Electromagnetic Compatibility—A Technological Barrier That Must Be Overcome

Even a single instance of conducted interference can cause 70% of domestically produced PCs to be classified as non-compliant products. Yet, conducted interference is just one of many metrics for electromagnetic compatibility in electronic products. Electromagnetic compatibility has now become a significant technical barrier hindering China's exports of electronic products.
   
Electromagnetic Conduction—Once caused 70% of SMEs to fail quality inspections.
   
As early as September 1996, the State Administration of Technical Supervision, together with the former Ministry of Electronic Industry, conducted a sample inspection of the quality of domestically produced microcomputers. The results were discouraging: the pass rate for PCs was only 61.5%. Among the comprehensive inspections covering seven major categories and 27 specific items,不合格 conduction interference emerged as the most prominent issue.
   
Conducted interference is an item in the electromagnetic compatibility testing of electronic products. In this spot check, 70% of the enterprises that failed the test had problems precisely in this area, and the electromagnetic compatibility indicators are mandatory requirements under national standards. Therefore, failure on this single item alone should be sufficient to classify a product as non-compliant—there is absolutely no room for negotiation.

What exactly is the conducted interference that has caused 70% of companies to “fall by the wayside”? Conducted interference is a concept used to measure the magnitude of electronic interference signals that electronic products emit into the power grid during operation. All electronic devices generate interference signals when they draw power from the grid. If these interference signals are too strong, they can degrade the overall power quality of the grid, thereby disrupting the normal operation of other electrical appliances. Consequently, most countries have strict regulations governing the conducted interference levels of electronic products, prohibiting the manufacture and sale of products with excessively high conducted interference.
   
Electromagnetic Interference—An Electromagnetic Compatibility Issue with Increasingly Serious Hazards
   
In fact, conducted interference is one of the most fundamental electromagnetic interference issues. It’s caused by substandard PC power supplies. Compatible computer manufacturers typically use inexpensive power supplies; all they need to do is add an additional filtering coil to ensure that the conducted interference passes the testing requirements. So, what exactly is electromagnetic interference?
   
Electromagnetic interference (EMI) refers to stray energy emitted by electronic devices or systems, or stray energy that enters such devices or systems from external sources. For example, high-frequency electromagnetic interference can occur between laptops and testing equipment, between printers and desktop computers, and between cellular phones and medical instruments. Electromagnetic interference encompasses conducted EMI (low-frequency), radiated EMI (high-frequency), electrostatic discharge (ESD), and EMI caused by lightning strikes.
   
Today, as humanity has entered the information age, electromagnetic waves—now recognized as a valuable resource—have been widely incorporated into information technology products across an extremely broad frequency range from 0 Hz to 400 GHz. These products—including automobiles, telecommunications devices, computers, and household appliances—are increasingly prevalent in both society and homes. Consequently, electromagnetic interference has also expanded—from low frequencies all the way up to the microwave band—radiating or conducting itself seamlessly into operating sub-devices, systems, and the surrounding environment, posing ever-more-serious threats to equipment, systems, and even ecosystems.

   
Electromagnetic interference from information technology equipment cannot be overlooked. Computers have evolved toward higher speeds, greater sensitivity, higher integration, and multifunctionality, making today’s systems complex devices that transmit low-voltage signals and incorporate numerous components and subsystems. High speeds and high densities exacerbate the system’s radiation, while low voltage and high sensitivity reduce its immunity to interference. Consequently, electromagnetic interference from the external environment and mutual interference within the system itself seriously threaten the stability, reliability, and security of computer and digital systems.
   
The use of microprocessors in homes, businesses, factories, and transportation vehicles is steadily increasing. In the future, as more transmitting and sensitive devices are deployed in various electronic environments, corresponding challenges will inevitably arise.
   
Now, with the advent of Bluetooth technology, this new type of transmitting device can be found in nearly all electronic devices. Bluetooth is a wireless frequency-hopping specification that enables automatic communication among electronic devices within a range of approximately 30 meters, operating in the 2.4 GHz ISM (Industrial, Scientific, and Medical Equipment) band. Worldwide, more than 1,200 companies have already adopted the Bluetooth specifications. By 2004, as many as 400 million devices will be using Bluetooth. Clearly, when exposed to incident wireless signals, devices employing Bluetooth technology should continue to function normally. However, what we cannot be certain of is whether nearby devices not designed for Bluetooth can operate without interference.
   
Electromagnetic leakage from information technology equipment poses a threat to information security. In the network era, information leakage is considered the greatest threat to cybersecurity. However, computer keyboards, displays, and other components can all cause information to leak out through radiation—this phenomenon is known as the TEMPEST effect. A more precise definition refers to the leakage of information caused by the emission of electromagnetic energy from electronic information devices.
   
In the past, someone in the United States conducted an experiment in New York: they installed a radiation-signal interception device called a “data scanner” on a car and slowly drove from Battery Park at the southern tip of Manhattan along Wall Street, monitoring the radiation signals emitted by computers working at various institutions along the way—including the Customs House, the Federal Reserve Bank, the World Trade Center, City Hall, the Police Headquarters, the New York Telephone Company, and the United Nations Headquarters. Surprisingly, the results revealed that New York is a massive information repository.
   

