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We present the results of gas sensing using the fluctuation-enhanced sensing method in selected two-dimensional materials (2DMs). We claim that gas sensing selectivity can be improved further by considering semiconducting two-dimensional materials doped by noble metal nanoparticles. The 2DMs’ structures exhibit some imperfections defined by their structure, occurring repeatedly there. These imperfections are adsorption–desorption centers responsible for gas-sensing properties and generating flicker noise of various intensities. We consider how these imperfections can be modulated and utilized for fluctuations-enhanced gas sensing. We propose the decoration of 2DMs by noble metal nanoparticles that impact flicker noise. Additionally, we consider utilizing localized surface plasmonic resonance induced by irradiation at selected wavelengths. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents a novel active inductor (AI) to improve the performance of a down‐conversion active mixer in terms of conversion gain (CG) and flicker noise. The proposed AI exhibits negative resistance and partially flat inductance over a wide frequency band of 0.5–4.5 GHz. The effect of inserting the AI between the source of the switching quad of a Gilbert cell mixer is theoretically analyzed. The proposed inductor‐less mixer, designed to operate at a 2.4‐GHz RF input frequency and a 10‐MHz IF output frequency, employs current reuse and self‐forward body bias (SFBB) techniques. The proposed circuit is simulated in Cadence Spectre‐RF using RF‐TSMC 0.18‐μm CMOS technology. Post‐layout simulations demonstrate that the proposed AI significantly reduces flicker noise by over 23 dB at an IF output frequency of 1 kHz and improves the CG by over 16 dB at an RF frequency of 2.4 GHz. The proposed mixer achieves a CG of 37.6 dB and a flicker noise corner frequency of 6 kHz. Additionally, it exhibits a third‐order intermodulation intercept point (IIP3) of −5.2 dBm and a double‐sideband noise figure (DSB‐NF) of 6.1 dB at the IF output frequency of 10 MHz. Operating with a 1.5‐V supply, the proposed mixer consumes 10.6 mW of power. [ABSTRACT FROM AUTHOR]

A Sigma-Delta modulator (SDM) realized with a fully differential third-order single-loop cascaded integrator feedforward (CIFF) architecture is proposed. A pair of low-frequency chopper switches are nested outside the chopper amplifier to further reduce the residual offset voltage. To reduce the power consumption and ensure linearity, a high-speed dynamic comparator is also used to implement a one-bit quantizer. The proposed architecture and the corresponding functionality are first simulated in MATLAB Simulink at the behavioral level. The results show that the designed modulator has an SNDR of 124.9 dB corresponding to an ENOB of 20.46 bits at a clock frequency of 256 kHz and 312.5 Hz input with a differential-mode voltage of 700 mV sinusoidal waveform. Based on SMIC 180 nm/1.8 V standard CMOS process on the Cadence platform, the subcircuit-level simulation is also performed, while the result shows that the proposed modulator can effectively achieve 115.52 dB SNDR, 18.90-bit ENOB, and 8.40 mW power consumption, which correspond to FoM W and FoM schreier of 0.067 pJ/step and 163.27 dB, respectively. The proposed modulator shows a significant advantage to be applied for high-precision analog-to-digital conversion applications such as high-quality equipment for audio, ECG and EEG signal sensing. [ABSTRACT FROM AUTHOR]

This paper presents an extensive characterization of the low-frequency noise (LFN) at room temperature (RT) and cryogenic temperature (4.2K) of 40-nm bulk-CMOS transistors. The noise is measured over a wide range of bias conditions and geometries to generate a comprehensive overview of LFN in this technology. While the RT results are in-line with the literature and the foundry models, the cryogenic behavior diverges in many aspects. These deviations include changes with respect to RT in magnitude and bias dependence that are conditional on transistor type and geometry, and even an additional systematic Lorentzian feature that is common among individual devices. Furthermore, we find the scaling of the average LFN with the area and its variability to be similar between RT and 4.2K, with the cryogenic scaling reported systematically for the first time. The findings suggest that, as no consistent decrease of LFN at lower temperatures is observed while the white noise is reduced, the impact of LFN for precision analog design at cryogenic temperatures gains a more predominant role.

In this paper, we have investigated the flicker noise (1/ $f$ ) in 45-nm RFSOI NFETs for quantum computing applications. 1/ $f$ noise characterization and analysis were performed in linear region at cryogenic temperatures down to 10K. A Lorentzian-like noise is also observed depending on bias conditions, possibly due to the floating body of PDSOI. The extracted frequency exponent $(\gamma)$ shows an inverted U-shape behavior with temperature mainly attributed to non-uniform energy distribution of traps in the gate dielectric. The dominant source of 1/ $f$ noise is carrier number fluctuation. Thermal-activation behavior of 1/ $f$ noise is studied, which shows the traps responsible for noise are not thermally activated. Volume trap densities are also extracted from 300K down to 10K. The volume trap density increases with a decrease in temperature, but no significant increase in normalized noise is observed at cryogenic temperatures in the measured NFETs. The non-uniform distribution along with the thermal inactive behavior of traps over the studied temperature range is expected to be a plausible reason for the temperature-independent behavior of normalized noise.

