（EMI & EMC CIRCUIT DESIGN THROUGH ISOLATION OF AD AND DC）

What’s the Difference Between EMI and EMC in Electronic Designs? 电子设计中的EMI和EMC有什么区别？

Electromagnetic interference and electromagnetic compatibility are both important considerations when designing and working with electronic components and systems.
电磁干扰和电磁兼容性是设计和使用电子元件和系统时的重要考虑因素。

• Electromagnetic interference (EMI) 电磁干扰

• Electromagnetic compatibility (EMC) 电磁兼容性

EMI is caused by electromagnetic emissions that may disturb the function of electronic devices and radio-frequency (RF) systems. Such devices and systems must be properly shielded from electromagnetic radiation for them to perform optimally. EMC measures how well these devices and systems can perform in the presence of any disruptive EMI.

（32MHz晶振布线与天线太近，造成电磁辐射超标）

图例解释：

在特殊发射杂散频段167MHz-223MHz中，限值为-54dBm，测试超标杂散点为191.99MHz，数据为-51.701dBm，超出限值2.299dBm。

EMI 是由电磁辐射引起的，电磁辐射可能会干扰电子设备和射频 （RF） 系统的功能。此类设备和系统必须适当屏蔽电磁辐射，才能使其发挥最佳性能。EMC 衡量这些设备和系统在存在任何破坏性 EMI 的情况下的性能。

EMI definition EMI 定义

EMI is typically present as undesirable noise in any electrical/electronic system. EMI occurs due to electromagnetic emissions that disturb functionality in radio-frequency (RF) or electronic devices. One way to protect the optimum functionality of systems and devices is the use of proper shielding from electromagnetic radiation. EMC will measure how these devices/systems will function properly in a disrupting EMI environment.

任何电气/电子系统中通常都存在不需要的噪声，即电磁干扰。电磁干扰是由于电磁辐射干扰射频（RF）或电子设备的功能而产生的。保护系统和设备的最佳功能的一种方法是使用适当的电磁辐射屏蔽。EMC将测量这些设备/系统如何在干扰的电磁干扰环境中正常运行。

Essentially, EMI is undesirable noise in a system that disrupts electronic, electrical, and RF systems.
从本质上讲，EMI 是系统中的不良噪声，会破坏电子、电气和射频系统。

There are four kinds of EMI: EMI有四种：

1、Conducted EMI: This type of EMI, which flows through wires, occurs via physical contact with the source of that EMI.
传导 EMI：这种类型的 EMI 流经电线，通过与该 EMI 源的物理接触而发生。

2、Differential-mode EMI: This low-frequency EMI will flow in an opposite direction through adjacent wiring.
差模 EMI：这种低频 EMI 将以相反的方向通过相邻的布线流动。

3、Common-mode EMI: This high-frequency form of EMI flows in the same direction through one or more electrical conductors.
共模 EMI：这种高频形式的 EMI 沿同一方向流过一个或多个电导体。

4、Radiated EMI: This is the most common type of EMI. It’s caused by radiating electromagnetic fields. Common signs of radiated EMI include “snow” on TV monitors and static noise on AM/FM radio receivers.
辐射 EMI：这是最常见的 EMI 类型。它是由辐射电磁场引起的。辐射 EMI 的常见迹象包括电视监视器上的“雪花”和 AM/FM 无线电接收器上的静态噪声。

（RADIATION THROUGH APERTURE）

EMC definition EMC 定义

1、EMC of an electrical, electronic, or RF device has two features: 电气、电子或射频设备的EMC具有两个特点：

2、The capability of working properly while in the presence of electromagnetic radiation.
在存在电磁辐射的情况下正常工作的能力。

（展频晶振工作原理）

The capability to not generate any additional EMI that may affect the proper operation of any other devices nearby.
能够不产生任何可能影响附近任何其他设备正常运行的额外EMI。

The EMC of any device may be improved by using a clever design and shielding, along with EMI filtering. A device’s EMC can be measured via compliance testing by using a dedicated test system that’s composed of antennas, near-field probes, and spectrum analyzers.
任何器件的EMC都可以通过使用巧妙的设计和屏蔽以及EMI滤波来改善。可以使用由天线、近场探头和频谱分析仪组成的专用测试系统，通过一致性测试来测量设备的 EMC。

EMC testing may prove to be expensive. However, it’s essential to ensure that an electrical/electronic design will function as expected and will not generate disruptive EMI.
EMC测试可能比较昂贵。但是，必须确保电气/电子设计按预期运行，并且不会产生破坏性 EMI。

EMI and EMC Compliance EMI 和 EMC 合规性

EMI and EMC compliance standards are not uniform worldwide. Myriad different regulatory bodies worldwide will each have their own specific standards.
EMI 和 EMC 合规标准在世界范围内并不统一。全球无数不同的监管机构都有自己的特定标准。

An example is the compliance standards in the European Union (EU) that differ from those in the United States. To further complicate matters, generally the military employs far more strict standards than do commercial industries. Commercial compliance standards will often vary depending on the specific industry and the end use of any device.
例如，欧盟 （EU） 的合规标准与美国的合规标准不同。更复杂的是，通常军方采用的标准比商业行业要严格得多。商业合规性标准通常会因特定行业和任何设备的最终用途而异。