Signal Integrity Analysis Of High-speed Narrow Pulse Transmission

In recent years, with the rapid development of integrated circuit technology, the clock frequency of electronic circuit system has been increasingly high and data transmission rate been increasingly rapid. However it leads to a growing signal integrity issues. As for signal integrity, it mainly studies the impact of physical interconnection on signals and power. More importantly, through signal integrity analysis, the noise in signal transmission can be partially and even totally eliminated. Therefore, it is of great importance for high-speed circuit design to have a good knowledge of signal integrity. Being a special high-speed signal, high-speed narrow pulse signal has been more and more widely used in ultra-wideband radar, ultra-wideband communication, semiconductor characterization testing, high-speed sampling and other areas. It has a very steep rising edge and a very narrow pulse width, the high-speed signal consisting of which could reach a communication rate as high as several tens of Gb/s and is very suitable as a data carrier of future high-speed communication. On the other hand, possessing more high-frequency component than high-speed signal, high-speed narrow pulse signal may be subjected to the problems of severe signal waveform distortion when encountering turning of power cables, vias, discontinuities of return path, over-dense traces layout and other common phenomena in PCB transmission, affecting transmission quality of signals and even leading to data loss. Confronted with a more serious signal integrity problem than high speed signals, high-speed narrow pulse signal faces a great challenge in PCB application.Given all of the above, from the perspective of signal integrity, the article presents a detailed signal integrity analysis of high-speed narrow pulse signal’s transmission in PCB. Firstly, it makes a theoretical analysis of the characteristics of the pulse waveform by using Fourier transform and matlab simulation, revealing relationship between signal bandwidth and edge rise time as well as pulse width, emphasizing that high-speed narrow pulse signal has more high-frequency component than high-speed signal in frequency domain. All of these have supported a theoretical foundation for the analysis of high-speed narrow pulse signal in the following text. Secondly, the article elaborates on the theoretical basis of signal integrity, including basic theory of transmission line,generation and characteristics of reflection noise as well as generating mechanism of crosstalk noise among transmission lines, focusing on the derivation of the telegraph equation and analyzing multiple reflection phenomena by giving some examples. Subsequently, it carries on a simulated analysis of methods commonly used in high-speed circuit design to improve signal integrity, such as inhibition of reflection noise by using terminating, reduction of crosstalk noise by extending space between transmission lines, reducing parallel coupling length of interconnection lines. Finally, based on Hyper Lynx, the article performs a simulated analysis of reflection and crosstalk noise in PCB transmission of high-speed narrow pulse signal and applies conventional methods of noise suppression to transmission process. Results of the simulation show that high-speed narrow pulse signals are experiencing more serious signal integrity problems than high-speed signals in the process of PCB transmission. By using conventional methods of noise suppression, it can still be obtained satisfactory results. When it comes to issues of high-speed narrow pulse signal in PCB transmission, the article could provide some useful guidance of layout and wiring methods for electronic engineering design.