Low Coupling Research Articles

MIMO-DRA with triple-band CP & low EM coupling: a methodical design approach

This article presents a methodical approach for designing a circularly polarized multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) with triple frequency bands and low mutual electromagnetic (EM) coupling. The MIMO configuration is composed of two identical circularly polarized DRA elements in an orthogonal arrangement. To achieve circular polarization (CP) radiation, each rectangular DR element is modified and rotated with respect to the feeding-aperture. Meanwhile, the low mutual coupling is obtained by arranging the DRA elements orthogonally, and also by etching a Y-shaped slot on the ground plane. The Y-shaped slot facilitates the increase of the coupling current path, which decreases the inter-port coupling. The simulated outcomes are validated through an experimental test of the fabricated prototype. The proposed concept provides triple impedance bands as well as triple CP bands with low EM coupling ( < −25 dB). This article fills a research gap by developing a circularly polarized triple-band MIMO-DRA that can be used for a variety of wireless applications, including WiMAX, Wi-Fi, WLAN, and satellite communication.

Impact of TSV bump and redistribution layer on crosstalk delay and power loss

The performance of a 3D IC is primarily reliant on the selection of an appropriate bump shape. The most prevalent bump shape (cylindrical) is experiencing substantial stress, power loss and crosstalk issues. TSV bump with a tapered structure have recently attracted considerable attention owing to its low volume fraction and coupling capacitance, that can substantially reduce the stress and crosstalk concerns. An impact of the redistribution layer (RDL), intermetal dielectric and high frequency skin effect are appropriately taken into account for the tapered TSV (T-TSV) with a cylindrical, barrel and tapered bump shape. A mathematical framework of the resistance–inductance–conductance–capacitance (RLGC) structure of the proposed T-TSV have been formulated by effectively considering the coupling, passivation and fringing capacitance of the RDL. In order to benchmark the proposed electrical equivalent circuit, the structural model of the T-TSV is validated against the fabrication based experimental results, and a subsequent analysis have been performed for the stress, crosstalk induced delay, and power loss. The proposed TSV structure is in good agreement with the experimental results with an average deviation of only 2.8%. Furthermore, irrespective of bump height, the tapered bump based T-TSV can effectively reduce the overall crosstalk induced delay, stress, power delay product (PDP), insertion and reflection losses with an average deviation of 20.22%, 22.30%, 23.55%, 8.01%, and 10.32%, respectively, when compared to the barrel and cylindrical bumps. In addition, it has been observed that the overall rate of change in PDP, power losses and crosstalk induced delay with considering RDL are 18.8%, 20.50%, and 25.22%, respectively independent of the bump shapes.

Free‐Form Micro‐Optics Enabling Ultra‐Broadband Low‐Loss Off‐Chip Coupling

AbstractEfficient fiber‐to‐chip coupling has been a major hurdle to cost‐effective packaging and scalable interconnections of photonic integrated circuits. Conventional photonic packaging methods relying on edge or grating coupling are constrained by high insertion losses, limited bandwidth density, narrow band operation, and sensitivity to misalignment. This work presents a new fiber‐to‐chip coupling scheme based on free‐form reflective micro‐optics. A design approach which simplifies the high‐dimensional free‐form optimization problem to as few as two full‐wave simulations is implemented to empower computationally efficient design of high‐performance free‐form reflectors while capitalizing on the expanded geometric degrees of freedom. This work demonstrates fiber array coupling to waveguides taped out through a standard foundry shuttle run and backend integrated with 3‐D printed micro‐optics. A low coupling loss down to 0.5 dB is experimentally measured at 1550 nm wavelength with a record 1‐dB bandwidth of 300 nm spanning O to U bands. The coupling scheme further affords large alignment tolerance, high bandwidth density, and solder reflow compatibility, qualifying it as a promising optical packaging solution for applications such as wavelength division multiplexing communications, broadband spectroscopic sensing, and nonlinear optical signal processing.

Spectral broadening of 2-mJ femtosecond pulses in a compact air-filled convex-concave multi-pass cell.

