Large Jitter Research Articles

How changes in the mean latency, jitter amplitude, and jitter frequency impact target acquisition performance

Interactive technologies require the user to frequently generate purposeful movements, where actions are guided towards targets. While delays between the movement onset and the corresponding update within the virtual space have been shown to impair target acquisition, the relative contribution of the individual latency parameters remains unclear. This paper investigates how changes in latency, the moment-by-moment variability in the latency (jitter amplitude) and the rate of variability (jitter frequency), affect the speed and accuracy of target acquisition at different mean latencies. Experiment 1 explored changes in the mean latency and jitter amplitude. As the mean latency increased, we observed substantial impairments in completion time and accuracy, with increased variability in performance. There was also an interaction between the mean latency and jitter amplitude: although large jitter amplitudes caused a small completion time impairment, this effect decreased as the mean latency increased. Experiment 2 isolated the effect of the jitter by investigating changes in the jitter amplitude and jitter frequency at a fixed mean latency. Here, we observed completion time impairments from 67ms amplitude and accuracy impairments from 134ms amplitude. Like Experiment 1, the effect of the amplitude was small. Notably, we found no evidence that changes in the jitter frequency significantly influenced performance. Overall, increases in the mean latency contributed most to the impairment, disrupting acquisition speed and accuracy as it increased. Large jitter amplitudes also disrupted speed and accuracy, but this was a comparatively small effect that was mediated by the mean latency.

SiPM joint likelihood reception for mobile LED-optical communication under pointing errors.

Light-emitting diode (LED)-optical communication is a novel spectrum communication with wide field of view (FOV), light weight, and long-distance free-space capabilities. Due to atmospheric turbulence attenuation and pointing errors caused by long-distance communication, this Letter proposes a multi-pixel channel joint maximum likelihood (JML) reception method using a highly sensitive silicon photomultiplier (SiPM). To evaluate the performance of the SiPM under mobile terminal jittering communication, we analyze the effect of optical transmitting power, pointing errors, and signal-to-noise ratio (SNR) gain on optical communication by comparing JML with signal channel using the maximum likelihood (ML) algorithm. Both simulation analysis and experimental results demonstrate that the proposed JML algorithm to process signals received from SiPM multi-pixel channels can effectively mitigate the impact of pointing errors on the bit error rate (BER) of optical communications by two orders of magnitude at large jitter radians and SNR.

Partial-order reduction in reachability-based response-time analyses of limited-preemptive DAG tasks

Response-time analysis (RTA) has been a means to evaluate the temporal correctness of real-time systems since the 1970 s. While early analyses were successful in capturing the exact upper bound on the worst-case response-time (WCRT) of systems with relatively simple computing platforms and task activation models, nowadays we see that most existing RTAs either become pessimistic or do not scale well as systems become more complex (e.g., parallel tasks running on a multicore platform). To make a trade-off between accuracy and scalability, recently, a new reachability-based RTA, called schedule-abstraction graph (SAG), has been proposed. The analysis is at least three orders of magnitude faster than other exact RTAs based on UPPAAL. However, it still has a fundamental limitation in scalability as it suffers from state-space explosion when there are large uncertainties in the timing parameters of the input jobs (e.g., large release jitters or execution-time variations). This could impede its applicability to large industrial use cases, or to be integrated with automated tools that explore alternative design choices. In this paper, we improve the scalability of the SAG analysis by introducing partial-order reduction rules that avoid combinatorial exploration of all possible scheduling decisions. We include systems with dependent and independent task execution models (i.e., with and without precedence constraint). Our empirical evaluations show that the proposed solution is able to reduce the runtime by five orders of magnitude and the number of explored states by 98% in comparison to the original SAG analysis. These achievements come only at a negligible cost of an over-estimation of 0.1% on the actual WCRT. We applied our solution on an automotive case study showing that it is able to scale to realistic systems made of hundreds of tasks for which the original analysis fails to finish.

