). To further enhance the impedance bandwidth, an inductive iris was added to improve impedance matching at the waveguide aperture. We varied the width of the iris to obtain the optimal width that provided the best gain and impedance bandwidth result of 17.1 dBi and 66% (~40% increase compared to the unflared antenna without iris). To experimentally verify the work, prototypes were fabricated and tested. We found good agreement between simulation and measurement. The results of this study indicate that gain and bandwidth can be enhanced through optimized geometrical modification of the SBF structure. Furthermore, our 3D-printed technique demonstrates a mass reduction compared with conventional metallic structures. [ABSTRACT FROM AUTHOR]

The macroscopic mechanical behavior of granular materials is closely related to the fabric anisotropy and contact force anisotropy. In order to investigate the microevolution of fabric and force anisotropy of rock masses containing non-coplanar intermittent joints under direct shear loading, this paper establishes a numerical model using the particle flow code (PFC) based on the distinct element method (DEM) and investigates the effects of non-coplanar intermittent joints on the evolutions in the fabric and force anisotropy and the distributions of contact forces of rock specimens by setting up specimens with different ligament angles of joints. Meanwhile, the shear strength, deformation characteristics and failure mode, energy dissipation were analyzed to deepen the understanding of the macroscopic mechanical behavior of the specimens from the microscopic mechanism. Three anisotropic tensors a ij c , a ij n and a ij t are defined to characterize the anisotropic behavior of the granular materials which can show the evolution law of fabric and mechanical anisotropy of the system under direct shear load. The findings indicate that the degree of fabric anisotropy increases with increasing ligament, and the length of the load side significantly influences the initial mechanical anisotropy of the specimen. Concurrently, a rise in the ligament angle impedes the progression of anisotropy within the specimen, leading to a substantial reduction in the macroscopic mechanical strength of the rock. [ABSTRACT FROM AUTHOR]

Herein, the microwave transmission method is proposed that demonstrates such advantages as non-invasiveness, excellent penetration performance, and fast detection. As a key component of the microwave method water content measurement instrument, the antenna is required to have a smaller radiation size than the inner diameter of the oil pipe. To address this technical challenge, a small-sized microwave projection method based on water content measurement antenna is designed in this study for the water content measurement of oil-water mixtures in downhole pipelines. Also, the half-cut antenna with a size of 17 × 45 m m 2 is proposed to operate in the frequency band of 2–6 GHz (The measured gain of the antenna varies from 2.48 dBi to 4.98 dBi). Then, the designed half-cut antenna is applied to the established water-content test environment for analysis as to the relationship between water content and the variation in transmission coefficient of the half-cut antenna. According to the test results, the relative water content error is about 0.31% between the simulation and measured results for the transmission coefficient S 21 in the range of 0%–30%, while that is about 0.16% for the transmission coefficient S 21 in the range of 40%–100%. The experimental results can be extended to the measurement of the part with high water content of the oil-water mixture in the pipeline, which provides a practical reference for field tests and basic research. [ABSTRACT FROM AUTHOR]

The graphene-based plasmonic antenna's operating frequency and performance are significantly controlled by the substrate dielectric material. In this article, a plasmonic microstrip antenna is designed and simulated for terahertz applications. The design procedure is performed by testing different dielectric substrate materials of the same thickness, such as RT5800, polyimide, quartz, silicon dioxide (SiO2), FR4, mica, silicon nitride (SiO3N4), and gallium arsenide (GaAs). Generally, the computed results reveal that the quartz substrate maintains suitable radiation performance with a minimum S11 values of − 45.67 dB, efficiency of 92.65%, gain of about 3.15 dB, and bandwidth values of 310 GHz. Furthermore, a modification is done in the antenna by increasing the substrate height to obtain tri-band radiation mode. The results indicate that the proposed antenna operates at tri-band frequencies when the substrate thickness is larger than 6 µm. However, a better antenna radiation performance is observed with a substrate thickness of 7 µm which operates at frequencies of 0.766, 3.285, and 4.510 THz. Additionally, the overall radiation performance obtained for the proposed antennas of a single band frequency with quartz and dual and triple band frequencies with GaAs is compared with previous study results done by other researchers and a reliable agreement with an advancement in present work, especially in terms of antenna size and bandwidth. Finally, it can be said that the implementation of a graphene patch conductor to develop milt-band resonance frequency is an easy technique with low profiles, simple and alternative to the implementing conducting material slots, or extensions along the patch radiating borders techniques. [ABSTRACT FROM AUTHOR]

Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented. [ABSTRACT FROM AUTHOR]

This article presents a millimetre‐wave (MMW) wideband multibeam antenna array with a pillbox transition using multilayer low‐temperature cofired ceramic (LTCC) technology. The mushroom structure with dual resonant modes offers wideband performance for radiating array, while an integrated pillbox reflector achieves multibeam scheme. To reduce the design complexity of electrically large pillbox system, two popular pillbox transitions are investigated with a unit model method. The proposed unit model can be used to predict the transmission performance of pillbox reflector in any incident angle. Moreover, the mushroom antenna array and power divider fed by quasi‐TEM wave are also designed using unit model, greatly simplifying the design of electrically large pillbox antenna array. In the final design, the long‐slot pillbox transition, rather than multi‐slot transition, is selected due to its ultrawideband performance and simple structure. The proposed LTCC prototype is analysed and fabricated, obtaining a good agreement between simulation and measurement. The measured results show a −10 dB impedance bandwidth of 17.6% from 31 to 37 GHz, and five beams with ±45° scanning range is achieved with sidelobe level lower than −10 dB. [ABSTRACT FROM AUTHOR]

We present a compact, filtering power divider (FPD) using integrated passive device technology (IPD) for mm‐wave applications. Our proposed FPD design integrates quarter‐wavelength coupled‐resonator bandpass filters with a Wilkinson power divider, using size reduction techniques. Coupled coplanar waveguides provide excellent coupling while occupying a small area, and metal‐insulator‐metal capacitors offer the required λ/4 phase shift without length extension. The center frequency of the filtering power divider/combiner (FPD/C) is located at 30‐GHz. We demonstrate our FPD design by fabricating four prototypes with parameter variations. The insertion loss, fractional bandwidth, and size of the FPD/C designed in this study are from 2.56 to 3.3 dB, from 9.67% to 19.4%, and from 0.592 to 0.220‐mm2, respectively. In addition, the return loss of all models at the center frequency is 28.5 dB or more, and the isolation is 16.6 dB or more. [ABSTRACT FROM AUTHOR]

This paper presents the design of 2.5D frequency selective surface (FSS) for X and Ku band applications. Proposed FSS's unit cell is constructed with two independent slitted rings on both side of the FR4 substrate and is connected with metallic vias. The FSS offers a wide stop band performance from 6.26 to 18 GHz, with a fractional bandwidth of 96.7% measured at S21 < −10 dB and has a low insertion loss (IL) of 0.018 dB. The footprint of the FSS is only about 0.11λL ${\lambda }_{L}$ with the shielding effectiveness of 83.365 dB, and the transverse electric and transverse magnetic mode performances are stable up to 70 degrees. Prototype FSS is fabricated and measured for its performance validation. The performance validation is carried out using applied wave research and the equivalent circuit model tools. [ABSTRACT FROM AUTHOR]

We demonstrate high-speed mid-wave infrared photoconductive detectors leveraging a lattice-mismatched, epitaxially grown InSb absorber material patterned with nanometer-scale hole arrays. We show that the nano-scale hole patterns allow for post-growth control over the detector response time by introducing recombination surfaces to increase non-radiative recombination. The photoconductive pixels are integrated into a microwave coplanar waveguide for high frequency characterization. The detector response is characterized as a function of temperature and hole-array dimensions. We show a detector response with characteristic time scales of tens of picoseconds and bandwidths up to 7 GHz at room temperature. The presented detectors offer a mechanism for engineering response times in long wavelength detectors for potential applications in high-speed sensing/imaging, free-space communication, ranging, or dual-comb spectroscopy. [ABSTRACT FROM AUTHOR]

