1. Signals must be analyzed for factors such as reflections, crosstalk, and radiation, which are caused by impedance mismatch, line spacing, and high-speed device and PCB board design. For transmission line judgment, high-speed signals are distinguished from low-speed signals by considering signal frequency and transmission path length. The signal circuit includes driving and loop paths, and it is important to note the return path when changing signal layers. The solution to crosstalk involves satisfying the 3W principle for signal spacing on the PCB board.