Jitter Problem Research Articles

Experimental Demonstration of an Operand Routing Network Prototype Employing Clock Control and Data Synchronization Scheme

We have previously proposed a clock distribution and data synchronization scheme to address a problem of jitter accumulated in Large Scale SFQ circuits such as Reconfigurable Data Paths processor (RDP). The RDP is divided into several stages clocked separately by an external jitter free system clock and FIFO buffers and clock controllers between the stages are used to synchronize data. In this paper we present architecture and experimental results of an RDP prototype that employed Operand Routing Network (ORN) and clock control and data synchronization scheme designed for ISTECSRL 10 kA/cm 2 advanced process. The circuit consisted of the ORN with 3 data inputs and maximum connection length equal to 1, three 8-bit input and six 10-bit output dual FIFO buffers, a 3-bit controller, a ladder type high frequency clock signal generator and six 8-bit output shift registers. Total it employed 6536 Josephson junctions and required a bias current of 0.74 A. The prototype was successfully tested at the frequencies up to 48 GHz.

The problem of jitter and its correction for diagnostics at ASDEX Upgrade

Different optical diagnostics are operated at fusion devices like ASDEX Upgrade. One of them is thermography for contactless temperature measurements of surfaces in the vessel using infrared cameras. These temperatures can be used for the calculation of the heat flux on the monitored surfaces. But for the correct analysis of the recorded data stable measurement conditions regarding mechanical aspects like vibrations are needed. Since these conditions are often not fulfilled the measurements are affected by jitter. This paper describes a method used at ASDEX Upgrade for the correction of 1D and 2D thermographic data to compensate the jitter. It is based on a correlation analysis and also deals with jitter in the subpixel range. Examples are shown for the correction of temperature data and also for the influence on heat flux calculations with corrected and uncorrected temperatures. The limits of the proposed algorithm are also mentioned.

Compact Passively Q-Switched Yb:YAG Multipass Ring Lasers

An efficient and compact continuous-wave Yb:YAG laser with a slope efficiency of 50.3% with respect to the absorbed power was demonstrated using a multipass ring cavity (MPRC). Large cavity length ranges can be implemented using MPRCs with the same optical elements but different beam configurations. When Cr:YAG was used as the saturable absorber for passive Q-switching, various pulse widths and repetition rates were obtained. When a two-mirror MPRC, which is a compact ring laser cavity was used, the spatial hole-burning effect was reduced, and the spontaneous noise from the gain medium was not directly incident on the saturable absorber, causing less perturbation of the population difference of the saturable absorber than that of a linear cavity. This indicates that MPRCs can reduce the time jitter problem of a passively Q-switched laser. In this study, a Yb:YAG MPRC laser with a 33 ns pulse width is demonstrated, and the timing jitter of the repetition period was restrained to around 11%. The obtained experimental results are in good agreement with simulation results.

Expedited forwarding end‐to‐end delay and jitter in DiffServ

AbstractThe scheduling disciplines and active buffer management represent the main components employed in the differentiated services (DiffServ) data plane, which provide qualitative per‐hop behaviors corresponding to the QoS required by supported traffic classes. In the first part of this paper, we compute the per‐hop delay bound that should be guaranteed by the different multiservice scheduling disciplines, so that the end‐to‐end (e2e) delay required by expedited forwarding (EF) traffic can be guaranteed. Consequently, we derive the e2e delay bound of EF traffic served by priority queuing–weighted fair queuing (PQ–WFQ) at every hop along its routing path. Although real‐time flows are principally offered EF service class, some simulations on DiffServ‐enabled network show that these flows suffer from delay jitter and they are negatively impacted by lower priority traffic. In the second part of this paper, we clarify the passive impact of delay jitter on EF traffic, where EF flows are represented by renewal periodic ON–OFF flows, and the background (BG) flows are characterized by the Poisson process. We analyze through different scenarios the jitter effects of these BG flows on EF flow patterns when they are served by a single class scheduling discipline, such as first‐input first‐output, and a multiclass or multiservice scheduling discipline, such as static priority service discipline. As a result, we have found out that the EF per‐hop behaviors (PHBs) configuration according to RFCs 2598 and 3246 (IETF RFC 2598, June 1999; RFC 3246, IETF, March 2002) cannot stand alone in guaranteeing the delay jitter required by EF flows. Therefore, playout buffers must be added to DiffServ‐enabled networks for handling delay jitter problem that suffers from EF flows. Copyright © 2008 John Wiley & Sons, Ltd.

