A tunable magnetic inductor

For integrated radio-frequency applications, tunable magnetic inductors are expected. A tunable magnetic inductor, based on magnetoimpedance effect, is presented in this paper. The proposed inductor is constructed with a magnetic inductor body, wound by an insulated coil, inducing a longitudinal dc bias magnetic field when a dc control current is flowing through. Formed by a conductive core coated by a high-permeability magnetic layer, the magnetic inductor body can be realized by either a thin-film structure or a composite wire. The reluctance models for both thin-film and composite wire structures are studied. A prototype tunable magnetic inductor, using a composite wire element, has been characterized. The results show that by varying the dc control current, the inductance L of the magnetic inductor can be tuned. The tunable range depends on the frequency of the current flowing through the inductor. A relative variation of inductance /spl Delta/L/L/sub 0/, up to 18% at low frequency (around 5 MHz), is achieved by applying a bias current of magnitude merely up to 15 mA. The quality factor varies from 5 to 17 in the measured frequency range. The proposed tunable inductor may be further optimized for high-frequency applications and has the potential to be realized in micro-electromechanical systems technology.     

Programmable active inductor-based wideband VCO/QVCO design

Programmable wideband voltage-controlled oscillator (VCO) and quadrature VCO (QVCO) circuits which adopt modified gyrator-C-type active inductors with PMOS transistors in the feedback path are presented here. New design equations are derived for an active inductor considering the effects of the parasitic capacitance of PMOS and are used to design a high-Q active inductor. The fabricated VCO and QVCO achieve frequency tuning ranges from 1.85 to 3.66 GHz and 1.55 to 3.61 GHz, respectively. The measured phase noise of VCO and QVCO range from 281.1 to 2111.3 dBc/Hz and from 280.1 to 2107.7 dBc/Hz at 3 MHz offset, respectively.     

Tunable ferroelectric capacitor-based voltage-controlled oscillator

Ferroelectric capacitors made from Ba(1-0.5)Sr0.5TiO3 (BST) are applied as varactors in tunable, high-frequency circuit applications. In this context, a voltage-controlled oscillator (VCO) has been designed and implemented using discrete RF bipolar junction transistor (BJTs) and tunable ferroelectric capacitor. The designed VCO has a tuning range from 205 MHz to 216.3 MHz with a power dissipation of 5.1 mW. The measured phase noise is -90 dBc/Hz at 100 kHz and -140 dBc/Hz at 1 MHz offset.     

Tunable MEMS capacitors using vertical carbon nanotube arrays grown on metal lines

In this work, tunable MEMS capacitors are realized using a vertically grown carbon nanotube array. The vertical CNT array forms an effective CNT membrane, which can be electrostatically actuated like the conventional metal plates used in MEMS capacitors. The CNT membrane is grown on titanium nitride metal lines, with a Al/Fe bi-layer as buffer layer and catalyst material respectively, using chemical vapor deposition process. Two different anchor configurations are investigated. A maximum capacitance of 400 fF and maximum tunability of 5.8% is extracted from the S-parameter measurements. Using the tunable MEMS vertical array capacitor a voltage controlled oscillator (VCO) is demonstrated showing promise for integrating CNTs for communications applications.     

The Inductance Enhancement Study of Spiral Inductor Using Ni–AAO Nanocomposite Core

The letter presents the fabrication and characterization of on-chip spiral inductors with Ni–anodic alumina oxide (Ni–AAO) nanocomposite core. Ni nanorods with 70 nm diameter are deposited and isolated in an AAO matrix to form a layer of nanocomposite on silicon substrate. About 3% inductance enhancement to the inductor with the nanocomposite core has been observed and the enhancement can be kept up more than 6 GHz. Because the proposed inductance enhancement scheme using ferromagnetic–AAO-based nanocomposite as inductor core employs a CMOS-compatible fabrication process with the characteristics that can be further improved, it is our belief that the scheme has a great potential application for future radio frequency integrated circuitry (RFIC) manufacture.      