In a highly integrated analog radio-over-fiber transceiver, seamless integration of the antenna-frontend is crucial as an antenna is generally implemented on a high-κ material, which is set to highly degrade the antenna's performance. This work is concerned with the radiation behavior improvement of a planar leaky-wave antenna with an inductive partially reflecting surface (PRS) on a high-κ substrate for the development of a highly directive antenna. To begin with, we show how a thin and single-mode resonance (SMR) inductive PRS on high-κ materials in a planar leaky-wave antenna is set to provoke two resonance frequencies (i.e., PRS and cavity resonances) to converge, thereby diminishing the antenna's broadside directivity. By applying an equivalent circuit model, we explain how a multi-mode resonance (MMR) PRS can adequately be applied to address the underlying challenges. Subsequently, the leaky-wave radiation behavior of an antenna with a heterogeneous substrate is investigated and analytical equations are derived and verified with a full-wave simulation. The effects of material permittivity and thickness in a heterogeneous-cavity antenna on leaky-wave performance are investigated using these approximate yet accurate-enough equations. To justify the findings, two 9 × 9 planar leaky-wave antennas are prototyped on heterogeneous substrates based on SMR and MMR PRS and the radiation performances are compared. Our investigations reveal that in the proposed scenario, an MMR PRS can significantly enhance the antenna's broadside directivity by over 4 dBi at the resonance frequency (27.5 GHz), which is also set to improve radiation pattern compared to a SMR-based antenna. Finally, a single-fed dual-band aperture-shared antenna with a large frequency ratio (S-band and Ka-band) is developed and fabricated on a high-κ substrate based on the proposed MMR PRS. [ABSTRACT FROM AUTHOR]

Numerous efforts have been undertaken to mitigate the Debye screening effect of FET biosensors for achieving higher sensitivity. There are few reports that show sub-femtomolar detection of biomolecules by FET mechanisms but they either suffer from significant background noise or lack robust control. In this aspect, deformed/crumpled graphene has been recently deployed by other researchers for various biomolecule detection like DNA, COVID-19 spike proteins and immunity markers like IL-6 at sub-femtomolar levels. However, the chemical vapor deposition (CVD) approach for graphene fabrication suffers from various surface contamination while the transfer process induces structural defects. In this paper, an alternative fabrication methodology has been proposed where glass substrate has been initially texturized by wet chemical etching through the sacrificial layer of synthesized silver nanoparticles, obtained by annealing of thin silver films leading to solid state dewetting. Graphene has been subsequently deposited by thermal reduction technique from graphene oxide solution. The resulting deformed graphene structure exhibits higher sensor response towards glial fibrillary acidic protein (GFAP) detection with respect to flat graphene owing to the combined effect of reduced Debye screening and higher surface area for receptor immobilization. Additionally, another interesting aspect of the reported work lies in the biomolecule capture by dielectrophoretic (DEP) transport on the crests of the convex surfaces of graphene in a coplanar gated topology structure which has resulted in 10 aM and 28 aM detection limits of GFAP in buffer and undiluted plasma respectively, within 15 min of application of analyte. The detection limit in buffer is almost four decades lower than that documented for GFAP using biosensors which is is expected to pave way for advancing graphene FET based sensors towards ultrasensitive point-of-care diagnosis of GFAP, a biomarker for traumatic brain injury. [ABSTRACT FROM AUTHOR]

This study explored the synthesis and sintering of potassium sodium niobate (KNN) nanoparticles, emphasizing morphology, crystal structure, and sintering methods. The as-synthesized KNN nanoparticles exhibited a spherical morphology below 200 nm. Solid state sintering (SSS) and laser-induced shockwave sintering (LISWS) were compared, with LISWS producing denser microstructures and improved grain growth. Raman spectroscopy and x-ray diffraction confirmed KNN perovskite structure, with LISWS demonstrating higher purity. High-resolution x-ray photoelectron spectroscopy spectra indicated increased binding energies in LISWS, reflecting enhanced density and crystallinity. Dielectric and loss tangent analyses showed temperature-dependent behavior, with LISWS-3 exhibiting superior properties. Antenna performance assessments revealed LISWS-3's improved directivity and reduced sidelobe radiation compared to SSS, attributed to its denser microstructure. Overall, LISWS proved advantageous for enhancing KNN ceramics, particularly in antenna applications. [ABSTRACT FROM AUTHOR]

