Low-frequency Flicker Research Articles

Flicker Noise in Diode Laser Spectroscopy

Low-frequency (flicker) noises of the intensity and frequency of diode laser (DL) radiation have been studied. A model of DL flicker noise and a method for minimizing flicker noise at which the relative photocurrent noise can be registered at a level of 5 × 10–7 with an averaging time of 100 ms are proposed. The results obtained can be used in the development of DL-based gas-analytical equipment for measuring low gas concentrations.

A Hybrid LED Driver With Improved Efficiency

A high-efficient hybrid light-emitting diode (LED) driver is introduced in this article. By combining the merits of conventional switching-converter-based and inductor-less driving solutions, the proposed topology fully utilizes the input power from the ac mains without causing considerable switching loss or excessive voltage stress. With the help of a small-size inductor and the hybrid scheme, the proposed driver automatically alternates between switching mode and linear mode as the rectified input voltage changes. In addition, the driver can be configured either in a single stage for a high power factor (PF) and high efficiency or in the second stage of a two-stage solution for alleviating harmful low-frequency flicker. The proposed driver-integrated circuit is implemented in a 0.35-μm high-voltage CMOS process and tested under 110-VAC 60-Hz input. Measurement results show that, when operating in the high PF configuration, the proposed driver achieves 95.1% power efficiency and 0.986 PF. For the low flicker configuration, it achieves 92% efficiency and 15% flicker while maintaining a 0.918 PF.

Формирование шкал времени устройств частотно-временного обеспечения методом структурного анализа

The relevance of reliable high-precision navigation is confirmed by the organizational structure of the satellite radio navigation system (SRNS) GLONASS, in which there are no regular structures of electronic protection, in contrast to the American SRNS GPS, provided with standard systems “Select available” and “Antispoofing”. Under these conditions, it is necessary to constantly verify the reliability of the SRNS sync signals for the consumer, which is possible only with the formation of its own high-precision time scale. Own time scale provides verification of the reliability of navigation signals, “hot start” of the navigation equipment of the consumer, reducing the integration limits of time periods when solving the navigation task. Compensating for the error of low-frequency flicker noise by optimal filtering is a complex problem due to nonstationary. For the organization of optimal filtering, it is necessary to determine the correlation function and estimate the filtering by dispersion, which is unattainable for non-stationary processes. This problem is solved in this paper by applying the Kolmogorov theory to form a time scale using the mathematical apparatus of structural analysis.

Low offset frequency 1/f flicker noise in spin-torque vortex oscillators

Low-frequency noise close to the carrier remains little explored in spin-torque nano-oscillators. However, it is crucial to investigate as it limits the oscillator's frequency stability. This work addresses the low offset frequency flicker noise of a spin-torque vortex oscillator in the regime of large-amplitude steady oscillations. We first phenomenologically expand the nonlinear auto-oscillator theory, aiming to reveal the properties of this noise. We then present a thorough experimental study of the oscillator's $1/f$ flicker noise and discuss the results based on the theoretical predictions. Thereby, we connect the oscillator's nonlinear dynamics with the concept of flicker noise and furthermore refer to the influence of a standard $1/f$ noise description based on the Hooge formula, taking into account the nonconstant magnetic oscillation volume, which contributes to the magnetoresistance.

Temporal whole field sawtooth flicker without a spatial component elicits a myopic shift following optical defocus irrespective of waveform direction in chicks

PurposeMyopia (short-sightedness) is the commonest visual disorder and greatest risk factor for sight threatening secondary pathologies. Myopia and hyperopia can be induced in animal models by rearing with optical lens defocus of opposite sign. The degree of refractive compensation to lens-induced defocus in chicks has been shown to be modified by directionally drifting sawtooth spatio-temporal luminance diamond plaids, with Fast-ON sawtooth spatio-temporal luminance profiles inhibiting the myopic shift in response to negative lenses, and Fast-OFF profiles inhibiting the hyperopic shift in response to positive lenses. What is unknown is whether similar sign-of-defocus dependent results produced by spatio-temporal modulation of sawtooth patterns could be achieved by rearing chicks under whole field low temporal frequency sawtooth luminance profiles at 1 or 4 Hz without a spatial component, or whether such stimuli would indiscriminately elicit a myopic shift such as that previously shown with symmetrical (or near-symmetrical) low frequency flicker across a range of species.MethodsHatchling chicks (n = 166) were reared from days five to nine under one of three defocus conditions (No Lens, +10D lens, or −10D lens) and five light conditions (No Flicker, 1 Hz Fast-ON/Slow-OFF sawtooth flicker, 4 Hz Fast-ON/Slow-OFF sawtooth flicker, 1 Hz Fast-OFF/Slow-ON sawtooth flicker, or 4Hz Fast-OFF/Slow-ON sawtooth flicker). The sawtooth flicker was produced by light emitting diodes (white LEDs, 1.2 –183 Lux), and had no measurable dark phase. Biometrics (refraction and ocular axial dimensions) were measured on day nine.ResultsBoth 1 Hz and 4 Hz Fast-ON and Fast-OFF sawtooth flicker induced an increase in vitreous chamber depth that was greater in the presence of negative compared to positive lens defocus. Both sawtooth profiles at both temporal frequencies inhibited the hyperopic shift in response to +10D lenses, whilst full myopic compensation (or over-compensation) in response to −10D lenses was observed.ConclusionsWhole field low temporal frequency Fast-ON and Fast-OFF sawtooth flicker induces a generalized myopic shift, similar to that previously shown for symmetrical sine-wave and square-wave flicker. Our findings highlight that temporal modulation of retinal ON/OFF pathways per se (without a spatial component) is insufficient to produce strong sign-of-defocus dependent effect.

