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In high-speed PCB board design, the ground plane is divided into digital part and analog part, but these two parts should be connected near the power supply to provide a short reactance path. At the same time, placing the circuit grounding through-hole fence around the high-speed power plane will produce a good suppression effect because it will produce two out of phase radiators.
A high-speed ground is added in the design of the high-speed circuit to prevent the analog circuit and the digital circuit from generating interference and radiation to the high-speed circuit. If the number of layers allows, place the high-speed power plane between the two ground planes, which will separate the high-speed power plane and the ground plane on the board.
In the design of high-speed circuit, because high-speed signal will produce transmission line effect on the shorter line, it is better to make the high-speed line as short as possible. Impedance control is used on the circuit board to ensure that the wiring has a consistent impedance across the circuit board.
In the design of high-speed circuits, the number of vias shall be minimized. Because each via adds impedance to the wiring, it is very difficult to design the via to have a specific impedance matching the wiring. Any through holes should be backdrilled to prevent signal resonance, and extra care should be taken to ensure that backdrilling on differential pairs is symmetrical. If it is necessary to use vias on high-speed traces, choose to use two vias in parallel to prevent impedance changes. This has two advantages: 1) it reduces the additional impedance of the wiring; 2) The total impedance of the two through holes in parallel decreases, thereby increasing the low resonance frequency of the through holes to the signal.