52 Gb/s 161 transmitter in 0.13 [micro sign]m SiGe BiCMOS technology

A52-Gb/s 16:1 quarter-rate clocking transmitter for high-speed serial data transmission is designed to utilise 0.13-mum SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. The quarter-rate transmitter consists of a 16:1 multiplexer (MUX), a voltage-controlled ring oscillator, a phase-locked loop (PLL), a pseudorandom data generator and an output amplifier. The voltage-controlled ring oscillator has a wide tuning range from 11 to 22 GHz with feedforward loop and delay interpolation. A continuous model of a third-order PLL is developed and used to optimise loop filter parameters and to estimate the PLL performance in a simulation. The PLL achieves a low phase noise of -124.6 dBc/Hz at 1 MHz offset. The 16:1 MUX features quarter-rate clock multiplexing with multi-phase voltage-controlled oscillator clocks. In the design of a 16:1 MUX, an edge-channelling 4:1 MUX is used to alleviate a duty cycle and a jitter problem.

Using UWB Gaussian pulses for inter-vehicle communications

Ultra-wideband (UWB) radio is a candidate technology for future wireless communications. It uses very short pulses, so that the spectrum of the emitted signals may spread over several GHz. An inter-vehicle communication system based on UWB technology is studied. Two waveforms are compared: Gaussian and monocycle pulses. A 2 GHz pulse generator is associated with an antipodal (AP) modulator in the first case and with a binary phase shift keying (BPSK) modulator in the second case. The numerical receiver and the detection algorithm are described. The performance of the matched filter receiver is evaluated in the case of multipath propagation with additive white Gaussian noise (AWGN). The European Telecommunication Systems Institute (ETSI) rural area (RA) channel has also been considered. The bit error rate (BER) values are calculated for the two UWB waveforms and the time jitter problem is also addressed. It is shown that the AP-coded Gaussian pulses waveform is the best signalling waveform among those studied here, with the supplementary advantages of a very low sensitivity to multipath effects and to jitter, together with much lower error rates.

IP Telephony and Delay Jitter Control—An Overview

Packet network based telephony has become an attractive application because of many advantages it offers in terms of costs and services. This article discusses some of the major technical challenges in the implementation of IP telephony. One of the challenges in IP telephony is that of delay jitter in the received audio. The problem of jitter in delays needs to be handled even in the newer networks having high bandwidth and low delays. In this paper, we discuss the jitter problem in detail and provide an overview of various methods used to tackle it. These include a new method proposed by the authors which offers performance gains in terms of packet loss and jitter over existing methods.

A 0.18-/spl mu/m 256-Mb DDR-SDRAM with low-cost post-mold tuning method for DLL replica

A delay-locked loop (DLL) must have a large delay line to work over a wide range of frequency. This makes the layout area larger. A hierarchy delay line solves this problem. But coarse and fine delay changing at the same time causes jitter. This DLL and voltage down converter (VDC) avoids the jitter problem.

Turbo Kodlanmış İşaretlerde Seyirme Etkisini Azaltan Yaklaşımlar

Turbo is a contemporary coding technique which is first proposed in 1993 having performance close to Shannon limit theory. In binary turbo coding, jitter problem arises because of phase distortion through the channel and the imperfect property of the receiver filters that are not capable of choosing exact coding instants. In this paper , a receiver is proposed which is very useful at the extraction of sampling instants. The receiver is composed of a non-linear element followed by notch filter matched to data rate of the binary sequences.

