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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]

This paper comprehensively analyses the specific absorption rate (SAR) for an ultra-wideband (UWB) wearable antenna designed for body-centric communication applications. The study is motivated by the extent of electromagnetic radiation in our surroundings, raising worries about health for wireless device users and wearable devices that utilize UWB technology. The proposed antenna is made of a foam substrate having a dielectric constant of 1.07, a thickness of 2 mm with a dimension of 36 × 48 × 2 mm 3 . The designed structure optimizes UWB (3.1–10.6 GHz) in connotation with the ISM band of 2.4 GHz. The proposed antenna works well over the wide frequency range resulting in a bandwidth of 11.53 GHz and a total gain of 8.05 dBi. An excellent impedance matching is obtained by creating a stub at the feed point which gives the maximum value of S11 as − 44.88 dB. The analysis focuses on the SAR values to measure the rate of electromagnetic energy absorption by human tissues over 1 and 10 g by constructing an equivalent three-layer body phantom model. The results indicate that the proposed antenna exhibits SAR values well within the limits set by international standards of 1.6 W/kg averaged over 1 g of tissue and 2 W/kg for 10 g of tissue, while maintaining efficient radiation characteristics across the UWB spectrum. [ABSTRACT FROM AUTHOR]

Theory and design aspects of the Slotted Waveguide Antenna (SWA) array for the simultaneous generation of Orbital Angular Momentum (OAM) modes are proposed in this paper. The proposed method is a novel approach to OAM generation that uses a simple feeding scheme and has better performance, especially in terms of mode purity. Due to its all-metallic structure, the high-power OAM beams with first-order modes ( + 1 & - 1 ) can be generated simultaneously along the propagation axis but in opposite directions, which improves the coverage and makes the proposed SWA be used in applications like radar target detection by mounting it on a mechanically rotating platform. The proposed theory is verified by the electromagnetic (EM) simulations, followed by the experimental verification done on the laboratory prototype. The near-field characteristics of the proposed antenna confirm the generation of first-order OAM beams with high mode purity. The far-field characteristics show the high gain and quasi-omnidirectional radiation pattern. Transmission of high-power OAM beams with good far-field characteristics makes the proposed antenna mitigate the issues of long-range OAM communication to a certain extent. However, the proposed antenna can be served well in strategic applications where the mostly high-power microwave is involved. [ABSTRACT FROM AUTHOR]

This research presents a frequency reconfigurable antenna analysis for wireless applications using multiple light sources. The antenna is constructed on a Roger substrate with (44×28) mm2 dimensions. The antenna comprises two parallel tuner arrangements in addition to a V-shaped radiating section. Two optical PIN photodiodes are connected to the two parallel monopole tuners, which serve as the antenna's switching component and are utilized to adjust the resonant frequency. These two PIN photodiode switches work in the 600-1050 nm wavelength range. To analyze the antenna performance, four different optical sources are used. They are white colour LED lamp, 650 nm optical fiber, red LEDs, and IR LEDs. In every case, the antenna performance analysis is carried out for all the four logic states of the switches (00, 01, 10, 11). Under white lamp test conditions, the antenna's maximum gain is 6 dBi, and when red LEDs are employed as the optical source, its maximum bandwidth is 21%. The antenna reconfigurable frequencies are 3.5 GHz and 5-5.8 GHz (5, 5.2, 5.5, 5.8 GHz). [ABSTRACT FROM AUTHOR]

This article presents a groundbreaking approach to osteoporosis detection and monitoring by integrating a new wearable monopole antenna design with advanced machine learning algorithm (neural network). Inspired by the intricate pattern of a Christmas snowflake, the system utilizes UWB electromagnetic waves and bone attenuation analysis for compact, noninvasive, and highly accurate bone health assessment. Fabricated entirely from textile materials, the antenna features remarkable performance metrics, including an impedance bandwidth of 4.9 to 12.6 GHz and a reflection coefficient consistently below −10 dB, within a compact form factor of 41.9 mm × 29.2 mm. Experimental validation and comparative studies demonstrate the effectiveness of this approach in precisely classifying osteoporosis levels, achieving an outstanding accuracy rate of 87%. This study signifies a significant advancement in osteoporosis detection and diagnosis, combining state-of-the-art antenna technology with advanced machine learning techniques. The developed system holds promise for early detection and personalized monitoring of osteoporosis, contributing to improved healthcare outcomes and enhanced quality of life for individuals at risk of bone-related diseases. [ABSTRACT FROM AUTHOR]