The elementary jumps in the electron current through conducting filaments of two nanometer-sized virtual memristor structures consisting of a contact of a conductive atomic force microscope probe to the Si3N4 layer with the thickness of 6 nm deposited onto the n + + -Si(001) conductive substrates are investigated. These structures are: (S1) the Si3N4/Si film; (S2) the Si3N4/SiO2/Si stack, a similar structure with 2 nm SiO2 sublayer between the film and the substrate. Usually, such investigations are performed by the analysis of the waveform of this current with the aim of extracting the random telegraph noise (RTN). Here, we develop a new indirect method, which is based on the measurement of the spectrum of the low-frequency flicker noise in the current without extracting the RTN. We propose that the flicker noise is caused by the motion (drift/diffusion) of nitrogen ions via vacancies within and around the filament. The number of these ions is estimated by taking into account the geometrical parameters of the filament. This allows us to estimate the root mean square magnitude i 0 of the current jumps, which are caused by random jumps of nitrogen ions, and the number M of these ions. This is fundamental for understanding the elementary mechanisms of the electron current flowing through the filament and the resistive switching in memristor devices. [ABSTRACT FROM AUTHOR]

Temperature dependence of the low‐frequency electronic noise in NiOx/β‐Ga2O3 p–n heterojunction diodes is reported. The noise spectral density is of the 1/f‐type near room temperature but shows signatures of Lorentzian components at elevated temperatures and at higher current levels (f is the frequency). It is observed that there is an intriguing non‐monotonic dependence of the noise on temperature near T = 380 K. The Raman spectroscopy of the device structure suggests material changes, which results in reduced noise above this temperature. The normalized noise spectral density in such diodes is determined to be on the order of 10−14 cm2 Hz−1 (f = 10 Hz) at 0.1 A cm−2 current density. In terms of the noise level, NiOx/β‐Ga2O3 p–n diodes perform excellently for new technology and occupy an intermediate position among devices of various designs implemented with different ultra‐wide‐bandgap semiconductors. The obtained results are important for understanding the electronic properties of NiOx/β‐Ga2O3 heterojunctions and contribute to the development of noise spectroscopy as the quality assessment tool for new electronic materials and device technologies. [ABSTRACT FROM AUTHOR]

We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional materials exhibiting gas-sensing properties, are considered. We present measurement setups and noise-processing methods for gas detection. The chemoresistive sensors show various DC resistances requiring different flicker noise measurement approaches. Separate noise measurement setups are used for resistances up to a few hundred kΩ and for resistances with much higher values. Noise measurements in highly resistive materials (e.g., MoS2, WS2, and ZrS3) are prone to external interferences but can be modulated using temperature or light irradiation for enhanced sensing. Therefore, such materials are of considerable interest for gas sensing. [ABSTRACT FROM AUTHOR]

This article continues a series of publications by the authors with the results of studying the variations in electrical resistivity in four layers of the geoelectric section. Precision soundings using the VES method have been carried out on a stationary multielectrode array with a maximum spacing of the supply electrodes of 3 km in the central part of the Garm geophysical test site in Tajikistan daily for 12 years. As a result of observations, a profile containing about 4500 pickets was obtained. Unlike conventional soundings, each picket of this profile corresponds not to a geographic point, but to a certain point in time. For the inversion of the time profile, specially developed precision algorithms with additional regularization of the inverse problem are used. The solution error is controlled by numerical simulation methods, during which the direct and then the inverse VES problem is solved first for profiles simulating the experimental profile, and the actual solution errors are estimated. Analysis has shown that the error in calculating the seasonal component of resistivity variations in layers 1–4 is 1–2%, and the error for flicker noise is from 1.3 to 3%. In this case, the total amplitude of seasonal variations in resistivity in the upper layer is more than 50%, and in the second layer it is 5.5%; the amplitude of variations in flicker-noise components for the same layers is estimated as 54 and 24%, respectively. In this paper we analyze the effect of external (exogenous) factors on resistivity variations at different depths. The fact of a significant effect of the groundwater level and soil temperature on the resistivity of the upper layer of the section with a thickness of 1.5 m has been established. For temperature, the coefficient of proportionality averaged over the entire layer is –0.58 ± 0.12%/deg, for the groundwater level, it is –0.8%/cm. For the second layer of the section (depth 1.5–10.2 m), an exact coincidence of the form of the seasonal variation of resistivity and atmospheric pressure is found. This coincidence is not accidental, since both atmospheric pressure and resistivity in layer 2 are characterized by an anomalous form of seasonal variation with two maxima and two minima during the year, which is completely atypical for seasonal changes in resistivity. At the same time, for relatively higher frequency (HF) variations (periods from several days to several weeks), there is no correlation effect. The authors attribute the possible reason for the observed effect to pressure regulation of competitive sources of groundwater inflow into the aquifer confined to the second layer of the section. It is assumed that the salinity and conductivity of water in competing sources differ sharply, which is quite plausible from geological considerations. Changes in atmospheric pressure change the inflow of water from these two sources, which leads to a change in the conductivity of the layer. The inertia of water exchange processes determines the absence of dependence of resistivity on atmospheric pressure at relatively high frequencies and the presence of such a relationship for variations with a characteristic duration of more than a month. [ABSTRACT FROM AUTHOR]

This article reports an improvement in the low-frequency noise characteristics in hafnium oxide-based (HfO2) field-effect transistors by different precursor materials at ALD process. The Hafniumoxide on the devices were fabricated once with organic precursor materials and once with chloridic precursor materials. The investigation shows an improvement in the noise behavior when using chloridic precursor materials. Regarding the main noise source, which are divided into fluctuation of the number of carriers (ΔN) and fluctuation of the effective transistor mobility (Δμ), the results show that the devices fabricated with organic precursor materials show typical behavior of ΔN noise, where the devices fabricated with chloridic precursor materials show typical behavior of Δμ noise.