Electromagnetic interference poses health risks to humans. Today, many medical devices rely on advanced electronic and information technologies. The susceptibility of these devices to electromagnetic interference directly affects people’s safety and even their lives. For example, cardiac pacemakers are often susceptible to electromagnetic interference from sources such as computers and mobile phones, which can alter their functionality. It is reported that a prosthetic limb controlled by bioelectric signals once caused its wearer to fall backward after being exposed to electromagnetic interference near high-voltage power lines. This illustrates how electromagnetic interference can indirectly harm human beings by disrupting the operation of medical devices.
   
Electromagnetic Compatibility—A Rapidly Developing Emerging Discipline
   
The IEC defines electromagnetic compatibility as follows: “Electromagnetic compatibility is a property of electronic equipment that enables it to perform its intended functions in an electromagnetic environment without causing intolerable interference.” Electromagnetic compatibility (EMC) technology is a rapidly developing, interdisciplinary field that integrates knowledge from various domains. It is grounded in the fundamental theories of electromagnetic fields and radio technology, while also drawing on numerous emerging technological areas, such as microwave technology, microelectronics, computer technology, communication and networking technologies, and new materials. The scope of EMC research is extremely broad, encompassing nearly all modern industrial sectors.
   
Electromagnetic compatibility encompasses the compatibility among circuit modules within a device, the compatibility between devices themselves, and the compatibility among systems. Interference between circuits is one of the primary causes of degraded device performance. Digital devices generate strong radiation because their pulse currents and voltages contain abundant high-frequency harmonics. In fact, it was only after digital circuits became widespread that electromagnetic interference issues began to become increasingly prominent. Interference between devices typically occurs through two main pathways: one is in the form of spatial electromagnetic wave interference, and the other is interference induced via power lines. Therefore, power-line filters are generally installed at the power input ports of devices.
   
The three key elements of electromagnetic compatibility (EMC) issues are: the source of electromagnetic interference, the coupling path, and the sensitive equipment. To address EMC problems, we must focus on these three aspects and eliminate one of them. To achieve effective EMC, it is essential to conduct in-depth research into the following five areas: thoroughly study the sources of electromagnetic disturbances—including their frequency-domain and time-domain characteristics, underlying mechanisms of generation, and mitigation measures; deeply investigate the propagation characteristics of electromagnetic disturbances; comprehensively examine the anti-interference capabilities of sensitive equipment; rigorously explore measurement methods for EMC issues; and thoroughly investigate EMC within and between systems.
   
The engineering approaches to electromagnetic compatibility include the test-and-modify method. During the design phase, one should as much as possible adopt electromagnetic compatibility design standards. After the prototype is completed, it undergoes testing; if it fails to meet the electromagnetic compatibility requirements, modifications are made until the requirements are satisfied. This approach is suitable for relatively simple devices but involves higher development costs. The system-design method, on the other hand, involves carefully predicting various potential electromagnetic compatibility issues during the product’s design process and taking appropriate measures from the very beginning of the design to prevent such issues. Typically, this method can resolve 80% of electromagnetic compatibility problems before the final product is even completed.
   
EMC—A technological barrier that domestically produced electronic devices must overcome.
   
Since the 1990s, many countries have successively enacted relevant laws, management regulations, and standards, and have implemented comprehensive management and supervision over the production and market distribution of electrical and electronic equipment, as well as the establishment of stations and enterprises engaged in activities involving electromagnetic radiation. In particular, extensive electromagnetic compatibility certification systems have been introduced to ensure public safety and protect public interests.

With the development of the market economy, as China seeks to participate in global competition in the technology market, all imported and exported electronic products must undergo EMC testing. Consequently, the Chinese government and relevant authorities are paying increasing attention to EMC issues and continuously developing mandatory standards in this area. Various government departments and military units have also begun establishing EMC laboratories and testing centers of different sizes.
   
However, one fact that must be squarely acknowledged is that the electromagnetic compatibility of China’s electronic products still lags significantly behind that of developed countries worldwide. Given the international emphasis on EMC design for electronic products—and the fact that many countries enforce EMC standards for electronics—EMC issues have become a significant technical barrier hindering the export of Chinese electronic products.

The EMC power amplifier independently developed by Nanjing Huakai Electronic Technology Co., Ltd. meets the EMC testing requirements of various standards:

Automotive Electronics: ISO11452-2, ISO11452-4, ISO11452-5, EMC-CS-2009

Information Technology: IEC61000-4-3, IEC61000-4-6

Military standard equipment level: MIL-STD-461F/GJB151B-2013 (10 kHz ~ 40 GHz, 200 V/m)

Military Standard System Level: MIL-STD-464C/GJB1389A-2005/GJB8848-2016 (1 kHz ~ 45 GHz, 27,460 V/m)

Aviation airborne equipment: RTCA/DO-160G