Coupling Bandwidth Research Articles

Analysis of Different Piezoelectric Materials on the Film Bulk Acoustic Wave Resonator

The performance of film bulk acoustic wave resonators (FBAR) is greatly dependent on the choice of piezoelectric materials. Different piezoelectric materials have distinct properties that can impact the performance of FBAR. Hence, this work presents the analysis of three different piezoelectric materials which are aluminum nitride (AlN), scandium aluminum nitride (ScAlN) and zinc oxide (ZnO) on the performance of FBARs working at resonance frequencies of 6 GHz until 10 GHz. The one-dimensional (1-D) modelling is implemented to characterize the effects of these materials on the quality (Q) factor, electromechanical coupling coefficient (k2eff) and bandwidth (BW). It is determined that employing ScAlN in FBAR results in the highest Q factor, ranges from 628 to 1047 while maintaining a relatively compact area (25 µm × 25 µm) and thickness (430 nm to 720 nm). However, ScAlN yields the narrowest BW, measuring 0.11 GHz at 6 GHz, as opposed to AlN and ZnO, which exhibit broader bandwidths of 0.16 GHz and 0.23 GHz, respectively.

Continuous wideband microwave-to-optical converter based on room-temperature Rydberg atoms

The coupling of microwave and optical systems presents an immense challenge due to the natural incompatibility of energies, but potential applications range from optical interconnects for quantum computers to next-generation quantum microwave sensors, detectors and coherent imagers. Several of the engineered platforms that have emerged are constrained by specific conditions, such as cryogenic environments, impulse protocols or narrowband fields. Here we employ Rydberg atoms that allow the wideband coupling of optical and microwave photons at room temperature with the use of a modest set-up. We present continuous-wave conversion of a 13.9 GHz field to a near-infrared optical signal using an ensemble of Rydberg atoms via a free-space six-wave mixing process designed to minimize noise interference from any nearby frequencies. The Rydberg photonic converter exhibits a conversion dynamic range of 57 dB and a wide conversion bandwidth of 16 MHz. Using photon counting, we demonstrate the readout of photons of free-space 300 K thermal background radiation at 1.59 nV cm−1 rad−1/2 s−1/2 (3.98 nV cm−1 Hz−1/2) with a sensitivity down to 3.8 K of noise-equivalent temperature, allowing us to observe Hanbury Brown and Twiss interference of microwave photons.

Small blind-area, high-accuracy ultrasonic rangefinder using a broadband multi-frequency piezoelectric micromachined ultrasonic transducer array

This paper presents a broadband ultrasonic rangefinder, with merits of a small blind area and high accuracy, based on a multi-frequency piezoelectric micromachined ultrasonic transducer (MF-PMUT) array. The coupling bandwidth between six types of resonant cells with adjacent resonant frequencies was studied and optimized, and these cells were then integrated into an array to broaden the bandwidth of the device. The array device showed a wide −6 dB fractional bandwidth of 108% in silicon oil. A wide bandwidth can contribute to obtaining the maximum steady-state with less excitation and reducing its residual ring-down, resulting in a small blind area. Pulse-echo ranging experiments demonstrated that the blind area was effectively reduced to 5 mm due to the multi-frequency array. For short distance measurements (<250 mm), the error was well controlled within ±0.3 mm and the 3σ accuracy was 0.445 mm. Compared with earlier reported PMUTs designed for bandwidth enhancement, the proposed broadband MF-PMUT array is much simpler in design and fabrication, revealing it as a promising candidate for short-distance high-accuracy measurements.

Revealing the finite-frequency response of a bosonic quantum impurity

Quantum impurities are ubiquitous in condensed matter physics and constitute the most stripped-down realization of many-body problems. While measuring their finite-frequency response could give access to key characteristics such as excitations spectra or dynamical properties, this goal has remained elusive despite over two decades of studies in nanoelectronic quantum dots. Conflicting experimental constraints of very strong coupling and large measurement bandwidths must be met simultaneously. We get around this problem using cQED tools, and build a precisely characterized quantum simulator of the boundary sine-Gordon model, a non-trivial bosonic impurity problem. We succeeded to fully map out the finite frequency linear response of this system. Its reactive part evidences a strong renormalisation of the nonlinearity at the boundary in agreement with non-perturbative calculations. Its dissipative part reveals a striking many-body broadening caused by multi-photon conversion. The experimental results are matched quantitatively to a perturbative calculation based on a microscopically calibrated model. Furthermore, we push the device into a regime where perturbative calculations break down, which calls for more advanced theoretical tools to model many-body quantum circuits. We also critically examine the technological limitations of cQED platforms to reach universal scaling laws. This work opens exciting perspectives for the future such as quantifying quantum entanglement in the vicinity of a quantum critical point or accessing the dynamical properties of non-trivial many-body problems.

