Cancellation of timing and amplitude jitter in symmetric linksusing highly dispersed pulses

We study the properties of symmetric dispersion compensation in optical links using highly dispersed pulse transmission. We show analytically that by splitting the dispersion compensation equally between the input and output of the link, complete cancellation of the timing and amplitude jitter can be obtained in systems where the power profile is symmetric about the center. We explain the dynamics of this cancellation and show, theoretically and experimentaily, that with practical system parameters, symmetric compensation may lead to a considerable improvement in performance     

Measurement of crosstalk-induced delay errors in integratedcircuits

Coupling between lines may cause a variation in the effective transition delay in a digital signal path if there exists a simultaneous transition in the coupled lines. The authors present a measurement method for this effect, using a specifically designed integrated circuit. It is shown that the effect may produce either an increase or a decrease in the critical path, therefore altering the maximum frequency specification of a synchronous sequential circuit     

Optical crosstalk-induced switching between bistable soliton states

It is shown that the controlled use of optical crosstalk can induce switching between bistable soliton states in a fiber whose intensity-dependent refractive index is described by the linear plus smooth step model. The closely related phenomena of soliton fission, soliton fusion, radiation stripping, and the soliton transparency-extinction transition are also examined. The evanescently coupled model equations use are discussed, and numerical results are given. It is stressed that the general features of the crosstalk-induced switching and related phenomena do not depend on the specific nonlinearity (the LSS model) chosen     

有关振荡器抖动的问答

人们在使用振荡器的经常会遇到问题,这里回答了有关振荡器波形抖动的一些问题,有助于工程师们把由抖动而引起的数据误差减至最小。     

Predicting data-dependent jitter

An analysis for calculating data-dependent jitter (DDJ) in a first-order system is introduced. The predicted DDJ features unique threshold crossing times with self-similar geometry. An approximation for DDJ in second-order systems is described in terms of the damping factor and natural frequency. Higher order responses demonstrate conditions under which unique threshold crossing times do not exist and total jitter is minimized. The DDJ predictions are verified with jitter measurements in a bandwidth-limited amplifier. The predictions for both first and second-order systems anticipate the features of the observed jitter.     

抖动测量三种方法

只要测试数据通信IC或测试电信网络,就需要测试抖动。抖动是应该呈现的数字信号沿与实际存在沿之间的差。时钟抖动可导致电和光数据流中的偏差位,引起误码。测量时钟抖动和数据信号就可揭示误码源。测量和分析抖动可借助三种仪器:误码率(BER)测试仪,抖动分析仪和示波器(数字示波器和取样示波器)。图1示出每种仪器能处理的位率。选用哪种仪器取决于应用,即电或光、数据通信以及位率。因为抖动是误码的主要原因,所以,首先需要测量的是BER。若网络、网络元件、子系统或IC的BER超过可接受的限制,则必须找到误差源。大多数工程技术人员希望…     

Universality of mode-locked jitter performance

It is shown experimentally that the jitter of actively mode-locked laser pulses is determined by two factors: first, by spontaneous noise associated with cavity loss, and second, by round-trip propagation time. As the round-trip time is increased, a characteristic frequency which defines the high-frequency limit of phase noise decreases. For a comparable round-trip time and cavity loss, the jitter of mode-locked lasers based on diverse gain media, whether semiconductor or erbium ion is universal and independent of the upper-state transition lifetime.     

Waiting time jitter reduction

When a pulse-stuffing multiplexer interfaces to asynchronous traffic, the pulse-stuffing mechanism introduces the low-frequency stuffing jitter called waiting-time jitter. Depending on the stuffing ratio, which relates a nominal asynchronous traffic rate to a multiplexer output rate, up to one unit interval peak-to-peak waiting-time jitter is generated. A large amount of waiting-time jitter can have harmful effects on a network and needs to be reduced. The author introduces three waiting-time jitter reduction methods, which are based on the forced stuffing concept. The concept and its implementations are discussed in detail     

采用频率抖动技术减小EMI

通过在芯片PWM控制电路中使用频率调整环节来减小开关电源的电磁干扰,为抑制开关电源电磁干扰提供新思路。     

CDMA系统的导频干扰抵消

CDMA蜂窝移动通信系统是一种采用多址技术的通信系统,即采用不同的地址码来区分用户、基站和信道.然而由于其在多径衰落信道中的自相关和互相关特性的不理想造成了码道之间的多址干扰.在扩频通信系统中,有效地抵消导频信道引入的多址干扰是进一步改善系统性能和提高系统容量的重要途径.     

