Effective Isotropic Radiated Power (EIRP)

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EIRP is Effective Isotropic Radiated Power, also called the Equivalent Isotropic Radiated Power. In antenna measurements, the measured radiated power in a single direction (that is, for a fixed and ) is known as the EIRP.

Typically, for an antenna radiation pattern measurement, if a single value of EIRP is given, this will be the maximum value of the EIRP over all measured angles.

EIRP can also be thought of as the amount of power a perfectly isotropic antenna would need to radiate to achieve the measured value.

As an example, suppose the radiated power is measured for an arbitrary antenna. Suppose the peak power is measured at ==90 degrees, and the value is EIRP = 20 dBm = -10 dB = [0.1 W = 100 mW]. Then a perfectly isotropic antenna radiating 20 dBm would produce the same measured power for the peak angles of our antenna.

The EIRP can be related to the power transmitted from the radio (P_t), the cable losses (possibly including antenna mismatch) L, and the antenna gain (G) by:

[Equation 1]

Often the cable losses L can be neglected, as they are generally a small fraction of a dB.

Total (full 3D) Measurements from a Single-Point (single-direction) Measurement

If the peak EIRP and the directivity (D) are known for an antenna, then the Total Radiated Power (TRP) can be found from the equation:

[Equation 2]

In this manner, if the directivity and peak angle for an antenna are known in advance, the measurement time can be greatly reduced by using equation [2].

See also Effective Isotropic Sensitivity (EIS).

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