Abstract Temperature dependence of the low‐frequency electronic noise in NiOx/β‐Ga2O3 p–n heterojunction diodes is reported. The noise spectral density is of the 1/f‐type near room temperature but shows signatures of Lorentzian components at elevated temperatures and at higher current levels (f is the frequency). It is observed that there is an intriguing non‐monotonic dependence of the noise on temperature near T = 380 K. The Raman spectroscopy of the device structure suggests material changes, which results in reduced noise above this temperature. The normalized noise spectral density in such diodes is determined to be on the order of 10−14 cm2 Hz−1 (f = 10 Hz) at 0.1 A cm−2 current density. In terms of the noise level, NiOx/β‐Ga2O3 p–n diodes perform excellently for new technology and occupy an intermediate position among devices of various designs implemented with different ultra‐wide‐bandgap semiconductors. The obtained results are important for understanding the electronic properties of NiOx/β‐Ga2O3 heterojunctions and contribute to the development of noise spectroscopy as the quality assessment tool for new electronic materials and device technologies.

Stochastic computing (SC) is widely known for its high error tolerance and efficient computing ability of complex functions with remarkably simple logic gates. The noise of electronic devices is widely used to be the entropy source due to its randomness. Compared with thermal noise and random telegraph noise (RTN), flicker noise is favored by researchers because of its high noise density. Meanwhile, unlike using RRAM, PCRAM and other emerging memory devices as the entropy source, using logic devices does not require any additional process steps, which is significant for industrialization. In this work, we systematically and statistically studied the 1/f noise characteristics of 14 nm FinFET, and found that miniaturizing the channel area of the device or lowering the ambient temperature can effectively increase the 1/f noise density of the device. This is of great importance to improve the accuracy of the SC system and simplify the complexity of the stochastic number generator (SNG) circuit. At the same time, these rules of 1/f noise characteristics in FinFET devices can provide good guidance for our device selection in circuit design. [ABSTRACT FROM AUTHOR]

In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage ( V t ) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are investigated. We report for the first time the significant statistical differences between these two device aging phenomena. The V t shift is relatively uniform among all the devices and gradually evolves over time. By contrast, the RTN degradation is evidently abrupt and random in nature and only happens to a small percentage of devices. The generation of new RTN traps by HCI during times of stress is demonstrated both statistically and on the individual device level. An improved method is developed to identify RTN devices with degenerate amplitude histograms. [ABSTRACT FROM AUTHOR]

This paper presents an injection locked digitally controlled ring oscillator (IL-DCRO). To reduce jitter variations, minimize oscillator spurious signals, and eliminate periodical phase error, a double edge-injection (window injection) scheme with synchronized edge directions is proposed. A combinational edge generator is utilized to substitute the sequential edge generators for injection timing requirements relaxation. By biasing devices in deep triode, digitally controlled delay cells currents are adopted for frequency tuning. This helps reducing the devices flicker (1/f) noise and minimize the DCRO overall phase noise. At 1 MHz offset of frequency, the proposed oscillator has a measured phase noise of −125.95 dBc/Hz and −115.6 dBc/Hz at oscillation frequencies of 913.4 MHz and 432.6 MHz, respectively. Fabricated in 350 nm CMOS process, with a maximum power consumption of 3.3 mW, and oscillating at 913.4 MHz, this DCRO achieves a tuned oscillator figure of merit (FoM) of −197.35 dBc/Hz. The core area of this edge-injection-based DRCO is only 0.08 mm2. [ABSTRACT FROM AUTHOR]

We describe challenges encountered in the design of continuoustime delta-sigma modulators that target high resolution (>16 bits) over wide bandwidths (several hundreds of kHz). The linearity of the feedback DAC and flicker noise introduced by the loop filter are primary problems that need to be addressed. We describe two techniques that are inherently more linear than prior-art DACs, namely the virtual-ground-switched resistor DAC and the zapped virtual-ground-switched dual return-to-open DAC. Flicker noise can be eliminated by chopping, but one needs to pay careful attention to minimize chopping artifacts. Example multi-bit and singlebit designs achieving in excess of 100 dB SNDR over a 250 kHz bandwidth, designed in a 180 nm CMOS technology, are used to illustrate the efficacy of the techniques described in this article. [ABSTRACT FROM AUTHOR]

This paper presents a noise reduction technique using common-mode feedback in active CMOS mixers. The proposed technique decreases the common-mode noise, thus reducing the common-to-differential conversion noise arising from mismatch and process variations. In addition, the proposed technique reduces sensitivity to process, voltage, and temperature (PVT) variations due to negative feedback. A negative feedback theory is adopted to analyze the low-noise performance of the proposed technique. The theoretical analysis is validated by simulations and measurements. The conventional and proposed mixers are fabricated in a 65-nm CMOS process. Measurement results of the proposed mixer operating at an RF of 2.1 GHz show a conversion gain of 21.5 dB, the input-referred third-order intercept point (IIP3) of -16.2 dBm, and a flicker noise figure of 8.7 dB at 10 kHz while it dissipates 3.45 mW from a 1.5 V supply voltage. Measurements also show common-mode noise reduction of 10.1 dB at 10 kHz, without degradation of other characteristics. It is demonstrated that the proposed mixer can be applied to decrease phase noise of a self-oscillating mixer (SOM) due to the low common-mode flicker noise mixer.

