* Chapter 2 - Electromagnetic Compatibility Flashcards
Electromagnetic Compatibility
The ability of a device, equipment, or system to operate properly in its intended electromagnetic environment without introducing significant electromagnetic interference (EMI) into the environment.
Electromagnetic Interference (EMI)
The transference of electromagnetic energy from one device or system to another device or system operating in the same environment that causes interference with the normal operation of devices or systems.
Three Essential Elements to EMC Problems
1 - The source of EMI or electromagnetic transfer between an interfering source and the susceptible device or system.
2- the susceptible device or system that cannot perform as designed, configured or programmed because of EMI.
3- A coupling path that promotes the disturbance between the interfering source and the susceptible device or system.
The potential for EMI occurs when
devices or systems share a common electromagnetic environment and their frequencies of operation overlap. If the devices or the systems operate over a different range of the electromagnetic spectrum, lower levels of MEI between them are expected.
Electromagnetic Spectrum
Light, radio waves, IR (infrared radiation), ultraviolet rays, x rays and gamma rays are collectively known as the electromagnetic spectrum. All of these are fundamentally similar in that the propagate at the speed of light.
Propagation
transmission of motion, light, sound, etc. in a particular direction or through a medium.
“the propagation of radio waves through space”
Conductive Coupling
the process of energy transfer between two independent metallic objects that is facilitated by their direct physical contact.
Inductive Coupling
electrical coupling in which the influence is that of mutual induction usually between two coils close together or wound on a common core.
Capacitive Coupling
the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit(s) nodes, induced by the electric field.
Electromagnetic Coupling
when the electromagnetic field in one circuit induces charge or voltage in others. The power transfer between the source and load circuit through the electromagnetic coupling mechanism is possible only when there is a change in the electromagnetic field of the source circuit.
What is a common mode unwanted signal?
Common mode is an interference on the signal due to noise formed by the victim circuit and the ground plane.
What is differential mode unwanted signal?
Differential mode signals are coupled into a pair of conductors because of radiation from an EMI source. It can also be a result of coupling between a given conductor and its return path. Twisting conductors can minimize differential mode interference.
How can common mode signals affect equipment?
- It can directly affect equipment operation, because the CM signal gets inside the equipment and causes logical errors.
- CM signal can be converted to a DM signal by the cable or equipment.
What frequency spectrum is conducted interference normally measured?
100kHz to 30Mhz
What frequency spectrum is usually taken to measure radiated interference?
30 MHz to 5 GHz
