Effect Of Bias Current Research Articles

Effect of bias current of active magnetic bearing on Sommerfeld effect characterization in an unbalanced rotor dynamic system

Effect of bias current of active magnetic bearing on Sommerfeld effect characterization in an unbalanced rotor dynamic system

Generation of wideband chaos without time delay signature using the microlaser with dispersive optical feedback

We propose and numerically demonstrate a method of generating wideband chaos laser without time delay signature by using a circular-side hexagonal resonator (CSHR) microlaser with optical feedback from a chirped fiber Bragg grating (CFBG). The theoretical model of the circular-side hexagonal resonator microlaser with chirped fiber Bragg grating feedback is established according to the Lang-Kobayashi equations. The effects of bias current, feedback strength and CFBG dispersion on the bandwidth of the chaos laser and the feedback time delay signature are investigated. The results show that the CFBG-feedback CSHR microlaser can generate a wideband chaos without feedback time-delay signature under the condition of high bias current with a wideband and flat small-signal modulation response and the bandwidth can reach 14 GHz.

Characterization of LEDs for visible-light communications

Recent advances in solid-state technologies have enabled the development of light-emitting diodes (LEDs) with favorable features such as long life expectancy, low-power consumption, and reduced heat dissipation. Visible-light communication (VLC) is a short-range wireless access technology that deploys LEDs as wireless transmitters in addition to their primary task of illumination. The major limitation for the design of high-speed VLC systems is the electrical (modulation) bandwidth of the LED. In this study, we investigate the electrical characteristics of a number of off-the-shelf LEDs. Specifically, we determine their frequency responses and match them to their small-signal models. The electrical bandwidths of measured LEDs vary from 250 kHz to 20 MHz and depend on the emitted color and internal circuitry. As a verification of our measurements, we use the sample LEDs as a transmitter in a VLC system setup and determine the supported data rates. The equivalent circuit model is utilized to compare with the measured modulation characteristic of the LED. Furthermore, the bias current effect on the modulation bandwidth is presented.

Design Requirement and DC Bias Analysis on HVDC Converter Transformer

The converter transformer plays a critical role in the high-voltage direct current (HVDC) transmission system, which connects but separates the AC grids and the converter. This paper briefly introduced the essential design requirement of the HVDC converter transformer in a system at ±800kV level and analyzed the DC bias influence on the transformer. The DC bias current effect simulations are analyzed in MATLAB and ANSYS Maxwell in this paper, respectively.

Experimental study on ZH-1SEFD for CSES in the ground simulating plasma environments

ZhangHeng-1 space electric field detector (ZH-1SEFD) is one of the main payloads aboard China Seismo-Electromagnetic satellite (CSES). The necessity and involved items of experimental verification and test evaluation of ZH-1SEFD in the ground simulating plasma environments (GSPE) are briefly introduced,and the normal orbit plasma environment conditions of CSES is discussed. It is found that the density and potential gradients along axial and radial directions exist objectively in the plasma environment of Italian IAPS-PC or other related systems, and then the axial and radial electric fields also exist in. Then the feasibility of the experimental verification and test evaluation of ZH-1SEFD in GSPE using IAPS-PC is demonstrated. On above basis, the major ideas, methods and system composition of experimental verification and test evaluation of ZH-1SEFD in GSPE are narrated. Experimental results show that, ZH-1SEFD sensor potential coupling and the active bias current effect in GSPE are in accordance with the related physical principle, and the sensor consistency is good. The further experimental results also show that, ZH-1SEFD can effectively detect and obtain the electric field information and its variation in the local plasma environments, and the combined channel consistency is also good. All these studies show that the ZH-1SEFD and its electric field measurement results are reliable.

Proximity‐Effect‐Induced Superconductivity in Nb/Sb2Te3‐Nanoribbon/Nb Junctions

AbstractNanohybrid superconducting junctions using antimony telluride (Sb2Te3) topological insulator nanoribbons and Nb superconducting electrodes are fabricated using electron beam lithography and magnetron sputtering. The effects of bias current, temperature, and magnetic field on the transport properties of the junctions in a four‐terminal measurement configuration are investigated. Two features are observed. First, the formation of a Josephson weak‐link junction. The junction is formed by proximity‐induced areas in the nanoribbon right underneath the inner Nb electrodes which are connected by the few tens of nanometers short Sb2Te3 bridge. At 0.5 K a critical current of 0.15 µA is observed. The decrease of the supercurrent with temperature is explained in the framework of a diffusive junction. Furthermore, the Josephson supercurrent is found to decrease monotonously with the magnetic field indicating that the structure is in the small‐junction limit. As a second feature, a transition is also observed in the differential resistance at larger bias currents and larger magnetic fields, which is attributed to the suppression of the proximity‐induced superconductive state in the nanoribbon area underneath the Nb electrodes.