Nonlinearity of dynamic systems plays a key role in neuromorphic computing, which is expected to reduce the ever-increasing power consumption of machine learning and artificial intelligence applications. For spin waves (magnons), nonlinearity combined with phase coherence is the basis of phenomena like Bose–Einstein condensation, frequency combs, and pattern recognition in neuromorphic computing. Yet, the broadband electrical detection of these phenomena with high-frequency resolution remains a challenge. Here, we demonstrate the generation and detection of phase-coherent nonlinear magnons in an all-electrical GHz probe station based on coplanar waveguides connected to a vector network analyzer which we operate in a frequency-offset mode. Making use of an unprecedented frequency resolution, we resolve the nonlocal emergence of a fine structure of propagating nonlinear magnons, which sensitively depends on both power and a magnetic field. These magnons are shown to maintain coherency with the microwave source while propagating over macroscopic distances. We propose a multi-band four-magnon scattering scheme that is in agreement with the field-dependent characteristics of coherent nonlocal signals in the nonlinear excitation regime. Our findings are key to enable the seamless integration of nonlinear magnon processes into high-speed microwave electronics and to advance phase-encoded information processing in magnonic neuronal networks. The authors realize the generation and electrical detection of nonlinear magnons in a ferrimagnetic insulator, giving rise to secondary nonlinear magnons with fine frequency structures on the order of a few MHz and specific propagation characteristics. [ABSTRACT FROM AUTHOR]

Summary The presented state of the art is a novel coplanar optically transparent antenna designed to operate in extended GSM, L‐band, and UWB applications for vehicular communication. The presented radiator operates using a coplanar waveguide feed mechanism without a separate ground plane layer with a minimal conductive surface to enhance the transparency of the proposed antenna. The proposed antenna design has dimensions of 40 × 20 mm2, and a transparent material of soda–lime glass is used as a substrate with a dielectric constant of 7. The radiating element over the substrate is the conductive film fluorine‐doped tin oxide (FTO) with a sheet resistance of 7 Ω/sq. The operating frequency range of the designed antenna is from 0.86 to 14.45 GHz, which encloses the E‐GSM (900 MHz), L‐band (1–2 GHz), and UWB (3.1–10.6 GHz) frequencies. The peak gains at the operating frequencies are 1, 1.6, and 4.34 dBi, respectively. The designed antenna is fabricated and measured, and the performance metrics are plotted and compared. Since the transparent antenna is designed, the tendency of a substance to conduct light is measured as the optical transmittance, and it is calculated as 95% in the glass reference and 82% in the air reference. [ABSTRACT FROM AUTHOR]

Summary This research proposes a novel low‐cost aperture coupled elliptic patch nanoantenna which works best when it has a stable radiation pattern and good gain. On the upper portion of the substratum, a cross‐shaped hole was additionally engraved from a metallic strip with a silver composition. Elliptical‐shaped silicon material is employed as a patch in this antenna design which is made on a substrate made of inexpensive glass epoxy. The silver substance makes up the nanometallic strip line at the substrate's base. A cross‐shaped hole has also been etched from a metallic strip with a silver composition on the upper section of the substrate. As the foam substrate to be used in between the feed and antenna substrates, Rohacell was adopted. A proposed simple cross‐shaped aperture enhanced the bandwidth of the planned antenna without degrading its radiation performance and is loaded on a proximity‐linked elliptical microstrip antenna. To achieve the highest coupling, the lowest back radiation, the least amount of spurious radiation, and good efficiency, the patch and feed line are positioned in the middle, at a right angle over the slot. The proposed antenna was simulated in HFSS, and optimum results were observed from the output. The results were evaluated based on radiation pattern, return loss, smith chart, radiation efficiency, and 3D polar plot for 300, 500, and 800 THz frequencies. Also, the impedance bandwidth, gain, and a number of bands were compared with other conventional methods and our proposed method proved to outperform the existing method in all aspects. [ABSTRACT FROM AUTHOR]

