Random Jitter Research Articles

A Silicon-Based Low-Power Broadband Transimpedance Amplifier

The analysis, design, and implementation of a 50-Gb/s transimpedance amplifier (TIA) in a 0.13- $\mu \text{m}$ SiGe BiCMOS process are presented. The proposed TIA, designed for use in a single-channel optical communication network, is comprised of three stages including: 1) a shunt-peaked, shunt-series feedback stage incorporating a transformer-based positive feedback; 2) an $RC$ -degenerated common-emitter stage; and 3) an inductively degenerated emitter follower. The TIA chip integrates an on-chip 100-fF input capacitor to emulate the photo-detector junction capacitor, and achieves a measured transimpedance gain of 41 dB $\Omega $ and an input-referred current-noise spectral density of 39.8 pA/ $\sqrt {Hz}$ over a 50-GHz bandwidth. The TIA achieves an open eye at 50 Gbps with random jitter of 2.3-ps rms (including the jitter contribution of the test fixture). The prototype chip occupies 0.58 mm2 (including pads) of die area and dissipates 24 mW of dc power from a 2-V supply voltage (i.e., less than 0.5 pJ/bit).

Channel likelihood correction for photon-counting array receivers in the presence of dead time and jitters.

This paper presents a modified channel likelihood model for optical communication systems with a photon-counting array receiver where photon-counting events are impaired by undesirable dead time and jitters. After the photon-counting detector detects a photon, the detector will go into a period of dead time under which it cannot detect any incident photons. In this context, the channel will have memory. We derive the channel likelihood in the presence of the detector dead time and the random jitter of the photon arrival. The impact of dead time and jitters on the performance of a pulse-position-modulated (PPM) optical communication system is also investigated. The simulation results indicate that the modified channel likelihood expressions can obtain a more obvious performance gain under the context of a stronger background noise, fewer detection elements, longer dead time and bigger jitter.

Jitter Sensitivity Analysis of the Superconducting Josephson Arbitrary Waveform Synthesizer.

We present the first jitter sensitivity analysis of a superconducting voltage reference waveform synthesizer with fundamentally accurate output pulses. Successful deployment of a reference waveform source at microwave frequencies will represent a new paradigm for radio frequency metrology. The programmable waveform synthesizer considered in this paper contains a 1.5 bit delta-sigma digital-to-analog converter (DAC) with a sampling frequency of 28 GHz. We quantify the impact of random and deterministic output pulse position jitter (PPJ) on: 1) the amplitude accuracy of the output fundamental tone and 2) the in-band signal-to-noise and distortion ratio (SNDR). The superconducting DAC features a complete lack of output pulsewidth jitter, and random PPJ up to 200 fs rms has a negligible impact on accuracy and SNDR for synthesized tones up to 1 GHz. However, application of nonzero dc bias current is shown to produce deterministic PPJ of up to 5 ps, which, in turn, is shown to degrade the in-band SNDR by 30 dB at 1 GHz unless eliminated with techniques discussed in this paper. We verify the predicted effects of random and deterministic PPJ with simulations in the range of 100 kHz-1 GHz and with experiments in the range of 100 kHz-3 MHz.

Stochastic Insulator-to-Metal Phase Transition-Based True Random Number Generator

An oscillator-based true random number generator (TRNG) is experimentally demonstrated by exploiting inherently stochastic threshold switching in the insulator-to-metal transition (IMT) in vanadium dioxide. Through experimentation and modeling, we show that the origin of stochasticity arises from small perturbations in the nanoscale domain structure, which are then subsequently amplified through a positive feedback process. Within a 1T1R oscillator, the stochastic cycle-to-cycle variations in the IMT trigger voltage result in random timing jitter, which is harnessed for a TRNG. The randomness of the IMT TRNG output is validated using the NIST SP800-22 statistical test.

Lidar using the backscatter amplification effect

Experimental data proving the possibility of lidar measurement of the refractive turbulence strength based on the effect of backscatter amplification (BSA) are reported. It is shown that the values of the amplification factor correlate with the variance of random jitter of optical image of an incoherent light source depending on the value of the structure constant of the air refractive index turbulent fluctuations averaged over the probing path. This paper presents the results of measurements of the BSA factor in comparison with the simultaneous measurements of the BSA peak, which is very narrow and only occurs on the laser beam axis. It is constructed the range-time images of the derivative of the amplification factor gives a comprehensive picture of the location of turbulent zones and their temporal dynamics.