Wideband coupling suppression with neutralization-line-incorporated decoupling network in MIMO arrays

In this paper, a novel neutralization-line-incorporated decoupling network (NLDN) is proposed for wideband multielement antenna arrays. Through introducing additional current path supplied by neutralization line (NL) between antenna elements and decoupling network (DN) between feeding lines but without extra matching network to counteract with the original path, the wideband antenna arrays are well matched and isolated based on network model derivation and node analysis. Four pairs of prototypes are designed to verify the decoupling effectiveness, including two-element symmetric H-plane and asymmetric E-plane coupled antenna arrays, one-dimensional linear and two-dimensional planar ones. Accordant simulated and measured results reveal that the proposed NLDNs for four examples can suppress mutual coupling to below −20 dB in over 20.6% bandwidths, with broadside gains increased, radiation patterns improved, envelope correlation coefficients decreased and total efficiencies enhanced. On account of its followable design process, implementable configuration and wideband decoupling capability, the approach has the potential to be employed in large-scale wideband MIMO antenna arrays.

Characteristics and factors of mode families of axial turbine runner

Axial turbines are widely used in hydropower systems. Owing to the complex hydraulic excitation force during operation, its flow-passing components, particularly the runner, are prone to severe vibrations. To further understand the vibration of the runner under different excitation forces, this study systematically investigated the modal characteristics of an axial turbine runner through numerical simulation using the example of a prototype Kaplan runner, including a shaft. The finite element method (FEM) and acoustic-structure coupling method were used to solve the natural modes of the runner in vacuum and the added mass effect of water, respectively. It was found that the modes of cantilever-blade structures without a shaft are mainly represented as vibrations of the blades, which can be classified into a series of mode families based on the single-blade modes, corresponding to a series of frequency bands with very small widths. The composition of members in each mode family depended strictly on the number of blades with a clear rule. For axial turbines, the modal vibration of the shaft and blades is prone to coupling, which leads to abnormal changes in some modes in the mode family, resulting in the scattering of the natural frequencies and greatly improving the possibility of resonance. The law of mode coupling was revealed, and the effects of the blade opening and bearing stiffness on the mode coupling and frequency bandwidth were explored. The stiffness of the bearing close to the runner significantly affected the frequency bandwidths. The greater the stiffness, the smaller are the bandwidths. This study can provide a reference for resonance cause analysis and vibration avoidance design of axial turbines and similar structures.

Ultra-broadband flat-top circular polarizer based on chiral fiber gratings near the dispersion turning point.

Based on the dual-resonance principle around the dispersion turning point, a scheme of chiral long-period fiber gratings (CLPGs) formed by twisting a high-birefringence (Hi-Bi) fiber is herein proposed to realise ultra-broadband flat-top circular polarizers. The coupling bandwidth is approximately seven times larger than that of traditional CLPGs. In addition, by introducing chirp characteristics in these CLPGs, an ultra-broadband flat-top circular polarizer with ∼200 nm@3 dB was conveniently achieved. Subsequently, by optimising the chirped CLPGs, a circular polarizer with a bandwidth extinction ratio of approximately 30 dB and a high level of ∼100 nm at 1 dB was realised. It was shown that the mode-controlling performances of the CLPGs can be remarkably improved, which has significant applications in light-field regulation. Finally, for the first time, it was proved that the CLPG cannot generate a vortex beam.

Service Function Chains Deployment for 5G Slice With Bandwidth Coupling

Network function virtualization (NFV) technology is the key technology to solve the flexibility problem of 5G network. Multiple service function chains (SFCs) that coexist on physical infrastructure within a slice share the resources of the infrastructure. Therefore, how to allocate resources to an SFC under QoS constraints and further, how to build a resource sharing model among multiple SFCs are significant. In this letter, we jointly consider the above problems and propose a coupling bandwidth resource allocation model (CBRA) for the resource sharing of multiple SFCs. In this model, we define the effective coupling bandwidth increment(ECBI) based on the statistical feature of traffic and construct the homogeneous traffic flows on the infrastructure within the slice as the coupled traffic. Furthermore, based on the CBRA model, we establish an integer linear programming (ILP) problem aiming at minimizing resource occupancy to solve the SFCs deployment and realize the joint resource allocation of multiple SFCs. Simulation results show that the deployment algorithm can achieve QoS guarantee and effectively save bandwidth for homogeneous business.

