Types of interference

Electromagnetic interference divides into several categories according to the source and signal characteristics.

The origin of noise can be man made or natural.

Continuous interference

Continuous, or Continuous Wave (CW), interference arises where the source regularly emits a given range of frequencies. This type is naturally divided into sub-categories according to frequency range, and as a whole is sometimes referred to as "DC to daylight".

• Audio Frequency, from very low frequencies up to around 20 kHz. Frequencies up to 100 kHz may sometimes be classified as Audio. Sources include:
  • Mains hum from power supply units, nearby power supply wiring, transmission lines and substations.
  • Audio processing equipment, such as audio power amplifiers and loudspeakers.
  • Demodulation of a high-frequency carrier wave such as an FM radio transmission.
• Radio Frequency Interference, RFI, from 20 kHz to a limit which constantly increases as technology pushes it higher. Sources include:
  • Wireless and Radio Frequency Transmissions
  • Television and Radio Receivers
  • Industrial, scientific and medical equipment
  • High Frequency Circuit Signals (For example microcontroller activity)
• Broadband noise may be spread across parts of either or both frequency ranges, with no particular frequency accentuated. Sources include:
  • Solar Activity
  • Continuously operating spark gaps such as arc welders
  • CDMA mobile telephony

Pulse or transient interference

Electromagnetic Pulse, EMP, also sometimes called Transient disturbance, arises where the source emits a short-duration pulse of energy. The energy is usually broadband by nature, although it often excites a relatively narrow-band damped sine wave response in the victim.

Sources divide broadly into isolated and repetitive events.

• Sources of isolated EMP events include:
  • Switching action of electrical circuitry, including inductive loads such as relays, solenoids, or electric motors.
  • Electrostatic Discharge (ESD), as a result of two charged objects coming into close proximity or even contact.
  • Lightning Electromagnetic Pulse (LEMP)
  • Nuclear Electromagnetic Pulse (NEMP), as a result of a nuclear explosion.
  • Non-Nuclear Electromagnetic Pulse (NNEMP) weapons.
  • Power Line Surges/Pulses

• Sources of repetitive EMP events, sometimes as regular pulse trains, include:
• Electric Motors
• Gasoline engine ignition systems
• Continual switching actions of digital electronic circuitry.

Raul Contreras CI : 19596032

EES

secc: 02

fuente:

http://en.wikipedia.org/wiki/Electromagnetic_compatibility#Types_of_interference