AI-Based Malicious Network Traffic Detection in VANETs

Inherent unreliability of wireless communications may have crucial consequences when safety-critical C-ITS applications enabled by VANETs are concerned. Although natural sources of packet losses in VANETs such as network traffic congestion are handled by decentralized congestion control (DCC), losses caused by malicious interference need to be controlled too. For example, jamming DoS attacks on CAMs may endanger vehicular safety, and first and foremost are to be detected in real time. Our first goal is to discuss key literature on jamming modeling in VANETs and revisit some existing detection methods. Our second goal is to present and evaluate our own recent results on how to address the real-time jamming detection problem in V2X safety-critical scenarios with the use of AI. We conclude that our hybrid jamming detector, which combines statistical network traffic analysis with data mining methods, allows the achievement of acceptable performance even when random jitter accompanies the generation of CAMs, which complicates the analysis of the reasons for their losses in VANETs. The use case of the study is a challenging platooning C-ITS application, where V2X-enabled vehicles move together at highway speeds with short inter-vehicle gaps.

GNSS receiver implementations to mitigate the effects of commensurate sampling frequencies on DLL code tracking

The sampling frequency of a digitized intermediate frequency signal has a strong effect on the measurement accuracy of Global Navigation Satellite System (GNSS) receivers. The delay-locked loop tracking error is significant when the sampling frequency is an integer multiple of the code chipping rate, the so-called commensurate sampling frequency, and the number of distinct instantaneous residual code phases is low. This results in distortions of the correlation shape and discriminator functions that lead to a significant accuracy degradation. These effects are most pronounced when the sampling frequency is low. Notwithstanding, it is generally good for receivers to keep the sampling frequency to a minimum owing to the processing load and power consumption. It creates a challenge for existing GNSS signal processing techniques. Random, sine and sawtooth jitters have been found to mitigate these distortions considerably. A software algorithm and two hardware receiver implementations of these solutions are proposed. A register-based architecture can be directly applied to the conventional receiver architecture, while the increase in resource and power consumption is insignificant. A RAM-based design cannot only considerably minimize utilized resources but also slightly reduce the power consumption compared to the conventional architecture.

A 32.75-Gb/s Voltage-Mode Transmitter With Three-Tap FFE in 16-nm CMOS

This paper describes a 32.75-Gb/s voltage-mode transmitter (TX) with three-tap feed forward equalization that is fabricated in a 16-nm FinFET CMOS technology. The TX uses a dual regulator architecture to allow independent control of output swing, output common-mode, and equalization. A hybrid impedance control scheme is presented where the total number of driver slices is used for coarse impedance control, and analog loop-based voltage control is used for fine impedance control of the TX. A finite-impulse response compensation circuit to compensate for the data dependent current due to equalization is also presented. The TX consumes 120.8 mW with 0.9- and 1.2-V supplies, provides 0.25–0.9 Vpp output swing, and achieves total jitter of 6.49 ps–pp and random jitter of 220 fs–rms at 32.75 Gb/s with bit error rate of 1e-12.

Design of 0.35-ps RMS Jitter 4.4–5.6-GHz Frequency Synthesizer with Adaptive Frequency Calibration Using 55-nm CMOS Technology

This paper demonstrates the design and implementation of a 5-GHz frequency synthesizer using 55-nm complementary metal-oxide semiconductor technology. The proposed synthesizer achieves an ultra-low 0.35-ps jitter with a high-resolution adaptive frequency calibration scheme that automatically chooses frequency-tuning curves and improves calibration accuracy. The proposed synthesizer employs a high-Q LC voltage-controlled oscillator, constant bandwidth, low, and even $$K_{\mathrm{VCO}}$$ technique using thermometer-weighted capacitor calibration, a low-power divider, and a charge-pump (CP) circuit to achieve low jitter. The oscillator comprises a modified digitally controlled capacitor and varactor array, which extend the tuning range and minimize the phase noise. A matched differential CP is adopted to reduce reference spurs and phase-noise performance. The proposed frequency synthesizer achieves an output frequency of 4.4–5.6 GHz with a chip area of $$0.33\hbox { mm}^{2}$$ . The power consumption is 20 mW from a 1.2-V supply at 5 GHz, and the reference spur is −67.99 dBc. The measured root mean-square random jitter and phase noise are 0.35 ps and −110.04 dBc/Hz at 1 MHz, respectively.

Multiple Two-Way Time Message Exchange (TTME) Time Synchronization for Bridge Monitoring Wireless Sensor Networks.