Multi-pass cell (MPC) based temporal pulse compressors have emerged in recent years as a powerful and versatile solution to the intrinsic issue of long pulses from Yb-based high-power ultrafast lasers. The spectral broadening of high-energy (typically more than 100 µJ) pulses has only been realized in gas-filled MPCs due to the significantly lower nonlinear coefficient of gases compared with solid-state media. Whereas these systems reach impressive performance in terms of spectral broadening with very low spatiotemporal couplings, they are typically complex setups, i.e., large and costly pressure-controlled vacuum chambers to avoid strong focusing, ionization, and damage to the mirrors. Here, we present spectral broadening of 2-mJ pulses in a simple and compact (60-cm-long) multi-pass cell operated in ambient air. Instead of the traditional Herriott cell with concave-concave (CC/CC) mirrors, we use a convex-concave (CX/CC) design, where the beam stays large at all times, both minimizing damage and allowing operation in ambient air. We demonstrate spectral broadening of 2.1-mJ pulses at 100 kHz repetition rate (200 W of average power) from 2.1 nm (pulse duration of 670 fs) to a spectral bandwidth of 24.5 nm, supporting 133-fs pulses with 96% transmission efficiency. We show the compressibility of these pulses down to 134 fs and verify that the spectral homogeneity of the beam is similar to previously reported CC/CC designs. To the best of the authors' knowledge, this is the first report of a CX/CC MPC compressor operated at high pulse energies in air. Because of its simplicity, small footprint, and low cost, we believe this demonstration will have significant impact in the ultrafast laser community.

Infraparticle States in the Massless Nelson Model: Revisited

We provide a new construction of infraparticle states in the massless Nelson model. The approximating sequence of our infraparticle state does not involve any infrared cut-offs. Its derivative w.r.t. the time parameter t is given by a simple explicit formula. The convergence of this sequence as t→∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t\\rightarrow \\infty $$\\end{document} to a nonzero limit is then obtained by the Cook method combined with stationary phase estimates. To apply the latter technique, we exploit recent results on regularity of ground states in the massless Nelson model, which hold in the low coupling regime.

FCNC B and K meson decays with light bosonic Dark Matter

We consider decays of B and K mesons into a pseudo-scalar or vector meson plus missing energy. Within the SM, these modes originate from flavor changing neutral current (FCNC) processes with two neutrinos in the final state. In this paper we consider the experimental upper bounds on these modes and interpret the difference between these bounds and the SM prediction as a window into new light invisible particles. In particular we consider the case where some new symmetry requires the new particles to be produced in pairs. We first construct the general low energy effective Lagrangian coupling an FCNC with two dark sector particles of spin zero, one-half and one. We then present numerical estimates for the constraints that can be placed on these interactions, finding that an effective new physics scale from mathcal{O} (10)- mathcal{O} (1011) GeV can be probed, with the exact value strongly depending on the interaction structure as well as the mass of the invisible particle. For we incorporate into our constraints the effect of using only the signal regions of NA62, and for the q2-dependent efficiency of Belle II.

A new capacitive coupler design for wireless capacitive power transfer applications

Capacitive power transfer (CPT) technology has become a promising alternative solution for wireless charging applications. This paper proposes a novel coupler design to form a resonant capacitor by inserting dielectric material between two bent metal plates for each primary and secondary circuit. The main purpose of the proposed coupler is to eliminate the external capacitors and solve the low coupling capacitance for CPT applications. A comparison to the conventional four-plate coupler is presented, which shows specifically higher coupling capacitance, lower required inductance, and lower cost. Finally, the effectiveness of the proposed coupler structure is verified by simulation and experimental results.

Compact UWB MIMO Antenna for 5G Millimeter-Wave Applications.

This paper presents a printed multiple-input multiple-output (MIMO) antenna with the advantages of compact size, good MIMO diversity performance and simple geometry for fifth-generation (5G) millimeter-wave (mm-Wave) applications. The antenna offers a novel Ultra-Wide Band (UWB) operation from 25 to 50 GHz, using a Defective Ground Structure (DGS) technology. Firstly, its compact size makes it suitable for integrating different telecommunication devices for various applications, with a prototype fabricated having a total size of 33 mm × 33 mm × 0.233 mm. Second, the mutual coupling between the individual elements severely impacts the diversity properties of the MIMO antenna system. An effective technique of orthogonally positioning the antenna elements to each other increased their isolation; thus, the MIMO system provides the best diversity performance. The performance of the proposed MIMO antenna was investigated in terms of S-parameters and MIMO diversity parameters to ensure its suitability for future 5G mm-Wave applications. Finally, the proposed work was verified by measurements and exhibited a good match between simulated and measured results. It achieves UWB, high isolation, low mutual coupling, and good MIMO diversity performance, making it a good candidate and seamlessly housed in 5G mm-Wave applications.