Soliton optical phase control by use of in-line filters

We address the problem of soliton phase jitter caused by fiber amplifier noise in a communication channel. An analytical expression for phase jitter is derived by use of perturbation theory. In the absence of filters the variance of the phase is found to be proportional to the cube of the propagation distance, but it increases only linearly if in-line filters are used. We verify with simulations that in-line filters maintain the phase jitter at a level that is tolerable for transoceanic links.

Design and implementation of a real-time MPEG-II bit rate measure system

MPEG-II transport stream delivery over a network generally requires network jitters to be kept under /spl plusmn/500 nsec. When the MPEG packets are transmitted in other transport formats, such as ATM, the jitter problem may become difficult to manage. In this situation, the MPEG decoding process is often complicated due to MPEG-decoder buffer under-run and over-run, consequently creating video breakup or unsynchronized audio-visual playback. Thus, developing a test tool that can monitor MPEG-II bit rate on line is an important topic. This paper presents a simple but effective method to measure bit rate at the receiver end. This method uses an off-the-shelf MPEG de-multiplexer chip together with an embedded processor to govern the time-stamps embedded in the MPEG-II stream. The collected time stamps are further used to derive the bit rate. Furthermore, the jitters as measured by comparing local clocks against the received program clock reference values in embedded MPEG streams are also calculated. A hardware test environment is set up for experiment. The results shows the usefulness of this tool in deployment.

Intelligent voice smoother for silence-suppressed voice over Internet

When transporting voice data with silence suppression over the Internet, the problem of jitter introduced from the network often renders the speech unintelligible. It is thus indispensable to offer intramedia synchronization to remove jitter while retaining minimal playout delay (PD). We propose a neural network (NN)-based intravoice synchronization mechanism, called the intelligent voice smoother (IVoS). The IVoS is composed of three components: (1) the smoother buffer; (2) the NN traffic predictor; and (3) the constant bit rate (CBR) enforcer. Newly arriving frames, assumed to follow a generic Markov modulated Bernoulli process (MMBP), are queued in the smoother buffer. The NN traffic predictor employs an online-trained back propagation NN (BPNN) to predict three traffic characteristics of every newly encountered talkspurt period. Based on the predicted characteristics, the CBR enforcer derives an adaptive buffering delay (ABD) by means of a near-optimal simple closed-form formula. It then imposes the delay on the playout of the first frame in the talkspurt period. The CBR enforcer in turn regulates CBR-based departures for the remaining frames of the talkspurt, aiming at assuring minimal mean and variance of distortion of talkspurts (DOT) and mean PD. Simulation results reveal that, compared to three other playout approaches, the IVoS achieves superior playout, yielding negligible DOT and PD, irrespective of traffic variation.

Method and system for on-line system identification

This invention relates to an improved method of on-line system identification for use with active control systems which requires less computation and reduces the problem of coefficient jitter in the filters of the active control system by using a fixed test signal which is designed to have a particular power spectrum.

Pulse train compression up to terabit rates using four-wave mixing in birefringent fiber

The nonlinear optical method of pulse train compression up to terahertz repetition rate is described theoretically. Degenerate four-photon mixing of counterpropagating pulses in birefringent fiber is proposed to compress pulse train. Analytical expressions of the intensity and period of compressed pulse train are derived. The timing jitter problem and limitations of the efficiency of the four-photon mixing caused by the attendant nonlinear optical effects are discussed.

Real-time confocal microscopy of the human in vivo cornea

A new confocal microscope has several unique features which differentiates it from other in vivo confocal imaging systems.is described. • The light source is a halogen lamp. This source has many advantages over the mercury or xenon arc lamps used in other confocal designs. The mercury or xenon arc lamps have the problem of arc jitter which results in changing illumination intensity. Filters are inserted in the lamp housing to remove both short ultraviolet and infrared light. • The microscope uses standard microscope objectives which are readily interchangeable. Other in vivo confocal systems are limited to a built in objective which is not removable. In these studies we used a Leitz 50X, NA 1.0 water immersion objective.• The detection system consists of an intensitified video camera with video output to a Sony U-matic tape recorder. In parallel with the video recording there is a video monitor in order that the operator can observe in real-time the confocal images of the subject's eye.