Radio-Frequency Planar Integrated Inductor With Permalloy-SiO$_2$Granular Films

We have designed and fabricated a radio-frequency (RF) planar integrated inductor using Permalloy-SiO$_2$granular film as the magnetic core. By controlling the composition and microstructure, we produced a granular film with excellent soft magnetic properties and high electrical resistivity. The inductance$L$of the inductor with granular Permalloy-SiO$_2$magnetic film increased 6% to 15%, compared to that of an air-core inductor, and the quality factor$Q$value was high, approaching 10 in the frequency range of 2–3 GHz. The controllable anisotropy of the granular film generated in deposition process gives the magnetic inductor a very high self-resonance frequency peak—over 6 GHz.     

Using a Single Toroidal Sample to Determine the Intrinsic Complex Permeability and Permittivity of Mn–Zn Ferrites

Analysis of the principle of the published lumped circuit methods for determination of the intrinsic complex permeability and permittivity of the Mn-Zn ferrites reveals that as long as the electric and the magnetic field distributions in the core(s) in two measurements are different, the two intrinsic values can be determined. Using this principle, we developed a set of general lumped circuit methods based on a toroidal Mn-Zn ferrite core as the measurement sample. We examined two possible different excitation modes: magnetic field excitation and electric field excitation. The two different excitation modes result in significantly different field distributions in the sample. Thus, high accuracy can be guaranteed in principle. For the magnetic field excitation, we present in this paper a general finite-difference method to solve the fields in the core and the impedance of the ferrite core inductor. To avoid the stray capacitance among the coils of the ferrite core winding inductor in the measurement, we made a set of short-ended coaxial test fixtures. We performed experiments to determine the intrinsic complex permeability and permittivity of a Mn-Zn ferrite core up to 10 MHz by using the two general methods and validated the measured intrinsic values experimentally.     

Wide‐Range Tunable Fluorescence Lifetime and Ultrabright Luminescence of Eu‐Grafted Plasmonic Core–Shell Nanoparticles for Multiplexing

Wide‐range, well‐separated, and tunable lifetime nanocomposites with ultrabright fluorescence are highly desirable for applications in optical multiplexing such as multiplexed biological detection, data storage, and security printing. Here, a synthesis of tunable fluorescence lifetime nanocomposites is reported featuring europium chelate grafted onto the surface of plasmonic core–shell nanoparticles, and systematically investigated their optical performance. In a single red color emission channel, more than 12 distinct fluorescence lifetime populations with high fluorescence efficiency (up to 73%) are reported. The fluorescence lifetime of Eu‐grafted core–shell nanoparticles exhibits a wider tunable range, possesses larger lifetime interval and is more sensitive to separation distance than that of ordinary Eu‐doping core–shell type. These superior performances are attributed to the unique nanostructure of Eu‐grafed type. In addition, these as‐prepared nanocomposites are used for security printing to demonstrate optical multiplexing applications. The optical multiplexing experiments show an interesting pseudo‐information “a rabbit in a well” and conceal the real message “NKU.”     

Monolithic double rectangular spiral thin-film inductors implemented with NiFe magnetic cores for on-chip dc-dc converter applications

This paper describes a simple, on-chip complimentary metal oxide semiconductor (CMOS) compatible thin-film inductor applied for the dc-dc converters. The double rectangular spiral types of the thin-film inductors were implemented with 15 µm-thick copper films upon 2.5 µm thick of the NiFe magnetic core. Prior to fabricating a high-voltage CMOS dc-dc converter circuit, the NiFe magnetic core was deposited on the polyimide film. Adapting a double-rectangular structure, the fabricated monolithic inductor exhibited not only high inductance of 1.6 µH but also high quality factor of 11.2 at 5 MHz. To simplify the integration process, the planarization process for the top magnetic core was eliminated. The performance of the dc-dc converter which combined with our proposed inductors was evaluated at a high power efficiency of 81% when the converter operated at a frequency of 5 MHz corresponding to input and output voltages of 3.3 V and 8.1 V, respectively.     