Summary: The proposed research is primarily investigated with a new methodology of utilizing parasitic constrictors (PCs) as self‐coupling‐self‐decoupling (SCSD) mechanism which has been strategically implemented in multiple‐input multiple‐output (MIMO) antenna design. The design asserts an uniplanar printed four‐port MIMO antenna configuration in a confined footprint of 0.6 λ2.9× 0.6 λ2.9× 0.015 λ2.9 (λ2.9 = lowest operating wavelength at 2.9 GHz), where the radiator and reflector act as an effective SCSD invoking spatial diversity. The orthogonally oriented radiators are composed of 4 × circular disc with a 45° tilt and cutaway for reducing near‐field condensed currents and improve 10‐dB impedance matching. The antennas are assisted with a uniquely designed coplanar wave guides as SCSD, with rotationally symmetric PC. The PC has coplanar slots and a thin metallic strip that connects to a center‐fed annular disc as intrinsic current neturalizer. A pair of inverted L‐shaped symmetric strips is introduced in the coplanar slots to effectively couple the near‐field currents for self‐induced resonance mechanism as well as self‐decoupled for isolation improvement. To validate the rational counterparts, a prototype antenna has been simulated, fabricated, and experimented to operate from (2.9–5.45) GHz. The potential outcomes show good convergence in simulated and experimental results, with effective 10‐dB IBW, isolation, and diversity parameters, and demonstrate its prospective in C‐band (5G) applications. [ABSTRACT FROM AUTHOR]

This article proposes a compact coplanar waveguide (CPW)-fed antenna to improve proposed antenna's bandwidth without altering its basic design. The proposed fractal shaped antenna comprises a CPW feed with a defective ground structure (DGS). The proposed antenna is operating at single frequency band (C), when the gap between two glass plates is filled with an air and covers two different frequency bands (S and C), when there is a LC material p-methoxy-benzylidene-p-n-butyl aniline (MBBA) with ZnO nanoparticles, further the proposed fractal antenna, resonating from 4.4 to 6 GHz frequency and offers 5.64 dBi peak gain with air gap and operates from 3.1 GHz to 6.8 GHz with a maximum obtained peak gain of 3.9 dBi when filled with MBBA dispersed with ZnO nano particles. IT also evident that the transition temperatures of pure MBBA are reduced when doped with ZnO nano particles. The results are compared and analyzed with the body of data available. [ABSTRACT FROM AUTHOR]

This paper outlines the design and analysis of a compact antenna and its multiple-input multiple-output (MIMO) arrangement for use in applications at millimetre wave (mmW). The antenna was constructed with the Rogers substrate RT Durioid 5880, which possesses a total dimension of 44 × 44 mm2 with a height of 1.575 mm. The coplanar waveguide fed (CPW) antenna was originally intended to function within a 30–50-GHz frequency spectrum. Subsequently, the MIMO configuration of the same antenna is designed and developed over which a metamaterial superstrate was positioned in the design. The proposed MIMO configuration offers a good impedance match over a wide frequency range, considerable gain, minimal coupling among the antennas, and a low ECC, in addition to attaining a high diversity gain. To further highlight the importance of the suggested work, a comparison with related studies has been established. [ABSTRACT FROM AUTHOR]

Rock slope landslides and underground construction destabilization are frequently attributed to shear impairment by intermittent joints, and the support by bolts represents an indispensable technique for reinforcing jointed rocks. Therefore, we conducted laboratory experiments on intermittently jointed rock-like materials that were anchored, employing various anchoring inclination angles and methods, to investigate the influence of bolt anchoring on the shear properties and acoustic emission characteristics of intermittently jointed rock-like materials. Experimental results revealed that the peak shear strength of the anchored intermittently jointed rock-like materials is proportional to the bolt inclination angle. The strain on the joint is inversely related to the peak shear strength and the bolt inclination angle. The full-length anchorage and end anchorage can drastically enhance the mechanical traits of intermittently jointed rock-like materials, effectively impeding the proliferation of shear cracks after reaching the peak shear strength. The anchorage inclination exhibits a positive correlation with the accumulative acoustic emission (AE) energy and, conversely, a negative correlation with the peak AE count. In geotechnical engineering, the anchoring effect of anchor bolts can enhance the integrity of fractured rock masses and improve overall stability. [ABSTRACT FROM AUTHOR]

