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The purpose of this paper is the analysis of the daily coordinate time series of the five permanent GPS (Global Positioning System) stations of the geodetic monitoring network of the Beni-Haroun Dam (Algeria), in order to assess the spectral content of the dam displacements. The coordinate time series analysis was based on the singular spectrum analysis to assess their principal components (trend, seasonal components and noise in phase space), the spectral analysis to identify their noise spectrum (white or colored) and the wavelet thresholding method to determine their noise in frequency space. The results showed that the primary signal present in the analyzed time series is mainly composed of a trend and an annual component. The trend and the annual signal explain more than 95% of the total signal in the three coordinates (x, y, z) for all studied stations. The analyzed time series in the three coordinates (x, y, z) are characterized by a linear drift less than 1 mm/year, their annual amplitudes are in the range of 0.5–2 mm, and the amplitudes of their semiannual, four-monthly and quarterly signals are in the range of 0–0.5 mm. The noise spectrum in the analyzed time series is flicker noise, and the noise level is in the range of 0.2–0.7 mm, 0.3–0.5 mm and 0.5–1.2 mm in, respectively, x-, y- and z-coordinates. The low values of trend and noise level in the analyzed station coordinates indicate that the Beni-Haroun Dam is qualified as stable.

This work presents a power-efficient and noise-efficient amplifier for ECG recordings. To improve power efficiency, all the transistors in the proposed amplifier is designed in sub-threshold region which gives high g $$_m$$ /I $$_D$$ ratio. To improve noise efficiency, inverter-based differential input stage is used in this proposed operational transconductance amplifier as it reduces noise by a factor of $$\sqrt{2}$$ when compared to it’s non-inverter based counterpart. In order to decrease flicker noise, large transistors are used in the input stage. Class A–B structure is used in the output stage for achieving high g $$_m$$ /I $$_D$$ ratio and for large output swing range. In 180 nm process the amplifier consumes 477 nW DC power from 1.8 V supply which indicates 7.5% decrease in power consumption when compared to recently reported papers. This amplifier achieves a noise efficiency of 2.68. Common mode rejection ratio and power supply rejection ratio is estimated as 98.5 dB and 104.5 dB respectively.

This paper presents the analysis of noise in Single Gate Extended Source TFET (SG-ESTFET) considering the absence and presence of interface trap charges, when the device is subjected to scaling and variation of parameters like device gate length (Lg), extended source length and height, SiGe mole fraction (x), oxide thickness (tox), gate dielectric material, and frequency (f). Furthermore, the influence of variation of dimensionality and material parameters in presence of noise on Drain Current Noise Power Spectral Density (Sid) and Gate Voltage Electron Noise Power Spectral Density (Svgee) are studied for different trap charge conditions. Assuming Gaussian distribution of trap charges at the interface, it is perceived that the effect of noise is more as compared to the case of absence of trap charges. In reference to other FET devices, present paper reports that, the proposed SG-ESTFET device under absence of trap charges, illustrates an improved Sid and Svgee value of 1.4 × 10−29 A2/Hz and 5.21 × 10−16 V2/Hz, respectively whereas under the presence of trap charges, Sid and Svgee value are 6.6 × 10−26 A2/Hz and 8.74 × 10−12 V2/Hz, respectively. Moreover, this study also reports that the generation recombination (G-R) noise is mainly prevailing at low and mid-frequencies in presence of trap charges while diffusion noise is prevailing at high-frequencies. Likewise, the flicker noise is observed to be noteworthy at low and medium-frequencies in absence of trap charges.

This paper presents a down-conversion active mixer with improved performance for direct conversion receivers in wireless local area networks. The effect of negative admittance on the Gilbert cell mixer performance is investigated in terms of flicker noise, conversion gain, and linearity. The proposed negative admittance is implemented using a modified negative capacitance connected in parallel to a negative resistance, which exhibits a high degree of freedom to achieve high negative capacitance along with low negative resistance. The proposed mixer is designed and simulated using TSMC 0.18 µm CMOS technology in Cadence Spectre-RF at the input frequency of 2.4 GHz and intermediate frequency of 10 MHz. Post-layout simulation results show using the negative admittance can improve the flicker noise more than 16.7 dB at the frequency of 1 kHz. The proposed mixer exhibits a conversion gain of 19.3 dB and a flicker noise corner frequency of 5 kHz. The double-side band noise figure is 7.57 dB at the output frequency of 10 MHz, and the third-order intermodulation intercept point (IIP3) is − 7.5 dBm. The power dissipation is 13.6 mW from the power supply of 1.8 V. Moreover, the linearity of the proposed mixer can be enhanced by choosing the proper values for transconductance of switching quad and negative resistance so that it achieves the IIP3 of + 7.9 dBm with the conversion gain of 7.6 dB.

This communication presents the performance analysis and impact of low frequency flicker noise on a dual dielectric pocket heterojunction silicon on insulator (SOI) tunnel FET (TFET). The proposed TFET structure is well optimized for different gate-source underlap length and various thickness of δp+ Si1-xGex layer. It offers an ON current of 1.16 × 10−4 A/μm providing a high ON/OFF ratio of 3.49 × 1012 and a super steeper sub-threshold swing of 2 mV/dec. The device performance is investigated with concern to interface traps while both Uniform and Gaussian trap distributions are considered. The analyses specify that the proposed device is insusceptible to ON current degradation in presence of interface traps in comparison to OFF current behaviour. Electrical noise performance is examined in presence of interface traps and different mole fraction of germanium (Ge) in δp+ Si1-xGex layer. The device is further tested for its parasitic capacitances and transconductance to drain current ratio (gm/ID) behaviour. The high ratio of obtained gm/ID makes it compatible for future low power applications.

