EIRP vs. ERP: Key Differences Explained

rf engineering
wireless technology
antenna gain
radio frequency
power

Let’s break down the difference between EIRP (Effective Isotropic Radiated Power) and ERP (Effective Radiated Power), two important concepts when dealing with radio frequency transmissions. Both relate to the power a transmitter radiates, but they use different reference points for antenna gain.

Here’s a summary of the major and minor differences:

  • EIRP stands for Effective Isotropic Radiated Power.
  • ERP stands for Effective Radiated Power.

The crucial difference lies in how antenna gain is measured:

  • In EIRP calculations, antenna gain is expressed in dBi (decibels relative to an isotropic radiator).
  • In ERP calculations, antenna gain is expressed in dBd (decibels relative to a half-wave dipole antenna).

This leads to a simple conversion:

  • EIRP (in dBm) can be found by adding 2.15 to the ERP value (in dBm). This is because a half-wave dipole has a gain of approximately 2.15 dBi.

EIRP and ERP are not just theoretical concepts. Regulatory bodies use them to set limits for radio frequency transmitting devices across a variety of wireless technologies:

  • These limits apply to indoor and outdoor wireless technologies such as GSM, LTE, 4G, 5G, LoRaWAN, and more.

To illustrate, here are the formulas for calculating EIRP and ERP:

EIRP formula

ERP formula

Finally, a visual comparison:

EIRP vs ERP

In essence, both EIRP and ERP represent the effective power radiated by a transmitter, but they use different reference antennas (isotropic and half-wave dipole, respectively) for their calculations. Understanding this difference is key for complying with regulatory limits and optimizing wireless system performance.

RF Interview Questions and Answers: Academic FAQ

A collection of frequently asked questions (FAQs) related to Radio Frequency (RF) engineering, useful for interview preparation and viva sessions.

rf engineering
interview question
radio frequency
Top 10 RF Interview Questions and Answers

Top 10 RF Interview Questions and Answers

Prepare for your RF job interview with these 10 frequently asked questions and detailed answers covering return loss, VSWR, compression points, isolators, and more.

rf engineering
interview question
radio frequency