This paper describes the implementation of low-power, low-phase-noise (PN), and robust startup tailless class-C voltage-controlled oscillator (TVCO) for 5G new radio (NR) technology. It features dual gate voltage control source biasing to generate fast startup and differential signal amplitude balancing, thus eliminating the requirement of the conventional tail current source, which introduces more parasitic capacitance that affects the oscillation frequency, phase noise, and power consumption. The TVCO is fabricated in 180 nm complementary metal-oxide semiconductor (CMOS) technology, oscillating at 2.59 GHz 5G NR carrier frequency with an output voltage swing of 1.7 V and low-phase-noise of -122 dBc/Hz at 1 MHz offset with supply voltage headroom of 0.7 V. Without additional features added, the TVCO consumes very low-power and a small die area of 0.98 mW and 0.49 mm2, respectively. The achieved figure of merit (FoM) is 190.36 dBc/Hz.

Subject and Purpose. The subject of research is the flicker noise present in informant signals of search-and-rescue radars, specifically its properties and the effect it may have on algorithms for detecting and identifying manifestations of human breath and heartbeat processes during rescue operations. The work has been aimed at creating a suitable description of flicker noise for developing optimal algorithms of digital signal processing for quick detection and identification of informant signals during rescue missions. Method and Methodology. The low-frequency flicker noise has been modeled within the polynomial equations technique, proceeding from an analysis of real data on noise components in the output signals from a coherent search-and-rescue radar. A comparative analysis is done for a variety of approximating functions suggested for representing the low frequency portion of the spectrum observed. Results. For the low-frequency range wherein spectral components of the informative signal owing to respiration and heartbeat of humans are concentrated, an adequate model of the fluctuating interference is the flicker noise model built on the basis of polynomial equations. The problem of optimized model representation of the noise in digital signal processing algorithms has been analyzed for the case of a coherent search-and-rescue radar. A model of the fluctuating process has been suggested, based on a polynomial approximation for the spectral function in the low-frequency range of the signals observed at the radar output. Conclusion. Spectral characteristics of both interference and informant signals have been investigated. A structural diagram has been proposed for a high sensitivity, coherent search-and-rescue radar implementing a signal storage algorithm based on the polynomial model of the fluctuating process. The advantages and disadvantages of the radar are discussed, with examples given of real signal implementations and of noise spectrograms. Methods of effective estimation of Doppler signal phases are presented. The paper suggests an analysis of basic requirements as to parameters and performance characteristics of the rescue radar.

Subject and Purpose. Designers of the research radars intended for detecting manifestations of biological activity of living organisms may be interested in the noise characteristics shown by their oscillators at offsets about 10–2 Hz or even 10–3Hz from the carrier frequency. Unfortunately, the producing companies do not practice regular information on noise performance of their products at frequencies below 1 Hz. The present authors have set the goal of deriving an analytical expression for the spectral density of flicker noise which should allow radar engineers estimating the probable noise performance of low-noise oscillators over any frequency range. Methods and Methodology. A great number of writers considering spectral properties of flicker noise tend to support the assertion that its spectral density increases continuously with a decrease in frequency, following the power law 1/f. Meanwhile, the present authors assume availability of a certain frequencyfmbelow which the spectral density should most likely remain unchanged, even to as low as zero frequency. Also, there is a range of frequencies above which the spectral density of flicker noise remains constant and the total spectral density is determined solely by thermal noise. Results.The spectral density of noise follows the power law 1/f throughout the range fromfm and up to the point where thermal noise starts to overbalance the flicker noise. The authors have proposed an approximating function to describe the behavior of the averaged spectral density of noise from the oscillator within the entire frequency range. Conclusions. The results obtained shall allow radio system designers to make estimates of the probable noise performance of low-noise oscillators in any frequency range, using only known reference data provided by the manufacturer.

A coupling mechanism between flicker noise and hot carrier degradation (HCD) is revealed in this work. Predicting the flicker noise properties of fresh and aged devices is becoming essential for circuit designs, requiring an understanding of the fundamental noise behaviors. While certain models for fresh devices have been proposed, those for aged devices have not been reported yet because of the lack of a clear mechanism. The flicker noise of aged FinFETs is characterized based on the measure-stress-measure (MSM) method and analyzed from the device physics. It is found that both the mean and deviations of the noise power spectral density increase compared with the fresh counterparts. A coupling mechanism is proposed to explain the trap time constants, leading to the trap characterizations in their energy profiles. The amplitude and number of contributing traps are also changing and are dependent on the mode of HCD and determined by the position of the induced traps. A microscopic picture is developed from the perspective of trap coupling, reproducing well the measured noise of advanced nanoscale FinFETs. The finding is important for accurate flicker noise calculations and aging-aware circuit designs. [ABSTRACT FROM AUTHOR]

The noise behavior of a proposed Ge-source counter-doped pocket-based double-gate tunnel FET (GS-PNPN-TFET) in the presence and absence of interfacial trap charge conditions is presented. The noise behavior was studied in terms of drain current noise power spectral density (Sid, unit A2/Hz) and gate voltage electron noise power spectral density (Svgee, unit V2/Hz) against variation of various device parameters, viz., body thickness (Tsi), pocket length (Lp), gate-oxide thickness (Tox), gate-oxide material, mole fraction, and doping density using Sentaurus TCAD software. Oxide–semiconductor interfacial trap charge of Gaussian distribution was used at two frequencies − 1 MHz and 10 GHz. Our analysis also includes the impact of temperature variation on noise. As per our findings, the noise spectrums are comparable for the presence and absence of interfacial trap charges in the proposed TFET. This is because the noise spectrum depends on on-current (ION) and the ION is negligibly influenced by the interfacial trap charges in the proposed TFET. However, off-current (IOFF) degrades when trap charges are present at the interface. In comparison with other FET devices, the proposed device offers improved Sid and Svgee values of roughly 1.82 × 10–29 A2/Hz and 5.5 × 10–20 V2/Hz, respectively, at 10 GHz frequency. Furthermore, the diffusion noise predominates at higher frequencies, while the generation–recombination noise is found to be dominant at low frequencies, as expected. Flicker noise is most noticeable at low and medium frequencies but fades away at higher frequencies. [ABSTRACT FROM AUTHOR]