This letter presents the design, fabrication and measurement of a 72 kHz to 113 GHz ultra‐broadband amplifier that includes a direct current (DC)‐blocking functionality. This amplifier module stands out with a high average gain of 12.5 dB in the frequency range from almost DC to 110 GHz. This work not only combines electrical interconnections but also mechanical design considerations, thermal requirements and practical application specific aspects. To ensure a low thermal resistance, the InGaAs amplifier IC is directly mounted on an aluminium submount, applying an advanced gluing concept, and interconnected to an input and output 50 Ω$\Omega$ grounded coplanar waveguide by wire bonds with a length of only 135 μm$\umu {{\rm m}}$. To enable convenient usage of the package, 1 mm connectors are utilized. This amplifier module exhibits excellent thermal behaviour and group delay characteristics, making it an ideal choice for use in optical data transmission experiments. [ABSTRACT FROM AUTHOR]

We propose a binary amplitude-modulated conformal meta-surface with every meta-element capable of functioning as the leaky wave passage or the null radiating spot through dynamically tuning the PIN diodes over the meta-elements with ON or OFF states. In particular, the staggered arrangement of the meta-elements forms a dense radiating array with 0.1 wavelength periodicity and every radiating patch consists of dual hourglass shaped slots stacked over the coupled feed of substrate integrated waveguide slits. Such a design, on the basis of binary amplitude-modulated conformal meta-surface frames, can achieve wide-angle steerable fan-beam scanning, while possessing the precise beam direction with less than one tenth of the 3 dB beamwidth. Thus, this should pave the way for building up more advanced contemporary conformal wireless communication systems over different platforms. [ABSTRACT FROM AUTHOR]

We demonstrate control and readout of a superconducting artificial atom based on a transmon qubit using a compact lumped-element resonator. The resonator consists of a parallel-plate capacitor with a wire geometric inductor. The footprint of the resonators is about 200 × 200 μm2, which is similar to the standard transmon size and one or two orders of magnitude more compact in the occupied area compared to coplanar waveguide resonators. We observe coherent Rabi oscillations and obtain time-domain properties of the transmon. The work opens a door to miniaturize essential components of superconducting circuits and to further scale up quantum systems with superconducting transmons. [ABSTRACT FROM AUTHOR]

The use of transmission lines is widely accepted in the design of multiple active and passive devices given their capabilities to operate with signals in the whole frequency spectrum. However, a factor that difficult their design is the coupling effect when there are multiple transmission lines in parallel. Depending of the application, this factor could have a beneficial or detrimental effect in transmission lines. In particular, superconducting parametric amplifiers experiment this effect. The focus of this paper to understand the crosstalk so future superconducting parametric amplifiers can be designed considering the crosstalk. The study was achieved using coplanar waveguide transmission lines, artificial coplanar waveguide transmission lines, and microstrip lines. Dimensions of state-of-the-art (SOTA) parametric amplifiers have been used to have a suitable comparison with the nowadays state of the art superconducting parametric amplifiers. [ABSTRACT FROM AUTHOR]

Aiming at the 3.5 GHz world interoperability for microwave access band and 5.8 GHz industrial scientific medical band, a dual‐band antenna operating in omnidirectional mode is proposed. The antenna uses a single‐layer dielectric substrate made of FR‐4, which is cheap and easy to process. It uses circular patches and metal branches to generate orthogonal electric fields to achieve circular polarization. At the same time, the upper patch is symmetrically slotted in a T shape, so that the patch produces two resonance frequencies. The measured impedance bandwidth of the antenna in circular polarization on‐body mode and linear polarization on‐body mode is 110 MHz (3.41–3.52 GHz) and 460 MHz (5.42–5.88 GHz), respectively. In addition, the antenna shows good performance under bending conditions and close to human tissue. At the same time, the low specific absorption rate value proves that the antenna is safe to wear on the human body. [ABSTRACT FROM AUTHOR]

This manuscript presents comprehensive modal analysis of a compact, half-mode SIW-fed slot-coupled dual-band antenna. The Characteristic Mode Analysis (CMA) is investigated in detail and presented for the first time to analyze the radiation behavior and frequency domain characteristics of the proposed structure. The number of dominant operative modes supported by the antenna is decided based on the number eigen factors, its corresponding values, and the characteristic angles. The antenna operates at 33 and 38.14 GHz with a return loss of 20.5 and 19.5 dB, a gain of 7.9 and 6.7 dBi, and an efficiency of 90% and 88%, respectively. Measured results are in close resemblance with the CMA, considering the difference between the conventional cavity modes and the characteristic modes of the proposed planar cavity configuration. The methodology can be extended to characterize any arbitrary shape radiating geometry. [ABSTRACT FROM AUTHOR]