Multipled block codes for all-optical transports

Multipled block codes (MBCs) for all-optical transport are investigated. Each block of the MBC comprises N subblocks, each n bits in length. A feature of the MBC family is that the clock component can be recovered through logical processing. First, coding efficiency is studied to show that choosing n=2N results in the maximum efficiency. Next, the jitter problem due to deviations in processing delays is investigated. Recovery of the clock component by the combined use of delay-and-multiply and delay-and-add logical processing is investigated. Numerical and simulation results show that the former causes no jitter when the pulse duty is chosen adequately, and only minor jitter is generated due to the latter. Applications of this type of line code to various systems such as trunk lines, cross connects, interconnects and local area networks (LANs) are discussed. Transmission frame processing suitable for photonic implementation is investigated. It is also shown that the applications of this type of line code to superbroadband cross connects, interconnects, and LANs are promising owing to simple clock recovery and frame processing capabilities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An automatic musical frequency detection and MIDI control system for brass instruments

Fundamental frequency detection algorithms optimized for use with instruments in the brass instrument family are presented. A new frequency tracking scheme based on adaptive periodic prediction is presented, and it is shown that this algorithm is equivalent to a high-precision adaptive comb filter. Frequency detection schemes that do not take into account the unique spectral and acoustical properties of a particular instrument family usually generate errors of three types: (1) octave and harmonic detection errors, (2) half-step errors that jitter rapidly about the true estimate, and (3) latency of detection. A frequency detection and live MIDI control system has been constructed for the trumpet, which significantly reduces detection errors and latency. By limiting the search range to the natural playing range of the trumpet, sampling rate and computation can be optimized, reducing latency in the estimates. By measuring and utilizing valve position in the frequency detection algorithm, the half-step jitter problem is completely eliminated, and latency can be further reduced. Schemes for reducing harmonic detection errors will be presented. The trumpet system as implemented will be quantitatively compared to two popularly available frequency to MIDI systems. A short demonstration of the trumpet performance system will be presented.

Novel approaches to the problem of latency jitter.

ABSTRACTThis paper deals with the issue of variable latencies of single potentials. A new method is proposed for obtaining estimates of single latency shifts, which allows furthermore a statistical test on the presence of latency jitter. In the Appendix, we give a precise description of the algorithmic procedure in order to allow an implementation of the new approach. A simulation study using real data from 41 children demonstrated that the procedure performed much better than the familiar Woody algorithm which produced highly unstable estimates. The new statistical test on presence of latency jitter was validated and also evaluated using simulations. The test was specifically sensitive to latency jitter but not to other types of variation of single potentials. In an application of real flashevoked potentials evidence for the presence of variable latencies was found.

Pulse distortion after propagating through an ionospheric bubble

An ionospheric bubble is first modeled based on in situ data measured on board a satellite. The effect such a bubble may have on radio signals propagating through it is next simulated by solving numerically a parabolic equation. Considerable pulse distortion is found. When the computational technique is applied to a frozen but moving bubble, these results imply that the pulse excess arrival time, the pulse width, and its skewness will fluctuate with time, leading to the pulse jitter problem often observed experimentally.

An electrically triggered 200 kV rail-gap switch for wide aperture excimer lasers

A wide aperture (7×7 cm2), high output energy (5 J in KrF and 13.8 J in XeC1), UV preionized excimer laser is described. A self-breakdown rail gap was employed as an output switch with the maximum voltage and current up to 230 kV and 300 kA, respectively. To solve the switching jitter problem associated with the self-breakdown, an electrical triggering was investigated. The measured minimum switching time delay and gap closing time were 40 and 10 ns, respectively. The number of channels up to 50 was observed with a uniform distribution over the 80-cm electrode length. The triggering jitter was measured to be less than a nanosecond. The maximum operation voltage of the triggered rail gap was 200 kV. The successful trigger operation was obtained in the range 30%–98% of the self-breakdown voltage.