A low-power 33 pJ/conversion-step 12-bit SAR resistance-to-digital converter for microsensors

In this paper, a low-power 12-bit successive approximation register (SAR) resistance-to-digital converter (RDC) for resistive microsensors with a figure-of-merit (FoM) of 33 pJ/conversion-step is presented. In the conventional resistive analog front-end (AFE), two-step conversion schemes, including a resistance-to-voltage converter and a voltage-to-digital converter are generally used. The presented SAR RDC can directly convert the resistance changes to digital codes. The proposed SAR RDC consists of a comparing stage, and a SAR operating stage. The preamplifier of comparing stage implements a correlated double sampling (CDS) technique to improve the low-noise characteristic and reduce the low-frequency flicker (1/f) noise. The RDC is designed using SAR scheme to achieve low-power consumption. The SAR RDC achieves a wide input resistance range of 2 MΩ. The SAR RDC is implemented with a 0.18 μm standard complementary metal–oxide–semiconductor (CMOS) process with an active area of 0.35 mm2. All functional blocks, including voltage and current references, oscillators, and timing generators, are integrated on the chip. The proposed RDC consumes 93.2 μW with 1.8 V power supply. The experimental results of the proposed SAR RDC achieve 11.3-bit resolution within a conversion time of 0.92 ms and a figure-of-merit (FoM) of 33 pJ/conversion-step.

A Highly Accurate Current LED Lamp Driver With Removal of Low-Frequency Flicker Using Average Current Control Method

This paper presents an average current control method for a light-emitting diode (LED) lamp driver that achieves a highly accurate current and removes low-frequency light flicker. The proposed LED lamp driver accurately maintains an average LED forward current by precisely adjusting the duration of the on- and off-times of the LED lamp driver. It also removes the low-frequency flicker by regulating the LED forward current without being affected by the low-frequency component of the ac line voltage. In addition, it reduces power consumption by eliminating the necessity of a high-voltage sensor or a high-side resistor, which causes conduction loss. The proposed average current controller was fabricated using a 0.18 μm bipolar, complementary metal-oxide-semiconductor, and double diffused metal-oxide-semiconductor process technology. The measurement results of the proposed LED lamp driver show that the variation in the average LED forward current is less than 0.6%, and the light flicker below 120 Hz is completely removed. In addition, the measured maximum power efficiency and power factor of the proposed LED lamp driver are 89.22% and 0.93, respectively.

An AC Input Inductor-Less LED Driver for Efficient Lighting and Visible Light Communication

This paper presents an ac-powered inductor-less light-emitting diode (LED) driver, which can simultaneously provide efficient illumination and data transmission capability by modulating light output. The proposed driver does not have passive components’ speed limitation compared to the conventional switching converter-based driving solutions for visible light communication (VLC). Besides this, harmful low-frequency flicker is mitigated with an accurate 1/ ${x}$ circuit and the dimming compensation method. In addition, the digitalized power stage and controller utilized in the proposed driver can achieve smooth transitions among multiple current paths, while the keep-and-restore technique and auxiliary turn-on switch help to further increase the VLC data rate. The integrated circuit of the proposed driver is implemented and fabricated with a 0.35- $\mu \text{m}$ , 120-V high-voltage CMOS process. Measurement results show that under a 110- $V_{\text {AC}}$ , 60-Hz input, the peak efficiency of the proposed design is over 89% and the low-frequency flicker is reduced to below 10%. The driver supports up to 8-Mb/s on–off keying non-return-to-zero data transmission for a 1-m distance between the LED module and the receiver.

