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In this paper, a novel multilayer microstrip implant antenna (MIA) design based on the Archimedean spiral (AS) radiator element is presented for dual-band biotelemetric health care monitoring system. The proposed AS-MIA design has a layered structure consists of the spiral antenna elements and superstrate, namely layer#1, layer#2 and layer#3, respectively. While achieving the dual-band multi-layer implantable antenna design, firstly, each of the radiating elements in the respective layers is designed to cover separately in the desired bands, that is, layer#1 and layer#2 operate in the ISM (Industrial, Scientific, and Medical 2.4–2.48 GHz) and MICS (Medical Implant Communication Services 402–405 MHz) bands, respectively. Subsequently the ultimate multilayered AS-MIA design is formed by combining the individually designed layers. The compact implantable antenna has a dimension of r = 5 mm radius and h = 3.81 mm height, owning the electrically size of 0.067 λ0 and h = 0.051 λ0, respectively, where λ0 is free space wavelength at 402 MHz in MICS band. Since the AS-MIA is intended to be used in an intra-arm smart health system, the simulated radiation performances of the antenna in a created numerical arm phantom are presented in the article. Also note that numerical analysis of the implant antenna was carried out using CST MW studio simulator based on finite integral method. The prototype of the implantable antenna was fabricated using Rogers 3210 substrate with electrical permittivity of εr = 10.2. In-vitro return loss measurements were realized in skin mimicking gels, suggested in the literature. It was observed that in vitro measurement and simulation results were quite compatible with each other, except for some discrepancies due to the manufacturing and material tolerances during the preparation of the prototype antenna and skin mimicking gels. The proposed AS-MIA offers a dual-band operation with 15 and 16% S11 bandwidth at each band of 402 MHz and 2.4 GHz respectively where |S11| ≤ 10 dB criterion along with 50-Ω system is considered. Also the proposed design can be a good candidate to be used in dual-band medical implant communication systems with its miniature size and reasonable radiation characteristics. [ABSTRACT FROM AUTHOR]

Cable-driven Continuum Robots (CCRs) represent a subset of flexible robotic systems with diverse applications encompassing medical, quality control, and search and rescue. Multi-segmented CCRs can independently actuate different CCR segments and deform into a series of connected circular arcs. While this method generates constant-curvature profiles, CCRs with varying radial cable offsets can generate shapes with varying curvatures. However, there are no kinematic models for such robots in the literature. This paper introduces optimization-based formulations to accurately estimate the deformed profile of CCRs, considering both variable cable offset and multi-segment configurations. The presented kinematic approach can predict the deformed profiles with an RMS error less than 5% of the total length of the robot. The application of the proposed method to determine the inverse kinematics of multi-segmented CCRs is demonstrated—even considering obstacles in the robot's workspace. Practical implementation of the formulation is illustrated using a 3-segmented CCR with a cable-driven soft gripper that imitates biological grippers such as an elephant's trunk or creeper vine to grasp objects. • Profile estimation for variably routed cable-driven continuum robot. • Forward and inverse kinematics of multi-segmented cable-driven continuum robot. • Experimental validation with and without an obstacle in robot workspace. • Example application of robot with soft gripper generating spiral profile for gripping. [ABSTRACT FROM AUTHOR]

• The model decipts spontaneous helical formation mechanism in linear structures. • Energy barrier prevents spontaneous curling between initial and final states. • Critical scale parameter is determined by nonlinear characteristic length. • A novel model is developed for flexible electronics and soft robotics. Tendrils initially exhibit straight morphologies before gradually transforming into helical conformations during longitudinal growth. Tendril-inspired helical structures possess advantageous physical properties and functions including versatile morphologies, adaptability, enhanced strength, and scalability. With advancements in nanoscience and nanotechnology, helical architectures across various length scales have been discovered or artificially synthesized. However, the fundamental mechanisms underlying the formation and evolution of helical structures remain elusive. This lack of mechanistic insight has impeded the controlled design and fabrication of helical structures, especially three-dimensional functional devices with integrated helical motifs. Here a mechanical model is systematically proposed for the spontaneous formation of the helical structures, based on the hypothesis of decoupled curling and warping phases. Applying nonlinear elasticity theory, a detailed analysis of the energetics and thermodynamics is presented, accounting for the large deformation that may emerge during planar curling. Additionally, differential relations between internal forces and associated displacements induced by bending and twisting of a slender curved beam under out-of-plane loading are derived, obtaining solutions via Laplace and inverse transforms. The theoretical solutions closely match ex- perimental evidence from shape memory polymers. Furthermore, the theoretical model is utilized to guide the fabrication of the smart helical antenna proposed in our previous work, and discuss the influence of configuration changes on the electromagnetic properties. Elucidating these fundamental mechanisms will facilitate the development of next-generation technologies exploiting helical architectures for diverse applications including flexible electronics, optics, and soft robotics. [ABSTRACT FROM AUTHOR]

Inspection robots are widely used in the field of smart grid monitoring in substations, and partial discharge (PD) is an important sign of the insulation state of equipment. PD direction of arrival (DOA) algorithms using conventional beam forming and time difference of arrival (TDOA) require large-scale antenna arrays and high computational complexity, making them difficult to implement on inspection robots. To address this problem, a novel directional multiple signal classification (Dir-MUSIC) algorithm for PD direction finding based on signal strength is proposed, and a miniaturized directional spiral antenna circular array is designed in this paper. First, the Dir-MUSIC algorithm is derived based on the array manifold characteristics. This method uses strength intensity information rather than the TDOA information, which could reduce the computational difficulty and the requirement of array size. Second, the effects of signal-to-noise ratio (SNR) and array manifold error on the performance of the algorithm are discussed through simulations in detail. Then, according to the positioning requirements, the antenna array and its arrangement are developed and optimized. Simulation results suggested that the algorithm has reliable direction-finding performance in the form of six elements. Finally, the effectiveness of the algorithm is tested by using the designed spiral circular array in real scenarios. The experimental results show that the PD direction-finding error is 3. 39 ° , which meets the need for partial discharge DOA estimation using inspection robots in substations. [ABSTRACT FROM AUTHOR]

