Electromagnetic problems have always troubled PCB designers. System design engineers must always monitor electromagnetic compatibility and issues. Unfortunately, even small design problems can cause electromagnetic problems. In this article, we will introduce what is electromagnetic issues, the reasons for electromagnetic issues, why is it important to avoid electromagnetic issues, how to reduce electromagnetic issues, how to test to minimize electromagnetic interference?
What is electromagnetic issues?
Electromagnetic compatibility, or EMC, involves the generation, propagation, and reception of electromagnetic energy, usually through poor design. Electromagnetic interference (EMI) refers to the harmful and destructive effects of electromagnetic compatibility (EMC), as well as electromagnetic interference from the environment. Excessive electromagnetic interference can cause defects or damage to the product. Any PCB designer should abide by EMC design rules to minimize the amount and impact of electromagnetic interference.
Electromagnetic compatibility (EMC) and related electromagnetic interference (EMI) are the two culprits that system design engineers have always paid close attention to, and they are also concerned about countless other problem areas. In particular, both hinder PCB layout and design engineers. Especially today, as circuit board design and component packaging continue to shrink, OEMs need higher speed systems.
EMC is related to the generation, propagation and reception of electromagnetic energy, which is not popular in PCB design. When different circuits, lines, paths and PCB materials are required to work together, it must be noted whether these signals are compatible and do not interfere with each other. On the other hand, electromagnetic interference (EMI) is electromagnetic compatibility (EMC) or harmful effects. In such an electromagnetic environment, the goal of PCB designers is to ensure the reduction of various energy elements in order to maintain the minimum interference effect.
The reasons for electromagnetic issues
There are two types of electromagnetic emissions, such as conducted electromagnetic interference and radiated electromagnetic interference. Conducted electromagnetic radiation will propagate through the system through the power supply or signal bus. At the time, the source of radiated EMI electromagnetic wave propagation-which can be an integrated chip or the electromagnetic wave generated by electromagnetic interference at the location of the PCB will be accepted by a receiver. This sensor may be a nearby device and will be severely disturbed.
As we all know, electromagnetic radiation is emitted from the edge of the pcb. The suspension of electromagnetic interference can be best described by the example of a drop of water hitting a puddle to produce water ripples. Electromagnetic waves propagating in the form of ripples will reach the edge of the PCB, where the two reference planes will act as slot antennas. This will radiate noise and produce electromagnetic interference to nearby equipment.
Electromagnetic radiation may also occur in high-frequency tracking, which is routing close to the edge of the PCB. Similarly, due to poor decoupling practices, electricity and ground planes also produce electromagnetic radiation. This can also cause unintentional currents, such as common mode (CM) and differential mode (DM) currents.
Why is it important to avoid electromagnetic issues?
The sources of electromagnetic interference are all around us, and we can classify them in several ways.
Artificial electromagnetic interference is generated by electronic circuits. On the other hand, naturally occurring electromagnetic interference may come from environmental factors such as cosmic noise and lightning.
Continuous interference is a source of electromagnetic interference that emits a constant signal, usually manifested as background noise. Pulse interference is intermittent, usually caused by switching systems, lightning, and other non-constant sources.
Narrowband signals such as those used in radio may encounter interference from oscillators and transmitters, although these sources only affect certain parts of the spectrum intermittently. Broadband interference affects high data signals like TV, which may come from many sources, including arc welding machines and solar noise.
How to reduce Electromagnetic issues?
Circuit board designers must follow the design principles of electromagnetic compatibility to maintain minimum electromagnetic interference. The basic causes of electromagnetic compatibility problems are quite common, mostly related to design defects, which can cause interference between circuits, circuits, through holes, PCB coils, and other components. These basic design principles can help prevent and solve these electromagnetic problems in printed circuit board design.
Designing a PCB ground plane is the most important step, it is the key to reducing electromagnetic interference. The ground plate is your first line of defense against electromagnetic interference, because all circuits require a ground plate to work. Increase the ground area inside the PCB as much as possible. The signal can be more easily dispersed with a larger area, reducing emissions, crosstalk and noise. Especially in multi-layer PCB board, solid ground plane is an ideal choice. Connect each component to a ground plane or point. Highly complex PCB designs usually include many regulated voltages, and each should have its own ground plane. Connect bypass or decoupling capacitors, Minimize signal length.Trace Layout
Traces are especially important for the design of the board. Proper use of tracking can ensure that the current is propagated correctly. However, if tracking is not arranged according to top-level EMC design rules, many problems will arise. Including avoid right angles, keep signals separate, Mind spacing, shorten return paths, use vias carefully.
Electronic components are the basic components of electronic circuits. However, if placed improperly, it may cause several EMI problems. Including Separate analog and digital parts，Separate analog and high-speed pieces，Be careful with high-speed components.
No matter what design rules you follow, some components will produce electromagnetic interference-especially small, high-speed components. Fortunately, shielding and filtering can minimize the effects of electromagnetic interference. Component and board shielding, Low-pass filtering, Cable shielding.
How to test to minimize electromagnetic interference us?
Various modeling techniques are used to measure electromagnetic radiation in electronic systems. In electromagnetic compatibility analysis, computer simulation is generally regarded as the most basic method. Computer simulation through integration technology has obtained accurate measurement results of basic parameters.
- Finite difference time domain modeling is used to measure the frequency response of common mode currents in high voltage applications.
- The common-mode current is evaluated by considering factors such as current-type antenna impedance and distributed circuit constants.
- The electrical coupling between the power plane and the ground plane also affects the common-mode current.
The electromagnetic compatibility of any circuit is related to the generation, propagation and reception of electromagnetic noise. In PCB design, electromagnetic noise is not a popular feature. We pay special attention to ensure that the signals do not interfere with each other, when it comes to lines, paths, or even the unified operation of the PCB.
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