Showing papers on "Noise (electronics) published in 2013"

Low-frequency 1/ f noise in graphene devices

Abstract: Low-frequency noise with a spectral density that depends inversely on frequency has been observed in a wide variety of systems including current fluctuations in resistors, intensity fluctuations in music and signals in human cognition. In electronics, the phenomenon, which is known as 1/f noise, flicker noise or excess noise, hampers the operation of numerous devices and circuits, and can be a significant impediment to the development of practical applications from new materials. Graphene offers unique opportunities for studying 1/f noise because of its two-dimensional structure and widely tunable two-dimensional carrier concentration. The creation of practical graphene-based devices will also depend on our ability to understand and control the low-frequency noise in this material system. Here, the characteristic features of 1/f noise in graphene and few-layer graphene are reviewed, and the implications of such noise for the development of graphene-based electronics including high-frequency devices and sensors are examined.

Observation of Radiation Pressure Shot Noise on a Macroscopic Object

Abstract: The quantum mechanics of position measurement of a macroscopic object is typically inaccessible because of strong coupling to the environment and classical noise. In this work, we monitor a mechanical resonator subject to an increasingly strong continuous position measurement and observe a quantum mechanical back-action force that rises in accordance with the Heisenberg uncertainty limit. For our optically based position measurements, the back-action takes the form of a fluctuating radiation pressure from the Poisson-distributed photons in the coherent measurement field, termed radiation pressure shot noise. We demonstrate a back-action force that is comparable in magnitude to the thermal forces in our system. Additionally, we observe a temporal correlation between fluctuations in the radiation force and in the position of the resonator.

On the definition of signal-to-noise ratio and contrast-to-noise ratio for FMRI data.

Abstract: Signal-to-noise ratio, the ratio between signal and noise, is a quantity that has been well established for MRI data but is still subject of ongoing debate and confusion when it comes to fMRI data. fMRI data are characterised by small activation fluctuations in a background of noise. Depending on how the signal of interest and the noise are identified, signal-to-noise ratio for fMRI data is reported by using many different definitions. Since each definition comes with a different scale, interpreting and comparing signal-to-noise ratio values for fMRI data can be a very challenging job. In this paper, we provide an overview of existing definitions. Further, the relationship with activation detection power is investigated. Reference tables and conversion formulae are provided to facilitate comparability between fMRI studies.

Properties of nonlinear noise in long, dispersion-uncompensated fiber links.

Abstract: We study the properties of nonlinear interference noise (NLIN) in fiber-optic communications systems with large accumulated dispersion. Our focus is on settling the discrepancy between the results of the Gaussian noise (GN) model (according to which NLIN is additive Gaussian) and a recently published time-domain analysis, which attributes drastically different properties to the NLIN. Upon reviewing the two approaches we identify several unjustified assumptions that are key in the derivation of the GN model, and that are responsible for the discrepancy. We derive the true NLIN power and verify that the NLIN is not additive Gaussian, but rather it depends strongly on the data transmitted in the channel of interest. In addition we validate the time-domain model numerically and demonstrate the strong dependence of the NLIN on the interfering channels' modulation format.

Properties of nonlinear noise in long, dispersion-uncompensated fiber links

Abstract: We study the properties of nonlinear interference noise (NLIN) in fiber-optic communications systems with large accumulated dispersion. Our focus is on settling the discrepancy between the results of the Gaussian noise (GN) model (according to which NLIN is additive Gaussian) and a recently published time-domain analysis, which attributes drastically different properties to the NLIN. Upon reviewing the two approaches we identify several unjustified assumptions that are key in the derivation of the GN model, and that are responsible for the discrepancy. We derive the true NLIN power and verify that the NLIN is not additive Gaussian, but rather it depends strongly on the data transmitted in the channel of interest. In addition we validate the time-domain model numerically and demonstrate the strong dependence of the NLIN on the interfering channels' modulation format.

Design Considerations for Interleaved ADCs

Abstract: Interleaving can relax the power-speed tradeoffs of analog-to-digital converters and reduce their metastability error rate while increasing the input capacitance. This paper quantifies the benefits and derives an upper bound on the performance by considering kT/C noise and slewing requirements of the circuit driving the system. A frequency-domain analysis of interleaved converters is also presented that sheds light on the corruption mechanisms due to interchannel mismatches. A background timing mismatch calibration technique is proposed and experimentally shown to reduce the image to -75 dB for input frequencies exceeding 500 MHz.