Noises in the GPS vertical coordinate time series, mainly including the white and flicker noise, have been proven to impair the accuracy and reliability of GPS products. Various methods were adopted to weaken the white and flicker noises in the GPS time series, such as the complementary ensemble empirical mode decomposition (CEEMD), wavelet denoising (WD), and variational mode decomposition (VMD). However, a single method only works at a limited frequency band of the time series, and the corresponding denoising ability is insufficient, especially for the flicker noise. Hence, in this study, we try to build two combined methods: CEEMD & WD and VMD & WD, to weaken the flicker noise in the GPS positioning time series from the Crustal Movement Observation Network of China. First, we handled the original signal using CEEMD or VMD with the appropriate parameters. Then, the processed signal was further denoised by WD. The results show that the average flicker noise in the time series was reduced from 19.90 mm/year0.25 to 2.8 mm/year0.25. This relates to a reduction of 86% after applying the two methods to process the GPS data, which indicates our solutions outperform CEEMD by 6.84% and VMD by 16.88% in weakening the flicker noise, respectively. Those apparent decreases in the flicker noises for the two combined methods are attributed to the differences in the frequencies between the WD and the other two methods, which were verified by analyzing the power spectrum density (PSD). With the help of WD, CEEMD & WD and VMD & WD can identify more flicker noise hidden in the low-frequency signals obtained by CEEMD and VMD. Finally, we found that the two combined methods have almost identical effects on removing the flicker noise in the time series for 226 GPS stations in China, testified by the Wilcoxon rank sum test. [ABSTRACT FROM AUTHOR]

We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional materials exhibiting gas-sensing properties, are considered. We present measurement setups and noise-processing methods for gas detection. The chemoresistive sensors show various DC resistances requiring different flicker noise measurement approaches. Separate noise measurement setups are used for resistances up to a few hundred kΩ and for resistances with much higher values. Noise measurements in highly resistive materials (e.g., MoS2, WS2, and ZrS3) are prone to external interferences but can be modulated using temperature or light irradiation for enhanced sensing. Therefore, such materials are of considerable interest for gas sensing.

It is known that flicker noise is the most intriguing noise component because it can be found in any type of material, object, device, or system. Despite the struggle of scientists to find a mutual model for the 1/f flicker noise law, there is still a challenge to describe the law in many cases. Herein, the studies of two‐level random telegraph signal (RTS) fluctuations analyzed for the state‐of‐the‐art high‐electron‐mobility transistors (HEMTs), fabricated based on AlGaN/GaN heterostructures, are presented. It is revealed that the shape of the fluctuations can be used to describe the formation of a 1/fγ spectrum with γ = 1, 2, 3. The data demonstrate that the 1/f spectrum can be obtained as a result of the interactions of the carriers in parallel channels along the length of a system. Experimentally registered RTS fluctuations have a spectrum described by 1/fγ behavior. The data are in good agreement with the theoretically predicted pulsed shape, allowing the generation of a 1/f spectrum. Based on the data analysis and the theoretical description of the fluctuations, the origin of 1/f fluctuations in nonequilibrium conditions is explained by interactions resulting in correlations of carriers in two parallel channels as the common feature in the HEMT devices. [ABSTRACT FROM AUTHOR]

A detailed simulation-based investigation on the noise behavior of SiGe source-based Epitaxial layer Tunnel field effect transistor (SiGe source ETLTFET) and Silicon Synthetic Electric field TFET (Si-SETFET) in the presence of interface trap charges having Gaussian distribution is presented in this paper. The results demonstrated that the flicker and G-R noises dominate the noise characteristics at low frequencies, while diffusion noise is the major contributor at high frequencies for both devices. The drain current noise spectral density (Sid) behavior of SiGe source ETLTFET in the presence of trap shows a reduced value than Si-SETFET. The preceding argument is supported by the observation of normalised Sid (Sid/IDS2) vs Drain current (IDS). The value of net Sid for SiGe source ETLTFET is found to be ~10−26 A2/Hz till 1 MHz. Furthermore, noise analysis at various temperatures shows that noise in presence of trap charges has a greater influence at lower temperatures in the higher drain current region. The result also revealed that the the Sid vs. frequency variation is a decreasing function of the Ge mole fraction in SiGe source ETLTFET. A brief comparison of net Sid among some of the reported studies and this study has also been presented. SiGe source ETLTFET is found to be more noise immune over a wider frequency range in comparison to the state of the art devices. [ABSTRACT FROM AUTHOR]

