Wireless Communication
EU RED Network Security Standard EN 18031
Wireless and communication detection
Mobile communication product certification
Bluetooth BQB Product Certification
FM/AM Product Certification
WiFi Product Certification
Wireless charging product certification
Interphone product certification
Base station certification
SAR testing
Receiver Product Certification
5G NR Product Certification
UWB Product Certification
Internet of Things authentication
Electromagnetic compatibility
Automotive Electronics EMC Testing
EMC rectification
EMC
Automotive Electronics
Electrical performance testing
EMS testing - radiation anti-interference testing system (including radar waves)
EMS Testing - Electrostatic Discharge
EMS Test - Transient Conducted Immunity Test
EMS Testing - Portable Transmitter Immunity
EMS Test - High Current Injection (BCI) Test
EMS test - low-frequency magnetic field anti-interference test
EMI Testing - Transient Conducted Emissions Testing System
EMI testing - low-frequency magnetic field emission
EMI Test - Radiation Emission Test
EMI Test - Conducted Emissions Test
Automotive Electronic Testing
Automotive Parts Inspection
Automotive ELV&VOC
Reliability testing
Temperature shock test
Vibration testing
Instrument panel/instrument panel three comprehensive vibration test
Comprehensive vibration test of door inner panel III
Sunvisor Three Comprehensive Vibration Test
Spoiler Three Comprehensive Vibration Test
Three comprehensive vibration tests of car front and rear bumpers
Three comprehensive vibration tests for lamp housing/lampshade
Comprehensive vibration test of outer circumference three
Automotive metal material testing
Performance testing of automotive lighting fixtures
Rapid temperature change test
Vibration
Common issues with vibration testing
Common issues with fatigue testing
Common issues with high and low temperature testing
Conducted Interference (CE) - Suzhou Lixun Standard
Electromagnetic Radiation Tolerance Test (RS) - Suzhou LCS Standard
Electrical Fast Pulse Withstand Test (EFT) - Suzhou LCS Standard
Voltage flicker test - Suzhou LCS standard
Electronic appliances
Household appliance product testing
Electrical accessory product testing
Household appliance testing
Chemical Testing
Introduction to PFAS Testing
MOSH/MOAH Mineral Oil Testing Service
MOSH/MOAH Mineral Oil Testing and Certification Report Service
Consumer Product Testing Services - WEEE Chapter
Ecological textile testing
Leather Footwear Inspection
Food contact material testing
Testing of toys and baby products
Hazardous substance testing
Electronic Cigarette Testing
Electronic cigarette detection
Reliability testing
Other tests - pencil hardness test
Mechanical testing - Packaging compression test
Climate environment testing - Xenon lamp aging test
Battery Testing
Power storage battery testing and certification
Consumer Electronics Battery Testing and Certification
power battery
Light electric vehicle batteries
Energy storage battery
Portable battery
Battery testing
battery test
Lamp Inspection
Inspection of ship lighting fixtures
COI Index Test for Medical Indoor Lighting
Lamp safety inspection
Luminaire energy efficiency testing
EMC testing of lighting fixtures
Integral Ball Laboratory
Photobiology Experiment
Light distribution test
Lamp aging test
Lamp IP waterproof
Lamp performance testing
Lamp reliability testing
Children's toy testing
Testing standards for toy products
China Certification
China's "national promotion" RoHS certification
China Energy Efficiency Label Certification
China Energy Conservation Certification
China CQC Certification
Tmall JD Quality Inspection Report
China SRRC Certification
Taiwan BSMI certification
Taiwan NCC certification
China CCC Compulsory Certification
Asia Certification
Vietnam certification
KC certification
KUCAS Certification in Kuwait
Singapore PSB certification
Iraq COC Certification
IMDA certification
VCCI Certification in Japan
JATE certification in Japan
PSE certification
BIS certification
Japanese TELEC certification
European Certification
RoHS certification
GOST certification in Russia
Russian EAC certification
Northern Ireland UKNI logo
Electrical ENEC certification
European D-MARK certification
Türkiye BTK certification
TSE certification in Türkiye
CE certification in Türkiye
RED certification
German TUV-SUD certification
CE-ERP certification
REACH certification
German GS certification
EU E-Mark certification
North American Certification
Ecuador VOC certification
Mexico NOM certification
IRAM certification
CPSC Certification in the United States
CSA certification
ASTM certification
FDA certification
CEC certification
ETL certification
ul certification
IC certification
Energy Star
FCC Certification in the United States
ASTM certification
Middle East Certification
Israel SII certification
Saudi SABER certification
GCC certification for the seven Gulf countries
Iran COI certification
Qatar COC Certification
Iraq COC Certification
Saudi EER Energy Efficiency Certification
Saudi SABER certification
Algeria PCA certification
PVOC certification
Australia Certification
New Zealand IC-F testing
VEET certification
LCP certification
GEMS certification
RCM certification
C-Tick certification
SAA certification
Africa Certification
Gabon COC certification
Algeria COC certification
Ethiopian VOC and COC certification
Mauritius VOC certification
Ghana COC certification
COC certification in Burundi
Zambia COC certification
Botswana COC Certification
Uganda PVOC certification
SABS certification in South Africa
South African LOA certification
Zimbabwe CBCA Certification
Nigeria SONCAP certification
Kenya PVOC certification
African COC certification
Other certifications
WEEE
Bluetooth BQB certification
IECEE registration
MHRA registration in the UK
TRAINING
Management system training
Laboratory technical training
Laboratory Process Consulting
Laboratory decoration construction
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Wireless Communication
Electromagnetic compatibility
Automotive Electronics
Automotive Parts Inspection
Electronic appliances
Chemical Testing
Electronic Cigarette Testing
Reliability testing
Battery Testing
Lamp Inspection
Children's toy testing
China Certification
Asia Certification
European Certification
North American Certification
Middle East Certification
Australia Certification
Africa Certification
Other certifications
TRAINING
Introduction to EMC filtering
Author.