Aiming at dipoles with different impedances, a wideband balun with adjustable impedance for the balanced port is proposed in this communication. The balun is directly connected to the dipole to form an antenna element, so it also needs to meet: no connection line is required; the overall size is less than a quarter of the wavelength. The proposed balun realizes balanced–unbalanced conversion through aperture coupling, and dual slot ensures its wide-band characteristics. Due to the high-impedance characteristics of the folded dipole (FD), the balun has achieved impedance conversion ratios of 6:1, 8:1, 10:1, and 12:1, and the corresponding bandwidths are 82.1%, 67.1%, 53.7%, and 44.4%, respectively. Finally, three types of wideband dipoles with different characteristic impedances are fabricated to verify the versatility of the balun. [ABSTRACT FROM AUTHOR]

Achieving highly directive radiation with broadband operation, low scattering, and thin profile for a circularly polarized (CP) antenna is particularly challenging and yet rarely reported. Here, we propose a strategy of a CP Cassegrain meta-antenna by combining a planar helical antenna, a metasurface main reflector, and a metamaterial subreflector. The main reflector is designed to achieve focusing for CP waves at 13 GHz. The subreflector is chessboard-configured chiral metamaterial slab composed of two different types of chiral meta-atoms, aiming to achieve spin- and direction-selective CP transmissions and reflections. The distance between two reflectors is half of focal length, which enables our antenna to be dubbed as a folded reflectarray. The low radar cross section (RCS) is achieved based on scattering cancellation technique by realizing near 180° reflection phase difference between two neighboring chessboard submeta-atoms. Thanks to the architecture of the two reflectors, the proposed antenna exhibits high gain and low profile simultaneously according to image theory. For verification, a planar CP Cassegrain antenna, excited by a left-handed CP (LCP) planar helical antenna, is numerically studied, fabricated, and experimentally measured. Numerical results are in good agreement with the experimental ones, showing a peak right-handed CP (RCP) gain of 26.6 dBi at 12.6 GHz. Furthermore, the backward monostatic RCS of the antenna is dramatically reduced over −10 dB in a broad bandwidth from 8.4 to 15.7 GHz when it is illuminated by an LCP planar wave. Our proposed Cassegrain antenna features simultaneously broadband, high gain, low profile, and low RCS, providing a new avenue to low-profile CP reflectarrays with invisibility. [ABSTRACT FROM AUTHOR]

The stable performance of ultra-high frequency radio frequency identification (UHF RFID) tag thread with normal mode helical dipole antenna (NMHDA) was required for industrialized application. The ununiform helical pitches and helical radiuses caused by the unstable tension in the preparation process and material properties of carrying yarn probably deteriorate the performance of UHF RFID tag thread with NMHDA, while previous work focused on the properties of UHF RFID tag thread with uniform structure by finite element simulation. This work conducted numerical experiments with the actual statistical distribution of helical pitch and helical radius, i.e. normal distribution, and discussed the influence of the distributed parameters on resonant frequency. And then, the relationship between structure uniformity and resonant frequency was explored.Furthermore, the relationship was put into practice of the design of UHF RFID tag thread with stable properties. The results show that the fluctuation of resonant frequency first decreases and then increases with the increase of the mean helical pitch (Sme), and the resonant frequency decreases with the increase of the standard deviation of helical pitch (Sst) and that of helical radius (rst). When the reactance of helical coil linearly changes with helical radius, the mean helical radius (rme) has a negligible effect on the fluctuation of resonant frequency. The importance of the factors for the resonant frequency conforms to the following order: rme>Sst>Sme>rst. Additionally, the stable reading range of prototype (14.13 ± 0.06 m) demonstrated the practice of these results in the design of UHF RFID tag thread with NMHDA. [ABSTRACT FROM AUTHOR]

Generating aircraft position, velocity, and attitude along a reference trajectory is useful in many path and mission planning applications. In applications simulating an inertial navigation system the body-frame accelerations and angular rates are also required. This work presents a method for generating a smoothed continuous-curvature reference trajectory from a series of waypoints using line, arc, clothoid, and Fermat spiral segments in a fillet smoothing framework. The geometry of the segments are used to generate the position, velocity, and attitude of an aircraft following the reference trajectory. A primary contribution of this article is the use of the path geometry, coordinated turn model, and curvilinear motion theory to obtain analytical solutions for the body-frame accelerations and angular rates of the aircraft along the reference trajectory. [ABSTRACT FROM AUTHOR]

We present a compact and gain-enhanced microwave helical antenna for manipulating ultracold 87Rb atoms coherently. By replacing the reflecting plate with an enhancing cup, the voltage standing wave ratio is reduced by 0.5 in the frequency range of 6.73–6.93 GHz, which covers the resonant frequency between the ground-state hyperfine levels of the 87Rb atom. The gain of the helical antenna is increased by 1.25–1.63 dBi, whose length is 89 mm. Applying the antenna to ultracold 87Rb atomic experiments, we achieve a Rabi frequency of 60(1) ×2π kHz of the oscillation between the hyperfine levels. [ABSTRACT FROM AUTHOR]

