Study On Application Of Eye Diagram Test In Serial Communication System

At present, the mainstream technology of data transmission has developed to serial signal transmission. The signal may be affected by noise, dielectric and so on during the transmission. These affects usually cause inter-symbol interference and influence the quality of signal. With data rate increasing rapidly, one significant problem appearing is that jitter plays an important role in degrading the system performance. Therefore, how to measure the quality of the signal becomes more important. Eye diagram is a fast and intuitive evaluation method of signal quality. For serial signals with different rates and protocols, the effect of noise and jitter on signal integrity are different. This paper analyzes the signal integrity problems of serial signals with different rates, through various eye diagram tests.Based on the project of the application research of digital fluorescence serial signal analyzer in network test, this paper focuses on how to assess the performance of high speed serial signals through eye diagram test. Specific serial signal test methods are provided for the project.This paper starting from the basic theory of serial signal integrity and eye diagram test, explores the relationship between eye diagram and serial signal quality through the eye diagram test based on MATLAB/Simulink simulation platform and experiments of different serial signals.Firstly, a digital transmission system for eye diagram measurement is designed on the Simulink platform to study the effect of various factors on the signal quality, such as filter, modulation and channel noise. The simulation results show that the noise induces signal amplitude distortion and zero crossing distortion, increases the bit error rate. The higher the bit rate of the transmitted signal, the more obvious the effect of noise on the signal. So the noise limits the transmission rate of the signal. Filtering and modulation can suppress the influence of the noise to some extent.Then, a new method of adding Gauss noise to the serial signal is presented. The eye diagram of the composite signal measured by the oscilloscope verifies the effect of noise on the signal as the simulation results show.Finally, the methods of how to produce and test different serial signals are designed, including four low-speed communication protocol signal (CAN, SPI, I2C and RS485), high-speed low voltage differential signal (LVDS) and 100Base-TX Ethernet signal. How to evaluate signal quality and assess the performance of serial communication system using eye diagram is further analyzed.The eye diagram of these signals show that the eye diagram can be a good reflection of noise and jitter in the serial communication system. The parameters of communication system can be adjusted to optimize its performance according to the results of eye diagram test. This paper provides a strong basis and reference for the test of digital fluorescence serial signal analyzer.