Free-Running Single-Photon Detection via GHz Gated InGaAs/InP APD for High Time Resolution and Count Rate up to 500 Mcount/s

Free-running InGaAs/InP single-photon avalanche photodiodes (SPADs) typically operate in the active-quenching mode, facing the problems of long dead time and large timing jitter. In this paper, we demonstrate a 1-GHz gated InGaAs/InP SPAD with the sinusoidal gating signals asynchronous to the incident pulsed laser, enabling free-running single-photon detection. The photon-induced avalanche signals are quenched within 1 ns, efficiently reducing the SPAD's dead time and achieving a count rate of up to 500 Mcount/s. However, the timing jitter is measured to be ~168 ps, much larger than that of the SPAD with synchronous gates. We adjust the delay between the gating signals and the incident pulsed laser to simulate the random arrival of the photons, and record the timing jitter, respectively, to figure out the cause of the jitter deterioration. In addition, the effects of the incident laser power and working temperature of the APD on the time resolution have been investigated, broadening the applications of the GHz gated free-running SPAD in laser ranging and imaging, fluorescence spectroscopy detection and optical time-domain reflectometry.

Frequency Source Design of Fast Locking Laser Range Radar

Given the bad ranging precision in continuous wave laser range radar systems because of the large jitter of the main oscillator frequency source, this paper introduces the fast locking method, which is based on Field Programmable Gate Array (FPGA) and modified mixed Charge Pump Phase Locked Loop (CPPLL), effectively improving the locking time of PLL frequency source. The input frequency is generated by a temperature compensation quartz crystal oscillator with high stability frequency (TCXO). It improves the PLL performance using the two-order active filter, reduces the phase detector dead-banding, and improves the frequency stability through the buffer insertion in PFD. The traditional PLL was improved by using preset voltage mode, which improves the PLL lock time. Finally, it analyzes the influence of frequency stability on the ranging accuracy of laser radar. The test results show that PLL lock time is up to 1.6ms. It can be applied to continuous wave laser radar ranging systems.

Robust Blood Sugar Monitoring in Diabetic Patients with Timing Jitter due to Human Factors

Blood sugar monitoring in diabetic patients is commonly provided with timing jitter caused by human factors. In this paper we address the problem by developing the robust H2 optimal finite impulse response (OFIR) filter under under possible disturbances, initial errors, and measurement errors. The filter is applied to data collected daily before breakfast from diabetic patients. It is shown that the robust H2-OFIR filter improves the accuracy of the OFIR filter by the factor of less than the fractional time jitter. That is, for large fractional timing jitter of 10% the improvement would be less than 10% that is small. Otherwise, it is worth using robust estimators.

Effect of sampling time jitter on robust [formula omitted] filtering estimates

In discrete-time processes, the sampling time jitter occurs naturally due to various unavoidable reasons, which make the model uncertain. Therefore, robust state estimators should be used. To find out if it is rational to design such estimators or if we can simply ignore the time jitter, in this paper we investigate its effect on the robust H2 optimal finite impulse response (OFIR) filter in a comparison with the OFIR filter. As benchmarks, we also use the maximum likelihood FIR, unbiased FIR, and Kalman filters. The robust batch H2-OFIR filter is developed for timing jitter under disturbances, initial errors, and measurement errors. For Gaussian errors, its iterative algorithm is designed using modified Kalman recursions. Numerical investigations and applications to blood sugar monitoring in diabetic patients with daily timing jitter have shown that the robust H2-OFIR filter improves the accuracy of the OFIR filter by the factor of less than the fractional time jitter. That is, for large fractional timing jitter of 10% the improvement would be less than 10% that is small. Otherwise, it is worth using robust estimators.