Several RF and microwave radiating devices, such as horn antennas, Fabry–Perot cavity antennas, and aperture-fed focusing devices, are excited through rectangular waveguides. The impedance matching of the overall system (from the waveguide feed to the radiating aperture) is a task of crucial importance that is often addressed by means of brute-force parameter-sweep full-wave analyses or blind optimization algorithms. In both cases, a significant amount of memory and time resources are required. For this purpose, we propose here a simple, yet effective solution, which only requires a single full-wave simulation and a semi-analytical procedure. The former is used to retrieve the antenna input impedance at the end of the waveguide port excitation. The semi-analytical procedure consists in a transmission-line equivalent circuit that models two waveguide discontinuities (namely two capacitive irises) within the waveguide section, whose position and geometric features are finely tuned to obtain a satisfactory impedance matching around the working frequency. The proposed method is shown to be effective in diverse and attractive application-oriented contexts, from the impedance matching of a Fabry–Perot cavity antenna to that of a wireless near-field link between two aperture-fed focusing devices. A remarkable agreement between full-wave simulations and numerical results is found in all cases. Thanks to its versatility, simplicity, and a rather low demand of computational resources, the proposed approach may become an essential tool for the effective design of waveguide-fed antennas. [ABSTRACT FROM AUTHOR]

Fused silica has become an interesting alternative to silicon for millimeter-wave (mmWave) applications. Unfortunately, there are a few reports on the measurement of fused silica's permittivity above 110 GHz that use electrical rather than optical methods. Given that mmWave applications use electrical circuits, additional electrical data would be useful to industry. To test the feasibility of electrical methods, we applied on-wafer techniques based on coplanar waveguide transmission lines to measure the complex permittivity of fused silica to 325 GHz. Our approach used the multiline thru-reflect-line algorithm on the scattering parameter measurements of transmission lines. Our method combined these results with dc measurements of the resistivity of the metals, simulations of the coplanar waveguide cross section, and dimensional metrology. In short, our measurements do not show significant dielectric dispersion for fused silica up to 325 GHz. The resulting complex permittivity was ϵ r = 3.87 ± 0.03 and a loss tangent tan δ < 0.005 from 320 MHz to 325 GHz. To support our conclusions, we performed an uncertainty analysis considering relevant sources of uncertainty. In the broader context, these results show that fused silica is a suitable substrate for mmWave electronics where the loss tangent must be less than 0.005 up to 325 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a portable tri-band MIMO antenna with 1 × 1 and 2 × 2 inputs and outputs is developed for wireless applications. A decagon-shaped ring and two U-shaped radiating structures make up the proposed antenna, which can generate three resonance frequencies. Without utilizing any decoupling structures, the suggested antenna achieves improved isolation. The coplanar waveguide structure supplies all of the antennas, which are printed on the front side of the FR-4 substrate, which has a surface area of 18 × 18 mm. The suggested antenna serves a wide range of applications, including WLAN (5.2 GHz), Wi-max (5.5 GHz), and 5G n34 band, with an impedance bandwidth of − 10 dB over 1.98–2.03 GHz, 3.55–3.70 GHz, and 4.8–6.4 GHz (2 GHz). For tri-band MIMO antenna, the gain is (0.28 dB, 1.3 dB and 2.7 dB) and efficiency is (80%, 83%, and 91.5%). For MIMO, tri-band antennas are placed in rotational symmetry with respect to the adjacent ports. Distance between MIMO tri-band antenna is 20 mm. Isolation for tri-band MIMO antennas is (− 40 dB, − 28.5 dB and − 27 dB). ECC for tri-band MIMO antenna is 0.003. The fabricated antenna and simulated results agree quite well. As a result, the suggested antenna can be employed for WLAN and 5G applications. [ABSTRACT FROM AUTHOR]