Plasmonic MIM and MSM Waveguide Couplers for Plasmonic Integrated Computing System

Plasmonic metal-insulator-metal waveguide (MIM WG) is a promising building block of devices of a plasmonic computing system, and metal-semiconductor-metal (MSM) WG offers high-speed detection of plasmon signals. MIM and MSM WG couplers are an essential component of any integrated computing system that requires an interface between the plasmonic devices and the electronic circuits. However, the MIM and MSM WG couplers have not yet been explored and systematically studied. This work analyzes and benchmarks various coupling schemes of the plasmonic MIM and MSM WGs to single out the best coupling approach. From the detailed numerical analysis and considering the trade-offs among coupling loss, total capacitance, system noise, and bandwidth, a holistic metric is introduced to quantify and compare the system-level performance of the couplers, and a novel coupling scheme is identified as the most attractive choice for coupling the two WGs.

Widening frequency bandwidth with parametric coupling in a wings-inspired low frequency MEMS energy harvester

Efficient energy harvesting with miniaturized harvesters for both low and random frequency vibrations remains a large challenge. This paper presents a wings-inspired design to implement a parametric coupling mechanism for widening the frequency bandwidth of a Micro-Electro-Mechanical System (MEMS) energy harvester (abbreviated as PCEH). The proposed PCEH is composed of two harvesting units, micro-fabricated by SU-8 with a serpentine geometry for decreasing working frequency, which like two wings, are placed at the bilateral of a flexible silicon middle support. When PCEH is excited, the flexible support can oscillate around its equilibrium position due to the lateral vibration of two wings. The parametric coupling is realized by alternately modulating the stiffness of each wing and verified by theoretical analysis, numerical simulation, and experimental measurements. Compared to those of non-parametric coupling energy harvesters (abbreviated as NPCEH), bandwidths and harvesting capacity of two wings in PCEH are increased by 55.4% and 73.7%, and by 3.3 and 2.5 times, respectively. The proposed PCEH opens a new way for widening the frequency bandwidth of energy harvesters at micro scale and lays a foundation for self-powered systems.

Study on Decoupling Control Strategy of Redundant Parallel Hybrid Vibration Isolation Platform

Background: The vibration isolation platform (VIP) can greatly reduce the risk of damage to dynamic equipment caused by external vibration interference and provide the most stable and reliable working environment for dynamic equipment. Objective: Aiming at the problems of small vibration isolation dimension, low bearing capacity, serious motion coupling, and narrow vibration isolation bandwidth in the field of vibration isolation of dynamic load equipment, a hydraulic redundant six degrees of freedom parallel vibration isolation platform (PVIP) with active and passive composite vibration isolation support is proposed. Methods: The dynamic coupling model of active and passive hybrid vibration isolation (APHVI) of redundant PVIP is established, and the matrix diagonal decoupling control strategy and fuzzy PI control theory are combined. Analysis of passive vibration isolation performance and APHVI performance of VIP is done. Results: The simulation results show that the effect of APHVI based on fuzzy PI decoupling control is better than that of passive vibration isolation and matrix diagonal decoupling control. Conclusion: Fuzzy PI control can effectively attenuate more than 98 % of the disturbance, significantly improve the vibration isolation performance and decoupling effect of the platform, and expand the effective vibration isolation bandwidth.

Wavelength selection in focusing non-uniform grating couplers: A coupling efficiency curve asymmetry and bandwidth analysis

We report a combined experimental and computational investigation of the multi-wavelength response of a series of focusing non-uniform grating couplers designed on multiple SOI thicknesses interfaced with two different fiber coupling schemes. In particular, we demonstrate either the existence of an asymmetry of the coupling efficiency curve shape, with respect to the tuning wavelength (1550 nm), related to the metastructure features, and how the photonic band structure of such metastructures can be calculated and exploited to evaluate their multi-wavelength response, in terms of multi-BW analysis. These results can be a positive stimulus for a further comprehension of the electromagnetic response of non-uniform grating couplers, particularly interesting as a valid option for integrated photonics applications.

Wide Bandwidth Silicon Nitride Strip-Loaded Grating Coupler on Lithium Niobate Thin Film

In this research, a vertical silicon nitride strip-loaded grating coupler on lithium niobate thin film was proposed, designed, and simulated. In order to improve the coupling efficiency and bandwidth, the parameters such as the SiO2 cladding layer thickness, grating period, duty cycle, fiber position, and fiber angle were optimized and analyzed. The alignment tolerances of the grating coupler parameters were also calculated. The maximum coupling efficiency and the −3 dB bandwidth were optimized to 33.5% and 113 nm, respectively. In addition, the grating coupler exhibited a high alignment tolerance.