Earlier, the authors carried out a unique experiment on long-term continuous precision monitoring of crustal resistivity variations in a highly seismic region. The result of this experiment can be considered a special type of VES profile, in which, instead of a linear coordinate, the sounding date changes from picket to picket. When processing precision monitoring data, it is necessary to solve the inverse VES problem with the highest possible accuracy. Standard programs for inversion of VES curves do not allow this, and even with very small fitting residuals, the actual error in reconstructing the resistivity can be huge due to equivalence effects. The authors have previously developed a special method for regularizing the residual functional, which multiply increases the accuracy in solving the inverse problem for the considered type of resistivity section, and a method for obtaining realistic, rather than underestimated estimates of the solution error. To do this, a package of synthetic resistivity profiles is formed that imitates a real section, the VES direct problem is solved, and time series of apparent resistivity are constructed, on which noise similar to real noise is superimposed. After that, the VES inverse problem is solved and the errors in reconstructing the model resistivity curves are analyzed. Such calculations were carried out both for the total signals and their components, obtained as a result of decomposition of the apparent resistivity series into physically determined components. The developed approach makes it possible to solve the inverse VES problem with heretofore unattainable accuracy. We emphasize that a reliable estimate of the solution errors is provided not by the convergence criteria of the inversion algorithm (they are almost always overly optimistic), but by direct calculations of the direct and inverse problems for synthetic profiles similar to real signals. In the present article, the profile of the experimental VES curves obtained in the course of this experiment is inverted. Series of resistivity variations are calculated in four layers of a geoelectric section with a duration of more than 12 years. It has been established that the upper layer of the section is characterized by trend and seasonal changes in resistivity with a large amplitude. Significant anomalous seasonal effects were found in the second layer of the section. For the third layer, the presence of small-amplitude seasonal effects was established, while there are no significant resistivity trends. Variations in the resistivity of the fourth layer are less reliably estimated; to detect the effects of external factors on electrical resistivity, it is necessary to use signal stacking methods. [ABSTRACT FROM AUTHOR]

As part of studies on the search for earthquake precursors, the authors have conducted an experiment on long-term precision monitoring of variations in the resistivity of the Earth's crust in a highly seismic region of Tajikistan. The primary data of this experiment can be considered a special type of VES profile, in which, instead of a linear coordinate, the sounding date changes from picket to picket. When processing precision monitoring data, it is necessary to solve the inverse VES problem with the highest possible accuracy. VES curve inversion programs commonly used in electric exploration do not allow this. The authors have previously developed a special method for regularizing the residual functional, which suppresses the effect of resistivity buildup, due to which the error in reconstructing the resistivity of rocks for profiles with a strong seasonal variation in resistivity is reduced by an order of magnitude. However, in some cases, the regularized algorithm strongly biases estimation of the amplitude of the seasonal resistivity variation in the lower layers of the section. In this paper, the operation of the proposed algorithm is tested in detail for nine model profiles simulating a real geoelectric section. The considered profiles differed in the characteristics of the seasonal variability of resistivity in the lower layers of the section (the phase and amplitude of seasonal effects varied). It is shown that resistivity buildup is effectively suppressed in all cases. For each model profile, the error in solving the inverse problem is estimated. The effect of a biased estimate of the amplitude of seasonal variation is studied. It is shown that in most cases, analysis of the solution makes it possible to reveal the presence of such distortions and qualitatively assess their character. It is also shown that for profile options supposedly closest to the experimental profile, the estimates have minimal bias. For all profiles, the ratio of the average and maximum errors in calculating the resistivity in different layers to the residual in the solution to the inverse problem was evaluated. This makes it possible to evaluate the actual error of the reconstructed resistivity values knowing only the fitting residual. The paper also studied the possible effect of increasing the accuracy in solving the inverse problem in the case of preliminary decomposition of the apparent resistivity curves into seasonal and flicker noise components. It is shown that for small fitting residuals, the results change insignificantly. According to the results obtained, the error in reconstructing the aperiodic (flicker noise) component of resistivity variations in the lower layers of the considered section can be decreased to 0.4%. The accuracy in reconstructing the seasonal component of resistivity variations depends on the amplitude and phase of seasonal effects in the model profile. For the considered profiles, the error varies from 1 to 2%. [ABSTRACT FROM AUTHOR]

Stochastic computing (SC) is widely known for its high error tolerance and efficient computing ability of complex functions with remarkably simple logic gates. The noise of electronic devices is widely used to be the entropy source due to its randomness. Compared with thermal noise and random telegraph noise (RTN), flicker noise is favored by researchers because of its high noise density. Meanwhile, unlike using RRAM, PCRAM and other emerging memory devices as the entropy source, using logic devices does not require any additional process steps, which is significant for industrialization. In this work, we systematically and statistically studied the 1/f noise characteristics of 14 nm FinFET, and found that miniaturizing the channel area of the device or lowering the ambient temperature can effectively increase the 1/f noise density of the device. This is of great importance to improve the accuracy of the SC system and simplify the complexity of the stochastic number generator (SNG) circuit. At the same time, these rules of 1/f noise characteristics in FinFET devices can provide good guidance for our device selection in circuit design.

In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage (Vt) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are investigated. We report for the first time the significant statistical differences between these two device aging phenomena. The Vt shift is relatively uniform among all the devices and gradually evolves over time. By contrast, the RTN degradation is evidently abrupt and random in nature and only happens to a small percentage of devices. The generation of new RTN traps by HCI during times of stress is demonstrated both statistically and on the individual device level. An improved method is developed to identify RTN devices with degenerate amplitude histograms.

The input-referred noise (IRN) is one of the most crucial performance indicators for the analog front-end (AFE) of neural recording devices. In this study, we present a novel design approach for a low-noise amplifier (LNA) based on the transistor optimization method in CMOS technology. Because flicker noise is predominant in neural recording applications, AFE has been designed to meet input-referred flicker noise specifications, whereas thermal noise contributions are monitored and controlled by flicker noise corner frequencies. Transistor optimization is accomplished using a lookup table that encapsulates its performance based on its current density. Initially, transistors are optimized based on the flicker noise performance; later, they may be further optimized based on their size, power consumption, transconductance, or thermal noise contribution. The proposed approach was validated by designing a folded-cascode amplifier with IRN ranging from 2 to 8 $\mu \text{V}_{\text {rms}}$ . The results of the simulation show that the errors of our design methodology are less than 10%, which is less than those of the $g_{m}/I_{D} $ and inversion coefficient methods. The proposed LNA achieves 2.1 $\mu \text{V}_{\text {rms}}$ while consuming 0.83 $\mu \text{W}$ from a 1.2 V supply.