Two of the main challenges in origami antenna designs are creating a reliable hinge and achieving precise actuation for optimal electromagnetic (EM) performance. Herein, a waterbomb origami ring antenna is introduced, integrating the waterbomb origami principle, 3D‐printed liquid metal (LM) hinges, and robotic shape morphing. The approach, combining 3D printing, robotic actuation, and innovative antenna design, enables various origami folding patterns, enhancing both portability and EM performance. This antenna's functionality has been successfully demonstrated, displaying its communication capabilities with another antenna and its ability to navigate narrow spaces on a remote‐controlled wheel robot. The 3D‐printed LM hinge exhibits low DC resistance (200 ± 1.6 mΩ) at both flat and folded state, and, with robotic control, the antenna achieves less than 1° folding angle accuracy and a 66% folding area ratio. The antenna operates in two modes at 2.08 and 2.4 GHz, ideal for fixed mobile use and radiolocation. Through extensive simulations and experiments, the antenna is evaluated in both flat and folded states, focusing on resonant frequency, gain patterns, and hinge connectivity. The findings confirm that the waterbomb origami ring antenna consistently maintains EM performance during folding and unfolding, with stable resonant frequencies and gain patterns, proving the antenna's reliability and adaptability for use in portable and mobile devices. [ABSTRACT FROM AUTHOR]

Controllable coupling between the odd and even fundamental modes of an asymmetric half-wavelength superconducting coplanar waveguide resonator is demonstrated. The resonant frequency of the even mode Ω e could be tuned by an external magnetic field, while the resonant frequency of the odd mode Ω o is field independent. To realize the tunability of Ω e , the central conductor of the NbN-based resonator was galvanically coupled to an array of Al-based rf-SQUIDs (radio frequency superconducting quantum interferometer device). These rf-SQUIDs are placed in only one resonator gap, ensuring its strong asymmetry. By adjusting the appropriate external magnetic flux Φ , equal frequencies of both modes were obtained. At this resonant point Ω o (Φ) = Ω e (Φ) an avoided level crossing of the eigenfrequencies was observed, demonstrating the coupling between the odd and even fundamental modes. [ABSTRACT FROM AUTHOR]

This paper proposed a frequency reconfigurable antenna that utilizes a multilayer structure of liquid crystal (LC) material. This antenna design incorporates a three-layer stacked structure to create an LC-injected cavity. The inverted microstrip line structure is designed to be in contact with the LC, serving as both a radiating element and a bias electrode. A parasitic patch is placed at the top of the antenna to enhance bandwidth. To prevent interference with DC and RF sources, a bias tee is integrated into the microstrip line input. Experimental results demonstrate that the proposed antenna exhibits excellent impedance matching and stable radiation patterns within the operational frequency range. By comparing the simulated performance of the existing LC antenna with our proposed design, the bandwidth is tripled at a center frequency of 30.3 GHz. In addition, the effective area of the proposed reconfigurable antenna (154 mm2) is 24.6% of the area of the previous reconfigurable antenna (625 mm2). [ABSTRACT FROM AUTHOR]

