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Microwave Tech

Microwave Tech

Microwave Tech

Microwave Tech

Electromagnetic compatibility design of high frequency circuit board
2021-09-22
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Author:Aure

Electromagnetic compatibility design of high frequency circuit board


PCB manufacturer: Electromagnetic compatibility refers to the ability of electronic equipment to work in a coordinated and effective manner in a variety of electromagnetic environments. The purpose of electromagnetic compatibility design is to enable electronic equipment to suppress all kinds of external interference, so that the electronic equipment can work normally in a specific electromagnetic environment, and at the same time to reduce the electromagnetic interference of the electronic equipment itself to other electronic equipment.

1. Adopt the correct wiring strategy

The use of equal routing can reduce the wire inductance, but the mutual inductance and distributed capacitance between the wires increase. If the layout allows, it is best to use a grid-shaped wiring structure. The specific method is to wire one side of the circuit board horizontally, and the other side of the circuit board. Connect with metallized holes at the cross holes.


Electromagnetic compatibility design of high frequency circuit board



2. Choose a reasonable wire width

Since the impact interference generated by the transient current on the printed lines is mainly caused by the inductance of the printed wires, the inductance of the printed wires should be minimized. The inductance of the printed wire is proportional to its length and inversely proportional to its width, so short and precise wires are beneficial to suppress interference. The signal lines of clock leads, row drivers or bus drivers often carry large transient currents, and the printed wires should be as short as possible. For discrete component circuits, when the printed wire width is about 1-5mm, it can fully meet the requirements; for integrated circuits, the printed wire width can be selected from 0-2 to 1-0mm.

Third, avoid electromagnetic radiation generated when high-frequency signals pass through printed wires

In order to avoid electromagnetic radiation generated when high-frequency signals pass through the printed wires, the following points should be noted when wiring the circuit board:

1- The bus driver should be next to the bus it wants to drive. For those leads that leave the circuit board, the driver should be next to the connector.

2- The wiring of the data bus should have a signal ground wire between every two signal wires. It is best to place the ground loop next to the least important address lead, because the latter often carries high-frequency currents.

3- Minimize the discontinuity of the printed wires, for example, the width of the wires should not change suddenly, and the corners of the wires should be greater than 90 degrees to prohibit circular routing.

4- The clock signal lead is most prone to electromagnetic radiation interference. When routing the wire, it should be close to the ground loop, and the driver should be close to the connector.

Fourth, suppress the crosstalk between the printed board wires

In order to suppress the crosstalk between the wires of the circuit board, when designing the wiring, you should try to avoid long-distance equal wiring, extend the distance between the wires as much as possible, and try not to cross the signal wires with the ground wires and the power wires. Setting a grounded printed line between some signal lines that are very sensitive to interference can effectively suppress crosstalk.

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