This paper presents a significant study of the influence of the electromagnetic field genertaed by a coplanar waveguide circular antenna loaded with a 3 × 3 array of the I-shaped metamaterial unit cell on people. The assessment is done through the simulation of the specific absorption rate (SAR), which quantifies the absorption rate of electromagnetic energy by the human body tissue. The standard limits range between 1 and 10 g of thigh tissues. After the implementation of the I-shaped metamaterial unit cell array, the antenna SAR achieves 0.111 and 0.0486 W/kg for 1 and 10 g of thigh tissues, respectively. [ABSTRACT FROM AUTHOR]

A segmented periodic slot array leaky‐wave antenna (LWA) is proposed for beamforming applications. The LWA consists of N $N$ segments, each with a unique propagation constant achieved through varying periodicity and slot size. By using segments with different propagation constants, the proposed LWA can achieve beamforming such as flat‐top beams and side‐lobe level (SLL) reduction. The LWA is based on a substrate‐integrated waveguide with periodic double transverse slots in the broad wall of the waveguide. The double slots allow for reflection‐canceling to suppress the broadside stopband and hence can achieve beamforming capabilities in the backward, broadside, and forward directions. Full‐wave simulations are used to demonstrate the proposed concept for flat‐top beamforming in the mm‐wave band at 30 GHz. Experimental demonstration is conducted using two prototypes for flat‐top beams and SLL reduction, with good agreement with full‐wave simulations. [ABSTRACT FROM AUTHOR]

A dielectric‐loaded slot antenna with the characteristic of broadband, low profile, and low cross‐polarization is presented. The antenna incorporating a low permittivity (εl=4.1 ${\varepsilon }_{l}=4.1$) and multiple high permittivity (εh=22 ${\varepsilon }_{h}=22$) rectangle dielectric is fed by two rectangle slot, which generates three slot modes and achieves measured 10 dB impedance bandwidth of 88% $ \% $ from 1.57 to 4.04 GHz covering the long term evolution (1.71–2.69 GHz) and sub‐6G (3.3–3.6 GHz). Furthermore, the presented slot antenna with a footprint of 0.81 × 0.56λ02 ${\lambda }_{0}^{2}$ and a low profile of 0.09λ0 ${\lambda }_{0}$ (λ0 ${\lambda }_{0}$ is the wavelength in the air region at the center frequency) appears the performance of measured peak gain of 9 dB without using any dielectric resonator mode. On the basis of the single‐polarized design, the dual‐polarized design with a profile of 0.09λ0 ${\lambda }_{0}$ is investigated and fabricated. According to the measured results, the dual‐polarized prototype achieves a 10‐dB impedance of 60% $ \% $ from 1.6 to 3 GHz. [ABSTRACT FROM AUTHOR]

This letter presents a coplanar waveguide‐fed printed monopole antenna backed by an artificial magnetic conductor (AMC) reflector. The proposed monopole antenna achieves circular polarization by loading the monopole with a printed coil and using an asymmetric ground plane. In addition, the AMC increases the antenna gain while maintaining a wide axial ratio (AR) bandwidth. The unit cell of the AMC is based on a Minkowski‐like prefractal geometry. The antenna is fabricated and measured with a total size of 1.07 λ0 × 1.07 λ0 × 0.25 λ0 at the operating frequency of 8.5 GHz. The measured results show a wide −10 dB impedance bandwidth of 26.9% (7.12–9.38 GHz), a wide 3 dB AR bandwidth of 22.23% (8–9.89 GHz) as well as a peak gain of 8.3 dBi at 8.5 GHz. This is significantly better than comparable antennas in addition to this design being the smallest in size. [ABSTRACT FROM AUTHOR]

A waveguide‐fed reflector antenna with high gain and multi‐beam capability is introduced and demonstrated at 220 GHz. Terahertz waves have a very small wavelength, which poses great challenges to the fabrication of terahertz antenna arrays and the connection with the T/R components. In this paper, a horn array with an element spacing less than one wavelength for terahertz frequency is presented and demonstrated, and its excitations are fan‐out using curved waveguides. The horn array is used as a feeding source of an offset parabolic reflector to achieve high‐gain and multi‐beam performance. The reflector antenna achieves four beam positions with θ = −0.7°, −0.2°, 0.2°, and 0.7°, and each beam obtains the gain of about 45 dBi. The experimental reflector antenna is fabricated and tested. Good experimental results further confirm the feasibility of the antenna and the potential application in Terahertz systems. [ABSTRACT FROM AUTHOR]

