In this paper, we propose a method to reduce a flicker (1/f) noise upconversion in voltage-biased RF oscillators. Excited by a harmonically rich tank current, a typical oscillation voltage waveform ...is observed to have asymmetric rise and fall times due to even-order current harmonics flowing into the capacitive part, as it presents the lowest impedance path. The asymmetric oscillation waveform results in an effective impulse sensitivity function of a nonzero dc value, which facilitates the 1/f noise upconversion into the oscillator's 1/f3 phase noise. We demonstrate that if the ω 0 tank exhibits an auxiliary resonance at 2ω 0 , thereby forcing this current harmonic to flow into the equivalent resistance of the 2ω 0 resonance, then the oscillation waveform would be symmetric and the flicker noise upconversion would be largely suppressed. The auxiliary resonance is realized at no extra silicon area in both inductor-and transformer-based tanks by exploiting different behaviors of inductors and transformers in differential-and common-mode excitations. These tanks are ultimately employed in designing modified class-D and class-F oscillators in 40 nm CMOS technology. They exhibit an average flicker noise corner of less than 100 kHz.
Building owners are transitioning towards a smart lighting solution for illumination purposes. LED (Light Emitting Diode) lighting application has become a norm given its high efficacy and energy ...efficiencies. This paper presents an approach to monitor the percent flicker conformance of interior building lighting to international standards. The focus is on flickers induced by LED lightings. This experiment utilises a TCS34725 RGB (red, green, blue) colour sensor to measure the flicker parameters of interior lighting spaces. Light-sensitive photodiodes in the sensor detect changes in lighting intensity, and output digitised values. A Raspberry Pi4 minicomputer processes the data measured for comparison to several standards. Non-conformance is reported to building owners to take corrective actions and minimise flicker discomfort exposure to building occupants. A flicker risk level factor is determined to gauge the severity when flickers are present. This method may be used to replace luminaires or fix flickering lighting issues in buildings. The results show that the monitoring system is functional. The proposed measurement and data processing method can be incorporated into any smart building hub for automation and building performance analysis. The method may also be used to measure non-LED lighting flickers.
Summary
Recently, both utilities and consumers have paid great attention to voltage fluctuation (flicker) problem, which is defined as low‐frequency fluctuation on the base signal of voltage. For ...mitigating the flicker, identification of its source is the first step. In this paper, a new method is proposed for identifying the location of flicker sources in a multi‐flicker sources power network in a more reliable and precise manner by a minimum number of monitoring points. This method is based on the wavelet transform (WT), the approximate model of the line and flicker power theory. In addition, in this method, a new factor is proposed for determining the contributions of individual consumers and utility providers in the global flicker level of a common coupling bus‐bar. For validating the performance of the proposed method, comprehensive simulations have been performed in MATLAB environment on a single‐ and multi‐flicker sources system based on IEEE 34 node test feeder. As proved by the results, the proposed method is able to identify the contributions and locations of flicker sources with higher reliability and accuracy compared with other methods.
Oscillator Flicker Phase Noise: A Tutorial Hu, Yizhe; Siriburanon, Teerachot; Staszewski, Robert Bogdan
IEEE transactions on circuits and systems. II, Express briefs,
02/2021, Letnik:
68, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A deep understanding of how to reduce flicker phase noise (PN) in oscillators is critical in supporting ultra-low PN frequency generation for the advanced communications and other emerging high-speed ...applications. Unfortunately, the current literature is either full of conflicting theories and ambiguities or too complex in mathematics, hiding the physical insights. In this brief, we comprehensively review the evolution of flicker noise upconversion theories and clarify their controversial and confusing parts. Two classes of such upconversion mechanisms in voltage-biased <inline-formula> <tex-math notation="LaTeX">LC </tex-math></inline-formula>-tank oscillators (nMOS-only and complementary) are specifically compared and numerically verified using a commercial simulation model of 28-nm CMOS. We identify that non-resistive terminations of both 2nd and 3rd harmonic currents contribute to oscillation waveform asymmetries that lead to the flicker noise upconversion. Further, we discuss three <inline-formula> <tex-math notation="LaTeX">1/f^{3} </tex-math></inline-formula> PN reduction mechanisms: waveform shaping, narrowing of conduction angle, and gate-drain phase shift.
The standing standardized measure for the assessment of flicker severity, the light flickermeter (IEC TR 61547-1:2020), evaluates the flicker irritability level in reference conditions as a necessary ...simplification. This misestimates the actual level in the presence of other factors known to influence flicker visibility. One such factor is noise, which interacts with the visual system under specific circumstances. However, direct effect of noise or any auditory stimuli on the flicker visibility threshold is not yet understood. This paper is concerned with the design of experiments aimed at determining whether the critical flicker frequency (CFF) is subject to change when the observer is exposed to pulsating sounds. The paper describes the work done in designing the experiments and also reveals data from a preliminary campaign. Data collected so far are insufficient to establish a direct link between pulsating sound and CFF, but are used to adjust the conditions of a wider campaign. Mathematical tools are developed to evaluate the experiment results using a probabilistic framework.