Herein, high‐resistivity silicon substrates with specific He+ ion implantations to mitigate the parasitic surface conduction effect are studied. Several postimplantation thermal annealing conditions are investigated. Substrate performance is assessed at radiofrequencies (RFs) using the small‐signal characterization of coplanar waveguides (CPW) structures. The best effective resistivity (ρeff) of 4 kΩ cm is achieved with the wafer annealed at 600 °C for 2 h. This ρeff value is also stable as a function of DC bias applied to the CPWs. Those high RF performances originate from the nature of the defects created by ion implantation. Defects are deeply analyzed using spectroscopy measurement and scanning transmission electron microscopy. Combining these measurements, it is shown that {311} defects are probably responsible for the achieved high RF performances. Finally, the link between charge carriers trapping in the RF domain and defects nature is discussed to develop a defects engineering strategy for low‐loss RF substrates. The proposed fabrication method enables the fabrication of RF passivation layer locally over the wafer, and thus the cointegration of RF devices with fully depleted silicon‐on‐insulator technology. [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 paper introduces compact Printed Ridge Gap Waveguide (PRGW) phase shifters tailored for millimeter-wave applications, with a focus on achieving wide operating bandwidth, and improved matching and phase balance compared to single-layer technology. This study proposes a unique approach to achieve the required phase shift in PRGW technology, which has not been previously explored. This study also introduces a novel analytical approach to calculate the cutoff frequency and propagation constant of the PRGW structure, a method not previously addressed. Furthermore, the utilization of multi-layer PRGW technology enables the realization of multi-layer beamforming networks without crossing, thereby supporting wideband operation in a compact size. The proposed design procedure enables the realization of various phase shift values ranging from 0 ∘ to 135 ∘ over a broad frequency bandwidth centered at 30 GHz. A 45-degree phase shifter is fabricated and tested, demonstrating a 10 GHz bandwidth (approximately 33% fractional bandwidth) from 25 GHz to 35 GHz. Throughout the operating bandwidth, the phase balance remains within 45 ± 5 ∘ , with a deep matching level of −20 dB. The proposed phase shifter exhibits desirable characteristics, such as compactness, low loss, and low dispersion, making it a suitable choice for millimeter-wave applications, including beyond 5G (B5G) and 6G wireless communications. [ABSTRACT FROM AUTHOR]

Communication systems need antennas with wide bandwidths to provide large throughput, while imaging radars benefit from high gain for increased range and wide bandwidths for high-resolution imaging. This paper presents the design and evaluation of a wideband, high-gain antenna that achieves an average gain of 9.7 dBi over a bandwidth of 1.49 GHz to 3.92 GHz by using multiple in-phase radiating apertures. The antenna has a unique structure with a central rectangular short-circuited patch sandwiched between two back-to-back U-shaped radiating patches and two flanking H-shaped short-circuited patches. Each of the U-shaped patches employs a coplanar waveguide as feeding to achieve ultra-wideband impedance matching. Benefiting from design arrangement, in-phase electrical field distributions appear at the gaps between the patches that result in equivalent radiating magnetic currents in the same direction. Theory analysis shows that the close-spaced, same-direction magnetic currents created by the radiating apertures intensify the radiation and increase antenna gain within its impedance bandwidth. Simulated data show that the use of the coplanar waveguide feeding and short-circuited patches increase the bandwidth from 65 MHz to 2.43 GHz. Moreover, the short-circuited patches increase the gain by 3.45 dB at 2.4 GHz. Simulation and measurement results validate the design and show that the antenna features a maximum gain of 11.3 dBi and an average gain of 9.7 dBi in a fractional bandwidth of 89.8%. Because of the high gain values and the wide bandwidth, the antenna is particularly suited for long-range communication systems and high-resolution radar applications. [ABSTRACT FROM AUTHOR]

Quasi‐(2D) formamidinium lead‐iodide (FAPbI3) perovskites are winsome materials for high‐performance photodetectors (PDs). Between Ruddlesden‐Popper (RP) and Dion‐Jacobson (DJ) phases, the latter exhibits lower non‐radiative recombination and higher mobility compared to the relatively easily synthesized former. For efficient charge separation and transport, graphene‐assisted two‐terminal coplanar PD leveraging the DJ phase perovskite is proposed. Diamino octane (DAO), incorporated into 3D FAPbI3 perovskite, resulted in DJ phase [DAO(FA)n‐1PbnI3n+1], n being predefined integers 1≤ n ≤ ∞, demonstrating a vertical gradient heterostructure of n phases. Superior crystallinity and thermal stability of the quasi‐2D films are confirmed via synchrotron‐based studies. Band‐edge of the 3D film blue‐shifted consistently from 810 nm, while passing through the quasi‐2D phases, to ≈500 nm for the 2D phase. The dynamic range of photoresponsivity (R) of PDs reflected the absorption trend, with the 2D perovskite being infrared blind. Graphene's high carrier mobility coupled with the perovskite's high absorbance resulted in an unprecedented high R of ≈107 A W−1 and specific detectivity of 9.77 × 1016 Jones under 42.25 nW cm−2 of 405 nm illumination for the predefined n = 2 film. This underscores the potential of the DJ phase quasi‐2D perovskite@graphene in realizing stable, sensitive, and spectrally tunable PDs. [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]

