Study On The Crosstalk And Reflection Of The High Speed PCB Design

The printed circuit board (be short for PCB) has been widely applied to various kinds of electronic devices, due to its small size and high integration. The PCB has been developed to carry out the high density, high speed and multiple stratification, with the rapid development of the integrated circuit technologies. Which may cause electromagnetic coupling problem in high frequency and signal integrity problems because of the rapid change of the clock signal in the microstrip lines such as overshoot, ringing, reflection and crosstalk and so forth. In this case, the coupling and reflection may lead to spurious triggered or error receiving data, which will fail in signal transmission. Among these signal integrity problems, reflection and crosstalk are the two of the most serious issues. So in this paper, we make a deep research on the reflection and crosstalk. The main research contents are as follows:1. In this chapter, firstly, the distributed parameter model of the homogeneous transmission line and the homogeneous transmission line equation are studied based on the multi-conductor transmission line theory. Secondly, two kinds of transmission line structure are commonly used in the high-speed PCB and its characteristics parameters are researched according to the distributed parameter model of the homogeneous transmission line. Lastly, a new method is proposed to solve the distributed capacitance of the microstrip line based on the finite difference method and the conform technique, then the characteristic impedance of the microstrip line is solved,which is laid a foundation for the solving crosstalk and reflection problems of the microstrip lines.2. The forming mechanism of reflection and crosstalk in high-speed PCB design is deeply researched in this chapter. Then the factors that affect the signal reflection are analyzed by the simulation and the theory. As a result that the impedance mutation is the fundamental cause of the signal reflection, then the effect of different end impedance matching on the suppression reflection is analyzed. At the same time the factors that affect the crosstalk between the two microstripe lines are analyzed and simulated. Which can provide theoretical support for the high-speed PCB design.3. In this chapter, a new method is proposed to solve the coupling source between the microstripe lines and the space transient electromagnetic interference source based on the CARSON reciprocity theorem. The new method avoids calculating the complex scattered field, reducing the amount of calculation. In the new method , firstly, the coupling source between the microstripe lines and the space transient electromagnetic interference source is solved, then the crosstalk problem caused by the coupling source is studied by the use of Finite Difference Time Domain(FDTD) method. In this paper, the crosstalk between microstrip lines caused by electric dipole is taken as an example, then the coupling model which is between electric dipole and microstripe line is established, at the same time the coupling source is solved based on the CARSON reciprocity theorem, lastly, the crosstalk between the micorstripe lines caused by the coupling source is analyzed based on the FDTD method in five cases. Compared with the practical engineering,the crosstalk of the source end is analyzed deeply, which has a great significance for the practical engineering.