Effect Of Jitter Research Articles

Steerable reflector-assisted communication in obstructed line-of-sight FSO link with optimal mitigation of dust-induced signal fading

This paper introduces an effective technique for bridging free-space optical (FSO) communication between end-to-end nodes with obstructed direct line-of sight (LOS) by incorporating a steerable mirror-and-lens-assisted (MLA) reflector assembly. The consistency of the proposed MLA-assisted FSO system is then experimentally evaluated and contrasted against a plane mirror (PM) reflector over a test-bed link set in a laboratory-fostered dusty environment for analyzing the system performance in terms of the received beam irradiance, received signal quality and noise-inflicted signal distortions. Furthermore, an intensity-dependent steerable MLA system is implemented to cater for the beam misalignment errors during the FSO link operation. It is observed that the proposed MLA assembly, in contrast to the PM reflector, can effectively harvest and focus the dust-induced scattered information-laden laser beam to a narrow-beam spot with intense irradiance level at the receiver aperture. Finally, the signal eye diagram is obtained for analyzing the signal quality in the presence and absence of background light. Based on the experimental study, it is apparent that the MLA reflectors not only aids in establishing a reliable direct LOS-obstructed FSO link but also effectively mitigates the dusty channel-induced beam fading effect and enhances the system immunity to noise and jitter effects.

Jitter Decomposition of High-Speed Data Signals From Jitter Histograms With a Pole–Residue Representation Using Multilayer Perceptron Neural Networks

In the stringent timing requirements of high-speed systems, the effect of jitter on the bit-error rate and overall timing error can no longer be overlooked. As jitter timing budgets are normally specified in the form of individual jitter components, a fast and reliable jitter decomposition technique plays an integral part in the design and verification of high-speed data links. This article presents a machine learning approach to extract the random and deterministic jitter components from the timing histograms of the eye diagram. Training data are generated using the dual-Dirac model, and a preprocessing technique is proposed using vector fitting to create a rational function representation of the jitter probability distribution function. Numerical results indicate that the proposed method is able to perform jitter decomposition accurately and generalize well under different circumstances. In addition, results show that the preprocessing step is able to accelerate the training process and improve the overall performance of the neural networks significantly.

A 600-MS/s DAC With Over 87-dB SFDR and 77-dB Peak SNDR Enabled by Adaptive Cancellation of Static and Dynamic Mismatch Error

This paper presents a Nyquist-rate current-steering digital-to-analog converter that achieves a peak spurious-free dynamic range better than 87 dB and a peak signal-to-noise-and-distortion ratio better than 77 dB over a 265-MHz signal band. It is enabled by a fully integrated digital calibration technique that measures and cancels both static and dynamic mismatch errors over the first Nyquist band, and various circuit-level techniques that mitigate the effects of jitter and inter-symbol interference.

Synchronous Constant Elapsed Time Speed Estimation Using Incremental Encoders

This paper proposes a high-performance speed measurement method for variable speed electric drives using incremental encoders. It is based on the well-known constant elapse time (CET) method. However, the principle of speed estimation is changed from event driven to ready on demand. This helps to remove the jitter effect, caused by the asynchronous nature of the CET method, and make the speed estimation time constant regardless of the current speed. The proposed method can be implemented on modern motion control microcontrollers. Experimental results using a vector controlled permanent magnet synchronous motor (PMSM) are provided to confirm the performance of the proposed algorithm and the improvements with respect to conventional methods. Synchronous the CET method of speed estimation allows to double the accuracy compared to the original CET method for the same behavior of the speed loop, or to increase the speed response time twice for the same accuracy.

