Reducing data dependent jitter utilising adaptive fir pre. Data dependent jitter generated over rg58 cable at 10 gbs and the resulting jitter histograms. Period jitter tends to be important in synchronous circuitry such as digital state machines. Data dependent jitter ddj data dependent jitter is correlated with either the transmitted data pattern or aggressor crosstalk data patterns caused by phenomena such as phase errors in serialization clocks, channel filtering, and crosstalk categories duty cycle distortion dcd intersymbol interference isi. Deterministic jitter is further divided into periodic jitter, datadependent jitter, and bounded uncorrelated jitter.
The information, which consists of the systematic contribution of isi, is removed from the original measurement. Depending on characteristics of the signal and transmission topology, previously transmitted symbols can affect the edge cross over time. This approach is applied to each edge and an average rj computed from all the separate measurements. Pdf datadependent jitter limits the biterror rate ber.
The easiest way to deliberately add ddj to a link is to insert a bandlimiting element. Another common name for ddjisi is pattern dependent jitter pdj. Agilent 86100cu401 agilent 86100du401 advanced eye analysis. Accurate jitter decomposition in highspeed links iowa state. To confirm the derived equation, simulations have been done with a first order rc low pass circuit for various system bandwidths, bit. Understanding sdaiii jitter calculation methods page 12 of 12 conclusions the sdaiiicompletelinq calculates jitter on long serial data waveforms using one of several dualdirac based models, and finds components of datadependent jitter directly from tie measurements. Closedform equation of data dependent jitter in first order. This paper focuses on the alleviation of data dependant jitter introduced by the limited offchip bandwidth. Agilent 86100cu401 agilent 86100du401 advanced eye. In particular, it is a form of deterministic jitter which is correlated with the sequence of bits in the data stream. Deterministic jitter has a known nonnormal distribution. Signal jitter can be composed of several types from several mechanisms datacorrelated datauncorrelated total. Examples of data dependent jitter are dutycycle dependent jitter also known as dutycycle distortion and intersymbol interference.
Data dependent jitter of transmitter for nonframed prbs and sdhframed signal weresimulated. Wo2004036231a2 method and apparatus for determining. The last two columns are for data dependent jitter, one is obtained from the cadence simulations, and the other one is calculated using our proposed model. Different threshold crossing times that arise from the firstorder response. The jitter components of a data signal can be classified into deterministic jitter dj and random jitter rj. Pdf datadependent jitter in serial communications researchgate. Estimating datadependent jitter of a general lti system from step response behnam analui, james buckwalter, and ali hajimiri abstract we present a method for estimating data dependent jitter ddj introduced by a general lti system, based on the systems step response. Data dependent jitter ddj is a specific class of timing jitter. Analysis and equalization of datadependent jitter semantic. Estimating datadependent jitter of a general lti system from. An analysis for calculating data dependent jitter ddj in a firstorder system is introduced. Datadependent jitter in serial communications core. Referring next to figure 5, an example applying the method and apparatus of the invention will now be shown.
Understanding jitter, its components, and separation. This histogram approximates the pdf by counting the number of edges occurring within the time period delimited by each bin in the histogram. By behnam analui, james buckwalter and ali hajimiri. Software for dsa8300 sampling oscilloscopes datasheet. Nrz data is generated stochastically and ddj is a probability density function pdf with discrete values of. The method comprises the steps of dividing an acquired waveform into a plurality of waveform slices and categorizing each of the plurality of waveform slices according to at least a sequence of n bit values prior to a bit value being observed. If random jitter is excessive, other means of jitter cleaning may be needed for example, use of retimers.
As a result, this numeric simulation only considers ddj. Analysis and equalization of datadependent jitter chic. Data dependent jitter and crosstalk are not observed in clock jitter analysis usually. For the 001 and 101 sequences, the firstorder ddj pdf consists of a double dirac function as modeled in 1. The eye diagram is a common way to highlight the problem of signal recovery and presence of jitter as depicted in figure1. Figure 1 setup and hold time requirement for errorfree operation. The intricacies of signal integrity in highspeed communications. Ddjs pdf is always a series of pulses at the locations where a specific bit pattern experiences a cross over. Understanding sdaiii jitter calculation methods page 12 of 12 conclusions the sdaiiicompletelinq calculates jitter on long serial data waveforms using one of several dualdirac based models, and finds components of data dependent jitter directly from tie measurements. Timing jitter consists of random jitter rj and deterministic jitter dj. Data dependent jitter, a prominent form of the deterministic jitter of data symbols, arises from the impairment of channels and is a major contributor to isi 51. A combined clock and data recovery circuit with adaptive.