Getting to grips with jitter

The word 'jitter' in the communications context has come to mean any random or periodic variation in timing of a regular event from its intended or nominal timing. On the one hand, jitter can refer to arrival time variations for IP packets, or, on the other, to variations on clock signals in digital systems, as well as many other things. A big problem with jitter is just measuring it     

Data-dependent jitter in serial communications

We present a method for predicting data-dependent jitter (DDJ) introduced by a general linear time-invariant LTI system based on the system's unit step response. We express the exact DDJ of a first-order system and verify the validity of the solution experimentally. We then propose a perturbation technique to generalize the analytical expression for DDJ. We highlight the significance of the unit step response in characterizing DDJ and emphasize that bandwidth is not a complete measure for predicting DDJ. We separate the individual jitter contributions of prior bits and use the result to predict the DDJ of a general LTI system. In particular, we identify a dominant prior bit that signifies the well-known distribution of deterministic jitter, the two impulse functions. We also show a jitter minimization property of high-order LTI systems. We verify our generalized analytical expression of DDJ for several real systems including an integrated CMOS 10-Gb/s trans-impedance amplifier by comparing the theory and measurement results. The theory predicts the jitter with as low as only 7.5% error.     

Turn-on jitter of external-cavity semiconductor lasers

Analytical expressions, validated by numerical simulations, are obtained for the turn-on delay jitter of semiconductor lasers subjected to weak optical feedback in short external cavities. The results show explicitly that displacement of the external reflector on optical wavelength scales causes significant changes in the switch-on dynamics of the laser. It is found that more than a 400% increase of jitter can occur under certain circumstances. The demonstrated sensitivity of laser switch-on dynamics to reflector location is considered to be particularly relevant to the performance of packaged laser diodes     

Analysis and equalization of data-dependent jitter

Data-dependent jitter limits the bit-error rate (BER) performance of broadband communication systems and aggravates synchronization in phase- and delay-locked loops used for data recovery. A method for calculating the data-dependent jitter in broadband systems from the pulse response is discussed. The impact of jitter on conventional clock and data recovery circuits is studied in the time and frequency domain. The deterministic nature of data-dependent jitter suggests equalization techniques suitable for high-speed circuits. Two equalizer circuit implementations are presented. The first is a SiGe clock and data recovery circuit modified to incorporate a deterministic jitter equalizer. This circuit demonstrates the reduction of jitter in the recovered clock. The second circuit is a MOS implementation of a jitter equalizer with independent control of the rising and falling edge timing. This equalizer demonstrates improvement of the timing margins that achieve 10/sup -12/ BER from 30 to 52 ps at 10 Gb/s.     

一种偏置电路噪声消除的VCO

基于0.18 μm CMOS工艺,设计并制作了一种偏置电路噪声消除的VCO。通过在偏置电路与VCO的尾电流源之间插入选通电路,可以实现对偏置电路的噪声电压的低通滤波。分析表明,该低通滤波器的拐点频率与选通电路的导通电阻、关断电阻以及开关时钟占空比相关。电路测试表明,加入选通电路之后,VCO的近端相噪下降约20 dB,大大降低了偏置电路的相噪贡献。     

Statistical analysis of jitter estimation in ADC

Analytical expressions for jitter estimation under conditions of sinusoidal signal at ADC input are obtained for the case of no prior knowledge of jitter value. Statistical analysis of the obtained estimates is conducted. Numerical modeling results are presented. Applicability limits for the suggested estimates are obtained.     

The effect of timing jitter on MC-DS-CDMA

In this paper, we consider the effect of timing jitter on the performance of a multicarrier direct-sequence code-division multiple-access system for both uplink and downlink transmission, assuming orthogonal spreading sequences. Theoretical expressions are derived for the performance degradation caused by the timing jitter, in the presence of a multipath channel. Assuming an additive white Gaussian noise channel, perfect power control, and full load, it is shown that the performance degradation for the downlink transmission is independent of the number of subcarriers, of the spreading factor, and of the spectral contents of the jitter at the receiving mobile station, but only depends on the jitter variance. Under the same assumptions, we point out that, if the jitter spectra of all transmitting mobile stations are the same, the degradation on the uplink is the same as the degradation on the downlink.     

Adaptive Reference Echo Cancellation

The AREC (adaptive reference echo cancellation) algorithm is presented for an echo canceler used in full-duplex two-wire digital transmission on digital subscriber loops. The AREC algorithm incorporates a decision-directed estimation of and compensation for the far-end signal which is a source of interference to the conventional echo canceler adaptation algorithm. The AREC algorithm thus offers much faster convergence and shorter coefficient wordlengths than the conventional algorithm. Analysis and simulation of the performance and convergence of both AREC and conventional echo canceler adaptation algorithms are carried out. Included in the analysis is the effect of receiver delay and coefficient wordlength requirements. A simple and robust startup procedure is proposed and investigated by simulation.     

Experimental investigation of soliton optical phase jitter

The soliton optical phase stability versus amplified spontaneous noise is investigated in a recirculation loop experiment in the presence of in-line filters. The behavior of phase fluctuations is shown to be in good agreement with numerical simulations. The phase standard deviation is kept below 0.15×π for distances up to 8000 km. We, therefore, demonstrate the feasibility of phase-shift keying on solitons for long-haul transmission systems