Miniaturized microstrip antennas are efficiently utilized in MICS band wearable and implantable medical applications. However, the properties of the materials employed for antenna fabrication influence its resultant parameters and play a vital role in its performance. Rogers have been widely used as a substrate material in various antenna designs. In this work, a proof of concept study has been conducted to determine how altering the substrate used in antenna construction affects antenna performance. Using the laser-induced breakdown spectroscopy (LIBS) approach, the elements present in the two distinct substrate raw materials were compared to investigate potential effects on the antenna's performance. Given their accessibility and widespread use, two types of Rogers' substrates, RO 3210 and RO 4003, were selected. Furthermore, two identical antenna designs were modeled and fabricated using the two substrate materials. The reflection coefficient (S11) and other antenna parameters were determined and compared. Moreover, the recorded LIBS spectra were evaluated using principle component analysis and partial least square regression techniques. The LIBS spectra showed different copper and iron contents between the two Rogers (i.e., other dielectric properties), leading to a frequency shift. Additionally, impurities in the fabricated material increase the possible losses. Consequently, the elemental contents of the utilized Rogers control the antenna's performance and can ensure its safety in wearable and implant applications. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)) has promising potential applications in radio-frequency filters due to their excellent piezoelectric properties, flexibility, and stability. In this paper, a flexible film bulk acoustic wave filter is investigated based on P(VDF-TrFE) as piezoelectric film. A new method based on three-step annealing is developed to efficiently remove the porosity inside the P(VDF-TrFE) films so as to improve its properties. The obtained film achieved high β-phase content beyond 80% and a high piezoelectric coefficient of 27.75 pm/V. Based on the low porosity β-phase films, a flexible wide-band RF filter is designed, which consists of a bulk acoustic wave resonator and lumped inductor-capacitor elements as a hybrid configuration. The resonator sets the filter's center frequency, while the lumped LC-based matching network extends the bandwidth and enhances out-of-band rejection. The testing results of the proposed wide-band filter show its good performance, with 12.5% fractional bandwidth and an insertion loss of 3.1 dB. To verify the possibility of folding and stacking the flexible bulk acoustic wave devices for high-density multi-filter integration in MIMO communication, bending tests of the filter are also conducted with the bending strain range up to 5500 με. The testing results show no noticeable performance degradation after four bending cycles. This work demonstrates the potential of β-phase P(VDF-TrFE) bulk acoustic wave filters to expand the scope of future flexible radio-frequency filter applications. [ABSTRACT FROM AUTHOR]

Recently, electromagnetic metamaterials are of great interest to researchers because of their unusual electromagnetic properties. The proposed work presents a metamaterial as a superstrate for enhancing the performance parameters of a conventional patch antenna. The metamaterial unit cell is examined using classical waveguide theory to confirm its metamaterial properties such as permittivity and permeability at the resonant frequency. The proposed meta-structure comprises of a 5 × 5 array of circular-shaped split ring resonators backed with wire strips and placed above an inset-fed rectangular patch antenna that resonates at 9.96 GHz. The metamaterial superstrate improves the gain, impedance bandwidth, and radiation efficiency by 2.4 dBi, 770 MHz, and 18.4%, respectively and simultaneously reduces reflection coefficient by 5 dB. Several benefits such as compact size, simpler structure, low profile, and low cost have been obtained from this design. EM simulation of the proposed composite structure has been carried out with the help of the HFSS EM simulator and measurement has been done for validation. [ABSTRACT FROM AUTHOR]

In this study, narrow (edge) wall standing wave slotted waveguide antenna design is proposed. This antenna operates at 2.812 GHz in S frequency band. Also, the design equations and slot characterization method are given in this study. This antenna is designed with two flanges to shape the elevation pattern and to increase the antenna gain. This antenna provides low cross polarization without using any polarizer or any other structure. The designed antenna is suitable for high gain and high-power applications. The performance of the proposed design is examined with simulations and verified with measurements. [ABSTRACT FROM AUTHOR]