Flicker noise causes decoherence in Josephson junction-based superconducting qubits, thus limiting their practical potential as building blocks for quantum computers. This is due to limited length and complexity of executable algorithms, and increased dependency on error-correcting measures. Therefore, identifying and subsiding the atomic sources of flicker noise are of great importance to the development of this technology. We developed a method that combines ab initio DFT calculations and quantum dynamics to model charge transport across a Josephson junction, by which it is possible to more accurately assess different defects as sources of flicker noise. We demonstrate the use of our method in an investigation of various atomic defects, including vacancies, trapping, and substitutions, in an Al|Al2O3|Al Josephson junction. This demonstration both reveals weaknesses in previous attempts to pinpoint the atomic sources of flicker noise and highlights new candidates.

The problem of calculating the uncertainty bands for a linear regression with correlated initial data is considered. The conformance factors for regression uncertainty bands with different models of errors in the initial data are obtained by the Monte-Carlo method. The linear regression coefficients are estimated by the generalized method of least squares. The following models of measurement error are considered: Gaussian white noise, exponentially correlated noise, and flicker noise. A comparative analysis of the uncertainty bands of linear drift is conducted for these models.

This study applied a vapor cooling condensation system for depositing p-ZnO:LiNO3, i-Ga2O3, and n-Ga2O3:Si layers on sapphire substrates to fabricate solar-blind p-i-n deep-ultraviolet photodetectors (DUV-PDs). The deposited i-Ga2O3 absorption layer was measured to exhibit high performance levels. Therefore, when the resulting solar-blind p-i-n DUV-PDs were operated at a reverse bias voltage of − 5 V, the dark current and the DUV (250 nm)/visible (500 nm) rejection ratio were 1.45 pA and 2.5 × 104, respectively. Moreover, when the solar-blind p-i-n DUV-PDs were operated at a reverse bias voltage of − 5 V, the photoresponsivity, noise power density, noise equivalent power, and specific detectivity were 0.73 A/W, 2.45 × 10−26 A2/Hz, 4.80 × 10−13 W, and 1.97 × 1012 cmHz0.5W−1, respectively. Furthermore, flicker noise was the dominant low-frequency noise source in the photodetectors. These results demonstrated the effectiveness of the proposed solar-blind p-i-n DUV-PDs.

The accuracy by which velocities can be estimated from GNSS time series is mainly determined by the low-frequency noise, below 0.2–0.1 cpy, which are normally described by a power-law model. As GNSS observations have now been recorded for over two decades, new information about the noise at these low frequencies has become available and we investigate whether alternative noise models should be considered using the log-likelihood, Akaike and Bayesian information criteria. Using 110 globally distributed IGS stations with at least 12 years of observations, we find that for 80–90% of them the preferred noise models are still the power law or flicker noise with white noise. For around 6% of the stations, we found the presence of random-walk noise, which increases the linear trend uncertainty when taken into account in the stochastic noise model of the time series by about a factor of 1.5 to 8.4, in agreement with previous studies. Next, the Generalised Gauss–Markov with white noise model describes the stochastic properties better for 4% and 5% of the stations for the East and North component, respectively, and 13% for the vertical component. For these stations, the uncertainty associated with the tectonic rate is about 2 times smaller compared to the case when the standard power-law plus white noise model is used.

Global Navigation Satellite System (GNSS) coordinate time series contains significant information on plate movement and crustal deformation. Through using GAMIT/GLOBK software, we obtained the coordinate time series of Anhui Continuously Operating Reference System (AHCORS) from 2013 to 2018.5. Then power spectral density method and the maximum likelihood estimation method were applied to determine the optimal noise model of AHCORS for the first time. Our results show that the White Noise plus Flicker Noise (WN+FN) model represents the best model for this region. We then solved the linear trend of the obtained coordinate time series using CATS software. Overall, the velocity uncertainty with colored noise is 7 ~ 10 times of that with white noise only, while the average horizontal velocity based on the Eurasian plate is 6.43 mm/a during this period, with a direction of E29.10°S. With respect to the vertical velocity, there is a tendency of subsidence in the north and uplift in the south, with maximum subsidence reaching up to 32.82 mm/a, which appears at station SZDS in Dangshan, Suzhou. The rapid subsidence at this area is most likely due to extraction of groundwater and mineral resources in recent years.

Understanding the noise content of the Global Positioning System (GPS) coordinate time series is a prerequisite for a realistic assessment and uncertainty of unknown parameters. Variance component estimation methods [e.g., restricted maximum likelihood estimator (REML)] are used to assess the noise content of GPS coordinate time series. For large-scale data, namely over a wide range of spatial and temporal scales, the previous methods’ efficiency could significantly improve. Meanwhile, the estimation method, including repeated inversion of large matrices, has led to intensive computations and large storage requirements. By quantifying the REML estimator by decorrelation property of discrete wavelet transformation, the current research has offered FREML (fast REML) for accurate and fast approximation of noise content. For evaluating the method’s efficiency, 360 synthetic daily time series with different lengths $$N=2048$$ , 4096, and 8192 observation epochs were used. The time series composed of linear trends, periodic signals, offsets, transient displacements, gaps (up to 10%), and a combination of white, flicker, and random walk noises. The FREML algorithm’s outcomes were compared with existing software that uses a maximum likelihood approach to quantify the uncertainties (e.g., Hector). The results indicated that both methods provided equivalent results for noise components, unknown parameters (rate, offset, and transient displacement), and their uncertainties. Moreover, the FREML method reduced the computation time by a factor of 2–14 compared to Hector software, depending on the amount of data and missing epochs. For more assessment of the method, the FREML method was applied to the 36 real time series with noise models as (i) white plus flicker noise and (ii) combination of white, flicker, and random walk noises. The results demonstrated that the two methods’ outcomes were close, and the FREML method speeded up the estimation of noise and unknown parameters.

