Can I add a ground wire between the differential signal lines
1. Can I add a ground wire between the differential signal lines?
In the middle of the differential signal, the ground wire cannot be added. The most important point of the application principle of differential signals is to take advantage of the benefits of mutual coupling between differential signals, such as flux cancellation and noise immunity. If ground is added in the middle, the coupling effect will be destroyed.
2. Does rigid-flex board design require special design software and specifications? Where can I undertake this type of circuit board processing in China?
Software for general PCB design can be used to design Flexible Printed Circuits. It is also produced for FPC manufacturers in Gerber format. Because the manufacturing process is different from general PCBs, various manufacturers will have restrictions on the minimum line width, minimum line pitch, and minimum via (via) according to their manufacturing capabilities. In addition, copper foil can be laid at the turning points of the flexible circuit board for reinforcement. As for the manufacturers, you can find "FPC" on the Internet.
3. What is the principle for properly selecting the ground point of the PCB and the case?
The principle of selecting the ground point of the PCB and the casing is to use the chassis ground to provide a low-impedance path to the return current and control the path of this return current. For example, in the vicinity of high-frequency devices or clock generators, the ground of the PCB can be connected to the chassis ground by fixing screws to minimize the area of the entire current loop and reduce electromagnetic radiation.