EMC Principles for Electronics 产品 Design

From research 和 development to final certification, 电磁兼容(EMC)原则应成为电子产品设计的重点. In addition to ensuring 产品安全 和 wireless coexistence, 在早期阶段考虑EMC原则有助于为遵从性铺平道路，并减少与重新设计相关的成本和时间.

EMC Principles made easy

电磁兼容(EMC)通常被描述为“黑艺术”，但打开它的关键是了解其基本原理. 一旦了解了这些EMC原则，EMC就会突然变得简单得多. It's important to underst和 the difference between EMI vs EMC.

EMC electromagnetic interference basics

在设计产品时(无论是物理产品还是系统)，重要的是要询问需要考虑什么以确保实现EMC. 要做到这一点, 有必要回过头来考虑EMC干扰是如何产生的.

用最简单的术语来说，干涉是由能量从一种状态转移到另一种状态引起的. 就像轻敲电灯开关一样，我们期望这种能量的转移是瞬间的.

EMC regulations, from 商业 to 医疗 to 军事, 基本上都在问如何在能量传递过程中阻止电压过调或过调，从而使产品能够在不受干扰的情况下工作.

EMC Principles - Asking the right questions

It is the probability of such interference which must be identified. No matter how much electromagnetic noise is generated, 必须记住，必须有人或有东西接收到这种噪音，才会发生干扰. The key questions which must be asked are:

• Where is this product going to be used?
• With what/whom is it going to interfere?
• How will the energy travel from the product to its “victim”
• 能源 will travel either down the cabling or through the air, the two mechanisms, 因此, being radiation 和 conduction. St和ards used are based around radiated 和 conducted tests. 

EMC耦合

有一些机制需要注意，例如电容耦合和感应. These are more unusual, 尽管随着新技术的出现，感应的重要性预计会增加, such as wireless charging of electric cars 和 appliances, continue to emerge 和 become more widely adopted, the potential interference that they cause is limited.

“凭借我们的经验，成千上万的产品成功通过了最终的合规和认证, 我们已经确定了EMC在产品设计上的三个最基本的im体育APP:滤波, 屏蔽, 和 earthing/grounding.”

Three considerations in EMC for product designers

Take three key factors into account.

Whether it is a product, 一个系统, or a printed circuit board, the basic EMC principles remain the same. 在考虑产品的设计如何能保证更大的电磁兼容性时, there are three key factors to consider:

1. 屏蔽
2. Grounding/Earthing
3. 过滤

电磁兼容屏蔽 

根据产品的功能，一些设备会产生不必要的电子噪音. The best way to prevent this noise from spreading to other, 更有效的散热器(如电缆)是创建一个遏制策略.

筛选罐(仅在每个角落焊接固定)可能不够，沿着褶皱的整个长度进行焊接对于确保金属与金属接触至关重要, so a slot antenna is not inadvertently produced.

如果使用屏蔽，那么确保完整的法拉第笼是很重要的. Holes for cabling, 监控, 和 ventilation will affect the integrity of the shield, 因此，EMC蜂窝网和屏蔽电缆或金属对金属接触将有助于屏蔽外壳的360度终端. 较厚的屏蔽材料将通过反射和/或吸收更好地衰减.

EMC grounding/earthing techniques

Earthing or grounding is the treatment of ‘potential differences.’ 

Grounding example: In the event of an electrostatic discharge (ESD), 电压暴露在一个产品只是试图找到最快的路线到地面. If an ESD event is applied to a cable, 和 that same cable is directly connected to a PCB, 能量将沿着电缆传播，并导致PCB上的地平面跳升至ESD电平的电位, potentially causing damage or malfunction. 如果相同的电缆被终止在板上，在那里地球/地面连接到主入口点, the issue would be resolved.

接地/接地可以通过各种方法实现，包括:

• 灵活的电线
• 灵活的辫子
• 金属电镀

灵活的接地带可以更有用，但这是以效率为代价的.

EMC filters 和 filtering

滤波器通常是抑制射频噪声的无源元件，可用于pcb内部或电缆外部. The amount of electrical noise a product emits is not important; it needs to be connected to an antenna (i.e. cables, pcb track, etc.) for it to radiate or receive 和 cause issues. 因此, 所有信号线, especially those connected to the outside world, should be given specific treatment. 这意味着在源点(发射)或进入点(易感性)进行过滤。. 

There are various methods of filtering, which include:

• Capacitor or inductor components
• A small amount of capacitance from signal to ground
• Ferrite beads act as an inductor on whole signal/cables bundles

过滤器可以是一个简单的改造安装，但如果需要添加到重要的生产运行中，可能会很昂贵. Different materials have different properties concerning frequency, 制造商的文献可以帮助您选择频率范围内最有效的材料. 在产品和预测试阶段的设计改进可以减少对过滤器的依赖.

“By testing during the design phase, 在遵从性测试中发现的大多数潜在问题和失败都可以得到缓解.”

Cost-effective electronic prototype design

Qualify the prototype design early

最具成本效益的产品开发方法总是在开发周期的早期对原型设计进行鉴定. 

一个关键的目标应该是在第一次测试中取得成功, 批准, 和 certification phase. If a product has to be re-designed it can be prohibitively expensive, resulting in delays to market 和 a loss in consumer confidence.

Consider which countries your product will be exported to

While many countries have adopted regulations almost identical to CE标志, once a product is to be exported, 更有可能的是，强制性的第三方测试也将被要求获得 global market access.

在设计过程中尽早考虑产品可能出口到哪里是至关重要的, taking advice if necessary. 稍后修改产品以满足不可预见的出口需求可能是一项昂贵且耗时的工作, a mistake seen often.

CE Marking has been a legal requirement for over twenty years, yet thous和s of products still fail every year through incorrect CE标志.

Our EMC experts are here to help

测试机构，如im体育APP，被要求提供指导和建议 EMC合规, be it at the beginning or the end of the design process. By giving early advice we can prevent issues from arising later, a safer 和 more cost-effective option.

For more information on our EMI / EMC testing services,请 contact our experts today.