Low-frequency electronic noise in single-layer MoS2 transistors.

Abstract: Ubiquitous low-frequency 1/f noise can be a limiting factor in the performance and application of nanoscale devices. Here, we quantitatively investigate low-frequency electronic noise in single-layer transition metal dichalcogenide MoS2 field-effect transistors. The measured 1/f noise can be explained by an empirical formulation of mobility fluctuations with the Hooge parameter ranging between 0.005 and 2.0 in vacuum (<10(-5) Torr). The field-effect mobility decreased, and the noise amplitude increased by an order of magnitude in ambient conditions, revealing the significant influence of atmospheric adsorbates on charge transport. In addition, single Lorentzian generation-recombination noise was observed to increase by an order of magnitude as the devices were cooled from 300 to 6.5 K.

Analyte sensors having a signal-to-noise ratio substantially unaffected by non-constant noise

Abstract: Systems and methods of use involving sensors having a signal-to-noise ratio that is substantially unaffected by non-constant noise are provided for continuous analyte measurement in a host. In some embodiments, a continuous analyte measurement system is configured to be wholly, transcutaneously, intravascularly or extracorporeally implanted.

Identification of power distribution network topology via voltage correlation analysis

Abstract: We consider the problem of reconstructing the topology of a portion of the power distribution network, given a dataset of voltage measurements. By using an approximate model for the grid voltage magnitudes, we show that these signals exhibit some specific correlation properties, that can be described via a sparse Markov random field. By specializing the tools available for the identification of graphical models, we propose an algorithm for the reconstruction of the grid topology. Via simulations, we show how the algorithm performs well also when an exact nonlinear model of the grid voltages is adopted, when realistic power demand profiles are considered, and when the voltage measurements are affected by measurement noise.

High-speed and high-efficiency superconducting nanowire single photon detector array.

Abstract: Superconducting nanowire single photon detectors (SNSPDs) have separately demonstrated high efficiency, low noise, and extremely high speed when detecting single photons. However, achieving all of these simultaneously has been limited by detector subtleties and tradeoffs. Here, we report an SNSPD system with <80 ps timing resolution, kHz noise count rates, and 76% fiber-coupled system detection efficiency in the low-flux limit at 1550 nm. We present a model for determining the detection efficiency penalty due to the detection recovery time, and we validate our method using experimental data obtained at high count rates. We demonstrate improved performance tradeoffs, such as 68% system detection efficiency, including losses due to detector recovery time, when coupled to a Poisson source emitting 100 million photons per second. Our system can provide limited photon number resolution, continuous cryogen-free operation, and scalability to future imaging and GHz-count-rate applications.

Low-Noise Wide-Band Amplifiers in Bipolar and CMOS Technologies

Abstract: 1 Introduction- 2 Noise in Integrated Circuits-Mechanisms and Models- 3 Low-Noise Wide-Band Amplifiers with Inductive Sources: Lamps- 4 Low-Noise Wide-Band Amplifiers with Capacitive Sources: Camps- 5 Low-Noise High-Speed CMOS Detector Readout Electronics- 6 General Conclusions

Random attractors for non-autonomous stochasticwave equations with multiplicative noise

Abstract: This paper is concerned with the asymptotic behavior of solutions of the damped non-autonomous stochastic wave equations driven by multiplicative white noise. We prove the existence of pullback random attractors in $H^1(\mathbb{R}^n) \times L^2(\mathbb{R}^n)$ when the intensity of noise is sufficiently small. We demonstrate that these random attractors are periodic in time if so are the deterministic non-autonomous external terms. We also establish the upper semicontinuity of random attractors when the intensity of noise approaches zero. In addition, we prove the measurability of random attractors even if the underlying probability space is not complete.

Theoretical analysis of mode instability in high-power fiber amplifiers

Abstract: We present a simple theoretical model of transverse mode instability in high-power rare-earth doped fiber amplifiers. The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo-optic effect, leading to transverse mode instability. The temporal and spectral characteristics of the instability dynamics are investigated, and it is shown that the instability can be seeded by both quantum noise and signal intensity noise, while pure phase noise of the signal does not induce instability. It is also shown that the presence of a small harmonic amplitude modulation of the signal can lead to generation of higher harmonics in the output intensity when operating near the instability threshold.