LCS
Source:
Post time:
2026-04-02
In PCB design, filtering is essential: on the one hand, other methods cannot completely suppress the conducted noise entering and exiting the equipment. When electrical signals enter and exit the equipment, effective filtering must be carried out; On the other hand, changes in the output state of integrated chips or other reasons can generate certain noise on the chip's power supply, which can affect the normal operation of the chip itself or other chips. Filtering measures are essential and the most commonly used countermeasures. In principle design, many filtering measures are often taken into account, such as decoupling capacitors, three terminal capacitors, magnetic beads, power filtering, interface filtering, etc. However, in PCB design, if the position of the filtering device is not properly placed, the filtering effect will be greatly reduced, and even the filtering effect will not be achieved.
The general consideration for installing filter components is the principle of proximity. For example:
Decoupling capacitors should be placed as close as possible to the power pins of the IC;
Power filtering should be placed as close as possible to the power input or output;
The filtering of local functional modules should be close to the entrance of the module;
The filtering of external interfaces (such as magnetic beads) should be placed as close as possible to the connectors.
There are many commonly used filtering devices, including resistors, inductors, capacitors, ferrite beads, etc.
1、 Resistance
Resistors cannot be used alone for filtering purposes. They are generally combined with capacitors to form RC filters.
The characteristics of resistors are shown in the following figure. Due to the presence of lead inductance (ESL) and parasitic capacitance, there are significant differences in the high and low frequency characteristics of resistors, which should be taken into account when designing filters.
2、 Inductance
The high and low frequency characteristics of the inductor are shown in the above figure. Due to the presence of lead resistance (ESR) and parasitic capacitance, the inductance has a self resonant frequency f. The inductance exhibits characteristics of inductance in the frequency range below f. However, in the frequency range above f., it exhibits characteristics of capacitance. This is something that needs special attention when calculating the insertion loss of a filter.
3、 Ferrite magnetic beads
Ferrite magnetic beads are also commonly used devices for filtering. Ferrite used for electromagnetic noise suppression is a magnetic material composed of a mixture of iron, nickel, and zinc oxides, with high electrical resistivity and high magnetic permeability (approximately 100-1500). Ferrite magnetic beads are connected in series on the signal or power path to suppress differential mode noise. When current flows through ferrite, low-frequency current can flow almost without attenuation, but high-frequency current will suffer significant losses and be converted into heat dissipation. Ferrite magnetic beads can be equivalent to a series connection of resistance and inductance, but both the resistance and inductance values vary with frequency. The frequency characteristics of typical ferrite magnetic beads are shown in the figure.
Ferrite magnetic beads have better high-frequency filtering characteristics compared to ordinary inductors. Ferrite exhibits resistance at high frequencies, equivalent to an inductor with a very low quality factor, so it can maintain high impedance over a wide frequency range, thereby improving high-frequency filtering efficiency.
4、 Common mode inductor
Inserting the transmission wire into the center can simultaneously suppress the common mode high-frequency noise of each wire to ground. The usual practice is to wrap two identical coils around the same ferrite ring, where the ferrite magnetic loss is small. The winding method allows the magnetic flux in the magnetic ring of the two coils to overlap with each other when a common mode current flows through them, thereby having a considerable inductance and suppressing the common mode current. However, when the two coils flow through a differential mode current, the magnetic flux in the magnetic ring cancels each other out, with almost no inductance, so the differential mode current can pass through without attenuation.
5、 Capacitor
Capacitors are the most widely used components in EMC design of PCBs. Capacitors can be divided into three types based on their functions:
Decouple: Breaking the coupling between ports of a system or circuit to ensure normal operation.
Bypass: Provide a low impedance path to ground where transient energy is generated. It is one of the essential conditions for good decoupling.
Energy storage (Bulk): Energy storage capacitors can ensure that the voltage does not drop when the load quickly becomes heaviest.
For EMI filters, the dielectric material requirements for capacitors are not high; The absolute capacitance value, temperature coefficient of the capacitor, and voltage variation coefficient are usually not important.
In EMC design, the function of filtering is basically to attenuate high-frequency noise, so filters are usually designed as low-pass filters. The typical structural form of the filtering circuit is shown in the following figure:
Related articles
New articles
Media Center
Latest News
Contact Us
National 24-hour service hotline
400-116-2629
Group Headquarters
E-mail: webmaster@lcs-cert.com
Address: Shenzhen City, Baoan District, Shajing Street, Nga side of the school of Wei Juji Industrial Park, Building A 1 ~ 2 floor, Building C 3 floor
WeChat Inquiry
Reservation
Contact Us
National 24-hour service hotline
Address：Juji Industrial Park, Xueziwei, Ngabian, Shajing Street, Baoan District, Shenzhen Building A 1~2F, Building C 3F
WeChat public number
Share industry dry goods
WeChat consultation
Please note consulting services
Follow Jitterbug
Mobile website
di complaint mailbox: customer.complaint@lcs-cert.com complaint telephone tel: 18126445450 certificate report verification of authenticity mailbox: verification@lcs-cert.com