In this article, we present a novel dual-band bandstop filtering cable by surrounding inner wire with asymmetric bridge-connected spiral-shaped defected structure on outer conductor. The simulation results demonstrate that the proposed dual-band bandstop filtering cable can be modeled by two parallel RLC resonance circuits in cascade and the performance can be easily adjusted by changing the structural parameters. The well-designed dual-band bandstop filtering cable can be fabricated by core wire surrounding with polytetrafluoroethylene (PTFE) dielectric layer and polyimide defected conductor layer with asymmetric bridge-connected spiral-shaped defected structures. The proposed filtering cable with ten asymmetric bridge-connected spiral-shaped defected resonators on defected conductor layer has a compact size of diameter 1.66 mm and length 200 mm, and its insertion loss in experimental results is greater than 20 dB at 0.88 and 1.3 GHz. Compared with the traditional microstrip bandstop filter, the proposed dual-band bandstop filtering cable can achieve better stopband and passband performance within more compact size. In essence, it is a cable replacement technology, which can improve electromagnetic compatibility (EMC) performance at system level and equipment level, and has the potential to be widely used in wireless system. [ABSTRACT FROM AUTHOR]

In modern manufacturing, the long-term handling of heavy objects is a main factor leading to muscle pain in the waist and lower back. Robots play an important role in reducing the burden on workers by compensating for the gravitational force. Energy-conserving passive mechanisms are commonly used in assistive robots because of their reliability and durability. One such mechanism is a spiral pulley and spring couple, which is a compact and reliable solution to provide a constant assistive force. A spiral pulley has a predesigned changing radius to balance the increasing restoring force of the spring as it extends. This allows the mechanism to exert a constant torque within the designed range. A crucial aspect of such a mechanism is the calculation of the shape of the spiral pulley. Accurate calculations enable the mechanism to provide a more optimal balancing ability. In this study, an innovative spiral pulley was designed by considering the cable tension variation along the cable attached to the pulley. The balancing performance of the proposed pulley was evaluated based on its accuracy in providing a balanced torque and an effective range. A comparative experiment using a conventional spiral pulley confirmed the effectiveness of the proposed pulley. [ABSTRACT FROM AUTHOR]

This study developed a debris removal robot for the Fukushima Daiichi Nuclear Power Plant. The creative robot contest for decommissioning the nuclear reactors of the Fukushima Daiichi Nuclear Power Station is an annual competition based on problem-based learning. It aims to stimulate students' interest in decommissioning nuclear reactors while simultaneously imparting problem-solving skills. The development of our debris removal robot started with this contest. The proposed robot can travel in a pipe, has a 3 m telescopic arm, and is equipped with a debris removal device known as a spiral catcher. This report provides an overview of this robot. We expect that complex robot development will be achieved by putting forth several ideas from various fields and fostering advanced problem-solving skills by encouraging students to address difficult tasks. Therefore, we successfully fostered the social implementation skills of students and developed a debris removal robot. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study presents a novel configuration of a cuboidal quad-port ultra-wideband multiple-input and multiple-output antenna with WLAN rejection characteristics. The designed antenna consists of four F-shaped elements backed by a partial ground plane. A 50 Ω microstrip line is used to feed the proposed structure. The geometry of the suggested antenna exhibits an overall size of 23 × 23 × 19 mm3, and the antenna produces an operational bandwidth of 7.6 GHz (3.1–10.7 GHz). The notched band characteristic at 5.4 GHz is accomplished by loading a pair of spiral electromagnetic bandgap structures over the ground plane. Besides this, other diversity features such as envelope correlation coefficient, and diversity gain are also evaluated. Furthermore, the proposed antenna system provides an isolation of −15 dB without using any decoupling structure. Therefore, to validate the reported design, a prototype is fabricated and characterized. The overall simulated performance is observed in very close agreement with it's measured counterpart. [ABSTRACT FROM AUTHOR]

Limited by the effective launch capacity of a rocket, the deployable antenna is very important in the design of spaceborne antenna array. Compared to traditional deployable antenna, flexible coilable antenna array has higher surface precision and better vibration control and therefore is more suitable for high frequency communication. In order to minimize the weight of satellite and reduce cost of its launch, a design guideline to the geometry parameters of flexible coilable antenna array is crucial. Existing models cannot be directly applied to interaction and large deformation between coilable membrane and conical spiral antenna in the flexible coilable antenna array. Hence, the geometry parameters of the conical spiral structure and the thickness of the coilable membrane in the flexible coilable antenna array have not been optimized yet. In this paper, the interaction between the coilable membrane and the concial spiral antenna is analyzed in the antenna array. A concise formula is derived to predict the critical force that flattens the conical spiral antenna by a coiling scroll. Combined with a theoretical model to predict the deformation of the membrane, the model provides an important theoretical support for the lightweight design and mechanical design of flexible coilable antenna array, such as the thickness of the coilable membrane. The proposed design is validated by experiments. The above findings have potential applications in the effective reduction of antenna array weight and satellite launch costs. [ABSTRACT FROM AUTHOR]

Dynamic electric field frequency actuated helical and spiral structures enable a plethora of attributes for advanced photonics and engineering in the contemporary era. Nevertheless, leveraging the frequency responsiveness of adaptive devices and systems within a broad dynamic range and maintaining restrained high-frequency induced heating remain challenging. Herein, we establish a frequency-actuated heliconical soft architecture that is quite distinct from that of common frequency-responsive soft materials. We achieve reversible modulation of the photonic bandgap in a wide spectral range by delicately coupling the frequency-dependent thermal effect, field-induced dielectric torque and elastic equilibrium. Furthermore, an information encoder prototype without the aid of complicated algorithm design is established to analogize an information encoding and decoding process with a more convenient and less costly way. A technique for taming and tailoring the distribution of the pitch length is exploited and embodied in a prototype of a spatially controlled soft photonic cavity and laser emission. This work demonstrates a distinct frequency responsiveness in a heliconical soft system, which may not merely inspire the interest in field-assisted bottom-up molecular engineering of soft matter but also facilitate the practicality of adaptive photonics. Frequency responsiveness within a broad dynamic range in adaptive systems while also reducing high-frequency induced heating remains a challenge for advanced photonics. Here, authors report a frequency-actuated heliconical soft architecture with reversible modulation of the photonic bandgap in a wide spectral range. [ABSTRACT FROM AUTHOR]

