From the circuit of electromagnetic compatibility, circuit board design should be familiar with the components of the electromagnetic compatibility, these properties with the usual properties of components of the requirements are different, if not for electromagnetic interference suppression for the purpose of these indicators are not listed in the instructions for use of these properties, main performance characteristics change components at high frequency the selected components, and high frequency performance of them is the first step for electromagnetic compatibility design, especially in the electromagnetic compatibility of these components and products (such as the key element of electromagnetic compatibility) more should pay attention to the choice of the product has been verified.
The circuit board is divided into different modules according to their functions always, from the electromagnetic compatibility view circuit can be divided into the following several function blocks.
Circuit 1, electromagnetic interference, such as digital circuit, usually the microprocessor and peripheral circuit, switching power supply.
Circuit 2, need protection against interference, such as analog input and conversion of small signal processing circuit, A/D conversion circuit part.
Circuit 3, and is independent of the disturbance, such as passive components of the network, load etc..
Circuit4, the interface circuit board, usually the interference by the interface to input or output circuits is also possible circuit and is independent of the disturbance, mainly to see if it has enough to interference suppression ability. If the operational amplifier is quite strong in the low end of the anti-interference ability, according to the different design is generally not affected by low frequency interference signals, so it can be in the low frequency end as circuit and irrelevant, but for some frequency points to the high frequency interference signals are very sensitive when it became a circuit protection without interference the.
Divide the circuit module in the performance according to the electromagnetic compatibility, can take different measures according to different types of electromagnetic compatibility. The circuit is easy to produce interference can be taken to reduce the interference or jamming circuit isolation measures. Interference circuit is sensitive to interference and interference circuit isolated does not produce itself. Circuit and is independent of the disturbance can be moved to the one-sided or two-sided board price cheap. The interface circuit need to be especially careful to increase the anti-interference measures against interference, and should avoid the interference signal to go outside.
The circuit of analog and digital circuit interference and interference effects should partition line, separated by distinct isolation belt intermediate. Analog circuits because of no interference so power supply layer and the formation can not handle, can be used for wiring when necessary, because of its easy interference so sensitive to the length of the wire should be as short as possible in order to improve the anti-interference performance. Every piece of analog and digital circuit connection through the isolation filter.