Weight-assisted exoskeleton knee joint plunger cylinder control optimization

In order to solve the problem of large jitter in the knee joint during the squatting process of the self-developed weight-assisted exoskeleton system, the AMESim-based knee plunger cylinder simulation model was established, the causes of jitter were analyzed from the simulation perspective, and the control strategy of the knee plunger cylinder was optimized and simulated. The results show that the optimized control strategy can realize the squatting motion of the exoskeleton system smoothly, and the test verification was carried out on the prototype. The results show that the optimized control strategy can better realize the human–machine flexibility of the exoskeleton squatting process, solve the problem of large jitter, and provide technical support for the realization of the exoskeleton movement down the stairs.

A low-jitter timing generator based on completely on-chip self-measurement and calibration in a field programmable gate array.

This paper presents a high-stability and low-jitter Arbitrary Timing Generator (ATG) designbased on the Xilinx Field Programmable Gate Array (FPGA) and its special integrated delay line. In recent years, FPGA-based or application specific integrated circuit-based delay lines have been used to achieve picosecond-level timing resolution. Devices with pure digital delay methods can only acquire triggers at the clock rising edges when triggered externally. Therefore, there is a large time irregularity caused by the uncertainty of the entry time of the trigger, which is difficult to compensate and leads to a large time jitter of outputs. We describe the designof an ATG that includes jitter self-measurement and calibration methods, which is available for both internal and external trigger modes. This structure is completely based on the FPGA's own resources and has the advantages of being simple and flexible. Experimental results show a sub-nanosecond timing resolution of 78 ± 20ps with a minimum of 120ps and a time jitter of 160 ± 20ps in the external trigger mode after compensation.

Two-dimensional correlation analysis for x-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on the local chemical environment. The technique relies on measuring the photoelectron spectrum upon x-ray photoionisation, and the resolution is often limited by the bandwidth of the ionising x-ray pulse. This is particularly problematic for time-resolved XPS, where the desired time resolution enforces a fundamental lower limit on the bandwidth of the x-ray source. In this work, we report a novel correlation analysis which exploits the correlation between the x-ray and photoelectron spectra to improve the resolution of XPS measurements. We show that with this correlation-based spectral-domain ghost imaging method we can achieve sub-bandwidth resolution in XPS measurements. This analysis method enables XPS for sources with large bandwidth or spectral jitter, previously considered unfeasible for XPS measurements.

Overcome the Brightness and Jitter Noises in Video Inter-Frame Tampering Detection.

Digital video forensics plays a vital role in judicial forensics, media reports, e-commerce, finance, and public security. Although many methods have been developed, there is currently no efficient solution to real-life videos with illumination noises and jitter noises. To solve this issue, we propose a detection method that adapts to brightness and jitter for video inter-frame forgery. For videos with severe brightness changes, we relax the brightness constancy constraint and adopt intensity normalization to propose a new optical flow algorithm. For videos with large jitter noises, we introduce motion entropy to detect the jitter and extract the stable feature of texture changes fraction for double-checking. Experimental results show that, compared with previous algorithms, the proposed method is more accurate and robust for videos with significant brightness variance or videos with heavy jitter on public benchmark datasets.

Stabilization of a Harmonic Mode-Locking by Shifting the Carrier Frequency

Harmonically mode-locked soliton fiber lasers have been intensively investigated in recent years due to their wide range of applications. Drawback of these lasers is relatively large timing jitter which is significantly higher than the timing jitter in lasers operating at fundamental frequency. We report the stabilizing frequency shift effect in harmonic mode-locking ring soliton fiber laser that is studied theoretically and numerically. It is known that a harmonic mode-locking regime in a fiber laser occurs due to interpulse repulsion, which leads to a uniform distribution of pulses in the cavity. We demonstrate that the frequency shift contributes to an increase in the hardness of interpulse interactions and can led to stabilization of the periodic arrangement of pulses. The experiment carried out confirms the theoretical predictions and the results of numerical simulation.