In this paper, the design of a low sidelobe level (SLL) 10 × 10‐element series‐fed patch antenna array is presented. A ridge waveguide‐based nonuniform feeding layer is employed to excite the array. Each column of the antenna array includes a tapered 10‐element series fed patch antenna array. By using a simple and compact center‐fed ridge waveguide, a low loss feeding layer is achieved. The coupling between the ridge waveguide and the standard WR‐75 flange is performed by employing a proposed stepped transition. The measured results indicate that the maximum gain is 24.1 dBi and the SLL is lower than −20 dB in both H‐ and E‐planes at 12.7 GHz. The proposed low SLL planar series‐fed patch antenna array can be utilized as an acceptable candidate for radar applications. [ABSTRACT FROM AUTHOR]

This paper presents an alternative approach to improve the achievable beam scan angle of a traditional multi‐beam waveguide lens antenna. Due to the focusing mechanism by manipulating the geometrical curvatures of the waveguide lens, the angular scan range is limited in the conventional waveguide lens design using dual‐focal points of excitations because the geometrical curvatures of the waveguide lens only provide two design freedoms. To overcome this limitation, a solution of treating the waveguide lens as a transmit array consisting of non‐identical elements is proposed so that each element of the antenna array can be well calibrated to improve the maximum scan angular range, where a third focus point of excitation can be created by adding another design freedom from the differentiation between non‐identical elements. Each element of this new transmitting array can be well calibrated with the help of a mathematical expression to improve the maximum angular scan range. Numerical simulations show that the proposed antenna architecture exhibits better radiation characteristics than the traditional waveguide lens antenna. Radiation characteristics are studied and compared for both types of lens antennas to validate the design concept. The proposed triple‐focal point provides a higher gain than the traditional lens antenna with fewer antenna elements. The gains of the beams at ±10°, ±20°, ±30°, and ±40° are found to be 27.78, 26.94, 26.19, and 24.04 dBi, respectively. From the comparison, it is seen that the variation in gain by the proposed triple‐focal array design is more stable than the conventional dual‐focal point design. Plain Language Summary: The paper investigates an alternative approach to improve the achievable beam scan angle of a traditional multi‐beam waveguide lens antenna. To overcome this limitation, a solution of treating the waveguide lens as a transmit array consisting of non‐identical elements is proposed so that each element of the antenna array can be well‐calibrated to improve the maximum scan angular range. Key Points: This paper proposes a solution of treating the waveguide lens as a transmit array of non‐identical elementsEach element of the antenna array can be calibrated to improve the maximum scan angular range, where a third focal point can be createdThe triple‐focal point excitation is realized by creating a third‐phase variation mechanism on elements to obtain the triple‐focused beams [ABSTRACT FROM AUTHOR]

In modern communication systems, ultra-wideband (UWB) technology has garnered substantial attention due to its superior attributes compared to traditional narrowband communication systems. Over the past decade, UWB technology has also found applications in microwave-based imaging systems. This study introduces a simple planar coplanar waveguide-fed circular shape arc slot antenna designed specifically for biomedicine and microwave medical imaging applications. The proposed design is implemented on a 1.6-mm-thick FR4 substrate with a relative permittivity of 4.4 and a loss tangent of 0.0009. The antenna has physical dimensions of 26 mm × 29 mm and achieves an impressive bandwidth of 16.6 GHz, spanning 2.4 to 19 GHz. It exhibits a peak gain of 2.5 dBi and consistent omnidirectional radiation characteristics. Thorough temporal analysis validates the antenna's performance within acceptable limits, which is further affirmed through practical fabrication and testing, demonstrating strong agreement with simulation results. [ABSTRACT FROM AUTHOR]