The Winner-Take-All Mechanism for All-Optical Systems of Pattern Recognition and Max-Pooling Operation

The winner-take-all (WTA) mechanism based on the inhibitory dynamics of vertical-cavity surface-emitting laser with an embedded saturable absorber (VCSEL-SA) neurons is proposed for the first time. The WTA mechanism is shown numerically in a photonic spiking neural network (SNN). The effect of bias current on WTA time window is analyzed based on the proposed SNN. Moreover, a pattern recognition approach is presented numerically based on the WTA mechanism in all-optical neural network consisting of VCSEL-SA neurons. For the pattern recognition, the robustness of noisy inputs is examined. The effects of bias current, strength of inhibition and weight matrix on the speed of pattern recognition are analyzed carefully. Furthermore, the max-pooling operation is implemented numerically in the all-optical VCSEL-SA neural network model based on the WTA mechanism for the first time. The results hold great promise for the development of energy-efficient and high-speed photonic spiking neural network.

Unstable Playback Response of CPP-GMR Read Head Induced by Electromagnetic Interference: Structural Dependence

Although several studies have claimed that the current perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) technology is the most attractive technology to achieve ultrahigh capacities of data storage applications, there are still recent studies indicating the inaccuracy of the reading head response caused by the electromagnetic interference (EMI). To improve the precision of the head response, we report a dependence of the physical dimension of CPP-GMR read head on the readback signal distortion due to the EMI. The simulations were based on micromagnetic modeling. The EMI impacts on the head response were analyzed as a function of structural parameters of the head, including the length of stripe height (SH) and read width (RW). Then, the readback characteristics of the head, including the spin-transfer induced noise, power spectral density, and bit-error-rate (BER), were discussed. It was found that an alternation of either SH or RW influences the noise profile. Adjusting the length of RW demonstrates a more influential impact on the noise than that of SH. The frequency spectrum of the head response was also carried out. The physical explanations regarding the results found in this article were given through the behavior of the demagnetization field. The effects of bias current on the head output were additionally investigated. Moreover, the BER of the head with varying the head dimensions was characterized. From findings, the appropriate sizing of the CPP-GMR sensors for an areal density of 1 Tb/in2 was predicted. The results can be utilized to design CPP-GMR read heads at ultrahigh areal densities.

Effect of Bias Current on Complexity and Time Delay Signature of Chaos in Semiconductor Laser With Time-Delayed Optical Feedback

The effect of bias current on the complexity and time-delay signature of chaotic signals in semiconductor lasers with polarization preserved optical feedback has been studied experimentally and theoretically. The peak value of the autocorrelation coefficient and the normalized permutation entropy at the feedback round trip time are used to quantify the time delay signature and complexity, respectively. The results show that the time-delay signature is approximately in an inverse relationship with the complexity of chaos when the semiconductor laser is subject to low or strong optical feedback. However, the inverse relationship disappears when the laser operates at higher bias currents with intermediate feedback strength. The simulation results are qualitatively agreed with the experimental results.

Bias Current Effect on Second Harmonic in Asymmetric Magnetoimpedance Response in Amorphous Microwires

The influence of bias current on the second harmonic in the nonlinear magnetoimpedance in an amorphous microwire with a helical anisotropy is studied theoretically. The voltage response of the microwire is found in the framework of a rotational model. It is shown that the application of the bias current leads to the asymmetry in the field dependence of second harmonic. The second harmonic amplitude is analyzed as a function of the external field, current amplitude and the value of the bias current. The conditions of maximum field sensitivity of the second harmonic are found.

Flexible Optical Cross-Connect Structures Supporting WDM Multicast With Multiple Pumps for Multiple Channels

We not only propose three flexible optical cross-connect (OXC) structures, with the ability of wavelength-division multiplexing (WDM) multicast, but also experimentally demonstrate two WDM multicast schemes based on four-wave mixing in a semiconductor optical amplifier (SOA). One-to-ten WDM multicast of 25-Gb/s QPSK signals is achieved with three pumps, and the power penalties for all signals are less than 1.7 dB. For the first time, dual-channel WDM multicasts are simultaneously realized with only two pumps. One-to-six multicast for one input with the largest power penalty of 1.28 dB is obtained, whereas one-to-three multicast for the other input with the power penalty of 1.27 dB is also realized. The demonstrated schemes can be applied to the proposed OXC structures, according to the different requirements. The effect of bias current on conversion efficiency and optical signal-to-noise ratio is also discussed, and the optimal value is given.

Harmonic and Intermodulation Distortion in Direct Intensity Modulated Quantum Cascade Lasers

In this paper, nonlinear distortion in a quantum cascade laser arising from direct intensity modulation is studied. Harmonic and intermodulation distortion expressions for small sinusoidal modulation signals are derived using a perturbation method. The expressions are validated by making a comparison with a large signal simulation of a quantum cascade laser equivalent circuit. The effects of bias current, optical modulation depth, and modulation frequency on harmonic and intermodulation distortion are examined.

