According to the regulatory bodies issuing the guidelines and directives for electromagnetic compatibility, electromagnetic interference should be lower than the specified values for a device.
Emissions testing measures the amount of electromagnetic emissions from the product under test during its normal operation.
Immunity testing measures the reaction of the product under test when subjected to electromagnetic interferences and disturbances.
Electromagnetic interference testing is critical during the development process for electronic devices and consumer goods
In the product development process for electronic devices and consumer goods, electromagnetic interference (EMI) from wireless communication devices is a big concern. EMI or electromagnetic compatibility (EMC) problems (due to internally generated interference or from nearby communication devices) influence product quality. Product quality assurance standards aim to ensure products are capable of working in the presence of spurious electromagnetic signals, which are generated both internally and externally. The EMI generated should be within the acceptable limits set by regulatory authorities. Compliance with regulatory EMI/EMC requirements is mandatory for any electronic product in development. Products are subjected to electromagnetic interference testing to confirm compliance with these regulatory requirements and to check their immunity to EMI.
Electromagnetic Interference Testing
All operating electronic products use the frequency bands from the electromagnetic spectrum. When a designer is designing a new product, they must account for the fact that it will also operate in the same public spectrum. Electromagnetic interference is an inherent electromagnetic phenomenon in which the device operating in the spectrum generates and transmits spurious signals. These spurious signals are collectively called electromagnetic interferences, and this interference can be either radiated or conducted. Both types of interference radiating from a product are electromagnetic pollutants, and they disturb the operation of the appliances and devices in their vicinity.
According to regulatory bodies issuing guidelines and directives for electromagnetic compatibility, electromagnetic interference should be lower than a device’s specified limits. With each class of equipment, the limit varies. Achieving an EMI testing certificate proves the product is electromagnetically compatible and ready to operate in the presence of other electronics devices.
EMI testing, which is sometimes called EMC testing, is a critical part of product development. It is the best method to identify EMI issues in a product during the development stage. EMI or EMC testing can be classified into two categories:
Emissions testing measures the amount of electromagnetic emissions from the product under test during normal operation. If emissions are below the specified values issued by the regulatory committees for that class of products, then the product passes the emissions test. Emissions testing provides assurance that the device under test will not produce harmful interferences for other devices operating in the same environment.
Immunity testing measures the reaction of a product under test when subjected to electromagnetic interferences and disturbances. If the device operates normally under all test conditions, the device passes the immunity test. This test assures the electromagnetic immunity of a product when operating within its expected environment.
Electromagnetic Interference Testing Routines
The EMI testing routine is determined by the class of the product, its intended application environment, and the regulatory requirements. Regulatory requirements differ with the product market. In the United States, requirements for consumer electronics are set by the FCC. Outside the United States, the acceptable standards for EMI testing are issued by bodies such as the ISO and IEC.
There is a wide range of electromagnetic phenomena affecting products. Almost all EMI problems can be simulated with the help of EMI testing. The list below gives some of the EMI testing conditions commonly simulated to assure EMC:
Radiated magnetic fields - Radiated magnetic fields interfere with the intentional electromagnetic fields associated with equipment and disrupt their operation. EMI testing helps in identifying the susceptibility to radiated magnetic fields.
Voltage dips, power interruptions, surges, lightning surges - In voltage-sensitive equipment, it is ideal to conduct EMI testing to check how voltage quality problems like voltage dips, surges, and interruptions affect system operation.
Radiated and conducted electromagnetic noises - Radiated and conducted electromagnetic noises are detrimental to the normal operation of devices. EMI testing helps in devising mitigation methods to limit their effects.
Electrostatic discharges and electrical fast transients - Electrostatic discharge and fast transients are capable of destroying components and devices. EMI testing helps determine the limit of ESD and the duration up to which the device can withstand it.
Harmonics and flickers - In consumer electronics, harmonics and flickers are a common threat. EMI testing is useful for planning countermeasures for these issues.
Electromagnetic interference testing is an indirect examination conducted by affiliated regulatory bodies. If a product under test passes electromagnetic interference testing, then it is considered electromagnetically immune and ready to go out in the market. Cadence offers a suite of design and analysis tools to assist with handling system design issues caused by electromagnetic interference.