PCB Tech - 11 Experiences of High Frequency Circuit Board Layout

High frequency circuit is very concerned about impedance matching and wiring. As like as two peas, it can be produced exactly according to the manufacturer's reference. After all, the design of the manufacturer has been calculated comprehensively.

When drawing PCB at the beginning, please do not arrange your high-frequency wiring according to the common signal line. It is the right way to obtain reference design from the chip manufacturer. General chip data manual or related manual will have wiring reference for high-frequency part.

The whole high frequency part can be perforated more to increase the connectivity of the ground. If the ground copper coating has a great influence on the high-frequency wiring, the interference signal of 100k-300k will appear in the power

Remember not to separate the ground, at least to ensure that one side of the ground is a complete ground. There is no guarantee that all the copper wires will be separated from each other.

Do not place crystal oscillator next to high frequency layout. High frequency affects high frequency, this is a common sense, try to put it far away. Of course, other signal lines should not be too close to the high-frequency line, and high-frequency has an impact on the low-frequency.

High frequency line placement improves the quality of signal passing holes. High frequency itself should need a shielding cover or shielding layer, but the circuit board layout can not provide shielding cover. At this time, we can only use PCB itself to make a shielding layer. Through hole can be understood as that shielding layer, and the ground below is another layer. The above may not be able to increase the shielding because it needs to be exposed for debugging.

No matter the drawing of schematic diagram or the design of PCB copy board, we should consider the high frequency working environment in which it is located, so as to design an ideal PCB copy board.

Almost every software has automatic layout, but as a PCB engineer, you should abandon him and make layout by yourself, which can make PCB production more effective and reasonable.

Generally, the fixed position components related to mechanical size are placed first, then special and large components are placed, and finally small components are placed. At the same time, the wiring requirements should be taken into account. The placement of high-frequency components should be as compact as possible, so that the wiring of signal lines can be as short as possible, so as to reduce the cross interference of signal lines.

The original should not be too close to the edge, and it is better to leave a 3-5mm. Power socket, switch, interface between PCB reading board and indicator light are positioning plug-ins related to mechanical size. Generally, the interface between power supply and PCB should be placed at the edge of PCB, and there should be a distance of 3mm-5mm between the power supply and the PCB edge; the LED should be placed accurately according to the needs; the switch and some fine-tuning components, such as adjustable inductance and adjustable resistance, should be placed close to the edge of PCB to facilitate adjustment and connection; components that need to be replaced frequently must be placed in the position with fewer devices For easy replacement.

Whether the layout is reasonable or not directly affects the life, stability and EMC (electromagnetic compatibility) of the product. It must be considered comprehensively from the overall layout of the circuit board, the accessibility of wiring and the manufacturability, mechanical structure, heat dissipation, EMI (electromagnetic interference), reliability, signal integrity and so on.