Low-Jitter CMOS Digital PLL for the generation of the clock in synchronous serial communication systems

The major building block of linear systems is the Phased Locked-Loop(PLL). Contrasting to analog PLL, the clock period profile of digital PLL (DPLL) is often segmented. Hence the phase and/or frequency tracking of traditional PLL’s may suffer from large jitter when Voltage Controlled Oscillator (VCO) operating point shifts from one clock period segment to another. To address this issue, a Low-Jitter CMOS Digital PLL for the generation of the clock in synchronous serial communication systems is presented in this paper. The design of the PLL will be implemented by considering important CMOS parameters like propagation delay, jitter performance, and power dissipation. Designing of digital PLL includes the design of a phase detector, LPF, Error amplifier, and VCO. The VLSI realization of digital PLL is implemented using the TANNER EDA software tool using a 0.18μm CMOS process.

Temporal quantization deteriorates the discrimination of interaural time differences.

Cochlear implants (CIs) often replace acoustic temporal fine structure by a fixed-rate pulse train. If the pulse timing is arbitrary (that is, not based on the phase information of the acoustic signal), temporal information is quantized by the pulse period. This temporal quantization is probably imperceptible with current clinical devices. However, it could result in large temporal jitter for strategies that aim to improve bilateral and bimodal CI users' perception of interaural time differences (ITDs), such as envelope enhancement. In an experiment with 16 normal-hearing listeners, it is shown that such jitter could deteriorate ITD perception for temporal quantization that corresponds to the often-used stimulation rate of 900 pulses per second (pps): the just-noticeable difference in ITD with quantization was 177 μs as compared to 129 μs without quantization. For smaller quantization step sizes, no significant deterioration of ITD perception was found. In conclusion, the binaural system can only average out the effect of temporal quantization to some extent, such that pulse timing should be well-considered. As this psychophysical procedure was somewhat unconventional, different procedural parameters were compared by simulating a number of commonly used two-down one-up adaptive procedures in Appendix B.

13.2: Equalizer and Clock/Data Recovery Circuits in SDICs for Intra‐Panel Interface

This work presents a front‐end circuits including of the equalizer and clock/data recovery (CDR) circuits in the source driver ICs (SDICs) for the TFT‐LCD intra‐panel interfaces. For 4K2K LCD TV, the data rate of SDICs has been increased to 5Gbps per lane, so it is a challenge to develop the front‐end circuits when they suffered from the serious ISI and large jitters in received data. In the front‐end circuits meeting the BOE’s CHPI specification, a cascade equalizer are used to widen the eye diagram to reduce BER and a dual loop CDR circuits are used to tolerate the large input jitter and power noise.

An All-Digital On-Chip Peak-to-Peak Jitter Measurement Circuit With Automatic Resolution Calibration for High PVT-Variation Resilience

A new, all-digital on-chip peak-to-peak (p-p) jitter measurement circuit (OCJM) that features automatic resolution calibration for high PVT-variation resilience without a reference clock and off-line calibration is presented in this paper. The OCJM uses a front-end self-referenced circuit (SRC) to eliminate the jitter-free reference signal and a back-end p-p jitter detector (PPD) to perform p-p jitter measurements. The key design of the proposed OCJM is that the SRC and the PPD share a Vernier delay line (VDL) so that the run-time PVT information automatically extracted from the SRC operation can be carried onto the PPD to achieve automatic on-line resolution calibration. Besides this feature, the OCJM uses on-chip direct p-p jitter measurement with only 1-time readouts to eliminate the huge power consumption of the off-chip data communication while avoiding data loss of a possible large jitter caused by PVT variations during off-chip data communication. These techniques make the proposed OCJM suitable for any-time, any-site jitter measurements for SoC applications. The proposed OCJM is fabricated in a 28-nm CMOS. The measurement results show that the timing resolution and minimum measurable jitter range specifications are met under extreme PVT conditions while achieving 98% clock cycle and energy reduction compared to the conventional OCJM designs.