This paper reports the investigation of conventional junctionless tunnel FET (JL-TFET) and N+ pocket-doped junctionless vertical tunnel FET (JL-VTFET). The investigation is done by analyzing the effect on the ID–VGS characteristics (a) under a wide range of temperature and (b) in the presence of acceptor interface trap charges. This work also examines the performance of noise and its impact on the digital inverter. Comparison has been made on the TCAD simulated results of both the devices. It is observed that the degradation of drain current (ID) is less in JL-VTFET and also it has better noise performance than that of conventional JL-TFET. Its net drain current noise spectral density (Sid) reaches 10–15 A2/Hz till 1 MHz and decreases with further increase in frequency. The contributions of generation–recombination noise and flicker noise are found to be more in low and moderate frequency, whereas diffusion noise dominates at high frequency. Furthermore, the impact of interface traps is studied using complementary JL-VTFET digital inverter application and compared with the one without interface traps. The transient characteristics show an average delay of 15 ps and 27 ps in the absence and presence of interface traps, respectively.

Terahertz (THz) photodetector has attracted great attention from worldwide scientists for its applications in security check, biomedical treatment, and astronomical observation. In the performance evaluation of the THz photodetector, the noise level is one of the critical parameters. The Gallium Arsenide (GaAs) blocked-impurity-band (BIB) detector, which is fabricated from intrinsic GaAs-based photoconductive detectors, reveals an attractive advantage of low dark current value and high signal to noise ratio (SNR). In this work, the epitaxial GaAs BIB detector was fabricated and its noise behavior under various bias was investigated at the temperature of 3.5 K. The measured noise consists of flicker noise (1/f noise), shot noise, thermal noise and measurement noise. The effect of bias and operation temperature (TOpe) on the noise characteristics of a GaAs-based BIB detector has been studied by numerical simulation for suppressing device noise. According to the simulation, the total noise gradually increases with TOpe, and dominated by the shot noise. Our work may provide useful theoretical support to solve the critical epitaxial growth bottleneck of GaAs BIB detector and improve its performance for the applications of astronomical observation, security check, etc.

Electrochemical noise data generated during the stress corrosion cracking (SCC) experiments under free corrosion potential performed on a high-strength carbon steel exposed to acidified sodium chloride solution and poisoned with sodium sulfide have been statistically analyzed. The electrochemical noise, observed as spontaneous potential fluctuations, was analyzed using the maximum entropy method and the discrete Fourier transform. In all the specimens tested, a low-frequency (LF) noise was obtained which characteristically indicated LF or flicker noise. Throughout the experiments, consistent noise behavior was observed, with the only significant perturbation being that associated with major transients that occurred when the specimens actually failed. In the statistical analysis of results, all the parameters used bear close correlations with the spectral density curves, noise amplitudes and the roll-off slopes. For this alloy, the results obtained from the electrochemical investigation and the scanning electron microscopy micrographs show the cracking behavior to be consistent with the hydrogen-induced cracking.

In this paper, we demonstrate the simulation of a graphene-based three-terminal junction using semi-classical drift–diffusion modeling. The DC and AC simulations are carried out separately and characterized at different temperatures and frequencies. The simulated structure is compared with previous results, and the noise spectrum is simulated to explore its behavior using graphene as an active region. At room temperature, the three-terminal junction demonstrates responsivity of up to 594.56 mV/mW, with mobility of 4000 $$\hbox {cm}^{2}/\hbox {Vs}$$ and a push–pull input signal of 100 mV at 1 KHz. The corresponding noise-equivalent power is as low as 19.4 $$\hbox {pW}/\hbox {Hz}^{1/2}$$ . The simulated structure is able to obtain much higher responsivity and lower noise equivalent power by taking advantage of the higher mobility of the graphene. The voltage noise spectrum of the device is analyzed using equivalent two-dimensional geometry. At lower frequencies, flicker noise is found to dominate, due to the variation in charge carrier density.

We present investigations of the 1/f noise fluctuations with the different setup temperatures of the tunable laser diode. The measurements are reported from the terminal of the external photodiode using LAB View Signal Express software. The fast Fourier transform method has been implemented, the power spectral density is evaluated at different operation temperatures of the diode laser. The amplitude A of 1/f noise at 1 kHz, and the relation between the frequency exponent factor α and temperatures has been demonstrated. The results show that the power spectral density of the 1/f noise, as well as the value of α decreases as the temperature, increase.

Swept source optical coherence tomography (OCT) technology and OCT-angiography (OCT-A) are two recent developments that have the potential to significantly change our understanding of retinal pathology and retinal vascular pathophysiology. In order to correctly use these technologies to their full diagnostic potential, a thorough understanding of the technology as well as its benefits and limitations is essential. The aim of this review article is to provide an introductory understanding of how swept source OCT with a 1050 nm wavelength differs from conventional spectral domain OCT using 840 nm wavelength, and what the benefits are. The OCTARA™ swept source OCT angiography algorithm will be explained and compared with other algorithms. The cause and removal of projection artifacts, white band artifacts, black band artifacts, speckle noise and flicker noise in swept source OCT-angiography (OCT-A) will be explained. Layer segmentation boundaries and the reasons for them will be explained. The benefit of wide-field OCT-A will be discussed using case examples. Finally, the challenges of OCT choroidal angiography will be discussed.

In this paper, we develop the low frequency noise (LFN) model for symmetric double gate InAsSb channel n-MOSFETs and report noise performance of such devices as well as amplifier circuits built using them. Our noise model relies on the drain current Id which is obtained from the carrier concentration and Pao-Sah’s current formulation taking into account field dependent electron mobility and interface trapped-charge density Dit. The drain current model is calibrated with reported experimental data. The calculated values of Id and transconductance gm are utilized to find power spectral density of drain current as a function of drain and gate bias voltages, channel length, channel thickness, equivalent oxide thickness and also Dit. Moreover, we have studied the performance of low noise amplifiers (LNAs) with simultaneous noise and input matching (SNIM) topology using both InAsSb and Si channel devices, and computed the minimum noise figure and output noise power density and compared the results. Our investigation reveals that InAsSb MOSFETs exhibit better low noise performance in the strong inversion region of operation at which devices are biased to operate usually for analog circuit applications. Furthermore, the LNA with InAsSb channel MOSFET exhibits noise figure of 1.38 dB in strong inversion region enabling the amplifier suitable for many applications.