An axial mode solid dielectric helical antenna (DHA) has been proposed, which is fabricated by using the 3-D printing technique. Fed manners of this antenna have been studied, including conformal coaxial probe and conformal metal strip line. The operating mode of dielectric helix has been analyzed in detail. Circular polarization is achieved by choosing appropriate sizes of the dielectric helix. Furthermore, a miniaturized axial mode DHA with deployable property is implemented. Measured results indicate that the proposed antenna has good radiation performance, such as circular polarization, high gain, and high radiation efficiency. Specially, the radiation patterns of the DHA have good symmetry in the 2 dB axial ratio range. The significant advantage of miniaturized DHA is light in weight, which is only 2.7% of the weight of a metal helical antenna with similar radiation characteristics. The antenna is a good candidate in wireless communication system. [ABSTRACT FROM AUTHOR]

A smart gear sensor system has been developed for the condition monitoring of gear. This system includes a smart gear—the operation gear and a monitoring antenna. The analysis of the return loss of the monitoring antenna magnetically coupled with the smart gear gives the health condition of the gear. This research considers the effects of the distance and phase fluctuations between two components on the magnetic resonant return loss. The impacts of phase fluctuations include both static and high-speed conditions. Two experimental rigs have been built for the two cases. The coupling distance and static phase fluctuation are conducted via the first experimental rig. The second experimental rig performs both the coupling distance and phase fluctuation effect simultaneously while the smart gear rotates at high speed. During each test, the monitoring antenna return loss is captured thanks to a network analyzer. Analysis of the return loss data demonstrates that both the coupling distance and the change of the phase angle at the static condition and high speed have influenced the resonant return loss of the monitoring antenna. These findings are meaningful to the authors for evaluating and improving the accuracy of this gear health monitoring technique. [ABSTRACT FROM AUTHOR]

In this paper, a spiral array is designed to estimate two-dimensional direction of arrival (DOA), which allows a larger spacing between adjacent antennas of the array. The fourth-order cumulant is also utilized to create more virtual antennas, further enlarging the array aperture. The noise resistance of the high-order cumulant can help to construct an improved propagator, and there is no need for any priori knowledge of the source number to estimate the DOAs. With the help of the cumulant, a convex optimization is introduced to improve the estimation accuracy, which can overcome the estimation bias caused by the finite snapshots. Simulation results demonstrate the effectiveness of the proposed estimator. [ABSTRACT FROM AUTHOR]

Reliability of a wireless communication system depends on the performance metric of the oscillators employed. In this paper, we have discussed the commonly used oscillator architectures, their equivalent RLC circuits and the influence of the inductor performance on the oscillator design. Inductors designed for the oscillators are fabricated in 180 nm CMOS process. Inductors are implemented with 20 k Å top metal layer of the P1M6 layer architecture. Two-turns twisted and 3-turns spiral shape inductors are fabricated with and without the substrate shield, respectively. Twisted shape inductor with the floating substrate shield has higher Q-factor due to low substrate loss. To further validate the performance of inductors, digitally controlled oscillators (DCO's) are designed around the inductors and simulated for its phase noise performances. Inductors are designed on a (lossy) substrate with a resistivity of 2 Ω-cm. The twisted shape inductor has a Q-factor of 5.23 at the operating frequency of 1.8 GHz for the inductance value of 2.8 nH and has a self-resonance frequency (SRF) of 10 GHz. Whereas spiral shape inductor achieves the maximum Q-factor of 1.18 for the inductance value of 3.4 nH with SRF of 12.5 GHz. DCO's implemented with the designed twisted and spiral shape inductors has the phase noise of − 107 and − 92 dBc/Hz, respectively, at an offset of 1 MHz from 1.8 GHz of the center frequency. [ABSTRACT FROM AUTHOR]

Coil design and operating frequency are key factors impacting the efficiency of the inductive power transfer system. This article presents the modeling of printed circuit board spiral coils, design optimization and analysis on coil geometry, and operating frequency for medium-voltage (MV) applications, such as auxiliary power supplies for MV converters. Analytic model considering the geometric distribution of the magnetic field is proposed to calculate with high accuracy equivalent electrical parameters of coils. For a defined design space and constraints, a large number of coils are designed to determine their performances and select optimal coil geometries. Selected coil designs are prototyped and experimentally verified under design-specific conditions. In addition, further characterization is performed considering variations of several parameters that can be encountered in practice. [ABSTRACT FROM AUTHOR]

A boomerang-shaped ultra wide band (UWB) planar antenna has been presented for spectrum sensing applications. The presented antenna has been built upon a narrow band isotropic antenna design. In order to achieve a wider bandwidth, an exponential profile (similar to log spiral) is used. Simulation results show that the antenna has an impedance bandwidth of 163% (1.3–12 GHz) for VSWR≤2 with good radiation properties. In order to quantify the antenna performance, antenna radiation pattern and efficiency have been compared with previously reported designs. It is shown that the proposed design is able to achieve nearly omnidirectional patterns in more than one planes while achieving a maximum radiation efficiency of 92%. The overall dimensions of the proposed design are 193.6 mm × 196.5 mm. The prototype of the proposed antenna is manufactured using FR4 substrate ( ε r = 4.4 , h = 1.6 mm). [ABSTRACT FROM AUTHOR]