Phase noisehas become the single most critical factor to be addressed in the design of modern communication systems. Facing the challenging requirements of 5G cellular communication, our paper describes a new theoretical framework to calculate the phase noise of LC oscillators, relying on easy to implement closed form solutions for phase noise calculations. Using closed form phase noise solutions enables oscillator designers to easily implement multiple phase noise calculation options for a number of oscillator circuits, which would be very difficult to implement with the existing mathematically complex phase noise theories. The analytic methods of our theory rely on modeling all real oscillators as having non-ideal or latent behaviors in addition to their primary nature for generating a carrier wave operating at a single frequency with a single amplitude. It is a cascade of these non-ideal transformation processes that produce non-ideal oscillator outputs containing the phase noise sidebands. Enhanced qualitative and quantitative insights into oscillator phase noise performances are achieved by using this approach. We validate our methods by comparing their results with phase noise simulations carried out for a sample CMOS LC voltage-controlled oscillator in 90 nm RFCMOS process using SpectreRF simulator. The results for the oscillator's output 1/f2 thermal phase noise, 1/f noise upconversion into 1/f3 phase noise and the 1/f3 corner frequency of phase noise spectrum using our theory yields −136 dBc/Hz at 10 MHz offset, −21.3 dBc/Hz at 1 kHz offset and 2.6 MHz respectively. The corresponding values obtained with SpectreRF simulation are −135.9 dBc/Hz, −23.4 dBc/Hz and 2.1 MHz. The carrier frequency is 5.4 GHz with output power of 9.78 dBm.

A new technique to reduce flicker noise generated in light-fidelity (Li-Fi) transmission links based on the white light-emitting diode (LED) is proposed. Here, flicker noise with a frequency of 120 Hz, which is twice the frequency of AC power (60 Hz), is generated. The proposed technique is implemented in the receiver of the Li-Fi link. It can reduce flicker noise regardless of various digital modulation formats. In addition, there is no need to change the structure of the electrical circuit driving the LED to reduce the flicker noise. As a result, the non-return to-zero-on-off-keying (NRZ–OOK) signal waveform is tilted according to the flicker noise waveform. We implement the derivative equalization with a pseudo-flicker weight function to reduce the flicker noise. The derivative value of the NRZ–OOK signal mixed with flicker noise becomes larger than that without the flicker noise. In the proposed technique, the derivative value between adjacent sampling points is suppressed below the preset thresholds when it is greater than the preset threshold. Furthermore, a pseudo-flicker weight function is applied to accelerate the flicker noise reduction. As a result, using the proposed technique, a 2 dB signal-to-noise ratio (SNR) gain is obtained based on the bit error rate (BER) threshold (3.5 × 10−5) corresponding to 10% flicker modulation, which is known to have no serious effect on human health. This means that it is possible to implement a Li-Fi transmission link based on an illumination environment with a flicker modulation reduced from 10% to 7%. [ABSTRACT FROM AUTHOR]

This paper describes the implementation of lowpower, low-phase-noise (PN), and robust startup tailless class-C voltage-controlled oscillator (TVCO) for 5G new radio (NR) technology. It features dual gate voltage control source biasing to generate fast startup and differential signal amplitude balancing, thus eliminating the requirement of the conventional tail current source, which introduces more parasitic capacitance that affects the oscillation frequency, phase noise, and power consumption. The TVCO is fabricated in 180 nm complementary metal-oxide semiconductor (CMOS) technology, oscillating at 2.59 GHz 5G NR carrier frequency with an output voltage swing of 1.7 V and low-phase-noise of - 122 dBc/Hz at 1 MHz offset with supply voltage headroom of 0.7 V. Without additional features added, the TVCO consumes very low-power and a small die area of 0.98 mW and 0.49 mm², respectively. The achieved figure of merit (FoM) is 190.36 dBc/Hz. [ABSTRACT FROM AUTHOR]

We present design techniques for single-bit continuous-time delta–sigma modulators that attain high resolution (>16 bits) over a bandwidth (BW) that is more than ten times the audio range. We introduce the zapped, virtual-ground-switched dual return-to-open DAC which is immune to ISI and other transition-dependent errors. FIR feedback facilitates chopping, improves clock-jitter sensitivity and the loop filter’s linearity. We show that the compensation FIR DAC, which is typically bulky, can be implemented in an extremely power- and area-efficient manner in a single-bit modulator using a capacitive DAC and passive summation. Thanks to these techniques, the fabricated prototype achieves 103.2-/104.3-dB signal to noise and distortion ratio (SNDR)/signal to noise ratio (SNR) in a 250-kHz bandwidth while operating at 48 MS/s. Consuming 17.7 mW from a 1.8-V supply, the modulator occupies 1.1 mm 2 in a 180-nm CMOS process. The Schreier (SNDR) figure of merit (FoM) is 174.7 dB. [ABSTRACT FROM AUTHOR]