Elastic stabilization of an intrinsically unstable hyperbolic flow–structure interaction on the 3D half-space

The strong asymptotic stabilization of 3D hyperbolic dynamics is achieved by a damped 2D elastic structure. The model is a Neumann wave-type equation with low regularity coupling conditions given in terms of a nonlinear von Karman plate. This problem is motivated by the elimination of aeroelastic instability (sustained oscillations of bridges, airfoils, etc.) in engineering applications. Empirical observations indicate that the subsonic wave-plate system converges to equilibria. Classical approaches which decouple the plate and wave dynamics have fallen short. Here, we operate on the model as it appears in the engineering literature with no regularization and achieve stabilization by microlocalizing the Neumann boundary data for the wave equation (given through the plate dynamics). We observe a compensation by the plate dynamics precisely where the regularity of the 3D Neumann wave is compromised (in the characteristic sector).

Evaluation of a low speed stage coupling with regard to structure-borne sound propagation in a wind turbine

Due to recent advances in the field of broadband aerodynamic noise, tonalities of wind turbines (WT) are increasingly coming into focus in the wind industry. In this case, the structure is excited inside the drivetrain and the structure-borne sound propagates through the machinery and ultimately to the surfaces of the WT, where it is radiated into the ambient air. Since any tonalities are a system characteristic, they should be considered at an early stage of product development. On the one hand, great efforts are being made to develop ever lower-toned drivetrains. On the other hand, tonalities can efficiently be neutralised by systematically decoupling the excitations in the drivetrain from the sound-emitting surfaces of the wind turbine. In addition to the well-studied behaviour regarding the decoupling of non-torque rotor loads from the drivetrain, in this paper the influence of a low speed stage (LSS) coupling on the structure-borne sound propagation inside of an integrated drivetrain is investigated. In a previous study at the Center for Wind Power Drives, it could be shown that in an integrated drivetrain, the transfer paths through the main shaft and subsequently the main bearing becomes the dominant transfer path. This is in contrast to classic bearing configurations where the torque arms of the gearbox are the dominant transfer paths of excitations from the gearbox, revealing an increased potential of LSS Couplings especially for integrated drivetrains. Detailed numerical investigations are performed in order to understand and quantify the usage of a LSS coupling for lowering sound power levels of a WT.

Analog Models of Lithospheric‐Scale Rifting Monitored in an X‐Ray CT Scanner

AbstractRifting and continental break‐up are fundamental tectonic processes, the understanding of which is of prime importance. However, the vast temporal and spatial scales involved pose major limitations to researchers. Analog tectonic modeling represents a great means to mitigate these limitations, but studying the complex internal deformation of lithospheric‐scale models remains a challenge. We therefore present a novel method for lithospheric‐scale rifting models that are uniquely monitored in an X‐ray CT scanner, which combined with digital image correlation (DIC) techniques, provides unparalleled insights into model deformation. Our first models illustrate how the degree of coupling between competent lithospheric layers, which are separated by a weak lower crustal layer, strongly impacts rift system development. Low coupling isolates the upper crust from the upper lithospheric mantle layer below, preventing an efficient transfer of deformation between both layers. By contrast, fast rifting increases coupling, so that deformation in the mantle is efficiently transferred to the upper crust, inducing either a symmetric or asymmetric (double) rift system. Furthermore, oblique divergence may lead to en echelon graben arrangements and delayed exhumation of the lower crustal layer. The successful application of our novel modeling approach, yielding these first‐order insights, provides a clear incentive to continue running lithospheric‐scale rifting models, and to apply advanced monitoring techniques to extract as much information from models as possible. There is indeed a broad range of opportunities for follow‐up studies within (and beyond) the field of rift tectonics.

Coupling Coordination Degree between Ecological Environment Quality and Urban Development in Chengdu–Chongqing Economic Circle Based on the Google Earth Engine Platform

Rapid urbanization often exerts massive pressure on the resources relied upon by the ecological environment. It is necessary to quickly evaluate the interaction and mutual influence between regional urbanization and the ecological environment. This paper uses the Google Earth Engine (GEE) platform, integrates MODIS and night light remote sensing data sets, and computes the remote sensing-based ecological index (RSEI) and the coupling coordination degree (CCD) to measure the coupling coordination and analyze the spatiotemporal changes in the Chengdu–Chongqing Economic Circle (CCEC) for 2010, 2015, and 2020. Our results demonstrate four key findings. Firstly, the CCD varies spatially; it peaks at the Chengdu and the West Chongqing Plains, decreasing outwards along the mountains, with the lowest degree of coupling in the central, southern, and northern edge areas of the CCEC. Additionally, it has shown a trend of maintaining unchanged first and then increasing, mainly responding to policy decisions. Secondly, the changes between the different coupling levels were almost stable and mainly occurred between adjacent levels. Thirdly, the coupling level of towns spreads outwards from the centers at Chengdu and Chongqing and has an overall upward trend in time. Fourthly, in the most recent year, the coupling types present a distribution pattern of one developing axis connected with two peaks. Specifically, the environment system lagging type aggregates in Chengdu, Chongqing, and their surrounding areas, and the others mainly are economic system lagging type. The high internal coupling type also mainly occurs in the high and low coupling levels. Under this context, constructive suggestions for developmental optimization in the study area were proposed.