A study of fundamental limitations to statistical detection of redshifted H I from the epoch of reionization

Abstract: In this paper, we explore for the first time the relative magnitudes of three fundamental sources of uncertainty, namely, foreground contamination, thermal noise, and sample variance, in detecting the H I power spectrum from the epoch of reionization (EoR). We derive limits on the sensitivity of a Fourier synthesis telescope to detect EoR based on its array configuration and a statistical representation of images made by the instrument. We use the Murchison Widefield Array (MWA) configuration for our studies. Using a unified framework for estimating signal and noise components in the H I power spectrum, we derive an expression for and estimate the contamination from extragalactic point-like sources in three-dimensional k -space. Sensitivity for EoR H I power spectrum detection is estimated for different observing modes with MWA. With 1000 hr of observing on a single field using the 128 tile MWA, EoR detection is feasible (S/N >1 for k ≲ 0.8 Mpc -1 ). Bandpass shaping and refinements to the EoR window are found to be effective in containing foreground contamination, which makes the instrument tolerant to imaging errors. We find that for a given observing time, observing many independent fields of view does not offer an advantage over a single field observation when thermal noise dominates over other uncertainties in the derived power spectrum.

Surpassing Fundamental Limits of Oscillators Using Nonlinear Resonators

Abstract: In its most basic form an oscillator consists of a resonator driven on resonance, through feedback, to create a periodic signal sustained by a static energy source. The generation of a stable frequency, the basic function of oscillators, is typically achieved by increasing the amplitude of motion of the resonator while remaining within its linear, harmonic regime. Contrary to this conventional paradigm, in this Letter we show that by operating the oscillator at special points in the resonator’s anharmonic regime we can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit. We develop a comprehensive model that accounts for the major contributions to the phase noise of the nonlinear oscillator. Using a nanoelectromechanical system based oscillator, we experimentally verify the existence of a special region in the operational parameter space that enables suppressing the most significant contributions to the oscillator’s phase noise, as predicted by our model.

Variable Switching Frequency PWM for Three-Phase Converters Based on Current Ripple Prediction

Abstract: Compared with the widely used constant switching frequency pulse-width-modulation (PWM) method, variable switching frequency PWM can benefit more because of the extra freedom Based on the analytical expression of current ripple of three-phase converters, variable switching frequency control methods are proposed to satisfy different ripple requirements Switching cycle $T_{s}$ is updated in DSP in every interruption period based on the ripple requirement Two methods are discussed in this paper The first method is designed to arrange the current ripple peak value within a certain value and can reduce the equivalent switching frequency and electromagnetic interference (EMI) noise; the second method is designed to keep ripple current RMS value constant and reduce the EMI noise Simulation and experimental results show that variable switching frequency control could improve the performance of EMI and efficiency without impairing the power quality

Rate Gain Region and Design Tradeoffs for Full-Duplex Wireless Communications

Abstract: In this paper, we analytically study the regime in which practical full-duplex systems can achieve larger rates than an equivalent half-duplex systems. The key challenge in practical full-duplex systems is uncancelled self-interference signal, which is caused by a combination of hardware and implementation imperfections. Thus, we first present a signal model which captures the effect of significant impairments such as oscillator phase noise, low-noise amplifier noise figure, mixer noise, and analog-to-digital converter quantization noise. Using the detailed signal model, we study the rate gain region, which is defined as the region of received signal-of-interest strength where full-duplex systems outperform half-duplex systems in terms of achievable rate. The rate gain region is derived as a piecewise linear approximation in log-domain, and numerical results show that the approximation closely matches the exact region. Our analysis shows that when phase noise dominates mixer and quantization noise, full-duplex systems can use either active analog cancellation or baseband digital cancellation to achieve near-identical rate gain regions. Finally, as a design example, we numerically investigate the full-duplex system performance and rate gain region in typical indoor environments for practical wireless applications.

Waveguide integrated low noise NbTiN nanowire single-photon detectors with milli-Hz dark count rate

Abstract: Superconducting nanowire single-photon detectors are an ideal match for integrated quantum photonic circuits due to their high detection efficiency for telecom wavelength photons. Quantum optical technology also requires single-photon detection with low dark count rate and high timing accuracy. Here we present very low noise superconducting nanowire single-photon detectors based on NbTiN thin films patterned directly on top of Si3N4 waveguides. We systematically investigate a large variety of detector designs and characterize their detection noise performance. Milli-Hz dark count rates are demonstrated over the entire operating range of the nanowire detectors which also feature low timing jitter. The ultra-low dark count rate, in combination with the high detection efficiency inherent to our travelling wave detector geometry, gives rise to a measured noise equivalent power at the 10−20 W/Hz1/2 level.