Signal and Noise in FET-Nanopore Devices.

The combination of a nanopore with a local field-effect transistor (FET-nanopore), like a nanoribbon, nanotube, or nanowire, in order to sense single molecules translocating through the pore is promising for DNA sequencing at megahertz bandwidths. Previously, it was experimentally determined that the detection mechanism was due to local potential fluctuations that arise when an analyte enters a nanopore and constricts ion flow through it, rather than the theoretically proposed mechanism of direct charge coupling between the DNA and nanowire. However, there has been little discussion on the experimentally observed detection mechanism and its relation to the operation of real devices. We model the intrinsic signal and noise in such an FET-nanopore device and compare the results to the ionic current signal. The physical dimensions of DNA molecules limit the change in gate voltage on the FET to below 40 mV. We discuss the low-frequency flicker noise (<10 kHz), medium-frequency thermal noise (<100 kHz), and high-frequency capacitive noise (>100 kHz) in FET-nanopore devices. At bandwidths dominated by thermal noise, the signal-to-noise ratio in FET-nanopore devices is lower than in the ionic current signal. At high frequencies, where noise due to parasitic capacitances in the amplifier and chip is the dominant source of noise in ionic current measurements, high-transconductance FET-nanopore devices can outperform ionic current measurements.

Further Characterization of the Predominant Inner Retinal Degeneration of Aging Cln3 Δex7/8 Knock-In Mice.

Neuronal ceroid lipofuscinosis (NCL) is the most common group of neurogenetic storage diseases typically beginning in childhood. The juvenile form (JNCL), also known as Batten disease, is the most common form. Vision-related problems are often an early sign, appearing prior to motor and mental deficits. We have previously investigated disease progression with age in the Cln3 Δex7/8 KI mouse model for JNCL and showed a decline of visual acuity and a predominant decline of the inner retinal function in mice, similar to human disease. The aim of this study was to further characterize this degeneration by means of flicker ERGs. For the scotopic flicker ERG, we found a significantly lower magnitude for Cln3 Δex7/8 KI mice already at 6months of age for low stimulus frequencies, while the difference declines with increasing frequency. Under photopic conditions there was no magnitude difference at 6months, but a cumulative magnitude reduction with further aging. For both conditions the phases were similar for both groups. There was a similar magnitude reduction for the responses of both the slow and fast rod pathway in the 15 Hz experiments, and there were no differences in response phase. Low-frequency flicker responses seem to be sensitive to very early disease manifestations, and while the degeneration is associated with a reduction of predominating inner retinal responses in the scotopic flash ERG, this predominance seems not to be related to a selective involvement of the slow and fast rod pathways.

Oxide thickness dependent compact model of channel noise for E-mode AlGaN/GaN MOS-HEMT

In this paper, a compact channel noise model for gate recessed enhancement mode GaN based MOS-HEMT which is valid for all regions of operation is proposed. The compact noise model consists of high frequency thermal noise and low frequency flicker noise. The drain current, which is one of the most important parameters for compact noise model is developed by incorporating interface and oxide traps, mobility degradation due to vertical electric field, velocity saturation effect and self-heating effect. The flicker noise model is derived by considering mobility and carrier fluctuation due to traps present in both oxide and interface layer. The thermal noise and flicker noise models are validated by comparing the results with TCAD simulation and experimental results from literature respectively. Effect of thermal and flicker noise power spectral density (PSD) variation with different oxide thickness has also been analyzed.

A high-resolution tunneling magneto-resistance sensor interface circuit

In this paper, a chopper instrumentation amplifier and a high-precision and low-noise CMOS band gap reference in a standard 0.5 [Formula: see text] CMOS technology for a tunneling magneto-resistance (TMR) sensor is presented. The noise characteristic of TMR sensor is an important factor in determining the performance of the sensor. In order to obtain a larger signal to noise ratio (SNR), the analog front-end chip ASIC weak signal readout circuit of the sensor includes the chopper instrumentation amplifier; the high-precision and low-noise CMOS band gap reference. In order to achieve the low noise, the chopping technique is applied in the first stage amplifier. The low-frequency flicker noise is modulated to high-frequency by chopping switch, so that the modulator has a better noise suppression performance at the low frequency. The test results of interface circuit are shown as below: At a single 5 V supply, the power dissipation is 40 mW; the equivalent offset voltage is less than 10 uV; the equivalent input noise spectral density 30 nV/Hz[Formula: see text](@10 Hz), the equivalent input noise density of magnetic is 0.03 nTHz[Formula: see text](@10 Hz); the scale factor temperature coefficient is less than 10 ppm/[Formula: see text]C, the equivalent input offset temperature coefficient is less than 70 nV/[Formula: see text]C; the gain error is less than 0.05%, the common mode rejection ratio is greater than 120 dB, the power supply rejection ratio is greater than 115 dB; the nonlinear is 0.1% FS.

SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst

We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOI/SOAR during two nights along the decline of a superoutburst in 2006 Sep 12-24 and in quiescence over 50 days following the superoutburst. Three-dimensional eclipse mapping of the outburst light curves indicates that the accretion disc is elliptical (eccentricity e=0.13) and that superhump maximum occurs when the mass donor star is aligned with the bulge of the elliptical disc. The accretion disc is geometrically thin both in outburst and in quiescence; it fills the primary Roche lobe in outburst and shrinks to about half this size in quiescence. The stability of the eclipse shape, width and depth along quiescence and the derived disc surface brightness distribution indicate that the quiescent accretion disc is in a high-viscosity, steady-state. Flickering mapping of the quiescent data reveal that the low-frequency flickering arises from an azimuthally-extended stream-disc impact region at disc rim and from the innermost disc region, whereas the high-frequency flickering originates in the accretion disc. Assuming the disc-related flickering to be caused by fluctuations in the energy dissipation rate induced by magneto-hydrodynamic turbulence (Gertseema & Achterberg 1992), we find that the quiescent disc viscosity parameter is large (alpha ~ 0.2-0.4) at all radii. The high-viscosity quiescent disc and the inferred low disc temperatures in superoutburst are inconsistent with expectations of the disc-instability model, and lead to the conclusion that the outbursts of V4140 Sgr are powered by mass transfer bursts from its donor star.

Low-Frequency Noise in Gate Tunable Topological Insulator Nanowire Field Emission Transistor near the Dirac Point**Supported by the National Basic Research Program of China under Grant No 2012CB921703, the National Natural Science Foundation of China under Grant Nos 11174357 and 11574379, and the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB07010300.

Low-frequency flicker noise is usually associated with material defects or imperfection of fabrication procedure. Up to now, there is only very limited knowledge about flicker noise of the topological insulator, whose topologically protected conducting surface is theoretically immune to back scattering. To suppress the bulk conductivity we synthesize antimony doped Bi2Se3 nanowires and conduct transport measurements at cryogenic temperatures. The low-frequency current noise measurement shows that the noise amplitude at the high-drain current regime can be described by Hooge's empirical relationship, while the noise level is significantly lower than that predicted by Hooge's model near the Dirac point. Furthermore, different frequency responses of noise power spectrum density for specific drain currents at the low drain current regime indicate the complex origin of noise sources of topological insulator.

Reducing flicker noise in chemical vapor deposition graphene field-effect transistors

Single-layer graphene derived from chemical vapor deposition (CVD) holds promise for scalable radio frequency (RF) electronic applications. However, prevalent low-frequency flicker noise (1/f noise) in CVD graphene field-effect transistors is often up-converted to higher frequencies, thus limiting RF device performance. Here, we achieve an order of magnitude reduction in 1/f noise in field-effect transistors based on CVD graphene transferred onto silicon oxide substrates by utilizing a processing protocol that avoids aqueous chemistry after graphene transfer. Correspondingly, the normalized noise spectral density (10−7–10−8 μm2 Hz−1) and noise amplitude (4 × 10−8–10−7) in these devices are comparable to those of exfoliated and suspended graphene. We attribute the reduction in 1/f noise to a decrease in the contribution of fluctuations in the scattering cross-sections of carriers arising from dynamic redistribution of interfacial disorder.

Observation of reduced 1/f noise in graphene field effect transistors on boron nitride substrates

We have investigated the low frequency (f) flicker (also called 1/f) noise of single-layer graphene devices on h-BN (placed on SiO2/Si) along with those on SiO2/Si. We observe that the devices fabricated on h-BN have on average one order of magnitude lower noise amplitude compared with devices fabricated on SiO2/Si despite having comparable mobilities at room temperature. We associate this noise reduction to the lower densities of impurities and trap sites in h-BN than in SiO2. Furthermore, the gate voltage dependent noise amplitude shows a broad maximum at Dirac point for devices on h-BN, in contrast to the M-shaped behavior showing a minimum at Dirac point for devices on SiO2, consistent with the reduced charge inhomogeneity (puddles) for graphene on h-BN. This study demonstrates that the use of h-BN as a substrate or dielectric can be a simple and efficient noise reduction technique valuable for electronic applications of graphene and other nanomaterials.