Humans perceive a stable average intensity image without flicker artifacts when a television or monitor updates at a sufficiently fast rate. This rate, known as the critical flicker fusion rate, has ...been studied for both spatially uniform lights, and spatio-temporal displays. These studies have included both stabilized and unstablized retinal images, and report the maximum observable rate as 50-90 Hz. A separate line of research has reported that fast eye movements known as saccades allow simple modulated LEDs to be observed at very high rates. Here we show that humans perceive visual flicker artifacts at rates over 500 Hz when a display includes high frequency spatial edges. This rate is many times higher than previously reported. As a result, modern display designs which use complex spatio-temporal coding need to update much faster than conventional TVs, which traditionally presented a simple sequence of natural images.
For over 150 years, researchers have investigated the anti-predator function of animal patterns. However, this work has mainly focused on when prey remain still, and has only recently started to ...incorporate motion into the study of defensive coloration. As motion breaks camouflage, a new challenge is to understand how prey avoid predators while moving around their environment, and if a moving prey can ever be camouflaged. We propose that there is a solution to this, in that a ‘flicker fusion effect’ can change the appearance of the prey in the eyes of their predators to reduce the chances of initial detection. This effect occurs when a high contrast pattern blurs at speed, changing the appearance of the prey, which may help them better match their background. Despite being widely discussed in the literature, the flicker fusion effect is poorly described, there is no clear theoretical framework for testing how it might reduce predation, and the terminology describing it is, at best, rather confusing. Our review addresses these three key issues to enable researchers to formulate precise predictions about when the flicker fusion effect occurs, and to test how it can reduce predation.
The fight against terrorist threats is highly relevant in the modern world. When developing devices for countering terrorism, their reliability and stability are very important. One such device is a ...device for detecting people behind optically opaque obstacles, which can detect the movement of people behind a wall and determine their number. However, the influence of interference effects that occur when summing up the reflected signals arriving by different propagation paths and, accordingly, having different phase shifts, leads to the fact that the observed image of the target can flicker and even disappear from the device screen for a considerable time, which is unacceptable in combat conditions. This article discusses various ways to eliminate interference, and on the basis of theoretical calculations, the most effective and cost-effective ways to eliminate the influence of interference effects in devices for detecting people behind optically opaque barriers are proposed. The obtained theoretical conclusions are confirmed experimentally.
This review presents the current knowledge of the usage of critical flicker fusion frequency (CFF) in human and animal model studies. CFF has a wide application in different fields, especially as an ...indicator of cortical arousal and visual processing. In medicine, CFF may be helpful for diagnostic purposes, for example in epilepsy or minimal hepatic encephalopathy. Given the environmental studies and a limited number of other methods, it is applicable in diving and hyperbaric medicine. Current research also shows the relationship between CFF and other electrophysiological methods, such as electroencephalography. The human eye can detect flicker at 50-90 Hz but reports are showing the possibility to distinguish between steady and modulated light up to 500 Hz. Future research with the use of CFF is needed to better understand its utility and application.
Eliminating the flickers in digital images captured by rolling shutter cameras is a fundamental and important task in computer vision applications. The flickering effect in a single image stems from ...the mechanism of asynchronous exposure of rolling shutters employed by cameras equipped with CMOS sensors. In an artificial lighting environment, the light intensity captured at different time intervals varies due to the fluctuation of the power grid, ultimately resulting in the flickering artifact in the image. Up to date, there are few studies related to single image deflickering. Further, it is even more challenging to remove flickers without a priori information, e.g., camera parameters or paired images. To address these challenges, we propose an unsupervised framework termed DeflickerCycleGAN, which is trained on unpaired images for end-to-end single image deflickering. Besides the cycle-consistency loss to maintain the similarity of image contents, we meticulously design another two novel loss functions, i.e., gradient loss and flicker loss, to reduce the risk of edge blurring and color distortion. Moreover, we provide a strategy to determine whether an image contains flickers or not without extra training, which leverages an ensemble methodology based on the output of two previously trained markovian discriminators. Extensive experiments on both synthetic and real datasets show that our proposed DeflickerCycleGAN not only achieves excellent performance on flicker removal in a single image but also shows high accuracy and competitive generalization ability on flicker detection, compared to that of a well-trained classifier based on ResNet50.
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