In this work, a simulation-based performance study of vertical super-thin body (VSTB) MOSFET vis-a-vis various other MOS devices was presented. Use of appropriate doping profile greatly improves on to off current ratio (ION/IOFF) and subthreshold swing (SS). Improvement in input characteristics (ID–VGS) by gate–source (G/S) and gate–drain (G/D) overlap technique was explained with the help of electron density, mobility, and velocity of the device in off and on-states. Device performance shows negligible deviations in presence of different effects like stress, strain, tunneling, and velocity saturation. VSTB FET supports the downscaling of device size by offering excellent electrostatic integrity and low supply voltage operation. Values of off-current (IOFF), peak on-current (ION), peak transconductance (gm), SS, and DIBL for channel length (L) of 20 nm are 0.00145 nA/µm, 327.85 µA/µm, 974 µS/µm, 65.1 mV/dec, and 39.6 mV/V, respectively. Noise impact on device performance for three different noise sources (diffusion, generation–recombination/G–R, and flicker noise) was studied at two different frequencies (f = 1 MHz and 10 GHz). Maximum values of unit-gain cut-off frequencies (fTmax) obtained for channel lengths (L) of 20, 25, and 30 nm are 86.26, 80.47, and 76.22 GHz, respectively.

An all-digital phase locked loop (ADPLL) taking new approach for design of the loop filter is presented. A feedback loop in the time domain by modeling the DCO and TDC as an appropriate model in the state-space form is proposed. Then, a model predictive control (MPC) method for designing loop filter in order to generate an optimal control signal is employed. The proposed loop filter can overcome latency issue that inevitably exists in most of digital systems. Furthermore, the proposed MPC loop filter achieves rapid transient response time and enables us to model other noise sources resulted from oscillator pulling and flicker noise which are common problems in many modern transceivers and the effects of which can be dramatically removed without degrading the overall phase noise performance. Simulation results confirm the capability of the proposed design and show it is significantly more robustness against these problems compared to conventional digital PLL.

An energy efficient complementary metal-oxide-semiconductor (CMOS) temperature sensor and signal conditioning circuit with auto zeroing technique has been enunciated in this paper. In the present study, a novel CMOS temperature sensor based on sub-threshold MOS operation has been presented, which is designed for Aerospace applications. The proposed sensor does not use bipolar junction transistor (BJT) for sensing; instead it utilizes the temperature dependency of the threshold voltage of MOSFET. The proposed temperature sensor is designed to sense −30 to 150 °C and its sensitivity is 1.4 mV/°C while the power consumption is 60 nW. The accuracy of sensor is mainly limited by offset and flicker noise (1/f) noise, which is cancel by the autozeroing circuit with the help of switch capacitor circuit. The sensor circuit is designed with biasing sub circuit for controlling the curvature correction. The proposed temperature sensor and signal conditioning are simulated in a Cadence Analog Design Environment with UMC90 nm library. The simulation result shows an inaccuracy of −1/+0.7 °C.

The seasonal signal and long-term trend in the height time series of 10 IGS sites in China are investigated in this paper. The offset detection and outlier removal as well as the removal of common mode error are performed on the raw GPS time-series data developed by the Scripps Orbit and Permanent Array Center (SOPAC). The seasonal-trend decomposition procedure based on LOESS (STL) is utilized to extract precise seasonal signals, followed by an estimation of the long-term trend with the application of maximum likelihood estimation (MLE) to the seasonally adjusted time series. The Up-components of all sites are featured by obvious seasonal variations, with significant phase and amplitude modulation on some sites. After Kendall’s tau test, a significant trend (99% confidence interval) for all sites is achieved. Furthermore, the trends at sites TCMS and TNML have significant changes at epochs 2009.5384 and 2009.1493 (95% confidence interval), respectively, using the Breaks For Additive Seasonal and Trend test. Finally, the velocities and their uncertainties for all sites are estimated using MLE with the white noise plus flicker noise model. And the results are analyzed and compared with those announced by SOPAC. The results obtained in this paper have a higher precision than the SOPAC results.

Current CMOS (Complementary Metal Oxide Semiconductor) technologies show an increasing susceptibility to a rising amount of failure sources. This includes also radiation induced soft errors, which requires countermeasures on several design levels. Hereby, BBICS (Bulk Built-In Current Sensors) represent a promising approach on circuit level. However, it is expected that these circuits, like similar sensors measuring substrate effects, are strongly susceptible to substrate noise. The intention of this work is an in-depth noise analysis of representative bulk sensors based on extracted layout data. Thereby, several aspects are considered, like sensor activation thresholds, impact of the distance to the noise source, and noise generation by test circuits. Results indicate that already noise RMS level of 5 to 9 % of the supply voltage can lead to false detections, which are values in the same order of magnitude of noise generated by test circuits.

The problem of negative variance components is probable to occur in many geodetic applications. This problem can be avoided if non-negativity constraints on variance components (VCs) are introduced to the stochastic model. Based on the standard non-negative least-squares (NNLS) theory, this contribution presents the method of non-negative least-squares variance component estimation (NNLS-VCE). The method is easy to understand, simple to implement, and efficient in practice. The NNLS-VCE is then applied to the coordinate time series of the permanent GPS stations to simultaneously estimate the amplitudes of different noise components such as white noise, flicker noise, and random walk noise. If a noise model is unlikely to be present, its amplitude is automatically estimated to be zero. The results obtained from 350 GPS permanent stations indicate that the noise characteristics of the GPS time series are well described by combination of white noise and flicker noise. This indicates that all time series contain positive noise amplitudes for white and flicker noise. In addition, around two-thirds of the series consist of random walk noise, of which its average amplitude is the (small) value of 0.16, 0.13, and 0.45 $$\text{ mm/year }^{1/2}$$ for the north, east, and up components, respectively. Also, about half of the positive estimated amplitudes of random walk noise are statistically significant, indicating that one-third of the total time series have significant random walk noise.