A simple method to estimate gain-bandwidth product and the secondpole of the operational amplifiers

A method for realizing a sine-wave voltage-controlled oscillator (VCO) with a linear frequency to control voltage characteristics over three decades of frequencies, or more, in one sweep is discussed. The method employed is the conversion of a simple integrated square-wave VCO into a sine-wave VCO by separating the first-harmonic component and providing frequency shifting to achieve the desired output range. The sources of distortion of the output waveform are shown to be higher-order components of the square-wave used and higher-order components produced in the mixer. Possible improvements of the circuit are suggested, including the use of higher-order filters to reduce distortion and the use of a square-wave VCO operating at higher frequencies to provide operation at higher frequencies or over wider sweep ranges     

Novel Hybrid Voltage Controlled Ring Oscillators Using Single Electron and MOS Transistors

This paper proposes two kinds of novel hybrid voltage controlled ring oscillators (VCO) using a single electron transistor (SET) and metal-oxide-semiconductor (MOS) transistor. The novel SET/MOS hybrid VCO circuits possess the merits of both the SET circuit and the MOS circuit. The novel VCO circuits have several advantages: wide frequency tuning range, low power dissipation, and large load capability. We use the SPICE compact macro model to describe the SET and simulate the performances of the SET/MOS hybrid VCO circuits by HSPICE simulator. Simulation results demonstrate that the hybrid circuits can operate well as a VCO at room temperature. The oscillation frequency of the VCO circuits could be as high as 1 GHz, with a -71 dBc/Hz phase noise at 1 MHz offset frequency. The power dissipations are lower than 2 uW. We studied the effect of fabrication tolerance, background charge, and operating temperature on the performances of the circuits     

The controlled fabrication and geometry tunable optics of gold nanotube arrays

Arrays of vertically aligned gold nanotubes are fabricated over several square centimetres which display a geometry tunable plasmonic extinction peak at visible wavelengths and at normal incidence. The fabrication method gives control over nanotube dimensions with inner core diameters of 15-30 nm, wall thicknesses of 5-15 nm and nanotube lengths of up to 300 nm. It is possible to tune the position of the extinction peak through the wavelength range 600-900 nm by varying the inner core diameter and wall thickness. The experimental data are in agreement with numerical modelling of the optical properties which further reveal highly localized and enhanced electric fields around the nanotubes. The tunable nature of the optical response exhibited by such structures could be important for various label-free sensing applications based on both refractive index sensing and surface-enhanced Raman scattering.     

Computer-aided design of air-gapped magnetic core inductors with minimum DC winding resistance

The method of computer-aided design of air-gapped inductors operating with de bias current is described. An algorithm for the minimum de resistance of the winding for a desired value of the inductance is given. Simultaneously, this permits us to determine the optimal length of the air gap, to choose a suitable operating point on the normal magnetization curve and to calculate the minimum number of turns of the winding under given inductor operation conditions, i.e., the ac voltage value across the inductor and its frequency, and the value of the de bias current superimposed in the same winding. The method presented here uses the normal magnetization curve of the core material and the family of relative incremental permeability curves of this material.     

Core/multishell nanowire heterostructures as multicolor, high-efficiency light-emitting diodes

We report the growth and characterization of core/multishell nanowire radial heterostructures, and their implementation as efficient and synthetically tunable multicolor nanophotonic sources. Core/multishell nanowires were prepared by metal-organic chemical vapor deposition with an n-GaN core and InxGa1-xN/GaN/p-AlGaN/p-GaN shells, where variation of indium mole fraction is used to tune emission wavelength. Cross-sectional transmission electron microscopy studies reveal that the core/multishell nanowires are dislocation-free single crystals with a triangular morphology. Energy-dispersive X-ray spectroscopy clearly shows shells with distinct chemical compositions, and quantitatively confirms that the thickness and composition of individual shells can be well controlled during synthesis. Electrical measurements show that the p-AlGaN/p-GaN shell structure yields reproducible hole conduction, and electroluminescence measurements demonstrate that in forward bias the core/multishell nanowires function as light-emitting diodes, with tunable emission from 365 to 600 nm and high quantum efficiencies. The ability to synthesize rationally III-nitride core/multishell nanowire heterostructures opens up significant potential for integrated nanoscale photonic systems, including multicolor lasers.     