Coupling and interaction between science and technology finance and green development: Based on coupling coordination degree model and panel vector autoregression model

Exploring the coupling and coordination between science and technology finance and green development is a critical action that needs to be addressed in achieving high-quality development in China. Based on the coupling coordination degree model and panel vector autoregression (PVAR) model, this paper uses the relevant data of 274 cities in China from 2003 to 2020 to study the relationship between science and technology finance and green development. The results show that: 1) The relationship between science and technology finance and green development has changed from low coupling coordination to medium coupling coordination in the sample period. 2) The Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta regions are at a relatively high level of coupling and coordination as a whole, while other regions are at a relatively low level of coupling and coordination. 3) Through the analysis of the spatial characteristics of the coupling coordination degree, it is found that the coupling coordination degree of China’s urban science and technology finance and green development is generally positive spatial autocorrelation. Spatial correlations continue to strengthen over time. 4) By establishing a PVAR model, we examined the interaction between science and technology finance, green development, and their coupling coordination. Science and technology finance, green development and their coupling coordination degree are themselves affected. We have comprehensively and objectively grasped the matching status of China’s urban science and technology finance and green development, providing a reference for promoting the adaptation of science and technology finance to green development.

New Design of a Compact 1×2 Super UWB-MIMO Antenna for Polarization Diversity

This paper proposes a new design of compact coplanar waveguide (CPW) fed -super ultra-wideband (S-UWB) MIMO antenna with a bandwidth of 3.6 to 40 GHz. The proposed antenna is composed of two orthogonal sector-shape monopoles (SSM) antenna elements to perform polarization diversity. In addition, a matched L-shaped common ground element is attached for more efficient coupling. The FR-4 substrate of the structure with a size of 23 × 45 × 1.6 mm3 and a dielectric constant of 4.3 is considered. The proposed design is simulated by using CST Microwave Studio commercial software. The simulation shows that the antenna has low mutual coupling (|S21| &lt; -20 dB) with |S11|&lt;−10 dB, ranging from 3.6 to 40 GHz. Envelope correlation coefficient (ECC) is less than 0.008, diversity gain (DG) is more than 9.99, mean effective gain (MEG) is below – 3 dB, and total active reflection coefficient (TARC) is less than -6 dB over the whole response band is reported. The proposed MIMO antenna is expected efficiently cover the broadest range of frequencies for contemporary communications applications.

Dual‐Function Tactile Sensor with Linear Pressure and Temperature Perception at Low Degree of Coupling

Multiinformation tactile perception is highly important for detecting the change of external environment and realizing the compliant control of the robot. However, the integration of dual‐mode or multimode sensors with low coupling remains a challenge. Herein, a dual‐function tactile sensor with linear pressure and temperature perception is reported. The pressure detection part contains the pyramid conductive film and flexible hemispherical electrode, which works as the piezoresistive material. A spiral nickel film works as a temperature‐sensitive material for sensing the temperature of objects during approaching and while contacting. As a result, the dual‐function sensor can detect the pressure in 0–100 kPa with a sensitivity of 11.5 kPa−1, while the temperature is in 25–65 °C with a sensitivity of 0.0032 °C −1. To be state of the art, the tactile sensor array is used for an active safety control of robotic arms, which can realize the perception and timely avoidance of sudden changes in external temperature and object collisions.

Design and testing of a large-workspace XY compliant manipulator based on triple-stage parallelogram flexure

This paper proposes a new XY compliant parallel manipulator with large workspace and low coupling motion by resorting to planar arrangement of multistage parallelogram mechanisms. The triple-stage parallelogram flexure is chosen as the basic mechanism for motion transmission and decoupling. Its fixed and moving ends adopt planar and spatial connections, respectively. By this connecting scheme, more types of general multistage parallelogram flexures can be constructed. The driving stiffness and resonant frequency of the manipulator are derived based on statics analysis of theoretical mechanics and dynamics analysis via Lagrangian equation. The accuracy of the analytical model is confirmed by performing finite element analysis simulation, and the performance variances of three manipulators are compared. Moreover, a prototype of the XY compliant manipulator has been fabricated and tested. Results show that the workspace of the parallel manipulator is 1.51 cm × 1.48 cm, and the coupling ratios of the two axes are 1.11% and 1.06%, respectively. The volume ratio is introduced as a compactness indicator for comparison study versus existing designs. The centimeter-level stroke can promote the application of XY parallel manipulators in more industrial scenarios.