A detection and compensation technique for LO phase mismatches is presented to reduce noise in the mixer. Based on theoretical analysis and simulation, this work shows that the LO phase mismatch degrades the noise figure, gain, and linearity of the mixer. To compensate the LO phase mismatch, a new concept of the mixer is proposed, and its prototype is fabricated in 0.18-μm CMOS technology. In addition, a current bleeding mixer, which is known for low flicker noise topology, is also fabricated for comparative purposes. From the measured results, the proposed mixer reduces the flicker noise corner frequency by almost half when it is compared to the current bleeding mixer. Moreover, the proposed mixer improves gain and linearity without additional power consumption.

Application of flicker noise spectroscopy in diagnosing the functional state of the cardiovascular system to obtain distinctive features for normal state and a series of catastrophic arrhythmias is discussed. Power spectra are assessed for singular and regular ECG signal components, from which the informative features are extracted.

Proper analysis and subsequent interpretation of GPS position time series is an important issue in many geodetic and geophysical applications. The GPS position time series can possibly be contaminated by some abrupt changes, called offsets, which can be well compensated for in the functional model. An appropriate offset detection method requires proper specification of both functional and stochastic models of the series. Ignoring colored noise will degrade the performance of the offset detection algorithm. We first introduce the univariate analysis to identify possible offsets in a single time series. To enhance the detection ability, we then introduce the multivariate analysis, which considers the three coordinate components, north, east and up, simultaneously. To test the performance of the proposed algorithm, we use synthetic daily time series of three coordinate components emulating real GPS time series. They consist of a linear trend, seasonal periodic signals, offsets and white plus colored noise. The average detection power on individual components, either north, east or up, are 32.3 and 47.2% for the cases of white noise only and white plus flicker noise, respectively. The detection power of the multivariate analysis increases to 70.8 and 87.1% for the above two cases. This indicates that ignoring flicker noise, existing in the structure of the time series, leads to lower offset detection performance. It also indicates that the multivariate analysis is more efficient than the univariate analysis for offset detection in the sense that the three coordinate component time series are simultaneously used in the offset detection procedure.

We demonstrate the use of two dual-output Mach-Zehnder modulators (DO-MZMs) in a direct comparison between a femtosecond (fs) pulse train and a microwave signal. Through balanced detection, the amplitude-to-phase modulation (AM-PM) conversion effect is suppressed by more than 40 dB. A cross-spectrum technique enables us to achieve a high-sensitivity phase noise measurement (−186 dBc/Hz above 10-kHz offset), which corresponds to the thermal noise of a +9 dBm carrier. This method is applied to compare a 1-GHz fs monolithic laser to a 1-GHz microwave signal generated from photodetection of a free-running 500 MHz mode-locked laser. The measured phase noise is −160 dBc/Hz at 4-kHz, −167 dBc/Hz at 10-kHz, and −180 dBc/Hz at offset frequencies above 100-kHz. The measurement is limited by the free-running 500-MHz laser’s noise, the flicker noise of the modified uni-traveling carrier photodiode and the thermal noise floor, not by the method itself. This method also has the potential to achieve a similar noise floor even at higher carrier frequencies.

The features of measurements of the parameters of low-frequency noise with a spectrum of the form 1/fγ of electronic components are considered. Expressions for the systematic error in determining the exponent γ from the results of single measurements of the spectral power density of the noise by a direct estimate at two frequencies, taking thermal and shot noise of the monitored article into account, are obtained and analyzed. Recommendations on minimizing the total error in determining γ are given.

In general, high-rate GPS data sets are subject to common mode error (CME), multipath error, and high-frequency random noise, which adversely affect the GPS positioning accuracy. In order to improve the precision and reliability of GPS positioning, a multiscale multiway principal component analysis (MSMPCA) denoising method is introduced here. The 1-Hz GPS coordinate time series at ten stations from the California Real Time GPS Network are employed to assess the performance of MSMPCA. Its results are compared with those of the classical denoising methods, including wavelet denoising, PCA, multiway PCA, and multiscale PCA. The results indicate that MSMPCA is able to eliminate not only high-frequency random noise but also low-frequency errors and CME. Furthermore, quantitative analysis shows that MSMPCA is more accurate than the classical denoising methods. Spectral analysis shows that a combination of white plus flicker noise is considered to be the adequate model for the noise characteristics of all three components. Both white and power-law noise amplitudes are smallest in the north component and largest in the vertical component. MSMPCA decreases the mean amplitudes of white noise from 1.3 to 0.0, 0.9 to 0.0, and 2.8 to 0.1 mm in north, east, and vertical components, and those of power-law noise from 4.6 to 1.2, 3.9 to 1.1, and 19.9 to 8.4 mm, respectively. MSMPCA is a promising alternative for removing noise of various frequencies (0.00025---0.5 Hz) from high-rate GPS signals.

Each of the GPS time series that describes the changes of topocentric components consists of a deterministic and a stochastic part, whose character influences the errors of the deterministic parameters. As to the uncertainties of reliable velocities of permanent satellite station systems, surveys that estimate and take into account any dependencies that may affect subsequent operational efficiency are very important. For this analysis, we used 42 stations from the IGS (International GNSS Service) network from Europe, processed at the Military University of Technology EUREF Permanent Network Local Analysis Centre (MUT LAC). The deterministic part of the GPS time series was removed using the least squares method. The seasonal periods in topocentric components were determined assuming the existence of the residual Chandler oscillation (1.67 cpy), as well as the annual tropical (1 cpy) and draconitic (1.04 cpy) oscillations with their harmonics up to 4th. We assumed the character of the residue as a combination of white and powerlaw noise. The obtained results show, that in the case of the European sub-network of IGS stations we are dealing with the coloured noise between white and flicker noise with the amplitudes between 3 to 6 mm/year-k/4 for horizontal components and between 6 to 15 mm/year-κ/4 for the vertical ones, where κ is a spectral index. Finally, we showed that the amplitudes and spectral indices of noise are reduced after performing a spatio-temporal filtering. All the elicited results referred to the uncertainties of velocities by estimating them before and after filtration and the simulation of their values for different lengths of the time series.