We report here that spiral and curl antennas are essentially the same when using the moment method. This aids in the understanding and design of the two antennas, and serves as the groundwork for new ideas regarding antennas. First, the spiral antenna height above the ground plane was gradually reduced, and at each height, the spiral configuration parameters were optimized for an axial ratio of less than 0.1 dB. It was found that the spiral antenna had configuration parameters almost the same as those for a curl antenna at a height of 0.15 wavelengths. Next, the curl antenna was analyzed with a reduced height. The antenna, at a height of 0.10 wavelengths, showed a 3 dB axial ratio bandwidth of 3%, with a VSWR of less than two. The analysis results are verified with experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band ultra-wideband conformal antenna for Wireless Capsule Endoscopy is proposed. The antenna uses polyimide as a substrate of side wall to achieve conformality, leaving space for other components of the Wireless Capsule Endoscopy. The feeding network of the conformal antenna utilizes the circuit characteristics of Complementary Split-Ring Resonator to achieve dual-band operation at 1.4 GHz and 4.0 GHz. Based on the principle of wideband characteristics of spiral antennas, the conformal antenna radiation structure is improved. A short-pin is loaded at an appropriate position to improve the impedance matching of the antenna and achieve ultra-wideband without changing the resonant points of the antenna. The operating bandwidth of the antenna can reach 30.3% (1.20 ~ 1.63 GHz) and 53.3% (3.33 ~ 5.75 GHz), respectively. In addition, the antenna is placed in different simulation models to verify the stability of its operation. Minced pork is used to verify effectiveness of the conformal antenna. The measured results show that the proposed antenna is suitable for capsule endoscopy. [ABSTRACT FROM AUTHOR]

This article reports the first chip-based demonstration (at any frequency) of a transceiver front end that transmits and receives electromagnetic waves with a helical distribution of wavefront phase [namely, orbital angular momentum (OAM)]. The CMOS chip consists of eight 0.31-THz modulator/detector units, with an integrated patch antenna, which are placed in a uniform circular pattern with a diameter of one free-space wavelength. The chip transmits OAM modes that are digitally switched among the $m\,\,=0$ (plane wave), +1 (left-handed), −1 (right-handed), and $(+1)+(-1)$ (superposition) states. The chip is also reconfigurable into a receiver mode that identifies different OAM modes with >10-dB rejection of mismatched modes. The array, driven by only one 310-GHz signal generation path, has a measured EIRP of −4.8 dBm and consumes 154 mW of dc power in the OAM source mode. In the receiver mode, it has a measured conversion loss of $\sim 30$ dB and consumes 166 mW of dc power. Using a low-cost 65-nm bulk CMOS technology, the terahertz (THz)-OAM chip has an area of only 2.1 $\times $ 2.6 mm2, which is the smallest among all prior OAM prototypes. The output OAM beam profiles and modes’ orthogonality are experimentally verified. The dynamic mode switching capability of the chip is also verified in the time domain across 1-m distance, and a full-silicon OAM link is demonstrated. [ABSTRACT FROM AUTHOR]

To receive a greater power and to demonstrate the soft bellows-shaped actuator's wireless actuation, micro inductors were built for wireless power transfer and realized in a three-dimensional helical structure, which have previously been built in two-dimensional spiral structures. Although the three-dimensional helical inductor has the advantage of acquiring more magnetic flux linkage than the two-dimensional spiral inductor, the existing microfabrication technique produces a device on a two-dimensional plane, as it has a limit to building a complete three-dimensional structure. In this study, by using a three-dimensional printed soluble mold technique, a three-dimensional heater with helical coils, which have a larger heating area than a two-dimensional heater, was fabricated with three-dimensional receiving inductors for enhanced wireless power transfer. The three-dimensional heater connected to the three-dimensional helical inductor increased the temperature of the liquid and gas inside the bellows-shaped actuator while reaching 176.1% higher temperature than the heater connected to the two-dimensional spiral inductor. Thereby it enables a stroke of the actuator up to 522% longer than when it is connected to the spiral inductor. Therefore, three-dimensional micro coils can offer a significant approach to the development of wireless micro soft robots without incurring heavy and bulky parts such as batteries. [ABSTRACT FROM AUTHOR]

A copper helical coil antenna was developed, characterized, and optimized for 2.45 GHz operations supplied by a microwave semiconductor oscillator. The application field of interest is laser-induced breakdown spectroscopy enhanced by microwave. Simulations using the Ansys HFSS demonstrate the superior localized E-field strength of the helical coil antenna, compared with other antenna-type structures. Simulation results show that E-field strength at the tip of the antenna has a logarithmic trend for increasing the coil pitch. The optimum pitch is 5 mm for a coil diameter of 6.5 mm upon consideration of the system compactness. Despite the antenna's open-circuit end, the presence of target samples does not interfere with the E-field and H-field distribution of the antenna and the surrounding environment. Applications in microwave-enhanced laser-induced breakdown spectroscopy (MWLIBS) confirm the importance of the antenna reflector. The electric field strength was over 100 times higher than the previous capacitor-like antenna. The antenna configuration angle was then experimentally optimized for maximum enhancement effects in the spectrochemical analysis of Al2O3. The antenna angle of 60° from the laser beam propagation achieved maximum enhancement in the emission signal of Al I. [ABSTRACT FROM AUTHOR]

An efficient noninvasive system for simultaneous transmission of wireless power and data is vital for continuous human health monitoring. In this article, we present a self-tuned spiral-shaped antenna with dual-band characteristics operating at 920 MHz and 2.4 GHz for efficient wireless power transfer (WPT) and data telemetry, respectively. To avoid vision blockage, the proposed smart contact lens (SCL) dipole antenna comprises two symmetrical spiral arms with inner and outer diameters of 10 and 14 mm, respectively. The SCL antenna was printed on a thin flexible polyimide substrate with a biocompatible polydimethylsiloxane (PDMS) coating. The influence of dispersed dielectric properties of PDMS on SCL antenna performance was investigated. Furthermore, the antenna was combined with a miniaturized rectifier and a micro-LED to demonstrate wireless LED illumination on a saline-filled model head. The power transfer efficiency (PTE) as a function of eye movement in the form of a path gain was also investigated. In addition, the PTE across the distance variations from 10 to 30 mm was computed, and a −17.85 dB was achieved at a separation of 12 mm. A specific absorption rate analysis was performed to determine human eye safety under radio frequency exposure from the external transmitter and the results complied with the International Commission on Non-Ionizing Radiation Protection guidelines. Furthermore, a theoretical link power budget analysis was experimentally validated using software-defined radio. Measurements of s-parameters were noted through the use of a saline solution to mimic a realistic human eye and were found to have a reasonable correlation with the simulated results. [ABSTRACT FROM AUTHOR]