Multiple slot modules for high field magnetic resonance imaging array coils.

Mitigating coupling effects between coil elements represents a continuing challenge. Here, we present a 16-bowtie slot volume coil arranged in eight independent dual-slot modules without the use of any decoupling circuits. Two electrically short "bowtie" slot antennas were used to form a "module." A bowtie configuration was chosen because electromagnetic modeling results show that bowtie slots exhibit improved efficiency when compared to thin rectangular slots. An eight-module volume coil was evaluated through electromagnetic modeling, bench tests, and MRI experiments at 4.7T. Bench tests indicate that worst-case coupling between modules did not exceed -14.5dB. MR images demonstrate well-localized patterns about single excited modules confirming the low coupling between modules. Homogeneous MR images were acquired from a synthesized quadrature birdcage transmit mode. MRI experiments show that the RF power requirements for the proposed coil are 9.2 times more than a birdcage coil. Whereas from simulations performed to assess the proposed coil losses, the total power dissipated in the phantom was 1.1 times more for the birdcage. Simulation results at 7T reveal an equivalent B1 + homogeneity when compared with an eight-dipole coil. Although exhibiting higher RF power requirements, as a transmit coil when the power availability is not a restriction, the inherently low coupling between electrically short slots should enable the use of many slot elements around the imaging volume. The slot module described in this paper should be useful in the design of multi-channel transmit coils.

A Miniaturized Full-Ground Dual-Band MIMO Spiral Button Wearable Antenna for 5G and Sub-6 GHz Communications.

A detachable miniaturized three-element spirals radiator button antenna integrated with a compact leaky-wave wearable antenna forming a dual-band three-port antenna is proposed. The leaky-wave antenna is fabricated on a denim (εr = 1.6, tan δ = 0.006) textile substrate with dimensions of 0.37 λ0 × 0.25 λ0 × 0.01 λ0 mm3 and a detachable rigid button of 20 mm diameter (on a PTFE substrate εr = 2.01, tan δ = 0.001). It augments users' comfort, making it one of the smallest to date in the literature. The designed antenna, with 3.25 to 3.65 GHz and 5.4 to 5.85 GHz operational bands, covers the wireless local area network (WLAN) frequency (5.1-5.5 GHz), the fifth-generation (5G) communication band. Low mutual coupling between the ports and the button antenna elements ensures high diversity performance. The performance of the specific absorption rate (SAR) and the envelope correlation coefficient (ECC) are also examined. The simulation and measurement findings agree well. Low SAR, <-0.05 of LCC, more than 9.5 dBi diversity gain, dual polarization, and strong isolation between every two ports all point to the proposed antenna being an ideal option for use as a MIMO antenna for communications.

Polymer spot size converter on silicon photonics chip for enabling high coupling to single-mode fiber.

Silicon photonics (SiPh) technology has gained considerable attention as a result of the growing demand for high-bit-rate optical interconnections. Low coupling efficiencies, resulting from the difference in spot size between silicon photonic chips and single-mode fibers (SMFs), remains a challenging issue. To solve this problem, we fabricated a novel, to the best of our knowledge, polymer spot size expander (SSE) device on the end face of a silicon chip. The fabrication of SSEs using self-written waveguide technology and a dipping method using UV-curable resin was highly reproducible. The spot size of the original 3.83 µm of the SiPh chip was expanded to approximately 7.82 µm at a wavelength of 1.55 µm, and the maximum coupling efficiency achieved with the SMF was -0.88 dB. In addition, the -3 dB tolerance of the coupling efficiency along the vertical optical axis was ±4.4 µm.

Simulation of the generation conditions and influence parameters of a self-mode-locked erbium-doped fiber laser.

The generation conditions and influence parameters of self-mode-locked pulses in fiber lasers are theoretically studied. By establishing the simulation model of a self-mode-locked erbium-doped fiber laser (EDFL) with a high-concentration erbium-doped fiber-based saturable absorber (SA), the effect of gain saturation energy, orientation angles of the polarizer and analyzer with respect to the fast axis of the fiber, laser coupling output ratio, dispersion value and condition on the self-mode-locked pulse generation and performances are quantitatively analyzed. The result shows that a low laser coupling output ratio can help the formation of a self-mode-locked pulse. The anomalous dispersion self-mode-locked EDFL has a relative high tolerance for dispersion value change but requires high gain energy for mode-locked pulse generation. The normal dispersion one possesses a low mode-locked pulse formation threshold but is relative polarization sensitive. This study is of important reference significance for the investigation of mode-locked fiber lasers.