Noise equivalent temperature difference (NETD) is the critical parameter for passive imaging detection. A modelling of the sensitivity performance including the f-1-type low flicker noise (1/f-noise) influence is presented, specifically investigated on the 1/f-noise to the sensitivity performance and the trade-offs between the low-noise amplifier (LNA)’s gain and the video frequency bandwidth. Measurement bench is set up, and results confirm that low-frequency modulation to the signal helps in improving the sensitivity performance. Based on the measurement results, it is concluded that signal power influences the 1/f-noise properties in detection diode. The amplifier’s output power is suggested to be lower than −30 dBm at least. This level is much lower than the point of P1dB (1 dB compressed point of the LNA).

The heterostructured thin films of the solar blind p-ZnO:LiNO3/i-MgZnO/n-MgZnO:In ultraviolet-B photodetectors were deposited at a low temperature using the vapor cooling condensation system. The photodetectors exhibited an absorption cut-off wavelength of 310 nm and did not response in the visible wavelength range. A low dark current of 20 pA and a high rejection ratio of 3.60 × 103 were measured when a reverse bias voltage of −1 V was applied. The associated photoresponsivity of 0.2 A/W, the noise equivalent power of 9.50 × 10−12 W and the specific detectivity of 3.16 × 1012 cm Hz1/2 W−1 were obtained. Furthermore, the dominant noise originated from the flicker noise.

The noise contribution of a DC offset cancelation (DCOC) circuit in a programmable gain amplifier (PGA) is studied for the first time in this paper. The analysis presented shows that the DCOC-induced noise may deteriorate the PGA's noise performance significantly if we do not pay enough attention to it. For an analog DCOC (ADCOC), it is concluded that the PGA's noise increases rapidly as the output DC offset decreases, thereby causing difficulties to achieve both low noise and low DC offset simultaneously. We propose an optimization technique that can effectively alleviate the noise issue by increasing the feedback amplifier's gain and the resistor's value simultaneously, while maintaining a reasonable DC gain. For a digital DCOC (DDCOC), the extra noise comes from the transistors of the current source (sink) bank. The transistors with a longer channel length are preferred for their lower thermal and flicker noise current. The proof-of-concept prototypes are designed in a 0.18-$$\upmu $$μm CMOS process, and a 3-stage PGA with ADCOC is fabricated. The measurement results validate the analysis and simulation results well.

According to the discussion of noise sources and up-conversion mechanisms of flicker noise, an LC oscillator with improved self-switched biasing and decoupling capacitor is presented. To minimize the 1/f3 phase noise, both source noise and conversion gain of flicker noise are desirable to reduce, rather than only one way in previous works. Flicker noise from tail-biasing transistors is reduced by self-switched biasing technology, and the up-conversion of flicker noise from cross-coupled pair is suppressed by decoupling capacitor at the same time. Phase noise and key parameters influencing phase noise are analyzed in detail. To guide the design, simple way to get optimum values of key parameters is also presented. This oscillator can work at low supply voltage to reduce power consumption considerably compared to conventional self-switched biasing. The proposed oscillator is fabricated in 0.18 μm CMOS process, and exhibits a low phase noise of ?77.5 dBc/Hz (FoM = 181) and ?122.8 dBc/Hz (FoM = 186) at 10 kHz and 1 MHz offset, respectively, from oscillation frequency of 2.55 GHz while dissipating 2.7 mA with 1.2 V supply voltage.

A wideband CG---CS-based balun-LNA is proposed, with high linearity (IIP2 and IIP3) for multi-standard radio applications. By taking advantage of the common-gate transistor's noise and distortion cancellation property in CG---CS-based balun topology, this balun-LNA just focuses on CS-stage's noise and linearity improvement. Post-distortion technique with a p-MOSFET as auxiliary transistor is adopted to suppress the 2nd and 3rd nonlinear terms of the main transistor in CS-stage, and then across 0.2---4.35 GHz, above 34 dBm IIP2 and 7.5 dBm IIP3 with typical process corner is achieved. In addition, in order to reduce the considerable substrate noise from the main transistor in CS-stage, a large resistor is connected between its bulk and source terminal, which reduces the substrate noise contribution from 7.68 to 0.2 % and improves the noise figure (NF) at 1 GHz about 0.38 dB. This balun-LNA was designed in 0.18-μm CMOS, operates from 0.2 to 4.35 GHz, and dissipates 17.8 mW with 1.5-V supply. With typical process corner, this amplifier provides 17.2-dB maximum voltage gain and 2.5---3.2 dB NF.

A 28-GHz voltage-controlled oscillator (VCO) with a wide tuning range and a low phase noise is presented in this paper. A PMOS-only cross-coupled pair with a lower flicker noise is exploited to provide the negative resistance. The mechanisms for enhancing the Q-factor of the LC tank at millimeter-wave (mm-wave) frequencies are analyzed and applied to optimize the proposed VCO design to obtain a low phase noise. To guarantee accurate oscillating frequencies, distributed interconnections are carefully modeled by EM simulations. Fabricated in a standard 90-nm CMOS process, the proposed VCO achieves a wide tuning range of 20.1 %, from 25 to 30.66 GHz and a low phase noise of −105.47 dBc/Hz at 1-MHz offset. The current of the core circuit is 10.5 mA under a single 1.2-V supply. The core area of the chip is 0.38 mm × 0.24 mm.

