Intentional Radiator compared with Equivalent Isotropically Radiated Power (EIRP)
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Intentional Radiator (IR)
- An Intential Radiatior is a device that intentionally generates and emits radio frequency energy by radiation or induction.
- Basically, it’s something that is specifically designed to generate RF, as opposed to something that generates RF as a by-product of its main function, such as a motor that incidentally generates RF noise.
- Regulatory bodies such as the FCC limit the amount of power that is allowed to be generated by an IR.
- The IR consists of all the components from the transmitter to the antenna but not including the antenna, as shown below:
The power output of the IR is thus the sum of all the components from the transmitter to the antenna, not including the antenna.
The components between the transmitter and the antenna that make up the IR include:
Using the flashlight analogy, the IR is all of the components up to the lightbulb socket, but not the bulb and lens. This is the raw power, or signal, and now the bulb and lens can focus the signal.
The components between the transmitter and the antenna that make up the IR include:
- the transmitter
- all cables
- connectors
- grounding
- lightning arrestors
- amplifiers
- attenuators
Using the flashlight analogy, the IR is all of the components up to the lightbulb socket, but not the bulb and lens. This is the raw power, or signal, and now the bulb and lens can focus the signal.
Equivalent Isotropically Radiated Power (EIRP)
- EIRP is the highest RF signal strength that is transmitted from a particular antenna.
- To understand this better, think of our flashlight example for a moment. Let’s assume that the bulb without the lens generates 1 watt of power. When you put the lens on the flashlight, it focuses that 1 watt of light.
- If you were to look at the light now, it would appear much brighter.
- If you were to measure the brightest point of the light that was being generated by the flashlight, because of the effects of the lens it may be equal to the brightness of an 8-watt bulb.
- So by focusing the light, you are able to make the equivalent isotropically radiated power of the focused bulb equal to 8 watts.
- It is important for you to know that you can find other references to EIRP as equivalent isotropic radiated power and effective isotropic radiated power.
- Regulatory bodies such as the FCC limit the amount of EIRP from an antenna.
- FCC regulates the maximum amount of power that goes into an antenna and the maximum amount of power that comes out of an antenna.
- The transmit power of most indoor WLAN radios varies in a range between 1 mW and 100 mW.
- Therefore, you usually do not need to concern yourself with power regulations when deploying indoor WLAN equipment. However, knowledge of power regulations is important for outdoor WLAN deployments.
Reference:
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.
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