Methods for testing and measuring EMI in electronic devices include radiated emissions testing, conducted emissions testing, and immunity testing.
Methods for Testing and Measuring Electromagnetic Interference in Electronic Devices
Electromagnetic interference (EMI) is a phenomenon that occurs when the electromagnetic emissions from one electronic device disrupt the functioning of another device in its vicinity. To ensure the proper functioning of electronic devices and adherence to regulatory standards, it is crucial to test and measure EMI. This article discusses the main methods used for this purpose.
1. Radiated Emissions Testing
- Open Area Test Site (OATS): OATS is a widely used method for measuring radiated emissions from electronic devices. The device under test (DUT) is placed on a non-reflective surface in an open area, and an antenna is used to measure the radiated emissions at different frequencies and distances.
- Anechoic Chamber: An anechoic chamber is an enclosed space designed to minimize reflections of electromagnetic waves. The walls are lined with absorbent material to create an environment that simulates free-space conditions. This method offers more controlled conditions compared to OATS, enabling more accurate and repeatable measurements.
2. Conducted Emissions Testing
Conducted emissions testing focuses on measuring the interference that travels along power lines, data cables, or other conductive paths. The two primary methods for this type of testing are:
- Line Impedance Stabilization Network (LISN): LISNs are used to measure conducted emissions on power lines. They provide a consistent impedance for the DUT, isolating it from the power source and ensuring accurate measurements.
- Transverse Electromagnetic (TEM) Cell: A TEM cell is a coaxial transmission line that simulates a uniform electromagnetic field. The DUT is placed within the cell, and its conducted emissions are measured by monitoring the voltage induced on a terminated load connected to the other end of the cell.
3. Immunity Testing
Immunity testing assesses the ability of a device to withstand EMI without malfunctioning. Common immunity tests include:
- Radiated Immunity: The DUT is exposed to a controlled electromagnetic field to determine its susceptibility to radiated interference. This test simulates real-world conditions where a device might be exposed to EMI from nearby sources.
- Conducted Immunity: This test evaluates the DUT’s ability to tolerate conducted interference on its power lines or data cables. It typically involves injecting a controlled level of EMI into the conductive paths and observing the device’s behavior.
- Electrostatic Discharge (ESD): ESD testing examines the DUT’s ability to withstand sudden discharges of static electricity. This is crucial for devices that may be subjected to electrostatic discharge during normal use, such as smartphones and other handheld electronics.
In conclusion, various methods are employed to test and measure electromagnetic interference in electronic devices, ranging from radiated and conducted emissions testing to immunity testing. These tests ensure that devices operate reliably in the presence of EMI and meet the required regulatory standards.