On the Impact of Voice Encoding and Transmission on the Predictions of Speaker Warmth and Attractiveness

Modern human-computer interaction systems may not only be based on interpreting natural language but also on detecting speaker interpersonal characteristics in order to determine dialog strategies. This may be of high interest in different fields such as telephone marketing or automatic voice-based interactive services. However, when such systems encounter signals transmitted over a communication network instead of clean speech, e.g., in call centers, the speaker characterization accuracy might be impaired by the degradations caused in the speech signal by the encoding and communication processes. This article addresses a binary classification of high versus low warm--attractive speakers over different channel and encoding conditions. The ground truth is derived from ratings given to clean speech extracted from an extensive subjective test. Our results show that, under the considered conditions, the AMR-WB+ codec permits good levels of classification accuracy, comparable to the classification with clean, non-degraded speech. This is especially notable for the case of a Random Forest-based classifier, which presents the best performance among the set of evaluated algorithms. The impact of different packet loss rates has been examined, whereas jitter effects have been found to be negligible.

Improving Full-Body Pose Estimation from a Small Sensor Set Using Artificial Neural Networks and a Kalman Filter

Previous research has shown that estimating full-body poses from a minimal sensor set using a trained ANN without explicitly enforcing time coherence has resulted in output pose sequences that occasionally show undesired jitter. To mitigate such effect, we propose to improve the ANN output by combining it with a state prediction using a Kalman Filter. Preliminary results are promising, as the jitter effects are diminished. However, the overall error does not decrease substantially.

Underwater Optical Wireless Communications with Chromatic Dispersion and Time Jitter

The obsolete communication systems used in the underwater environment necessitates the development and use of modern telecommunications technologies. One such technology is the optical wireless communications, which can provide very high data rates, almost infinite bandwidth and very high transmission speed for real time fast and secure underwater links. However, the composition and the optical density of seawater hinder the communication between transmitter and receiver, while many significant effects strongly mitigate the underwater optical wireless communication (UOWC) systems’ performance. In this work, the influences of chromatic dispersion and time jitter are investigated. Chromatic dispersion causes the temporal broadening or narrowing of the pulse, while time jitter complicates the detection process at the receiver. Thus, the broadening of the optical pulse due to chromatic dispersion is studied and the influence of the initial chirp is examined. Moreover, the effect of the time jitter is also taken into consideration and for the first time, to the best of our knowledge, a mathematical expression for the probability of fade is extracted, taking into account the influence of both of the above-mentioned effects for a UOWC system. Finally, the appropriate numerical results are presented.

Performance Analysis of Time Synchronization Protocols in Wireless Sensor Networks

The time synchronization protocol is indispensable in various applications of wireless sensor networks, such as scheduling, monitoring, and tracking. Numerous protocols and algorithms have been proposed in recent decades, and many of them provide micro-scale resolutions. However, designing and implementing a time synchronization protocol in a practical wireless network is very challenging compared to implementation in a wired network; this is because its performance can be deteriorated significantly by many factors, including hardware quality, message delay jitter, ambient environment, and network topology. In this study, we measure the performance of the Flooding Time Synchronization Protocol (FTSP) and Gradient Time Synchronization Protocol (GTSP) in terms of practical network conditions, such as message delay jitter, synchronization period, network topology, and packet loss. This study provides insights into the operation and optimization of time synchronization protocols. In addition, the performance evaluation identifies that FTSP is highly affected by message delay jitter due to error accumulation over multi-hops. We demonstrate that the proposed extended version of the FTSP (E-FTSP) alleviates the effect of message delay jitter and enhances the overall performance of FTSP in terms of error, time, and other factors.

Impedance-to-Time Converter Circuit for Leaky Capacitive Sensors With Small Offset Capacitance

Capacitive sensors suffer from problems of the parasitic and offset capacitors. Also, in some capacitive sensors, leaky resistors carry information along with the sensor capacitor. An accurate impedance-to-time converter (ITC) circuit for leaky capacitive sensors that is able to deal with these problems and estimate the sensor capacitor and leaky resistor is presented in this article. The proposed circuit is a modified relaxation oscillator, which combines dual slope and charge transfer methods to measure the sensor capacitor and leaky resistor. The output pulses of the oscillator are acquired, and pulsewidth corresponding to high and low pulse are extracted and averaged. The effect of dc errors and jitter are significantly reduced because of the averaging. A prototype of the proposed ITC has been developed and tested. Experimental results show that the proposed ITC can measure low values of the sensor capacitor (minimum 9.6 pF) in the presence of a wide range of leaky resistors (270 kΩ to 9.6 MΩ) and offset capacitors (9.6 pF to 543.4 pF) with a worst-case error of about 1.1%, as compared to the theoretical values. The targeted application for the designed circuit is the humidity sensor with a frequency range between 500 Hz and 5 kHz.

