Abstract
Pattern jitter is a primary contributor to the increase of the bit error rate (BER) in high-speed communications, which occurs in large part due to duty cycle distortion (DCD). By considering DCD caused by transmission links and the distribution of jitter in DCD due to the pattern of the transmission link, this paper proposes a precise control method based on the cross point of the eye diagram to minimize the jitter associated with DCD and to effectively decrease the BER of high-speed digital communications. By capitalizing on the theoretical basis that the main form of DCD is the offset of the cross point of the eye diagram, the technology presented here reconstructs the pattern waveform by using a digital method and incorporates a time variable to precisely control the data edge position during the reconstruction process, thereby stabilizing the cross point at 50% to correct its drift. Accordingly, after fanning out the original pattern buffer and then passing two controllable delay lines with different delays through the buffer in a process that is driven by digital logic operation, the cross point of the waveform is reconstructed by changing the relative time delay of the two signals. As a result, the change in the position of the cross point of the eye diagram is transformed into the precise control of the relative time delay, minimizing the DCD jitter. The theoretical model is verified by experiments, indicating that this method can control the cross point of the non-return-to-zero (NRZ) pattern in the range of 30% to 70% under 3 Gbps with a resolution as great as 1%. Furthermore, this approach can solve the problem of cross point drift of the eye diagram and can significantly decrease the BER caused by DCD jitter.
Highlights
With the rapid development of communication systems and very large scale integration (VLSI) and considering that the data transmission rate has increased rapidly in recent decades, jitter has become the bottleneck that limits the improvement of data transmission rates and lengths [1], [2]
Deterministic jitter is composed of duty cycle distortion (DCD), intersymbol interference (ISI), period jitter (PJ) and bounded uncorrelated jitter (BUJ)
The waveform is reconstructed by using a digital method, thereby correcting the cross point of the eye diagram and reducing the bit error caused by the jitter of the DCD
Summary
With the rapid development of communication systems and very large scale integration (VLSI) and considering that the data transmission rate has increased rapidly in recent decades, jitter has become the bottleneck that limits the improvement of data transmission rates and lengths [1], [2]. The method is applied to the rising and falling edges of the signal, which allows this method to add to the controllable fraction of the relative delay through the delay line In this case, the waveform is reconstructed by using a digital method, thereby correcting the cross point of the eye diagram and reducing the bit error caused by the jitter of the DCD. The horizontal axis of the eye diagram represents time, and the vertical axis represents signal amplitude, which contains abundant information [11]; the BER is essentially the cumulative distribution function (CDF) of the total jitter probability density function (PDF) of the left and right cross points of the time interval, in which a bit error occurs. Because the CDF is the integral of the PDF, the BER function is essentially a jitter CDF function, as shown in the following equation [13]
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