To optimally coordinate the operational safety, manoeuvrability, positioning reliability, and space expansibility of deep-sea stations, this study proposed a segmented spiral pressure hull with reference to the geometry of worm snails. The design addresses the disadvantages of existing ring-stiffened cylinder, segmented sphere, and circular toroid structures. This study numerically and experimentally examined the buckling performance of segmented spiral pressure hulls. The numerical, experimental, and analytical data exhibited satisfactory agreement. The proposed pressure hulls exhibited a favourable space expansibility and buckled in a nonlinear manner. The buckling loads varied slightly after the threshold number of segments. All the post buckling modes were local dents. The current findings may serve as a reference for the research and development of original deep-sea stations. [ABSTRACT FROM AUTHOR]

By periodically patterning the conductor surface, the so‐called spoof surface plasmon polaritons (SSPPs) in microwave band can be transmitted and SSPP mode devices with the cutoff frequency at high frequency end can be constructed. In this paper, the spiral slots are loaded in the edge and the feed port of a printed monopole antenna element and two rejection bands are achieved. The results indicate that in the intuitive physical sense, the slot‐typed band‐stop resonator in antenna structure actually works according to the SSPP mode mechanism. Furthermore, it is proposed that its structure size should be determined according to the principle that the slot resonant frequency is a bit lower than the asymptotic frequency of SSPP modes. [ABSTRACT FROM AUTHOR]

Recently, several pneumatic soft actuators have been applied to wearable and welfare devices to provide nursing care and physical support for the elderly and disabled. In this study, as a wearable soft actuator for holding body, a spiral shaped soft holding actuator that can wrap a user according to their body shape was proposed and tested. The construction and operating principle of the tested soft actuator with circumferential restraint mechanism using three extension type flexible pneumatic actuators (EFPAs) has been discussed. As a result, it was found that the tested actuator could hold elbows and knees when the joint is in motion. An analytical model of the spiral actuator was also proposed to achieve an optimal design. It can be confirmed that the proposed analytical model can predict the shape of the actuator when various EFPAs are pressurized. [ABSTRACT FROM AUTHOR]

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Recently, the demand for reliable and high-speed wireless communication has rapidly increased. Orthogonal frequency division multiplexing (OFDM) is a modulation scheme that is the newest competitor against other modulation schemes used for this purpose. OFDM is mostly used for wireless data transfer, although it may also be used for cable and fiber optic connections. However, in many applications, OFDM suffers from burst errors and high bit error rates. This paper presents the utilization of a helical interleaver with OFDM systems to efficiently handle burst channel errors and allow for Bit Error Rate (BER) reduction. The paper also presents a new interleaver, FRF, the initial letters of the authors' names, for the same purpose. This newly proposed interleaver summarizes our previous experience with many recent interleavers. Fast Fourier transform OFDM (FFT-OFDM) and Discrete Wavelet Transform OFDM (DWT-OFDM) systems are used to test the efficiency of the suggested scheme in terms of burst channel error removal and BER reduction. Finally, the general complexity of the FRF interleaver is different from that of the helical interleaver in terms of hardware requirements. The performance of the proposed scheme was studied over different channel models. The obtained simulation results show a noticeable performance improvement over the conventional FFT-OFDM and the FFT-OFDM systems with the helical interleaver. Finally, the disadvantage of the proposed FRF interleaver is that it is more complex than the helical interleaver. [ABSTRACT FROM AUTHOR]

A new method for calculating pulse current in a spiral winding of an induction system with a ferromagnetic shield is proposed for processing of nonmagnetic thin-sheet metal strips and for creating magnetoplastic and electroplastic effects by eddy currents in strips. The ferromagnetic shield is placed under the strip, and above it there is the spiral winding. The aim is developing the method for calculating pulse current of the induction system in discharge processes of a capacitor charged to certain voltage, taking into account influence of the ferromagnetic shield on distribution of time-varying magnetic field, electromagnetic forces of the induction system and density of currents in the strip. Electromagnetic parameters of the induction system are determined by computer simulation using the finite element method in the mode of harmonic currents. Current transients in an electric circuit are calculated by the new method using known mathematical dependences in the theoretical electrical engineering, and the distribution of current density and magnetic forces in the strip are calculated by the finite element method in the mode of transients. Influence of the ferromagnetic shield on electromagnetic processes in the induction system is established. Electromagnetic force between the spiral winding and the strip, current density in the strip, and moments of time at which the current and the force have maximum values are studied. [ABSTRACT FROM AUTHOR]

This article presents a wideband circularly polarized (CP) endfire antenna based on a compact normal-mode helix. The counter-wound helix element is used to achieve good omnidirectional CP radiation and is further extended into an array configuration in a log-periodic fashion. It operates at the $3\lambda $ /2 mode and is differentially fed by a double-sided parallel strip line. A wideband balun is used to feed the whole array. For experimental verification, the helices and the balun are fabricated using the selective laser melting (SLM) and printed circuit board (PCB) techniques, respectively. The measured results agree well with the simulated ones, with a wide impedance bandwidth of 50% and an axial ratio (AR) bandwidth of 46% being obtained. In addition, the proposed structure is very compact, with the dimensions of only $2.24\lambda _{0} \times 0.11\lambda _{0} \times 0.53\lambda _{0}$ at the lowest operating frequency. The proposed antenna successfully demonstrates that the omnidirectional normal-mode helix element has great potential for achieving wideband unidirectional CP radiation. [ABSTRACT FROM AUTHOR]