Numerical investigation of symmetry breaking and critical behavior of the acoustic streaming field in high-intensity discharge lamps

For energy efficiency and material cost reduction it is preferred to drive high-intensity discharge lamps at frequencies of approximately 300 kHz. However, operating lamps at these high frequencies bears the risk of stimulating acoustic resonances inside the arc tube, which can result in low frequency light flicker and even lamp destruction. The acoustic streaming effect has been identified as the link between high frequency resonances and low frequency flicker. A highly coupled three-dimensional multiphysics model has been set up to calculate the acoustic streaming velocity field inside the arc tube of high-intensity discharge lamps. It has been found that the velocity field suffers a phase transition to an asymmetrical state at a critical acoustic streaming force. In certain respects the system behaves similar to a ferromagnet near the Curie point. It is discussed how the model allows to investigate the light flicker phenomenon. Concerning computer resources the procedure is considerably less demanding than a direct approach with a transient model.

The frequency-response electroretinogram distinguishes cone and abnormal rod function in rd12 mice.

Early studies on Rpe65 knockout mice reported that remaining visual function was attributable to cone function. However, this finding has been challenged more and more as time has passed. Electroretinograms (ERGs) showed that rd12 mice, a spontaneous animal model of RPE65 Leber’s congenital amaurosis, had sizeable photopic responses. Unfortunately, the recorded ERG waveform was difficult to interpret because of a remarkably delayed peak-time, which resembles a rod response more than a cone response. Here, we compare flicker ERGs in animals with normal rod and cone function (C57BL/6J mice), pure rod function (cpfl5 mice), and pure cone function (Rho-/- mice) under different adaptation levels and stimulus intensities. These responses were then compared with those obtained from rd12 mice. Our results showed that normal rods respond to low frequency flicker (5 and 15 Hz) and that normal cones respond to both low and high frequency flicker (5–35 Hz). As was seen in cpfl5 mice, rd12 mice had recordable responses to low frequency flicker (5 and 15Hz), but not to high frequency flicker (25 and 35 Hz). We hypothesize that abnormal rods may be the source of residual vision in rd12 mice, which is proved correct here with double mutant rd12mice. In this study, we show, for the first time, that frequency-response ERGs can effectively distinguish cone- and rod-driven responses in the rd12 mouse. It is another simple and valid method for evaluating the respective contributions of retinal rods and cones.

Design and Implementation of a 46-kS/s CMOS SC Dual-Mode Capacitive Sensor Interface With 50-dB SNR and 0.7% Nonlinearity

This paper presents the design and implementation of a 46-kS/s CMOS switch-capacitor dual-mode capacitive sensor interface circuit for inkjet-printed capacitive humidity sensors. The specifications of the interface circuit, which includes a capacitance-to-voltage (C2V) converter combined with an analog-to-digital converter (ADC), are optimized at system level, emphasizing the C2V operation followed by the data converter. A closed form of the maximum output range of a single-stage C2V is provided to prevent cascade amplification. The gain-boosting technique is utilized in the operational transconductance amplifier design to improve the closed-loop linearity. The correlated double sampling technique attenuates the dc offset and low-frequency flicker noise from C2V. A 10-b successive approximation register ADC digitizes the output of C2V. The total area of the digital-to-analog (DAC) array is limited not only by the matching behavior, but also by the noise performance of C2V. The rail-to-rail ability is required to render the compatibility with various possible sensor inputs. A single-ended cascaded binary-weighted capacitive DAC is used to implement the charge redistribution binary search algorithm. The circuit is implemented in a 0.18- mu m CMOS technology and occupies an area of 1.2 mm(2). The tested prototype shows 0.69% nonlinearity in mode 1 and 1.38% nonlinearity in mode 2. The SNR of mode 1 is 50.1 dB and that of mode 2 is 36.5 dB, which meets the specification of 7.32 b in mode 1 and 5.32 b in mode 2. The total power consumption of the capacitive sensor interface is 70 mu W.

1/fNoise from Glauber Dynamics: Self-Consistent Interaction and Temperature Dependent Correlations

Low frequency flicker noise has been argued to occur in spatially extended metastable systems near a critical point (Bak et al., 1987). An Ising-Glauber model based method is suggested here to systematically obtain temperature dependentnth-order correlation functions forNarbitrary interacting two-level systems (TLSs). This model is fully consistent with existing methods to calculate1/fnoise spectra from TLSs and complements them. However, with as such noa prioriassumptions on the typical log normal distribution of fluctuation rates, it is shown that1/fαnoise manifests in two different cases: first in the thermodynamic limit on a 2D lattice with long range antiferromagnetic interactions at low temperatures and second in the case of a statistical ensemble of finite-sized spin clusters representing disorder, but where each cluster is ordered due to ferromagnetic interactions.