An Improved Dipole-Moment Model Based on Near-Field Scanning for Characterizing Near-Field Coupling and Far-Field Radiation From an IC

Abstract: In this paper, an improved dipole-moment model for characterizing near-field coupling and far-field radiation from an IC based on near-field scanning is proposed. An array of electric and magnetic dipole moments is used to reproduce the field distributions in a scanning plane above an IC. These dipole moments can then be used as noise sources for the IC. In order to ensure the accurate prediction of the near-field coupling from the IC, the regularization technique and the truncated singular-value decomposition method are investigated in this paper, together with the conventional least-squares method, to reconstruct the dipole moments from the near-field scanning data. A simple example is used to demonstrate the approach. The improved dipole-moment model is particularly useful for addressing radio-frequency interference issues where near-field noise coupling needs to be accurately analyzed.

Precise determination of the spectroscopic g-factor by use of broadband ferromagnetic resonance spectroscopya)

Abstract: We demonstrate that the spectroscopic g-factor can be determined with high precision and accuracy by broadband ferromagnetic resonance measurements and by applying an asymptotic analysis to the data. Spectroscopic data used to determine the g-factor are always obtained over a finite range of frequencies, which can result in significant errors in the fitted values. We show that by applying an asymptotic analysis to broadband datasets, precise values of the intrinsic g-factor can be determined with errors well below 1%, even when the exact form of the Kittel equation (which describes the relationship between the frequency and resonance field) is unknown. We demonstrate this methodology with measured data obtained for sputtered Ni80Fe20 (Permalloy) thin films of varied thicknesses, where we determine the bulk g-factor value to be 2.109 ± 0.003. Such an approach is further validated by application to simulated data that include both noise and an anisotropy that is not included in the Kittel equation that was ...

A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Abstract: We report Gemini-South GMOS observations of the exoplanet system WASP-29 during primary transit as a test case for differential spectrophotometry. We use the multi-object spectrograph to observe the target star and a comparison star simultaneously to produce multiple light curves at varying wavelengths. The 'white' light curve and fifteen 'spectral' light curves are analysed to refine the system parameters and produce a transmission spectrum from 515 to 720nm. All light curves exhibit time-correlated noise, which we model using a variety of techniques. These include a simple noise rescaling, a Gaussian process model, and a wavelet based method. These methods all produce consistent results, although with different uncertainties. The precision of the transmission spectrum is improved by subtracting a common signal from all the spectral light curves, reaching a typical precision of ~1x10^-4 in transit depth. The transmission spectrum is free of spectral features, and given the non-detection of a pressure broadened Na feature, we can rule out the presence of a Na rich atmosphere free of clouds or hazes, although we cannot rule out a narrow Na core. This indicates that Na is not present in the atmosphere, and/or that clouds/hazes play a significant role in the atmosphere and mask the broad wings of the Na feature, although the former is a more likely explanation given WASP-29b's equilibrium temperature of ~970 K, at which Na can form various compounds. We also briefly discuss the use of Gaussian process and wavelet methods to account for time correlated noise in transit light curves.

Origin of 1/f noise in graphene multilayers: Surface vs. volume

Abstract: Low-frequency noise with the spectral density S(f)∼1/fγ (f is the frequency and γ ≈ 1) is a ubiquitous phenomenon, which hampers operation of many devices and circuits. A long-standing question of particular importance for electronics is whether 1/f noise is generated on the surface of electrical conductors or inside their volumes. Using high-quality graphene multilayers, we were able to directly address this fundamental problem of the noise origin. Unlike the thickness of metal or semiconductor films, the thickness of graphene multilayers can be continuously and uniformly varied all the way down to a single atomic layer of graphene—the actual surface. We found that 1/f noise becomes dominated by the volume noise when the thickness exceeds ∼7 atomic layers (∼2.5 nm). The 1/f noise is the surface phenomenon below this thickness. The obtained results are important for continuous downscaling of conventional electronics and for the proposed graphene applications in sensors and communications.