The jitter tree dj rj ddj isi dcd pj correlated tj uncorr page 28 jitter dj jitter rj intersymbol interference isi duty cycle distortion dcd periodic jitter pj data dependent. We present a method for predicting datadependent jitter ddj introduced by a general linear timeinvariant lti system based on the systems unit step. Deterministic jitter dj is the type of jitter that is bounded has a finite peaktopeakvalue, repeatable and predictable. In any event, youd like to make sure you have enough margin that the parts from the qualification run satisfy the compliance lab.
Data dependent jitter ddj characterization methodology. The response is determined by both current state and previous state of data 45. This is referred to as data correlated jitter, and it is simply characterized by frequency bandwidth limited model or transmission line. Basic classification of jitter components using sampling scope. Datadependent jitter and crosstalkinduced bounded uncorrelated jitter in copper interconnects james buckwalter, behnam analui, and ali hajimiri california institute of technology, pasadena, ca 9 1 125 abstract this paper resolves the jitter impairment of non. Generally two random variables are correlated if changing one of the variables causes the other to change.
A 10gbs nrz receiver with feedforward equalizer and. A method for calculating the data dependent jitter in broadband systems from the pulse response is discussed. Dj can be subdivided further into data dependent jitter ddj and periodic jitter pj. Periodic jitter is caused by things such as switching power supplies and clocks leaking into the signal. Additive peaktopeak data dependent jitter with input nrz data at prbs 223. Input voltage swing is a singleended measurement operating in differential mode. We present a method for estimating data dependent jitter ddj introduced by a general lti system, based on the systems step response. In short, the tie measures how far each active edge of the clock varies from its ideal. Example waveform of simple data dependent jitter ddj. Mar 24, 2006 a method for calculating the data dependent jitter in broadband systems from the pulse response is discussed. Absolute jitter the absolute difference in the position of a clocks edge from where it would ideally be. Two measurements shown in figure 2 are relevant for defining the jitter performance. Deterministic jitter can either be correlated to the data stream datadependent jitter or uncorrelated to the data stream bounded uncorrelated jitter. The sda measures the jitter pdf by collecting a histogram of tie measurements.
Pdf we present a method for predicting datadependent jitter ddj introduced by a general. Data timing jitter is separated into random jitter rj and deterministic jitter dj 1. Datadependent jitter generated over rg58 cable at 10 gbs and the resulting jitter histograms. Datadependent jitter, a prominent form of the deterministic jitter of data symbols, arises from the impairment of channels and is a major contributor to isi 51. Controlled jitter generation for jitter tolerance and jitter.
Transmitter the transmitter contains a 650nm led with an integrated driver. Deterministic jitter can either be correlated to the data stream data dependent jitter or uncorrelated to the data stream bounded uncorrelated jitter. Furthermore, random jitter is the type of jitter lvds signal conditioners cannot eliminate or minimize. Jitter measurement instruments for datacomscomputing fields anritsu mp1800a left, anritsu mp2100a right jitter tolerance the ability and degree to which a receiver can withstand jitter in the received data signal and the maximum. Several techniques are available for measuring jitter on a single waveform. Index termsdatadependent jitter ddj, deterministic jitter. High speed interconnect data dependent jitter analysis. The dualdirac method then is used to separate rj from dj. The deterministic nature of data dependent jitter suggests equalization techniques suitable for highspeed. Measurements are able to estimate the jitter pdf, but are not able to determine the. The ddj relates to the system bandwidth, the bit rate, the input risefall time, and the number of maximum consecutive identical bits of the data pattern. The deterministic nature of data dependent jitter suggests equalization techniques suitable for highspeed circuits. For clock jitter, there are three commonly used metrics.
Data dependent jitter can be broken down into two partsdutycycle distortion dcd and intersymbol interference isi. From the table, it can be seen that, for each bit rate setting, when the interconnect line width w equals 2. The predicted ddj features unique threshold crossing times with selfsimilar geometry. As such, one may observe the histogram approximation of the probability distribution function, or pdf of the jitter or its behavior in frequency i. This may take the form of a long piece of cable, an actual backplane, or a lowpass filter. Extrapolating the pdf measuring the total jitter requires that the probability density function of the jitter is known exactly. Estimating datadependent jitter of a general lti system from step response. Data dependent jitter and crosstalkinduced bounded uncorrelated jitter in copper interconnects james buckwalter, behnam analui, and ali hajimiri california institute of technology, pasadena, ca 9 1 125 abstract this paper resolves the jitter impairment of nonreturntozero data in transmission lines.
The impact of jitter on conventional clock and data recovery circuits is studied in the time and frequency domain. Datadependent jitter ddj is a specific class of timing jitter. Dj includes sinusoidal sj or periodic jitter pj, crosstalk or bounded uncorrelated jitter buj, and data dependent jitter ddj, such as dutycycle. Jitter effects can be divided into two major categories. Of these, ddj is impacted directly by the data pattern. Dj is further categorized into data dependent jitter ddj, duty cycle distortion jitter, and bounded uncorre. Data dependent jitter ddj ddj is a part of deterministic jitter dj, and consists of dcd and isi.