High-Q Switched Oscillator With Capacitive Voltage Divider for Generating Mesoband High-Power Microwave Pulses

The switched oscillator (SWO) is a quarter-wave oscillator capable of generating mesoband high-power microwave (HPM) pulses. This paper presents a novel high-quality factor ( Q) SWO with a capacitive voltage divider (CVD). Unlike conventional SWOs, the transmission line energy of the proposed SWO is gradually coupled with the output load through the CVD. Thus, the proposed SWO can produce a mesoband pulse with a much higher power spectral density within the coupling bandwidth of a target in HPM effect testing. The frequency-domain output-voltage equation of the proposed SWO was obtained through a theoretical analysis of the equivalent circuit of the SWO. Through a numerical analysis, the time-domain output waveform of the proposed SWO was demonstrated to have a high quality factor, and the circuit parameters of the equivalent circuit of the SWO were set to achieve a high quality factor. The circuit parameters selected in the numerical analysis were used in an electromagnetic simulation to determine the design parameters of the parallel-plate transmission line (PPTL)-based SWO with the CVD built on a printed circuit board. The proposed SWO was fabricated and its performance was assessed. For a breakdown voltage of 8.7 kV, the output voltage of the fabricated SWO showed a quality factor of 25, which is more than two times larger than the quality factors of conventional SWOs. Thus, the proposed SWO was demonstrated to produce high- Q mesoband HPM pulses, and it has the potential to be applied in HPM effect testing. Moreover, the proposed SWO improves operator safety by preventing the output load from being charged by a high-voltage power supply.

Metal based grating coupler on a thin-film lithium niobate waveguide.

Thin-film lithium niobate (LN) has been proved to be an excellent platform for building compact active and nonlinear photonic components on a chip. The coupling of a sub-micron sized LN waveguide and a single-mode fiber remains as one challenging issue. An efficient grating coupler made of Au stripes on an LN ridge waveguide is demonstrated here. The fabrication of the grating is convenient, using just a standard lift-off process of metal films. The peak coupling efficiency of an optimized structure reaches 50.4%, i.e., -3 dB coupling loss, at 1.55 µm wavelength for the fundamental transverse-electrical mode, where the 1-dB coupling bandwidth is 58 nm. Experimentally, fabricated devices, with buried oxide layer thicknesses slightly off the optimal values, exhibit coupling efficiencies of 43.8% and 33.7% for 400 nm and 600 nm thick LN layers.

Realization of all-optical multiplexer–demultiplexer in mid-IR wavelengths using triple-core photonic quasi-crystal fiber

We report a wide bandwidth and low crosstalk Ge11.5As24Se64.5 triple-core photonic quasi-crystal fiber (TPQF) for the multiplexing–demultiplexing (MUX–DEMUX) operation in mid-IR region. In this numerical investigation, we explore the various MUX–DEMUX parameters such as coupling length, coupling length ratio, separation length, crosstalk and bandwidth. Further, the proposed TPQF based MUX–DEMUX exhibits high bandwidth of 263, 252, 214, 129 and 134 nm for low crosstalk of -36.47, -34, -31, -30 and -31.3 dB at the wavelengths of 2, 2.3, 2.9, 3.5 and 4μm, respectively. The proposed MUX–DEMUX characteristics are realized first time in TPQF at mid-IR wavelengths. Besides, the bandwidth is improved as 310, 292, 286, 148 and 164 nm for the very low crosstalk level of -45.8, -44, -42.3, -42.35 and -49.93 dB for the separation lengths of 5.5, 6.1, 6.6 and 7.4 mm wavelengths of 2/4-μm, 2.3/4-μm 2.9/4-μm and 3.5/4-μm, respectively, when phase of core 1 is about 1.2π. Thus, the proposed TPQF-based MUX–DEMUX is a suitable candidate for the development of mid-IR photonic devices such as wavelength division multiplexing (WDM) couplers and power splitters.