Tunable Water Channels with Carbon Nanoscrolls

Molecular dynamics simulations and theoretical analyses are performed to show that the flow rate of water through the core of carbon nanoscrolls (CNSs) can be adjusted over a broad range through the effective surface energy, which in turn can be tuned by an applied DC or AC electric field. The results suggest that the CNSs hold great promise for applications such as tunable water and ion channels, nanofluidic devices, and nanofilters, as well as tunable gene‐ and drug‐delivery systems.     

Manipulation of photonic nanojet using liquid crystals for elliptical and circular core-shell variations

We present theoretical studies on a tunable photonic nanojet (PNJ) created by adapting a shell and liquid crystal (LC) core architecture. The shell is made of indium tin oxide and the core is infiltrated with nematic LCs. The application of an external static electric field to the LCs modifies their refractive index, and this allows tuning the PNJ effect in the proposed system. In addition to nonresonant excitation, resonant PNJ excitation is also obtained from a hybrid structure. Both nonresonant and resonant internal field excitations of circular and elliptical PNJ configurations are examined by using a high-resolution finite-difference time-domain method. The calculated results indicate that the proposed PNJ configurations with tunable refractive indices lead to significant changes in some parameters such as decay length, focal distance, full width at half maximum and electric field intensity. Such PNJ designs can be employed in high-resolution optical sensors, optical trapping, and high-density data storage.     

A Proposed Capacitance Bridge Using a Modern Inductance Standard

A modern form of mutual inductor that comprises windings on a dust core toroid can be applied to the classic Carey Foster bridge to measure capacitance, avoiding the older forms of fixed or variable mutual inductance. When hermetically sealed, these closely coupled inductors offer stability in the 0.25% class.     

Widely tunable optical bandpass filter by use of polymer long-period waveguide gratings

We report the design and fabrication of a widely tunable optical bandpass filter based on using two identical long-period gratings formed along a polymer channel waveguide with a section of the waveguide core removed. The peak transmission of the passband of the fabricated filter is approximately 60% and the bandwidth of the passband is approximately 6 nm. The filter is thermally tunable over the C + L band (1520-1610 nm) for both TE and TM polarizations with a temperature control of approximately 30 degrees C.     

Circuit design of an integrable simulated inductor and itsapplications

Gyrator principles are used to design an integrable voltage-controlled simulated inductor with inductance variable from 0.1 to 250000 H or even higher. One of the features of this simulated inductor is that it contains two voltage-controlled current amplifiers with controlling terminals connected in parallel. For a resonant circuit consisting of such a simulated inductor and an external capacitor, the resonant frequency will be linear with the controlling voltage. It can be employed to realize a sine-wave oscillator or filter whose operation frequency is changed linearly with the controlling voltage. In this work a linear voltage-controlled sinusoidal oscillator, which was designed to have an oscillation frequency from several kHz down to 0.01 Hz, is taken as an example to illustrate an application of the simulated inductor. In this case the simulated inductor was made up of discrete components and the oscillator has been employed to provide standard signals for research on differential transformation of physiological spikes in medical science     

氧化硅/金纳米壳层的制备及其在纳米医学中应用的研究现状

氧化硅/金纳米壳层因具有由其核/壳相对尺寸所决定的特殊光学性能和良好的生物相容性, 所以在纳米医学等许多领域得到了广泛的重视. 本文综述了氧化硅/金纳米壳层的研究现状, 总结了相关的制备方法, 评述了在纳米医学中的重要应用, 并对其研究前景进行了展望.