In this paper, we present a millimeter-wave Fabry-Perot antenna with dual resonances, circular polarization, and stable gain. To achieve circularly polarized radiation, we integrate a receiver-transmitter circular polarizer into the partially reflective surface (PRS) of the antenna. The PRS is specifically designed with a positive reflective phase gradient, which contributes to a stable gain in the dual-resonance frequency band. For the radiation source, we adopt a linearly-polarized substrate-integrated waveguide cavity-backed slot fed by a printed ridge gap waveguide. Experimental measurements conducted on a fabricated prototype of the proposed antenna demonstrate its impedance and axial ratio bandwidths of 28.6–30.0 GHz and 28.6–29.6 GHz, respectively. Furthermore, the antenna exhibits a peak gain of 12.1 dBi and a gain fluctuation lower than 0.6 dB within the operational frequency band. [ABSTRACT FROM AUTHOR]

The research work proposed for the X-band microstrip line-based magnetic resonance imaging (MRI) coils has been accomplished with coplanar waveguide feeding and ha highlighted the design parameters to be employed in the internet of medical things (IoMT) features. The proposed research has focused on the wireless body area networks (WBAN) phenomenon in simulated human organs. It has been employed to study the electro-magnetic (EM) parameters of the simulated human organ and the functioning of wearable MRI coils on the human body. Therefore, these coils have been configured in triangle-shaped hierarchical structures, and each layer has been printed on both sides of the conductive strips. These proposed coils utilize a Bakelite substrate with a 1.6-mm thickness and an equivalent dielectric strength of 1.2. It has 69.9 × 85.2 × 1.6 mm3 dimensions and was fabricated using microwave integrated circuits (MIC). These coils have been generated at 8 GHz and this spectrum has been justified with the microwave X band (8–12 GHz) using the standard measured results. Hence, these coils have demonstrated 45.81-dB signal attenuation with a 1-dB standing wave ratio (SWR). Therefore, this research has extended to the different kinds of virtual simulation scenarios in diagnosis applications. Additionally, the research delves into the electromagnetic characteristics, encompassing electric and magnetic fields, the specific absorption ratio (SAR), and temperature. These characteristics are thoroughly analyzed using MRI phantom models within virtual environments. As a result of this comprehensive analysis, the suitability and efficacy of these MRI coils have met rigorous standards. These coils are highly demanded by complicated systems functioning in these bands for IoMT and MRI diagnosis applications. [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]

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]

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]

This paper presents a wideband ridge waveguide Magic-T based on an E- and an H-arm waveguide power divider using a stepped conducting T-junction transition. The Magic-T is designed to cover the full band of 18–40 GHz with a relative bandwidth of 76%. This bandwidth cannot be achieved by a Magic-T based on a conventional rectangular waveguide. Thus, the ridge waveguide ports have been employed and an 18–40 GHz ridge waveguide Magic-T has been fabricated and measured. It is demonstrated that the proposed Magic-T achieves better than 0.3 dB insertion loss and 15 dB return loss, less than 0.2 dB magnitude imbalance, and 2.5° phase imbalance. In addition, the measured data show good agreement with the simulation results, and high isolation is also obtained. [ABSTRACT FROM AUTHOR]

A wide-angle scanning phased array with dual circular polarization in the Ka-band is presented in this paper. To improve the scanning capability of the phased array, the microstrip element is modified by loading many metal posts at its center and periphery. In addition, a stripline coupler is designed to achieve dual circularly polarized (CP) radiation, and the inner conductor of the subminiature micro-push-on (SSMP) connectors for feeding the coupler is extended to the top layer of the multilayer element by introducing an open stub, which simplifies the assembly process between the SSMP connector and multilayer printed circuit board (PCB) due to through-hole soldering instead of blind-hole soldering. The proposed element can cover a frequency range from 28 GHz to 30.5 GHz with a relative bandwidth of 8.5% in the Ka-band. An 8 × 8 phased array is constructed based on this proposed element, and a wide-angle scanning range from −65° to +65° is obtained for the dual circular polarization. The proposed array has a gain fluctuation of 5.1 dB and an axial ratio (AR) of less than 3.3 dB during beam-steering. The prototype is fabricated and measured, with a good agreement between the measured and simulated results. The proposed phased array can be applied in a Ka-band millimeter-wave (MMW) communication system. [ABSTRACT FROM AUTHOR]

This paper proposes a co-planar waveguide-fed circularly polarized L-band antenna for GNSS Applications. The Fibonacci series inspired us to decide the physical dimensions of the radiating structure. The proposed antenna with the dimensions of 60 × 40 × 0.8 mm3 is fabricated by etching out several slots from the patch and ground plane as well. The circular polarization (CP) behavior is observed from different shaped slots in the ground plane as well as in radiating patches. The experimental and simulation results revealed good agreement over the entire operating frequency range. [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]

