EMC radiated test is one of the testing parameters on the EMC test, besides EMC conducted test. Advancement in electronic and information technology have changed all aspects of human life. We can stay connect with our electronic devices anytime and anywhere.
However, the electronic devices we use will emit an electromagnetic wave that affect both our bodies and other devices around it. EMC radiated test is very important to ensure that electronic devices have met the EMC standard requirements. It is also established to avoid various risks and interference due to unwanted electromagnetic waves from electronic devices.
In this article we will discuss everything related to radiated emission test in EMC standard requirements.
What is EMC radiated emission test?
EMC radiated test is measuring the electromagnetic fields strength that unintentionally generated from electronic devices. Usually, the radiated emission arise from switching voltages and electrical currents in all digital circuits.
EMC radiated test will ensure that unwanted emissions from electronic devices do not exceed the standard limits. Exceeding the standard limit will potentially making an interfere with other devices around. That is why during the testing the lab officer will check whether the radiated emission of the sample is below or above the standard limits.
EMC radiated emission testing process
EMC radiated test for DJID certification must be conducted at DJID’s accredited EMC laboratory. The testing requirements will refer to CISPR32 as the EMC standard for electronic devices with telecommunication technology. Following is the EMC radiated emission testing process.
EMC radiated test for electronic devices with telecommunication technology must be performed inside a chamber. Device Under Testing (DUT) will be placed on a special turntable or if the DUT size is quite big we can let keep it on the floor. The floor of the chamber where the table is located should be able to rotate 360 degrees during the EMC radiated testing process.
- Antenna receiver: placed across the DUT turntable and directed towards the DUT. The antenna receiver will record the unwanted emissions from the DUT.
- Automatic turntable: the DUT is placed on an automatic turntable to ensure all possible directions of the emitted emissions from the DUT are detected.
- Spectrum analyzer (EMI test receiver): this measuring equipment is connected to the antenna receiver to measure electromagnetic emissions from the DUT.
Cross the turntable, there is a receiver antenna that will receive radiated emissions from the DUT. The ranges of antenna height are from 1 – 4 meters, it can be adjusted against the position of the turntable where the DUT is placed. Currently, for EMC radiated test in Indonesia, the shortest distance between the antenna receiver and the DUT is 3 meters, while the furthest distance is 10 meters.
In order to increase the accuracy of measurement of EMC radiated test, the chamber floor must be coated with a material that can reflect electromagnetic emission such as aluminum or steel.
DUT classification
DUT is divided into two class categories based on their using environment.
- Class A: devices used in commercial or industrial environments, such as medical and automotive devices.
- Class B: devices used in household environments, such as home appliance devices.
Based on EMC standards, the emission limits for class B are much stricter than the emission limits for class A.
Testing measurement process
Frequency: the measurement of EMC radiated emission is performed in the frequency ranges of 30 MHz – 1 GHz and 1 – 6 GHz. Below is a comparison of EMC radiated emission limits for class A and B based on EMC standard of CISPR32.
| Frequency range | Class A Limits: Quasi-peak |
| 30 – 230 MHz | 50 dB(μV/m) |
| 230 – 1000 MHz | 57 dB(μV/m) |
| 1000 – 3000 MHz | 76 dB(μV/m) |
| 3000 – 6000 MHz | 80 dB(μV/m) |
| Frequency range | Class B Limits: Quasi-peak |
| 30 – 230 MHz | 40 dB(μV/m) |
| 230 – 1000 MHz | 47 dB(μV/m) |
| 1000 – 3000 MHz | 70 dB(μV/m) |
| 3000 – 6000 MHz | 74 dB(μV/m) |
As you can see on the table above, the emission limits for class B are much stricter than the class A. This is because the number of devices used in household environments is much bigger in number than in industrial environments.
Maximization of EMC radiated emission test
Once radiated emissions are detected, the EMC laboratory officer will perform a process called maximization in order to determine the maximum level of unwanted radiated emissions. The process involves the following steps:
- Varying the height of the receiver antenna
- Rotating the DUT during the testing process
- Changing the position of the receiver antenna vertically and horizontally
Failed during EMC radiated emission test
Sometime EMC radiated test can be fail during testing process. Simply said, the failure can be seen from the graph of radiated emission results that exceed the established standard limits.
These failures are generally related to the design and configuration of the DUT device which can cause radiated emissions to exceed the established limits. Common reasons for failure include:
- Noise on the cable
- Poor grounding
- Suboptimal PCB design
- Inappropriate additional equipment that causes greater radiation
If you have any question related to DJID certification, please don’t hesitate to contact us by sending enquiry to info@narmadi.com.
