1. Ground connection problem? A system is often divided into a number of PCB, power supply, interface, motherboard, etc., the ground wire between the boards is often interconnected, resulting in the formation of a lot of loop, such as 2. Low-frequency loop noise problem? When the signal or power supply between the PCB boards is connected to each other, for example, when the power supply or the signal from board A to board B is sent to board B, an equal amount of current must flow from the ground layer to board A (Kirchoff current law)

Can you provide some empirical data, formulas and methods to estimate the impedance of wiring?
When the requirements of impedance matching cannot be met, it is better to add the matching resistance in series at the end of the signal line or at the end of the signal line.
Can a ground wire be added in the middle of the differential signal line?
4. Why is my Protel software design not a complete picture in the DOS version of the computer? There are many old electronic engineers in the beginning of the PCB circuit diagram using the computer have encountered this problem, is my computer memory is not enough? My computer has 2GB of memory! But why are the graphics on the screen still missing arms and legs? Yes, there is a memory configuration problem, you only need to add the following lines to your config.sys file (this file is in the C: root directory, if not, create one), and restart the computer after the disk exits. 5. Why should the PCB file be converted into GERBER file and drilling data and then sent to the PCB factory for making boards? Most engineers are used to design PCB files and send them directly to PCB factory for processing. However, it is a popular practice internationally to convert PCB files into GERBER files and drilling data and then send them to PCB factory. Because electronic engineers and PCB engineers have different understanding of PCB, GERBER files converted from PCB factories may not be what you want. Common CAD software can generate files in both formats. How do I check that the GERBER generated is correct? All you need to do is import these GERBER files and d-code files in the free software Viewmate V6.3 to see them on the screen or to print them out. Drilling data can also be generated by various CAD software, normally in Excellon format, and displayed in Viewmate. No PCB can be made without drilling data. 6. How should we choose PCB plates? PCB panel selection must strike a balance between meeting design requirements, mass production and cost. Design requirements include electrical and mechanical parts. This material problem is usually important when designing very high speed PCB boards (frequencies greater than GHz). In the case of electricity, note whether the dielectric constant and dielectric loss are appropriate at the designed frequency. How can we avoid high frequency interference? The basic idea to avoid high frequency interference is to minimize the interference of electromagnetic field of high frequency signal, which is called Crosstalk. This may be to widen the distance between high speed signals and analog signals, or to add ground guard/shunt traces to the analog signal. Also note the digital to analog noise interference. 8. How can signal integrity be solved in high-speed design? Signal integrity is basically a matter of impedance matching. And the influencing factors of impedance matching with the construction of the signal source and the output impedance (the output impedance), line characteristic impedance, the load side, walk line topology architecture (topology), etc. The solution is to rely on termination and the topology of alignment. 9. How to realize differential wiring? There are two points to note when wiring a difference pair. One is that the length of the two lines should be as long as possible, and the other is that the distance between the two lines (which is determined by the difference impedance) should remain constant, that is, parallel. There are two ways to do this. One is that two lines are on the same side-by-side, and the other is that two lines are on the same over-under. In general, side-by-side is the former. 10. How do we implement differential wiring for clock signal lines with only one output end? It makes sense to use differential wiring because it must be both the source and the receiver of the signal. Therefore, if a clock signal has only one receiver, we cannot use differential wiring.