Phase stabilization of a relativistic backward wave oscillator by controlling the cathode characteristics for a slowly rising voltage pulse

We found that the start time in microwave generation of a relativistic backward wave oscillator (RBWO) for a slowly rising voltage pulse demonstrates a large jitter, which can be explained by the spread of explosive electron emission thresholds and plasma formation rates of the explosive emission cathode, and this large jitter is reduced greatly by a weak external RF signal. So, the effects of the emission threshold and plasma formation rate on the oscillation start time of a single RBWO and on the phase synchronization in two parallel RBWOs are investigated using particle-in-cell simulations. The 2D simulations show that a larger emission threshold and a faster plasma formation rate lead to a shorter start time due to the stronger shock excitation provided by the sharper beam current leading edge. For some special emission thresholds, the start time is abnormally long, which is due to the generation of other frequencies because of the shock excitation. The 3D simulations illustrate that with a larger emission threshold and a faster plasma formation rate, phase synchronization can be obtained in two parallel RBWOs even for a large voltage rise time. Therefore, we expect that by choosing the appropriate cathode emission threshold and plasma formation rate, it is possible to realize phase stabilization of an RBWO for a slowly rising voltage pulse even without an external RF signal.

Generation of ultrashort coherent radiation based on a laser plasma accelerator.

A laser plasma accelerator (LPA) has the potential to realize compact free-electron laser (FEL) radiation at the regular laboratory scale. However, large initial angular divergence and energy spread dramatically hinder ways to transport the beam and realize FEL radiation. Although methods have been proposed to solve these problems, the relatively large jitter, including transverse position jitter and energy jitter, still limits the advance of these experiments. In this paper a simple method to realize coherent harmonic generation based on a LPA beam is proposed. The scheme is very compact, adopting a high-power laser split from the driver laser, a short modulator and a short radiator which has a great tolerance to these typical types of jitter. Numerical simulations indicate that coherent third-harmonic radiation with gigawatt-level power and single spike spectra can be obtained, verifying the feasibility of the scheme and indicating the capability to generate ultrashort fully coherent radiation.

Radar Signal Sorting Algorithm Based on PRI for Large Jitter

The traditional PRI transform method has high estimation accuracy for the pulse repetition interval, but its anti-jitter capability is much worse. The modified PRI transform algorithm combines shifting time origins and overlapped PRI bins methods to improve the traditional PRI transform algorithm. Although it has a certain anti-jitter capability after the improvement, it still cannot be obtained in the case of large jitter. In this paper, the least squares method is introduced to segment the jitter signal to reduce the jitter effect, and then combine the traditional PRI transform method to sort the jitter signal. The simulation results show that the signal sorting method has a good effect in the case of large jitter.

Fog-Aided Verifiable Privacy Preserving Access Control for Latency-Sensitive Data Sharing in Vehicular Cloud Computing

VCC is an emerging computing paradigm developed for providing various services to vehicle drivers, and has attracted more and more attention from researchers and practitioners over the last few years. However, privacy preserving and secure data sharing has become a very challenging and important issue in VCC. Unfortunately, existing secure access control schemes consume too many computation resources, which prevents them from being performed on computing resource constrained vehicle onboard devices. Also, these cloud-based schemes suffer large latency and jitter due to their centralized resource management, and thus may not be suitable for real-time applications in VANETs. In this article, we thus propose a novel fog-to-cloud-based architecture for data sharing in VCC. Our scheme is a cryptography-based mechanism that conducts fine-grained access control. In our design, the complicated computation burden is securely outsourced to fog and cloud servers with confidentiality and privacy preservation. Meanwhile, with the prediction of a vehicle's mobility, pre-pushing data to specific fog servers can further reduce response latency with no need to consume more resources of the fog server. In addition, with the assumption of no collusion between different providers for the cloud and fog servers, our scheme can provide verifiable auditing of fog servers' reports. The scheme is proved secure against existing adversaries and newborn security threats. Experimental test shows significant performance improvement in edge devices' overhead saving and response delay reduction. Introduction