Signal-based acoustic emission data are analysed in this research work for identifying the damage modes in carbon fibre–reinforced plastic (CFRP) composites. The research work is divided into three parts: analysis of the shifting in the spectral density of acoustic waveforms, use of waveform entropy for selecting the best wavelet and implementation of wavelet packet transform (WPT) for identifying the damage process. The first two methodologies introduced in this research work are novel. Shifting in the spectral density is introduced in analogous to 'flicker noise' which is popular in the field of waveform processing. The entropy-based wavelet selection is refined by using quadratic Renyi's entropy and comparing the spectral energy of the dominating frequency band of the acoustic waveforms. Based on the method, 'dmey' wavelet is selected for analysing the waveforms using WPT. The slope values of the shifting in spectral density coincide with the results obtained from WPT in characterising the damage modes. The methodologies introduced in this research work are promising. They serve the purpose of identifying the damage process effectively in the CFRP composites. [ABSTRACT FROM AUTHOR]

Micro electromechanical systems (MEMS) micro-pressure sensors have wide applications in consumer electronics, industrial monitoring, and biomedicine. However, as the next-generation portable and wearable devices bloom in recent years, existing design of pressure sensors faces great challenges to break the trade-off between the sensitivity and nonlinearity in the miniaturization process. Here, we report a sandwich-like Graphene/h-BN/Graphene-resistor heterostructure sensing element for micro-pressure detection. This novel design decouples pressure-to-strain translation process and strain-to-electrical signal sensing process by the insulation of bottom graphene structure layer and top graphene piezoresistive layer. We reveal the effects of the heterostructure dimensions, layer number and pretension on the mechanical performance utilizing finite element method (FEM) simulation, and propose the design principle of the piezoresistors and patterning strategy of the heterostructure. Remarkably, the heterostructure exhibits ultra-high sensitivity per unit area, outperforming state-of-art graphene and silicon-based sensors by up to five orders of magnitude, as well as a significant reduction of the nonlinearity. Our work shows tremendous potential of 2D material heterostructure as a promising platform to break the miniaturization limitation of ultrasensitive pressure sensors. [Display omitted] • Graphene/h-BN/Graphene van der Waals heterostructure was proposed for pressure sensing with footprint reduced to 6×6 μm2. • Sensitivity and linearity were improved compared to suspending graphene-based sensor by a factor of 28 and 16, respectively. • Area-normalized sensitivity of heterostructure was 2 to 5 orders of magnitude superior to silicon and graphene-based sensors. [ABSTRACT FROM AUTHOR]

• Wafer-level DC and flicker noise characterization on 45-nm RFSOI nFETs. • Analysis of the impact of thickness scaling along with width scaling on flicker noise. • Investigation of volume trap densities and trap distribution for thick and thin oxide NFETs. • Model-to-hardware correlation using models derived from GLOBALFOUNDRIES PDK at room temperature. This work reports the impact of gate oxide thickness on flicker noise (1/ f) in 45-nm RFSOI NFET devices. In addition, the effect of finger width scaling on 1/ f noise parameters is studied in linear region. The dominant source of 1/ f noise is also analyzed. It is observed that thin oxide devices show carrier number fluctuation; however, for thick oxide devices, correlated number-mobility govern the noise. Extracted trap densities using 1/ f noise show higher volume trap densities in thin oxide devices. Moreover, trap distribution behavior is analyzed using frequency exponent. Further, GLOBALFOUNDRIES PDK is utilized to model 1/ f noise behavior of the devices. [ABSTRACT FROM AUTHOR]

A coupling mechanism between flicker noise and hot carrier degradation (HCD) is revealed in this work. Predicting the flicker noise properties of fresh and aged devices is becoming essential for circuit designs, requiring an understanding of the fundamental noise behaviors. While certain models for fresh devices have been proposed, those for aged devices have not been reported yet because of the lack of a clear mechanism. The flicker noise of aged FinFETs is characterized based on the measure-stress-measure (MSM) method and analyzed from the device physics. It is found that both the mean and deviations of the noise power spectral density increase compared with the fresh counterparts. A coupling mechanism is proposed to explain the trap time constants, leading to the trap characterizations in their energy profiles. The amplitude and number of contributing traps are also changing and are dependent on the mode of HCD and determined by the position of the induced traps. A microscopic picture is developed from the perspective of trap coupling, reproducing well the measured noise of advanced nanoscale FinFETs. The finding is important for accurate flicker noise calculations and aging-aware circuit designs.

Noises in the GPS vertical coordinate time series, mainly including the white and flicker noise, have been proven to impair the accuracy and reliability of GPS products. Various methods were adopted to weaken the white and flicker noises in the GPS time series, such as the complementary ensemble empirical mode decomposition (CEEMD), wavelet denoising (WD), and variational mode decomposition (VMD). However, a single method only works at a limited frequency band of the time series, and the corresponding denoising ability is insufficient, especially for the flicker noise. Hence, in this study, we try to build two combined methods: CEEMD & WD and VMD & WD, to weaken the flicker noise in the GPS positioning time series from the Crustal Movement Observation Network of China. First, we handled the original signal using CEEMD or VMD with the appropriate parameters. Then, the processed signal was further denoised by WD. The results show that the average flicker noise in the time series was reduced from 19.90 mm/year0.25 to 2.8 mm/year0.25. This relates to a reduction of 86% after applying the two methods to process the GPS data, which indicates our solutions outperform CEEMD by 6.84% and VMD by 16.88% in weakening the flicker noise, respectively. Those apparent decreases in the flicker noises for the two combined methods are attributed to the differences in the frequencies between the WD and the other two methods, which were verified by analyzing the power spectrum density (PSD). With the help of WD, CEEMD & WD and VMD & WD can identify more flicker noise hidden in the low-frequency signals obtained by CEEMD and VMD. Finally, we found that the two combined methods have almost identical effects on removing the flicker noise in the time series for 226 GPS stations in China, testified by the Wilcoxon rank sum test.