Effective Radiated Power (EIRP) is a crucial metric in radio frequency (RF) engineering and telecommunications. It represents the equivalent power that a reference isotropic antenna would need to radiate to produce the same power density as the actual antenna system at a specified distance in a given direction. In simpler terms, it's a measure of how powerful a radio transmitter appears to be, taking into account the transmitter's output power and the antenna's gain.
EIRP is particularly important for:
Regulatory Compliance: Many countries have regulations limiting the EIRP to prevent interference with other services and ensure efficient use of the radio spectrum.
Link Budget Analysis: In wireless system design, EIRP is a key component of the link budget, which determines if a signal can be reliably received at a desired location.
Antenna Performance: It helps compare the performance of different antenna systems under various conditions.
The EIRP Formula
The EIRP is typically calculated in decibels relative to a milliwatt (dBm). The fundamental formula for EIRP, considering transmit power, antenna gain, and path loss (though path loss is more for received power calculations, it's often considered in context of system performance), is:
EIRP (dBm) = Transmit Power (dBm) + Antenna Gain (dBi) - Path Loss (dB)
However, the most direct calculation of EIRP itself (without considering received signal strength or path loss) is:
EIRP (dBm) = Transmit Power (dBm) + Antenna Gain (dBi)
In this calculator, we are focusing on the core EIRP calculation. The 'Path Loss' input is included for common scenarios where users might be analyzing a system end-to-end, but the primary EIRP value is derived from transmit power and antenna gain. For the direct EIRP calculation, path loss is not subtracted.
Input Definitions:
Transmit Power (dBm): The power output from the radio transmitter, measured in decibels relative to one milliwatt. For example, 100 mW is approximately 20 dBm.
Antenna Gain (dBi): The increase in signal strength provided by the antenna in a specific direction, relative to an isotropic radiator (an ideal antenna radiating equally in all directions). Higher gain means the antenna focuses the power more effectively.
Path Loss (dB): The reduction in signal strength as it travels from the transmitter to the receiver due to factors like distance, atmospheric absorption, and obstructions. This is often considered when calculating the received signal strength, but for EIRP itself, it's not directly subtracted.
How the Calculator Works:
The calculator takes your Transmit Power (in dBm) and Antenna Gain (in dBi) and sums them to provide the Effective Radiated Power (EIRP) in dBm. The formula used is:
EIRP (dBm) = Transmit Power (dBm) + Antenna Gain (dBi)
This value represents the power that would be radiated by a theoretical isotropic antenna to achieve the same signal strength as your actual system.
function calculateEIRP() {
var transmitPowerInput = document.getElementById("transmitPower");
var antennaGainInput = document.getElementById("antennaGain");
var pathLossInput = document.getElementById("pathLoss"); // Included for context, not used in core EIRP calc
var transmitPower = parseFloat(transmitPowerInput.value);
var antennaGain = parseFloat(antennaGainInput.value);
// var pathLoss = parseFloat(pathLossInput.value); // Not used in primary EIRP calculation
var resultValueElement = document.getElementById("result-value");
// Input validation
if (isNaN(transmitPower) || isNaN(antennaGain)) {
resultValueElement.innerHTML = "Invalid Input";
return;
}
// EIRP Calculation: Transmit Power (dBm) + Antenna Gain (dBi)
var eirp = transmitPower + antennaGain;
// Display the result
resultValueElement.innerHTML = eirp.toFixed(2); // Display with 2 decimal places
}