Heptagonal Shaped UWB Antenna with DGS for Wireless LTE with Enhanced Bandwidth

The paper discusses about the implementation of Heptagonal shaped compact ultra-wideband planar Microstrip patch antenna with and without defected ground plane structure (DGS) with analysis of various parameters like return loss, VSWR bandwidth etc. A substrate made up of dielectric constant FR4 epoxy is utilized and the 2D and 3D radiation pattern are also discussed. DGS has helped to fine tune and increase the bandwidth &amp; its effects have been studied. A volume of 28x32x1.7 (1523.2 mm^3) is occupied by the size of antenna with dielectric constant of εr = 4.4, tanδ= 0.02. In order to provide fine tuning in the return loss graph, a 50Ω line with width of W=3mm direct line feeding method has been used for the micro-strip line and slots have been introduced in the ground plane structure, for achieving the good bandwidth coupling between the slots plays an important role. The antenna parameters including VSWR, Gain and return losses v/s frequency effects for the antenna with variation of slots and dimensions has been studied in this paper along with the analysis of important parameters such as return loss (dB), bandwidth, VSWR (Voltage Standing Wave Ratio) of patch antenna which has been performed using Ansoft HFSS v15 tool. The proposed design of the heptagonal shaped antenna operates as an ultra-wide band antenna ranging from 3.20 GHz to 10 GHz and beyond covering most of applications from LTE, Wimax (3.5/5.55GHz), Radio altimeter, RFID and ISM WLAN 5.2/5.8GHz etc.

Mode-field Matching Down-Tapers on Single-Mode Optical Fibers for Edge Coupling Towards Generic Photonic Integrated Circuit Platforms

Connections between standard single-mode fibers and waveguides in photonic integrated circuits tend to have relatively high coupling losses due to a difference in mode size and mode profile between both light guiding media. Edge coupling strategies involving specialty fibers are frequently used to obtain the best performance in terms of coupling efficiency, bandwidth and polarization independence. We propose the fabrication of free-standing down-taper structures on top of cleaved fiber facets by two-photon direct laser writing and show their performance for silicon, silicon nitride and indium phosphide generic chip platforms. We present a comprehensive analysis of the design of such taper structures that show unprecedented flexibility. We demonstrate their fabrication and fully characterize them in terms of output modal fields and coupling efficiencies. Furthermore, we experimentally compare the fabricated down-tapers with commercially available lensed fibers and demonstrate equal or better coupling efficiency for four out of the five investigated photonic integrated circuit platforms, with a measured improvement in coupling efficiency up to 1.43 dB.

Infrared Difference Spectroscopy of Proteins: From Bands to Bonds.

Infrared difference spectroscopy probes vibrational changes of proteins upon their perturbation. Compared with other spectroscopic methods, it stands out by its sensitivity to the protonation state, H-bonding, and the conformation of different groups in proteins, including the peptide backbone, amino acid side chains, internal water molecules, or cofactors. In particular, the detection of protonation and H-bonding changes in a time-resolved manner, not easily obtained by other techniques, is one of the most successful applications of IR difference spectroscopy. The present review deals with the use of perturbations designed to specifically change the protein between two (or more) functionally relevant states, a strategy often referred to as reaction-induced IR difference spectroscopy. In the first half of this contribution, I review the technique of reaction-induced IR difference spectroscopy of proteins, with special emphasis given to the preparation of suitable samples and their characterization, strategies for the perturbation of proteins, and methodologies for time-resolved measurements (from nanoseconds to minutes). The second half of this contribution focuses on the spectral interpretation. It starts by reviewing how changes in H-bonding, medium polarity, and vibrational coupling affect vibrational frequencies, intensities, and bandwidths. It is followed by band assignments, a crucial aspect mostly performed with the help of isotopic labeling and site-directed mutagenesis, and complemented by integration and interpretation of the results in the context of the studied protein, an aspect increasingly supported by spectral calculations. Selected examples from the literature, predominately but not exclusively from retinal proteins, are used to illustrate the topics covered in this review.

Enhancing isolation and bandwidth in planar monopole multiple antennas using thin inductive line resonator

This paper presents efficient mutual coupling reduction and bandwidth enhancement method in planar monopole multiple antennas. High isolation and bandwidth extension are achieved by integrating a thin inductive line resonator as reflector and parasitic element between the antenna elements. A 36.9% bandwidth (4.69–6.5 GHz) is achieved at 4.9 GHz, which encompasses the sub-6 GHz (4.8–5.0 GHz) 5G and 5.15–5.85 GHz WLAN bands. The thin inductive line resonator provides an effective means of controlling the electromagnetic wave propagation. Approximately 45 dB isolation and 4.9 dB maximum gain can be achieved between two parallel monopole antennas with 0.36λ0 spacing. The physical meaning of electromagnetic propagation in MIMO antenna is studied by discussing the coupling mode between antennas and the working mechanism of thin inductive line as parasitic elements and reflectors. Furthermore, a four-element antenna with orthogonal polarization diversity is also proposed based on the thin inductive line. Correlation coefficients (CC) are well below 0.05 across the operating bandwidth.