This article presents a deeply implanted stent antenna system for endovascular aneurysm repair (EVAR) to treat abdominal aortic aneurysm (AAA). The stent antenna is composed of multiple helical wires connected to form meshed rings incorporating a single feed wire, thereby precluding the random distribution of currents on the stent-struts. In addition to EVAR application, the key features of the proposed stent system are its better antenna characteristics, including an omnidirectional radiation pattern, high gain, and perfect impedance matching. The proposed stent antenna exhibits wide-band characteristics covering the frequency range from 850 to 950 MHz, including industrial, scientific, and medical bands (i.e., ISM 868 and 915 MHz). Moreover, the stent offers peak gain values of −20.75 and −19.04 dBi at the 868 and 915 MHz bands, respectively. Simulations were performed using the finite-element method and finite-difference time domain to evaluate the properties of the EVAR stent system. For validation, measurements were conducted with a 3-D printed AAA placed in a saline-filled American Society for Testing and Materials phantom and in minced pork. Good agreement between simulation and measured results was observed, thereby serving a first validation of the EVAR stent antenna attributes. A link budget analysis was performed to analyze the biotelemetry capabilities. [ABSTRACT FROM AUTHOR]

The current work investigates experimental characteristics of the PVT system integrated with CuO-water spiral flow heat exchanger and compared with noncooled PV module. The work describes detailed procedure of nanoparticles preparation, SEM characterizations, and heat extraction characteristics of nanofluid in PVT application. The heat exchanger was pasted at the back of polycrystalline PV module to form PVT system to examine cooling ability, power generation, thermal-electrical yield and overall efficiency at a different volume concentration of CuO nanoparticles at steady mass-flow rate of 0.08 kg/s. From the experiments, it was concluded that the CuO-water nanofluids assisted to lessen surface temperature of PV module by extracting heat that enhanced electrical efficiency by an average of 3.53%. It was also seen that electrical and thermal performance was improved at higher volume concentration and overall efficiency of 30.77% and 36.59% were obtained at 0.01% and 0.03% of volume concentration. [ABSTRACT FROM AUTHOR]

We present the design and analysis of 28 GHz CMOS power amplifiers using miniature coupled-line-based power combiners, which adopt single spiral structure with symmetrical layout to achieve miniature area and small amplitude imbalance (AI) and phase difference (PD). Coupled-line-based two power combiners and one 6-bit phase shifter (covering the 360° tuning range with excellent linearity) are designed and implemented. The first power combiner using two-turn spiral structure (combiner-1) achieves S21 of −3.93 dB and S31 of −3.97 dB at 28 GHz, corresponding to AI of 0.04 dB and PD of 0.11°. The second power combiner using three-turn spiral structure (combiner-2) achieves S21 of −3.9 dB and S31 of −3.86 dB at 28 GHz, corresponding to AI of −0.04 dB and PD of 0.02°. Three 28 GHz power amplifiers using the power combiners are designed and implemented. Excellent results are achieved. For instance, the third power amplifier (PA3) with combiner-2 comprises two ways of cascode input stage with wideband LC input matching network, followed by a common-source output stage with wideband LC inter-stage and output networks. PA3 occupies a chip area of 0.74 mm2 and achieves prominent output power (Pout) of 16.4 dBm, power gain of 22.1 dB, and power-added efficiency (PAE) of 32.6%. The eminent results of the power combiners, phase shifter, and power amplifiers indicate that they are suitable for 5G communication systems. [ABSTRACT FROM AUTHOR]

We present the design and analysis of noninverting single-spiral Ka-band (26.5–40 GHz) CMOS Wilkinson power dividers and their deriving quadrature couplers (QCs) and baluns. For the power dividers, a parallel capacitor is included at the input port (port 1) for input matching, and a parallel RC network is connected between the output ports (ports 2 and 3) for input matching and isolation. Noninverting single-spiral structure with transmission-line (TL) length of about λ/12 is adopted to achieve miniature area and small amplitude imbalance (AI) and phase difference (PD). To realize QC and balun, negative/positive phase-shift TLs with phase-shift of − 45°/45° and − 90°/90°, respectively, can be included at ports 2/3 of the power divider. Two power dividers and their deriving two QCs and two baluns are designed and implemented. Prominent result is obtained. For example, the miniature QC achieves excellent S11 of − 13.5 dB, S22 of − 14.5 dB, S33 of − 19.4 dB, S32 of − 10.5 dB, S21 of − 4.713 dB, and S31 of − 4.731 dB at 28 GHz. The corresponding AI and PD are 0.018 dB and − 0.1°, respectively. Moreover, S11 is smaller than − 10 dB from 10.4 GHz to over 50 GHz, corresponding to a fractional bandwidth (FBW) larger than 141.4%. The QC occupies a normalized chip area of 6.1 × 10–4 λ02, one of the smallest normalized chip areas ever reported for millimeter-wave QCs. [ABSTRACT FROM AUTHOR]

A novel EBG structure in the form of a square spiral cell with a via at its middle is presented in this work to improve the isolation between the antenna elements and also enhance the overall parameters of the proposed MIMO system. Wide BW is achieved for the 6-elements MIMO system operating in the frequency range from 3 GHz to 5 GHz which is suitable for 5G mobile applications. The single antenna element consists of four coupled sections printed on an FR4 substrate. To improve the performance and maintain the BW, the EBG structure is employed to increase the isolation between the antenna elements. The proposed EBG is designed to have a bandgap from 2.5 GHz to 6.5 GHz. The addition of the EBG structure between the radiating elements reduces the envelope correlation coefficient across the whole operating BW. SAR calculations are also performed using head and hand models. The performance of the proposed EBG loaded MIMO antenna is suitable to be a potential competitor for future 5G applications. [ABSTRACT FROM AUTHOR]