Analysis of Timing Accuracy and Sensitivity in a RF Correlation-Based Impulse Radio Receiver With Phase Interpolation for Data Synchronization

This paper presents an analytical method for the performance evaluation of the correlation-based impulse radio (IR) receivers, which detect the data based on synchronizing the received signal with a locally generated template pulse. In this paper, a phase interpolation technique is employed to preserve synchronization accuracy with low power consumption. The analytical method computes the spectral density of jitter at the phase interpolator output, resulting from both flicker and thermal noise components. The analysis considers the aliasing phenomenon due to the sampling of the noise to predict the induced jitter accurately. Bit error rate (BER) of the receiver is also statistically estimated in terms of the induced jitter on the template pulse, the noise effect of the receiver chain, and the template signal level. The proposed estimation procedure is validated by comparing its results with transient noise simulations. It is shown that increasing the template signal range in the correlator and improving the linearity of the phase interpolation transfer curve, at a given power consumption, enhances the receiver sensitivity by 2 and 3.5 dB, respectively. The BER estimation results also reveal that the effect of the template signal jitter on the sensitivity of the correlation-based IR receivers becomes dominant with the increasing input signal level.

Effect of quantum and thermal jitter on the feasibility of Bekenstein’s proposed experiment to search for Planck-scale signals

A proposed experiment to test whether space is discretized [J. D. Bekenstein, Phys. Rev. D 86, 124040 (2012); Found. Phys. 44, 452 (2014)] is based on the supposed impossibility of an incident photon causing a displacement of a transparent block by less than the Planck length. An analysis of the quantum and thermal jitter of the block shows that it greatly diminishes the possibility that the experiment could reveal Planck-scale signals.

FEL performance achieved at PAL-XFEL using a three-chicane bunch compression scheme.

PAL-XFEL utilizes a three-chicane bunch compression (3-BC) scheme (the very first of its kind in operation) for free-electron laser (FEL) operation. The addition of a third bunch compressor allows for more effective mitigation of coherent synchrotron radiation during bunch compression and an increased flexibility of system configuration. Start-to-end simulations of the effects of radiofrequency jitter on the electron beam performance show that using the 3-BC scheme leads to better performance compared with the two-chicane bunch compression scheme. Together with the high performance of the linac radiofrequency system, it enables reliable operation of PAL-XFEL with unprecedented stability in terms of arrival timing, pointing and intensity; an arrival timing jitter of better than 15 fs, a transverse position jitter of smaller than 10% of the photon beam size, and an FEL intensity jitter of smaller than 5% are consistently achieved.

Hard X-ray self-seeding commissioning at PAL-XFEL.

A wake monochromator based on a large-area diamond single crystal for hard X-ray self-seeding has been successfully installed and commissioned in the hard X-ray free-electron laser (FEL) at the Pohang Accelerator Laboratory with international collaboration. For this commissioning, the self-seeding was demonstrated with a low bunch charge (40 pC) and the nominal bunch charge (180 pC) of self-amplified spontaneous emission (SASE) operation. The FEL pulse lengths were estimated as 7 fs and 29.5 fs, respectively. In both cases, the average spectral brightness increased by more than three times compared with the SASE mode. The self-seeding experiment was demonstrated for the first time using a crystal with a thickness of 30 µm, and a narrow bandwidth of 0.22 eV (full width at half-maximum) was obtained at 8.3 keV, which confirmed the functionality of a crystal with such a small thickness. In the nominal bunch-charge self-seeding experiment, the histogram of the intensity integrated over a 1 eV bandwidth showed a well defined Gaussian profile, which is evidence of the saturated FEL and a minimal electron-energy jitter (∼1.2 × 10-4) effect. The corresponding low photon-energy jitter (∼2.4 × 10-4) of the SASE FEL pulse, which is two times lower than the Pierce parameter, enabled the seeding power to be maximized by maintaining the spectral overlap between SASE FEL gain and the monochromator.