Microwave couplers are used in large numbers in beamforming networks, and their miniaturization can lead to a significant size reduction in the overall phased array. While the miniaturization of 3 dB couplers in the transverse direction (width) has been given considerable attention in the literature, there is minimal to no information on reducing coupler length. This is because of the trade-off between aperture length, bandwidth and coupling strength. The Bethe–Hole theory requires adding multiple apertures in the longitudinal direction for wide bandwidth, thus increasing the device length. Another factor is the aperture size, which determines the coupling strength and puts additional strain on the compactness of a 3 dB coupler. Contrariwise, this paper proposes to merge two weak (and hence compact) coupling mechanisms to design a wideband 3 dB coupler. This is achieved by using a longitudinal rectangular slot and three cross-slots in the transverse direction. Because of weak coupling, the slot sizes are smaller than a conventional 3 dB coupler, hence yielding a device whose length is less than one guided wavelength ( λ g ) without compromising the bandwidth. The presented coupler is 0.63 λ g in length, which is smaller than the state-of-the-art while maintaining a fractional bandwidth of 37% that is comparable to half-mode substrate integrated waveguide (HMSIW) couplers. [ABSTRACT FROM AUTHOR]

A quad‐band linear to circular polarization (CP) conversion based on a reflective metasurface is presented. The unit cell of proposed reflective metasurface consists of two unequal tilted and crossed bi‐directional arrow strips with an elliptical ring printed on a grounded dielectric slab. The operating bandwidth of the proposed structure is enhanced by introducing two small slits into the long arrow. A reflective metasurface sheet is fabricated and measured for verification. The simulated and measured results show that the reflective metasurface converter successfully transforms linearly polarized incident waves into right‐hand circularly‐polarized waves in frequency bands 9.49–9.96 GHz and 20–31.8 GHz and into left hand circular polarized waves in frequency bands 12.2–14.44 and 31.8–32.1 GHz. Also, wide angular stability up to 50° oblique incidence along with high efficiency reveals the good applicability of the structure. The proposed reflective structure can be used in multiband satellite communication systems and multifunctional dual‐circularly polarized antenna systems. [ABSTRACT FROM AUTHOR]

The letter presents a low‐windage omnidirectional antenna for high‐speed aircraft in the UHF and L bands. It combines a planar biconical antenna with a printed tape parasitic branch monopole antenna. Upgrading the traditional restricted‐length biconical antenna to a double‐layer planar design meets the compact, lightweight, and low windage requirements of airborne use. To enhance bandwidth and meet the lightweight, compact criteria of high‐speed aircraft, the planar‐printed monopole antenna integrates parasitic stubs and loop antenna concepts. Experimental results exhibit excellent isolation between antenna elements, with over 15 dB segregation and operational spectrum return loss of 27% and 18% at 10 dB. The voltage standing wave ratio is below 2, with less than 5 dB variation in the horizontal radiation pattern across frequency bands. The antenna, measuring 20 mm × 190 mm × 270 mm and weighing around 0.5 kg, holds great promise for high‐speed aircraft applications. [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]

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A novel design by the combination of a triangular and semi-circular shape is presented here. Modifying the usual patch structures, this shape looks like a gauging trowel. A substrate of FR4 epoxy as dielectric material of dimension 30 mm × 30 mm × 1.6 mm is considered with a ground plane having same area as the substrate but with 0.01 mm height. A simple coplanar waveguide in form of concentric circular ring of uniform width is used here to improvise the antenna gain. Ansys HFSS software is applied for simulation and S-Parameter (< −10 dB), standing wave ratio, directivity and antenna gain are found out. The proposed antenna includes the complete band from 58 to 61 GHz (with S11 < −10 dB) leading to ultra-wideband characteristics with an antenna gain of 4.72 dBi at 59.7 GHz. The novelty of this lies in the mathematical analysis that has been done to establish a unique theoretical approach for determining resonant frequencies which has a strong agreement with simulated results. The measurement results of the fabricated antenna are in good agreement with the simulation results. [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]