In this paper, a new methodology for design of folded cascode (FC) and recycling folded cascode (RFC) OTAs based on 1/f noise reduction is presented. With a new formulation for input referred flicker noise based on Gm/Id characteristic in all operation regions significantly enhance of the noise performance is achieved. Also, this technique leads to the larger DC gain and gain-bandwidth, and phase margin degeneration. The amplifiers were simulated in the 0.18 μm CMOS technology and the simulation results confirm the theoretical analyses. Proposed design methodology exhibits 50 % reduction of input voltage noise @ 1 Hz for RFC compared to the FC amplifier, without increasing the power consumption and silicon area.

Landauer---Buttiker shot noise formula only considers the impact of Pauli exclusion principle on noise, but not the impact of Coulomb repulsion among carriers. A theory recently derived by the authors is able to include also the impact of Coulomb repulsion, and provides a computational methodology to obtain noise properties on a more complete physical basis. We review recent results from the application of this methodology with the use of in-house developed computational electronics tools. We show that in a one-dimensional FET, electrostatic repulsion among charge carriers in the channel can be responsible for strongly suppressed or enhanced shot noise with respect to the Poissonian Noise, or to the noise level provided by Landauer---Buttiker formula. This is very relevant for device and circuit design, since current semiconductor technology evolution has brought nanoscale FETs very close to the limit of one-dimensional FETs.

The velocity estimates and their uncertainties derived from position time series of Global Navigation Satellite System stations are affected by seasonal signals and their harmonics, and the statistical properties, i.e., the stochastic noise, contained in the series. If the deterministic model in the form of linear trend and periodic terms is not accurate enough to describe the time series, it will alter the stochastic model, and the resulting effect on the velocity uncertainties can be perceived as a result of a misfit of the deterministic model. The effects of insufficiently modeled seasonal signals will propagate into the stochastic model and falsify the results of the noise analysis, in addition to velocity estimates and their uncertainties. We provide the general dilution of precision (GDP) of velocity uncertainties as the ratio of uncertainties of velocities determined from to two different deterministic models while accounting for stochastic noise at the same time. In this newly defined GDP, the first deterministic model includes a linear trend, while the second one includes a linear trend and seasonal signals. These two are tested with the assumption of white noise only as well as the combinations of power-law and white noise in the data. The more seasonal terms are added to the series, the more biased the velocity uncertainties become. With increasing time span of observations, the assumption of seasonal signals becomes less important, and the power-law character of the residuals starts to play a crucial role in the determined velocity uncertainties. With reference frame and sea level applications in mind, we argue that 7 and 9 years of continuous observations is the threshold for white and flicker noise, respectively, while 17 years are required for random-walk to decrease GDP below 5% and to omit periodic oscillations in the GNSS-derived time series taking only the noise model into consideration.

The span of coordinate time series affects the determination of an optimal noise model. We analyzed position data recorded for 10 continuous Global Positioning System (GPS) sites from 1998.0 to mid-2009 on the Australian Plate to estimate the best noise model and thereafter obtain the true uncertainties of the velocity, employing the maximum likelihood estimation (MLE) method. MLE was employed to analyze the data in four ways. In the first two analyses, the noise was assumed to be a combination of flicker noise and white noise for the raw time series and spatially filtered time series. In the final two analyses, the spectral indices and amplitudes were simultaneously estimated for a power law noise plus white noise model for the raw time series and spatially filtered time series. We conclude that the noise model of GPS time series in Australia can be best described as the combination of flicker noise and white noise. Velocity uncertainties fall below ∼0.2 mm/yr when the time span exceeds ∼9.5 years. A comparison of noise amplitudes and maximum likelihood estimation values between the raw and spatially filtered time series suggests that traditional spatial filtering to remove common-mode errors might not be applicable to the raw time series of this region.

The purpose of this work is to propose a methodology to compute 1/f noise in MOS transistors under cyclo-stationary operation using the standard BSIM4 noise model. The proposed technique relies on a transient simulation, prior to the noise simulation, in which the average carrier quasi Fermi level in the channel is computed. Using this average quasi Fermi level and an energy distribution of traps, flicker noise parameters--NOIA, NOIB and NOIC--are recalculated in order to account for cyclo-stationary conditions. With these recalculated parameters, a noise simulation, using standard BSIM4 noise model, is performed. Simulation results are presented and compared to experimental data available in the literature, indicating the validity of the method.

We present a theoretical investigation of high-frequency electronic noise in field-effect transistors used as detectors of TeraHertz radiation. Calculations are performed using the hydrodynamic-Langevin approach and specialized to the case of InGaAs high-electron mobility transistors. The main physical phenomena associated with the effect of branching of the total current between channel and gate and the appearance of two-dimensional plasma waves are discussed. We demonstrate that thermally excited standing plasma waves originate series of resonant peaks in the corresponding noise spectral densities whose presence can be controlled by the embedding circuit. A significant damping of the high-frequency excess noise is found when the transistor is submitted to a two-lasers optical photo-excitation presenting a beating frequency in the TeraHertz range. Finally, we discuss the dependence of the damping effect, as well as a shift of the resonance peaks from the presence of channel ungated regions.

In the current paper, we report the 1/f noise measurement of nichrome Ni/Cr (80/20 %) thin films for two types of pressure sensors: relative pressure sensors and absolute pressure sensors. The normalized Hooge coefficient for nichrome thin film was found to be 1.89 × 10?10 for the relative pressure sensors and 4.64 × 10?11 for the absolute pressure sensors. We demonstrated that the normalized Hooge coefficient multiplied by the volume of the thin film become constant regardless of the sensor types and discuss the complexities arise for the miniaturization of MEMS sensors due to the bulk noise properties of piezoresistive thin films.