Output Current Optimization for Multibrick Parallel Discharge Drivers Based on Genetic Algorithm

By triggering the switches in sequence and controlling the brick charging voltage independently, a pulsed power system can generate flexible current waveform in the load, which could allow high-accurate magnetic pressure in experimental materials in the study of EOS data and dynamic response of material characterization. Currently, a 1.5-MA driver with 20 independent bricks has been developed, and a programmable 256-brick parallel discharge driver which is able to generate shaped current greater than 6.5 MA is under construction in the China Academy of Engineering Physics. In this paper, for these two multibrick parallel discharge drivers, the method of optimizing the output current waveform of the driver is studied by using the genetic algorithm and the corresponding optimization results of different target current waveforms are obtained. An experimental platform is set up for studying the gas switch breakdown characteristics. The self-breakdown and triggering breakdown experiments of the switch are conducted, and its breakdown characteristics are researched. Meanwhile, the effect of breakdown delay and jitter on the output current waveform is studied by simulation. This paper is of great significance to the actual operation of the multibrick parallel discharge drivers.

Timing jitter effect in microchip laser and its reduction by backward reflection in fiber delay line

A simple, efficient, and low-cost method is proposed to reduce the timing jitter in passively Q-switched microchip lasers by self-injection seeding. A portion of the output pulse of the microchip laser was incident into the fiber delay line, and then, the backward reflection light induced the formation of the pulse. With different lengths of fiber, it was found that the timing jitter of the microchip laser could be reduced effectively when the repetition rate of the microchip laser was about 0.8 times the reciprocal of the delay time. The standard deviation of the microchip laser was reduced from several hundred nanoseconds to less than 181 ps.

PLANETARY3D: A PHOTOGRAMMETRIC TOOL FOR 3D TOPOGRAPHIC MAPPING OF PLANETARY BODIES

Abstract. Planetary remote sensing images are the primary datasets for high-resolution topographic mapping and modeling of the planetary surfaces. However, unlike the mapping satellites for Earth observations, cameras onboard the planetary satellites generally present special imaging geometries and configurations, which makes the stereo photogrammetric process difficult and requires a large number of manual interactions. At the Hong Kong Polytechnic University, we developed a unified photogrammetric software system, namely Planetary3D, for 3D topographic mapping modeling of various planetary bodies using images collected by various sensors. Planetary3D consists of three modules, including: (1) the pre-processing module to deliver standardized image products, (2) the bundle adjustment module to alleviate the inconsistencies between the images and possibly the reference frame, and (3) the dense image matching module to create pixel-wise image matches and produce high quality topographic models. Examples of using three changeling datasets, including the MRO CTX, MRO HiRISE and Chang’E-2 images, have revealed that the automatic pipeline of Planetary3D can produce high-quality digital elevation models (DEMs) with favorable performances. Notably, the notorious jitter effects visible on HiRISE images can be effectively removed and good consistencies with the reference DEMs are found for the test datasets by the Planetary3D pipeline.

Evaluation of Synchronized SS-CDMA for QZSS Safety Confirmation System

In this paper, we investigate the realization of synchronized spread spectrum code division multiple access (synchronized SS-CDMA) for the quasi-zenith satellite system (QZSS) safety confirmation system during major disasters. The QZSS is expected to provide a highly accurate positioning service and allow two-way communication, which includes the terminal location and short messages. The proposed synchronized SS-CDMA scheme realizes direct access from mobile terminals to the satellite and the simultaneous transmission of many users using SS codes with a large spreading factor. All terminals synchronize their own clock and frequency with those of the global navigation satellite system (GNSS). In this scheme, maintaining orthogonality among users in both the time and frequency domains is the most important problem. In this paper, for the consideration of mobile use, the effect of residual timing jitter and frequency offset in a fading environment is evaluated by computer simulation. As a result, acceptable timing and frequency errors for terminals are clarified in order for the system to be viable using the GNSS.