The channels limited bandwidth produces isi, which varies the transition edge slope, inducing datadependent jitter ddj23. Total jitter pdf situated around the pulse edges of the transmitted data signal. This dissertation is brought to you for free and open access by the iowa state university capstones, theses and. Clock jitter analysis clock jitter analysis keysight.
This fact makes frequency domain instruments the first choice for ultralow phase noise clock signal measurements that are free of data dependent jitter. Datadependent jitter of transmitter for nonframed prbs and sdhframed signal weresimulated. Dj can be further classified into three subcategories. The deterministic nature of datadependent jitter suggests equalization techniques suitable for highspeed circuits. Dec 18, 2007 the information, which consists of the systematic contribution of isi, is removed from the original measurement. Agilent 86100cu401 agilent 86100du401 advanced eye analysis software make accurate and compliant jitter measurements on long patterns to ensure that digital communications systems approach errorfree performance, data test patterns that emulate actual traffic are often used. Rj is random variations of thresholdcrossing time often due to a noise source, e. Jitter specifications t a t min to t max, vcc vcc min to vcc max, vcc1 vcc1 min to vcc1 max, vdd vdd min to vdd max, vee 0 v, input data pattern prbs 2 23. Analysis and equalization of datadependent jitter article pdf available in ieee journal of solidstate circuits 4. This type of jitter depends on the data pattern and is due to the effects of inadequate bandwidth and reflections. An1957lvds signal conditioners reduce data dependent jitter. The results showed that jitter evaluation for transmitters should be identical to the framed pattern used at the final equipment testing. The assumption is made that the data dependant jitter dominates the total system jitter, hence the other deterministic jitter contributions, as well as the. Controlled jitter generation for jitter tolerance and.
A method for calculating the datadependent jitter in broadband systems from the pulse response is discussed. The deterministic nature of datadependent jitter suggests equalization techniques suitable for highspeed. Jitter measurements in serial data signals teledyne lecroy. Jitter and noise components probability distributions, spectral distributions, data dependent jitter and noise and ddpws vs. One way to measure the jitter pdf, and certainly an easy way to think of it, is to make a. This paper presents a closedform equation of data dependent jitter ddj in first order low pass systems. A perturbation technique is used to generalize the analytical.
A method for calculating the datadependent jitter in broadband. An1957lvds signal conditioners reduce data dependent. Clock division with jitter and phase noise measurements. Deterministic jitter is further divided into periodic jitter, data dependent jitter, and bounded uncorrelated jitter. Datadependent jitter in serial communications ieee journals. Some of these test patterns can be extremely long and. This assumes that the gaussian rj pdf appends to the dj pdf.
Correlation is an important concept which appears in two separate contexts in jitter analysis. Deterministic jitter dj is the type of jitter that is bounded has a. This fact makes frequency domain equipment the instruments of choice for ultralow phase noise clock signal measurements that are free of data dependent. A method as in claim 2 wherein the step of time shifted interpolation further comprises the step of filtering the respectively associated amount of data dependent jitter of step c to spread its effect over a selected transition portion of the each bit of the digital signal of interest with which the amount of data dependent jitter is associated.
Frequency domain equipment is also awkward for measuring data dependent jitter. Wo2004036231a2 method and apparatus for determining inter. A proposed framework for measuring, identifying, and. Effect of prbs pattern length on datadependent jitter.
The bertscope jitter map first determines the jitter of a single data bit edge, which eliminates any ddj effectsthe data is not changing. Pdf analysis and equalization of datadependent jitter. Examples of datadependent jitter are dutycycle dependent jitter also known as dutycycle distortion and intersymbol interference. The channels limited bandwidth produces isi, which varies the transition edge slope, inducing data dependent jitter ddj23. Agilent 86100cu401 agilent 86100du401 advanced eye analysis software make accurate and compliant jitter measurements on long patterns to ensure that digital communications systems approach error free performance, data test patterns that emulate actual traffic are often used. Total jitter tj data dependent jitter ddj data dependent pulse width shrinkage ddpws uncorrelated jitter uj transmitter qsq eye mask hit ratio sff8431, revision 4. Rj results from random processes, such as thermal noise, and follows a gaussian distribution. Both of these components of total jitter depend on the data signals. Bit, data pattern waveform, bathtub curves for jitter and noise, ber probability map, ber contour diagrams, qeye, probability distribution eye diagrams data pattern can be plotted after every signal path sp. More care must be used for a data signal, since no event transition occurs when the same bit repeats.
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