Understanding the destructive interference of noise involved in GPS coordinate time series is crucial for improving the reliability of GPS applications. The majority of the noise consists of both flicker and white noise, both of which are well characterized by a stochastic process following a power-law noise model. To simplify the noise removal for GPS coordinate time series, the noise is usually regarded as pure white noise rather than a mixture of flicker noise and white noise. This work proposes a wavelet-based integrated solution that merges the strengths of Shannon entropy and wavelet thresholding to remove flicker and white noise at the same time. A GPS coordinate time series, spanning 128 days from the GPS monitoring station at the Jinduicheng Mine in Shanxi, China, was selected to test the proposed algorithm. The results demonstrate that both flicker noise and white noise are worthy of attention because they can lead to a seriously misunderstandings about error in a GPS coordinate time series. The utility of our proposed algorithm in removing flicker and white noise is shown to be more comprehensive than the use of wavelet thresholding alone. The findings further reveal that the advance elimination of flicker noise is beneficial for subsequently utilizing wavelet thresholding to delete the white noise in a GPS coordinate time series. This will greatly improve the reliability of GPS coordinate time series, allowing such data to be applied to a wide range of fields.

Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 x 10(-6) at 0.02-1,000 s, reaching a minimum of 2 x 10(-7) at similar to 2 s. A frequency stability of 2 x 10(-15) is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd: YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

Thermal lens microscopy (TLM), due to its high temporal ( $${\sim }\mathrm{ms}$$ ) and spatial resolution ( $${\sim }\upmu \mathrm{m}$$ ), has been coupled to lab-on-chip chemistry for detection of a variety of compounds in chemical or biological fields. Due to the very short optical path length (usually below 100 $$\upmu \mathrm{m}$$ ) in a microchip, the sensitivity of TLM is unfortunately still 10 to 100 times lower than conventional TLS with 1 cm sample length. Optimization of the TLM optical configuration was made with respect to different pinhole aperture-to-beam size ratios for the best signal-to-noise ratio. In the static mode, the instrumental noise comes mainly from the shot noise of the probe beam when the chopper frequency is over 1 kHz or from the flicker noise of the probe beam at low frequencies. In the flowing mode, the flow-induced noise becomes dominant when the flow rate is high. At a given flow rate, fluids with a higher density and/or a higher viscosity will cause larger flow-induced noise. As an application, a combined microfluidic flow injection analysis ( $$\upmu \mathrm{FIA}$$ )–TLM device was developed for rapid determination of pollutants by colorimetric reactions. Hexavalent chromium [Cr(VI)] was measured as a model analyte. Analytical signals for 12 sample injections in 1 min have been recorded by the $${\upmu }$$ FIA–TLM. For injections of sub- $$\upmu $$ L samples into the microfluidic stream in a $$50\,\upmu \mathrm{m}$$ deep microchannel, a limit of detection of $$4\,\mathrm{ng}{\cdot }\mathrm{mL}^{-1}$$ was achieved for Cr(VI) in water at 60 mW excitation power.

This paper presents the design of a high conversion gain and low flicker noise down conversion CMOS double balanced Gilbert cell mixer using $$0.18\,\upmu \hbox {m}$$ 0.18 μ m CMOS technology. The high conversion gain and low flicker noise mixer is implemented by using a differential active inductor (DAI) circuit and cross-coupled current injection technique within the conventional double-balanced Gilbert cell mixer. A cross-coupled current bleeding circuit is used to inject the current to the switching stage to decrease the flicker noise. Instead of spiral inductor, a DAI with high tunability of the inductor and quality factor is used to tune out the parasitic capacitance effect and decrease the leakage current that has a harmonic component and produce the flicker noise. By tuning the DAI, the flicker noise corner frequency is reduced to 150 Hz. The proposed circuit is simulated with Cadence Spectra and the simulation results shows the NF of 11.2 dB, conversion gain of 23.7 dB and IIP3 of $$-6$$ - 6 dB for an RF frequency of 2.4 GHz. The excellent LO-RF, LO-IF, RF-LO and RF-IF isolations of $$-60, -110, -52$$ - 60 , - 110 , - 52 and $$-64$$ - 64 dB are achieved respectively. The total power consumption is 10.5 mW from a 1.8 V DC power supply.

A way of analytical calculation in the phase noise modeling of the LC-VCO topology without tail current resource is proposed. The noise current imported by the MOS channel is modeled to give approximate evaluation, and the period of the transistor noise is included in the model. Phase noise introduced by the tank loss resistance is also modeled to evaluate the circuit phase noise performance. The circuit has been implemented in a 65 nm CMOS technology. The chip occupies 951 × 705 um2 areas with the buffer and pads. The test result indicates that the VCO core consumes 1.125 mW with a 1.2 V power supply, the frequency of the VCO baseband is from 1.258 to 1.37 GHz, and the multiband frequency is from 0.86 to 1.37 GHz. The best performance of the LC-VCO shows a phase noise of ?129.57 dBc/Hz at 1 MHz offset frequency from a 1.3 GHz carrier, resulting in an excellent FoM of ?191.27 dBc/Hz.

This paper presents a new LNA merged mixer topology with improved linearity and noise figure for 866 MHz UHF RFID reader. A novel technique of inductive degeneration of the current bleeding PMOS devices has been utilized to reduce the RF signal leakage through this DC path. This technique along with common-mode inter-modulation feedback and tail capacitance tuning is employed to achieve the superior performance. The mixer was implemented in 130 nm IBM CMOS process and achieved an IIP3 of ?4.1 dBm, a DSB noise figure of 7.5 dB along with a flicker noise 1/f corner frequency of 45 kHz. In addition, with the noise and power matched merged LNA/transconductor, an S11 of ?19.1 dB and an RF-to-IF conversion gain of 17 dB was achieved using a 1.2 V supply. The mixer occupied a silicon area of only 0.54 sq. mm which includes all the center-tapped degeneration and stray tuning inductors.