Investigation of electronic aperture jitter effect in channel-interleaved photonic analog-to-digital converter.

The electronic aperture jitter effect originating from the electronic digitization is investigated in the channel-interleaved photonic analog-to-digital converter (PADC) system. The influence of the electronic aperture jitter to the effective number of bits (ENOB) of the PADC system is extracted and evaluated. According to the theoretical analysis, the electronic aperture jitter can be significantly suppressed by the channel-interleaving scheme. In the experiment, the effect of electronic aperture jitter is measured under different optical-electronic conversion (OEC) bandwidths and channel numbers. It is eventually found that the condition of the OEC bandwidth equaling to the Nyquist frequency of one single channel is critical to optimize the electronic aperture jitter and ENOB.

Colorado Ultraviolet Transit Experiment data simulator

The Colorado Ultraviolet Transit Experiment (CUTE) is a 6U NASA CubeSat carrying on-board a low-resolution (R~2000--3000), near-ultraviolet (2500--3300 {\AA}) spectrograph. It has a rectangular primary Cassegrain telescope to maximize the collecting area. CUTE, which is planned for launch in Spring 2020, is designed to monitor transiting extra-solar planets orbiting bright, nearby stars aiming at improving our understanding of planet atmospheric escape and star-planet interaction processes. We present here the CUTE data simulator, which we complemented with a basic data reduction pipeline. This pipeline will be then updated once the final CUTE data reduction pipeline is developed. We show here the application of the simulator to the HD209458 system and a first estimate of the precision on the measurement of the transit depth as a function of temperature and magnitude of the host star. We also present estimates of the effect of spacecraft jitter on the final spectral resolution. The simulator has been developed considering also scalability and adaptability to other missions carrying on-board a long-slit spectrograph. The data simulator will be used to inform the CUTE target selection, choose the spacecraft and instrument settings for each observation, and construct synthetic CUTE wavelength-dependent transit light curves on which to develop the CUTE data reduction pipeline.

Phase response theory explains cluster formation in sparsely but strongly connected inhibitory neural networks and effects of jitter due to sparse connectivity.

We show how to predict whether a neural network will exhibit global synchrony (a one-cluster state) or a two-cluster state based on the assumption of pulsatile coupling and critically dependent upon the phase response curve (PRC) generated by the appropriate perturbation from a partner cluster. Our results hold for a monotonically increasing (meaning longer delays as the phase increases) PRC, which likely characterizes inhibitory fast-spiking basket and cortical low-threshold-spiking interneurons in response to strong inhibition. Conduction delays stabilize synchrony for this PRC shape, whereas they destroy two-cluster states, the former by avoiding a destabilizing discontinuity and the latter by approaching it. With conduction delays, stronger coupling strength can promote a one-cluster state, so the weak coupling limit is not applicable here. We show how jitter can destabilize global synchrony but not a two-cluster state. Local stability of global synchrony in an all-to-all network does not guarantee that global synchrony can be observed in an appropriately scaled sparsely connected network; the basin of attraction can be inferred from the PRC and must be sufficiently large. Two-cluster synchrony is not obviously different from one-cluster synchrony in the presence of noise and may be the actual substrate for oscillations observed in the local field potential (LFP) and the electroencephalogram (EEG) in situations where global synchrony is not possible. Transitions between cluster states may change the frequency of the rhythms observed in the LFP or EEG. Transitions between cluster states within an inhibitory subnetwork may allow more effective recruitment of pyramidal neurons into the network rhythm. NEW & NOTEWORTHY We show that jitter induced by sparse connectivity can destabilize global synchrony but not a two-cluster state with two smaller clusters firing alternately. On the other hand, conduction delays stabilize synchrony and destroy two-cluster states. These results hold if each cluster exhibits a phase response curve similar to one that characterizes fast-spiking basket and cortical low-threshold-spiking cells for strong inhibition. Either a two-cluster or a one-cluster state might provide the oscillatory substrate for neural computations.