Fundamental issues in nonlinear wideband-vibration energy harvesting.

Abstract: Mechanically nonlinear energy harvesters driven by broadband vibrations modeled as white noise are investigated. We derive an upper bound on output power versus load resistance and show that, subject to mild restrictions that we make precise, the upper-bound performance can be obtained by a linear harvester with appropriate stiffness. Despite this, nonlinear harvesters can have implementation-related advantages. Based on the Kramers equation, we numerically obtain the output power at weak coupling for a selection of phenomenological elastic potentials and discuss their merits.

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

Abstract: Shot noise originates from the discrete nature of optical field detection. By exploiting correlations in the shot-noise spectrum of optical pulse trains, scientists improve shot-noise-limited optical pulse timing measurements by several orders of magnitude. A photodetected pulse train timing noise floor at an unprecedented 25 zs Hz−1/2 is reported.

Integer and fractional charge Lorentzian voltage pulses analyzed in the framework of photon-assisted shot noise

Abstract: We study the injection $n$ of electrons in a quantum conductor using voltage pulses applied on a contact. We particularly consider the case of Lorentzian voltage pulses. When carrying integer charge, they are known to provide electronic states with a minimal number of excitations, while any other type of pulses are accompanied with a neutral cloud of electron and hole excitations. We focus on the low-frequency shot noise arising when the excitations are partitioned by a single scatterer. Using periodic pulses, the physics can be discussed in the framework of the photon-assisted shot noise. Pulses of arbitrary shape and arbitrary charge are shown to give a marked minimum in the noise when the charge is an integer. The energy-domain characterization of the charge pulse excitations is also given using the shot-noise spectroscopy which reveals the asymmetrical energy spectrum of Lorentzian pulses. Finally, time-domain information is obtained from Hong-Ou-Mandel--type noise correlations when two trains of pulses generated on opposite contacts collide on the scatterer. For integer Lorentzian, the noise versus the time delay between pulse trains is shown to give a measure of the electron wave-packet autocorrelation function. In order to make contact with recent experiments, all the calculations are made at zero and finite temperatures.

Rigid DNA Beams for High‐Resolution Single‐Molecule Mechanics

Abstract: Bridging the gap: Rigid DNA linkers (blue, see picture) between microspheres (green) for high-resolution single-molecule mechanical experiments were constructed using DNA origami. The resulting DNA helical bundles greatly reduce the noise generated in studies of conformation changes using optical tweezers and were applied to study small DNA secondary structures.

Fluctuations of 1 / f Noise and the Low-Frequency Cutoff Paradox

Abstract: Recent experiments on blinking quantum dots, weak turbulence in liquid crystals, and nanoelectrodes reveal the fundamental connection between 1/f noise and power law intermittency. The nonstationarity of the process implies that the power spectrum is random--a manifestation of weak ergodicity breaking. Here, we obtain the universal distribution of the power spectrum, which can be used to identify intermittency as the source of the noise. We solve in this case an outstanding paradox on the nonintegrability of 1/f noise and the violation of Parseval's theorem. We explain why there is no physical low-frequency cutoff and therefore why it cannot be found in experiments.

Exploring the effect of noise on the Berry phase

Abstract: We experimentally investigate the effects of noise on the adiabatic and cyclic geometric phase, also termed the Berry phase. By introducing artificial fluctuations in the path of the control field, we measure the geometric contribution to dephasing of an effective two-level system for a variety of noise powers and different paths. Our results, measured using a microwave-driven superconducting qubit, clearly show that only fluctuations which distort the path lead to geometric dephasing. In a direct comparison with the dynamic phase, which is path independent, we observe that the Berry phase is less affected by noise-induced dephasing. This observation directly points towards the potential of geometric phases for quantum gates or metrological applications.

Performance improvement of continuous-variable quantum key distribution via photon subtraction

Abstract: It has been found that non-Gaussian operations can be applied to increase and distill entanglement between Gaussian entangled states. We propose here a method to improve the performance of entanglement-based (EB) continuous-variable quantum-key-distribution protocol by using the non-Gaussian operation, in particular, the subtraction operation, which can be implemented under current technology easily. Security analysis shows that the subtraction operation can well increase the secure distance and tolerable excess noise of the EB scheme and also the corresponding prepare-and-measure scheme.