Wireless sensor networks (WSNs) have been widely used to collect valuable information in Structural Health Monitoring (SHM) of bridges, using various sensors, such as temperature, vibration and strain sensors. Since multiple sensors are distributed on the bridge, accurate time synchronization is very important for multi-sensor data fusion and information processing. Based on shape of the bridge, a spanning tree is employed to build linear topology WSNs and achieve time synchronization in this paper. Two-way time message exchange (TTME) and maximum likelihood estimation (MLE) are employed for clock offset estimation. Multiple TTMEs are proposed to obtain a subset of TTME observations. The time out restriction and retry mechanism are employed to avoid the estimation errors that are caused by continuous clock offset and software latencies. The simulation results show that the proposed algorithm could avoid the estimation errors caused by clock drift and minimize the estimation error due to the large random variable delay jitter. The proposed algorithm is an accurate and low complexity time synchronization algorithm for bridge health monitoring.

Vibration-based bearing fault detection for operations and maintenance cost reduction in wind energy

Abstract Critical mechanical faults in wind turbine systems lead to considerable downtime and repair costs. Improving the detection and diagnosis of such faults thus brings about significant cost reductions for operations and maintenance (O&M) and electricity production. One of the most common defects in drivetrains are rolling element bearing faults. Detecting the faults in their incipient phase can prevent a more catastrophic breakdown and save a company time and money. This paper focuses on separating the bearing fault signals from masking signals coming from drivetrain elements like gears or shafts. The separation is based on the assumption that signal components of gears or shafts are deterministic and appear as clear peaks in the frequency spectrum, whereas bearing signals are stochastic due to random jitter on their fundamental period and can be classified as cyclostationary. A technique that recently gained more attention for separating these two types of signals is the cepstral editing procedure and it is investigated further in this paper as an automated procedure. The performance of the developed methods is validated on experimental data from the National Renewable Energy Laboratory (NREL) in the context of the wind turbine gearbox condition monitoring round robin study.

In-Place Calibration With Single Measurement in Time-Domain Microwave Breast Imaging

Microwave breast imaging requires a calibration process, which extracts the tumor response from the received signal. Existing calibration methods require more than two measurements. In this letter, we propose a calibration method called “in-place calibration” for time-domain microwave imaging. The method can obtain the received signal and the reference signal in a single measurement with the antenna array in place. It can minimize the measurement errors that occur due to environmental changes during calibration. The method also minimizes the error due to random clock jitter. The proposed in-place calibration is compared to array rotation calibration and differential calibration using homogeneous and heterogeneous breast phantoms. In most cases, in-place calibration provided better results than array rotation calibration.

A 1-to-2048 Fully-Integrated Cascaded Digital Frequency Synthesizer for Low Frequency Reference Clocks Using Scrambling TDC

Generation of low jitter, high frequency clock from a low frequency reference clock using classical analog phaselocked loops (PLLs) requires large loop filter capacitor and power hungry oscillator. Digital PLLs can help reduce area but their jitter performance is severely degraded by quantization error. Specifically, their deterministic jitter (DJ), which is proportional to the loop update rate becomes prohibitively large at low reference clock frequencies. We propose a scrambling TDC (STDC) to improve DJ performance and a cascaded architecture with digital multiplying delay locked loop as the first stage and hybrid analog/digital PLL as the second stage to achieve low random jitter in a power efficient manner. Fabricated in a 90 nm CMOS process, the prototype frequency synthesizer consumes 4.76 mW power from a 1.0 V supply and generates 160 MHz and 2.56 GHz output clocks from a 1.25 MHz crystal reference frequency. The long-term absolute jitter of the 160 MHz digital MDLL and 2.56 GHz digital PLL outputs are 2.4 psrms and 4.18 psrms, while the peak-to-peak jitter are 22.1 ps and 35.2 ps, respectively. The proposed frequency synthesizer occupies an active die area of 0.16mm2 and achieves power efficiency of 1.86 mW/GHz.

Performance of dynamical decoupling in bosonic environments and under pulse-timing fluctuations

We study the suppression of qubit dephasing through Uhrig dynamical decoupling (UDD) in nontrivial environments modeled within the spin-boson formalism. In particular, we address the case of (i) a qubit coupled to a bosonic bath with power-law spectral density, and (ii) a qubit coupled to a single harmonic oscillator that dissipates energy into a bosonic bath, which embodies an example of a structured bath for the qubit. We then model the influence of random time jitter in the UDD protocol by sorting pulse-application times from Gaussian distributions centered at appropriate values dictated by the optimal protocol. In case (i) we find that, when few pulses are applied and a sharp cutoff is considered, longer coherence times and robust UDD performances (against random timing errors) are achieved for a super-Ohmic bath. On the other hand, when an exponential cutoff is considered a super-Ohmic bath is undesirable. In case (ii) the best scenario is obtained for an overdamped harmonic motion. Our study provides relevant information for the implementation of optimized schemes for the protection of quantum states from decoherence.

Refractive turbulence strength estimation based on the laser echo signal amplification effect.

