Telecom Techniques Guide


What is Effective Isotropic Radiated Power of antenna?

Effective Isotropic Radiated Power (EIRP) is a measure of the radiated power by an antenna in a particular direction, accounting for both transmitter power and antenna gain. It’s essential for ensuring compliance with regulatory power limits in wireless communication systems and helps engineers select antennas for optimal signal strength and coverage. EIRP is expressed in decibels-milliwatts (dBm) and is a key parameter in applications like wireless networks, satellite communication, and microwave links, where controlling signal strength and avoiding interference are critical.

What is Effective Isotropic Radiated Power of antenna?

Effective Isotropic Radiated Power (EIRP) is a critical parameter in antenna engineering and wireless communication. It quantifies the power radiated by an antenna in a specific direction, considering both the antenna’s intrinsic gain and the power input to it. Here are the details of EIRP:


EIRP is a measure of the equivalent power that an isotropic antenna (an idealized point source radiating uniformly in all directions) would need to radiate to achieve the same power density in a particular direction as the actual antenna being analyzed.


  • EIRP is calculated using the following formula: EIRP (dBm) = Transmitter Power (dBm) + Antenna Gain (dBi)
  • Transmitter Power is the power input to the antenna, typically measured in decibels-milliwatts (dBm).
  • Antenna Gain represents the directional concentration of the antenna’s radiated power compared to an isotropic antenna, also measured in decibels-isotropic (dBi).

Role in Wireless Communication:

  • EIRP is crucial in wireless communication because regulatory authorities often limit the maximum transmitted power to control interference and ensure fair use of the radio spectrum.
  • Knowing the EIRP helps determine if a system complies with these power regulations.


EIRP is similar to Effective Radiated Power (ERP), but they have a subtle difference. While EIRP considers antenna gain relative to an isotropic radiator, ERP considers antenna gain relative to a dipole antenna. The choice between EIRP and ERP depends on regulatory requirements and conventions in different regions.


EIRP is typically expressed in decibels-milliwatts (dBm). It’s a logarithmic unit that provides a convenient way to express the power radiated by antennas and the power delivered to them.


EIRP is used in various wireless communication systems, including:

  • Wireless Networks: It helps ensure that wireless access points and devices comply with regulatory power limits, preventing interference.
  • Satellite Communication: EIRP is essential for satellite transmitters to ensure that signals are strong enough to reach Earth-based receivers.
  • Microwave Links: In point-to-point microwave links, EIRP calculations are critical to optimizing signal strength over long distances.

Antenna Selection:

  • Engineers use EIRP calculations when selecting antennas for specific applications. For example, in a wireless network, choosing an antenna with higher gain can increase EIRP, improving signal coverage and range.

In summary, Effective Isotropic Radiated Power (EIRP) quantifies the power radiated by an antenna in a specific direction, factoring in both transmitter power and antenna gain. It plays a crucial role in ensuring compliance with power regulations in wireless communication and helps engineers select the appropriate antennas for different applications.

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