A high-efficiency plasmonic lens composed of a single Archimedes-spiral slot with a cross section of an asymmetric slot is proposed. By adding an auxiliary nanocavity under the primary spiral slot, unidirectional plasmonic waves can be efficiently transmitted in the inward direction and focused on a hot spot in the center. Due to the asymmetric slot, the finite-difference time-domain (FDTD) method is used to numerically optimize the geometric parameters of the single spiral slot, which can achieve high-intensity unidirectional inward focusing. The proposed structure can decrease background noises and prevent cross-talk of nearby components in optical networks, which significantly improves the integration level of nanophotonic circuits and devices. [ABSTRACT FROM AUTHOR]

Self‐powered arbitrary wave monitoring is a hot research topic which aims to remove of the trouble associated with managing conventional power for continuous and real‐time acquisition of wave information from the marine environment. Herein, an effective approach is presented that simultaneously generates power from arbitrary motion waves and can sense and wirelessly transmit the wave information without requiring an external supply. The hybridized ellipsoidal device inspired from an elliptical trajectory of objects over shallow water waves, consists of six planar spiral coils arranged to cover the arbitrary direction of waves for power generation. Four magnetic force‐actuated triboelectric nanogenerators (TENGs) pairs along four sides as the arbitrary direction self‐powered wave motion sensors are integrated. Furthermore, all the required circuitry for signal processing and wireless transmission are integrally powered by the generated electricity to realize a self‐sustained wireless marine environment monitoring system. The generator can deliver peak power of 106 and 44.8 mW (at 3Hz) along with major and minor axis motion directions. The self‐powered sensors have excellent motion sensitivity thus the signals obtained from these sensors are utilized to acquire useful information related to the water waves which are very crucial parameters for real‐time monitoring of the marine environment. [ABSTRACT FROM AUTHOR]

Superconducting microcircuits and metamaterials are promising candidates for use in new generation cryogenic electronics. Their functionality is largely justified by the macroscopic distribution of electromagnetic fields in arranged unit cells, rather than by the microscopic properties of composite materials. We present a new method for visualizing the spatial structure of penetrating microwaves with microscopic resolution in planar superconducting macroscopic resonators as the most important circuit-forming elements of modern microelectronics. This method uses a low-temperature laser scanning microscope that examines the phase (i.e., direction) and amplitude of local radio-frequency currents versus the two-dimensional coordinates of the superconducting resonant structure under test. Phase-sensitive contrast is achieved by synchronizing the intensity-modulated laser radiation with the resonant harmonics of the microwave signal passing through the sample. In this case, the laser-beam-induced loss in the illuminated area will strongly depend on the local phase difference between the RF carrier signal and the spatially temporal structure of the focused laser oscillation. This approach eliminates the hardware limitations of the existing technique of radio-frequency microscopy and brings the phase-sensitive demodulation mode to the level necessary for studying the physics of superconducting metamaterials. The advantage of the presented method over the previous method of RF laser scanning micros-copy is demonstrated by the example of the formation of standing waves in a spiral superconducting Archimedean resonator up to the 38th eigenmode resonance. [ABSTRACT FROM AUTHOR]

In this article, Dual port excitation spiral shaped dielectric resonator multiple input multiple output (MIMO) antenna is explored for wideband application. Dual coaxial feeding in inner and outer edge of spiral geometry generates orthogonal hybrid modes. Merging of various hybrid modes lead to a wide bandwidth of operation. HE11δx, HE11δy and HE12δx, HE12δy orthogonal radiating modes are investigated at 8.7 GHz and 11 GHz resonant frequencies, respectively. Proposed antenna covers wide operating frequency range from 8–15.1 GHz to 7.8–14.6 GHz corresponding to excitation of Port‐1 and Port‐2, respectively, is achieved between ports. Isolation below −25 dB. Envelope correlation coefficient, diversity gain, Total active reflection coefficient, radiation pattern, channel capacity loss, gain, efficiency and various other characteristics of MIMO antenna are explored. This antenna can be used for various C and X band wireless applications. [ABSTRACT FROM AUTHOR]

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

Mobile applications (apps) are being widely used around the world. The long-term success and diffusion of a mobile app depends on it being well-tested, with respect to its performance and its reliability. Mobile app testing is typically carried out in multiple stages. An app is first tested for performance and reliability in a controlled lab-like environment during its development. However, the heterogeneity of in-the-field environments (including many device profiles, network speeds, etc.) is far greater than in a lab setting, with a small group of users. For this reason, a so-called Beta version of the app is typically rolled-out to a limited number of users, to get deeper insights into its performance and reliability in the field. After the Beta test results are analyzed, and refinements are incorporated, the application is released to all of its intended users. However, this work is based on a belief that field testing should be an automatic and ongoing process. Field test data, representing the actual performance and reliability of the app in the field, should be continuously fed back to the developer. To accomplish this, this paper proposes a framework for ongoing monitoring and field testing of mobile apps. This framework includes a library that mobile app developers can use to collect performance and reliability data during ongoing extensive field testing. These data are collected and presented using a web form to inform developers about the performance and reliability of their apps as they are being used by end-users in the field. [ABSTRACT FROM AUTHOR]

Spiral antennas are often used for communication applications. However, this antenna has a two-way radiation pattern. The back-lobe antenna can reduce the main lobe transmit power. This article discusses the design of a spiral antenna with a directional radiation pattern. The antenna substrate uses RO4350B with a thickness of 1.524mm and a dielectric constant of 3.66. On the antenna arms, there is a resistive load to extend the bandwidth and reduce the dimensions of the antenna. A balun is used to feed the Archimedean spiral antenna as a balanced antenna. The absorbed cavity is used to reflect the beam in an undesired direction. The simulation results show that the antenna's operating frequency is in the range of 2.5-12.5GHz for a return loss of less than-10 dB. The absorber helps suppress undesired radiation fields and reduces the back lobe of the antenna. In addition, the use of an absorber can reduce antenna gain. Therefore, the thickness of the absorber needs to be considered. The simulation results show the performance of this antenna. [ABSTRACT FROM AUTHOR]