Experimental data proving the possibility of lidar measurement of the refractive turbulence strength based on the effect of backscattering amplification are reported. It is shown, for the first time to our knowledge, that the values of the amplification factor correlate with the variance of random jitter of the optical image of an incoherent light source depending on the value of the structure constant of the air refractive index turbulent fluctuations averaged over the probing path.

Vibration-based bearing fault detection on experimental wind turbine gearbox data

Rolling element bearing faults are one of the most common defects in rotating machinery. The detection of these faults has lately attracted an increasing amount of attention in the industry. Detecting the faults in their incipient phase can prevent a more catastrophic breakdown of a machine and can save a company time and money. An often occurring problem in analyzing vibration measurements of a rotating machine is the presence of harmonic signal components originating from different machine parts. This paper focuses on separating the bearing fault signals from other masking signal content coming from elements like gears or rotating shafts. The separation is based on the assumption that signal components of gears or shafts are deterministic and appear as clear peaks in the frequency spectrum, whereas bearing signals are stochastic due to random jitter on their fundamental period and can be classified as cyclostationary. A technique that has recently gained more attention for separating these two types of signals is the cepstral editing procedure (CEP). This preprocessing method is investigated further in this paper as an automated procedure. The cepstral editing procedure makes use of the fact that deterministic components appear in the cepstrum as narrow peaks and removal of these cepstral peaks reduces the amplitude of the corresponding discrete components. The residual stochastic signal after cepstral editing should consist mainly out of bearing fault signals in certain frequency bands. To analyze the residual signal the squared envelope spectrum is examined. The issue of selecting the proper frequency band where to demodulate the signal necessary for enveloping is addressed through the use of spectral kurtosis. The performance of the developed methods will be validated on experimental data from the National Renewable Energy Laboratory (NREL). This data has been made available by NREL in the context of the wind turbine gearbox condition monitoring round robin study. As such other research teams from around the world have analyzed this data as well and published their findings. The measurements were done on a wind turbine gearbox in a healthy and damaged condition and the setup is documented extensively, making it well suited fora performance comparison. A summary of the findings on the NREL data is discussed in this paper.

Hot-Carrier Instability of nMOSFETs Under Pseudorandom Bit Sequence Stress

Hot-carrier instability under stress conditions emulating a random logic operation (random ON and OFF) has been investigated using pseudorandom bit sequence (PRBS) stress patterns. Furthermore, the impacts of PRBS stress on circuit-level operation have been compared with the conventional dc (static) and ac (periodic) stress conditions using hot-carrier-induced random timing jitter. It was observed that the recovery achieved by charge trapping and detrapping under dynamic stress conditions significantly affects the degree of hot-carrier degradation.

Random noise can help to improve synchronization of excimer laser pulses

Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications.

An Aerial Video Stabilization Method Based on SURF Feature

The video captured by Micro Aerial Vehicle is often degraded due to unexpected random trembling and jitter caused by wind and the shake of the aerial platform. An approach for stabilizing the aerial video based on SURF feature and Kalman filter is proposed. SURF feature points are extracted in each frame, and the feature points between adjacent frames are matched using Fast Library for Approximate Nearest Neighbors search method. Then Random Sampling Consensus matching algorithm and Least Squares Method are used to remove mismatching points pairs, and estimate the transformation between the adjacent images. Finally, Kalman filter is applied to smooth the motion parameters and separate Intentional Motion from Unwanted Motion to stabilize the aerial video. Experiments results show that the approach can stabilize aerial video efficiently with high accuracy, and it is robust to the translation, rotation and zooming motion of camera.

基于激光章动的空间光到单模光纤的耦合方法

Based on the theory of mode-field matching, the relationship between coupling efficiency and jitter amplitude, radius ratio of Airy disk and single-mode fiber mode field is analyzed. In order to reduce the effect of random angle jitter on coupling efficiency, an automatic coupling scheme for making space light into single-mode fiber based on laser nutation is designed. The miss distance is calculated by data acquisition card and the offset voltage is output. The influence factors of algrithm precision and the relationship between laser nutation signal frequency and jitter frequency are analyzed. The feasibility of the algorithm is verified by Matlab simulation and experiments. Accuracy of miss distance angle is about 3 μrad obtained by experiment. The system feasibility is verified by space laser communication system. The coupling efficiency of the system is 67% when there is no disturbance, and it is improved by 6.5% when the disturbance is introduced and the control system is used to compensate the disturbance. The system response speed reaches 40 Hz. The coupling system is simple in structure and accurate in control algorithm. The controller signal processing speed is fast, and it has a great significance on the coupling of space light to single mode optical fiber. © 2016, Chinese Lasers Press. All right reserved.