NiZn 페라이트코어를 이용하여 제작한 직교형 플럭스게이트 센서의 출력에 미치는 바이어스전류의 영향

Orthogonal fluxgate sensor was fabricated with cylinder-shaped NiZn ferrite core, Cu wire through the core and pickup coil wound on the core, and the bias current effect on the output sensitivity of it was investigated. The output ( sensitivity) of the sensor was largely dependent on the operation frequency, and the tendency of sensor output was similar to that of the impedance of pickup coil. The maximum output was obtained by adding the DC bias current of which value was over 50% of the excitation current. The output was saturated when the DC bias current was larger than 50% of the excitation current.

Bias Current Effect on Nonlinear Magnetoimpedance Response in Amorphous Wires with Circular Anisotropy

The effect of bias current on the appearance of higher harmonics in the nonlinear mag¬netoimpedance in amorphous wires with a circular anisotropy is studied. The rotational model to calculate the voltage response in the case of a weak skin effect is proposed. It is shown that the ap¬plication of the bias current may lead to significant increase of the second harmonic amplitude in the voltage. The conditions of maximum field sensitivity of the second harmonic are found.

Effect of bias current on the resisitivity and photoconductivity of oxygen-deficient La2∕3Sr1∕3MnO3−δ thin films

The influence of bias current on resistivity and photoconductivity in oxygen-deficient La2∕3Sr1∕3MnO3−δ thin films has been investigated. There exists a giant resistance drop induced by dc electrical currents alone especially near the temperature of resistance peak (TP). Moreover, the photoconductivity emerges only when the current exceeds a threshold and this effect is quite different from magnetoresistance induced by magnetic fields. It is found that the magnitude of photoconductivity increases with increasing of bias current and the threshold current increases with decreasing temperatures and increasing magnetic fields. The magnitude of photoconductivity achieves 10.2% at temperature of 100K with light density of 4.3mW∕cm2 and current of 1mA. The current-assisted electroresistance and photoconductivity are discussed based on the delocalization of localized state by light illumination and bias current.

An analysis of base bias current effect on SiGe HBTs

The anomalous dip in scattering parameter S/sub 11/ of SiGe heterojunction bipolar transistors (HBTs) is explained quantitatively for the first time. Our results show that for SiGe HBTs, the input impedance can be represented by a "shifted" series RC circuit at low frequencies and a "shifted" parallel RC circuit at high frequencies very accurately. The appearance of the anomalous dip of S/sub 11/ in a Smith chart is caused by this inherent ambivalent characteristic of the input impedance. In addition, it is found that under constant collector-emitter voltage (V/sub CE/), an increase of base current (which corresponds to a decrease of base-emitter resistance (r/sub /spl pi//) and an increase of transconductance (g/sub m/)) enhances the anomalous dip, which can be explained by our proposed theory.

Bias dependence of mode dynamics in a vertical-cavity surface-emitting laser

Results are presented showing the effect of bias current on mode competition in the large-signal modulation response of a vertical-cavity surface-emitting laser. The overshoot and turn-on delay between the LP01 and LP11 modes are observed to be strongly dependent on the bias current relative to the individual mode threshold currents in both experiments and simulations.

Modeling the zero and forward bias operation of PIN diodes for high-frequency applications

Silicon-based PIN diodes have been studied in a high-frequency switching application under moderate to high input voltage levels. A model suitable for full circuit simulators such as SPICE is proposed and tested. The model accurately describes the impedance behavior over changes in frequency, DC bias current and applied voltage level. A localized maximum in series resistance is accurately modeled and found to be a function of the diode’s transit time effect. The model also describes the nonlinear high current stored charge-DC bias current effect. The full circuit PIN diode model is verified with experimental observations.

Bias-current effect on giant magnetoimpedance in Co-based amorphous microwire

The giant magnetoimpedance (GMI) effect has been measured in Co 83.2B 3.3Si 5.9Mn 7.6 amorphous microwire as a function of direct current (dc)-biased current and measuring frequency, f. The GMI profile has a single peak for f⩽5 MHz, and two peaks at higher frequency. The maximum GMI ratio increases continuously with frequency up to 45% at 10 MHz. The influence of superimposed dc biasing is shown to result in asymmetrical GMI as well as in a shift of the axial hysteresis loop. Both effects are interpreted in terms of the relative contribution of domain wall and rotational processes to the transverse susceptibility.

The Effects of Disk Surface Topography on Baseline Instability of MR Head

Several factors which influence baseline instability (BLI) phenomenon in MR drive were investigated experimentally. In particular, the role of surface topography on BLI was studied in detail. The r esults show that BLI is linearly proportional to the surface waviness with a spatial wavelength of 0.4 to 5.0 min. BLI becomes worse as the surface waviness increases. On the other hand, surface roughness which has a spatial wavelength below 25 m has no effect on BLI. The results further show that the effect of bias current on the BLI is amplified on the disk with worse surface waviness. The disk surface waviness is dependent on the manufacturing process and becomes an inherent surface property of media. The disk surface waviness. therefore, can not be overlooked when evaluating the media for a high-performance hard disk drive. In general, waviness is reduced mainly during grinding and polishing process during manufacturing.