Analysis And Design Of PCB Signal Integrity

In order to satisfy the demands for miniaturization and multi-function of electronic equipment, modern printed circuit boards (PCB) are developed to the capacity of high-speed, high-density and high-integrity. When signal velocity and components' density increase, noise and disturbance are induced into signal by PCB's parasitical effect, and signal integrity (SI) problems become more and more critical. If SI is not designed properly, PCB would not work or even never work at all. This requires that SI should be designed rigorously in the phase of PCB design when engineers develop electronic products. So the analysis and design of PCB SI become one of hot research topics in the field of PCB design.SI problems mainly involve crosstalk, signal reflection and electromagnetic interference. Focusing on practical issues on PCB design, crosstalk and signal reflection are investigated thoroughly, and the methods of analysis and design of PCB SI are well studied in this thesis.The main work of this thesis is listed as follows:1. Crosstalk theory is analyzed briefly, and then both forward-crosstalk and backward-crosstalk on micro-strip lines and strip-lines are simulated respectively by using HyperLynx software. The simulation results show that crosstalk is much lower on strip-line than on micro-strip lines.2. The crosstalk simulation model of two parallel micro-strip lines is obtained by HFSS. Using the model, some important parameters about crosstalk, such as signal frequency, parallel length, space width and height of image plane, are studied,. Based on the simulation results, the methods of shortening the parallel length, increasing the space and reducing the height of image plane are presented to suppress crosstalk. Furthermore, "gap strip" is proposed to control crosstalk, and simulation results verify that using gap strip grounded properly can reduce crosstalk effectively.3. In PCB design field, slots on image plane, which are induced by vias and isolation between digital ground and analog ground, are common. When signal lines cross the slot, crosstalk would become more serious and is particularly studied. A method supplying a signal return-path to each signal line is presented to deal with the crosstalk, and simulation results are shown to demonstrate it.4. Finally signal reflection is analyzed by theory of transmission line and some other methods are introduced to decrease reflection. Various simulation results about those methods are presented to show their effect.Through the above work, design rules are proposed in this thesis to solve PCB signal problems such as crosstalk and signal reflection. The obtained conclusions are useful to design the PCB in practice.