Antenna Factor: Definition and Formulas

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The figure depicts a transmitting antenna and a receiving antenna in a wireless communication chain.

What is antenna factor

It’s a very useful parameter for EMC (Electromagnetic Compatibility) and EMI (Electromagnetic Interference) testing as it defines the relationship between the electric field around the antenna and the voltage produced by it.

Antenna Factor definition: The ratio of the incident electric field to the generated voltage output from the antenna is known as the antenna factor. This is expressed in the following antenna factor formula.

Antenna Factor Formula 1

Antenna factor can also be defined as the ratio of magnetic field to received voltage. It can be expressed as follows:

AFMagnetic = Hincident / Vreceived

The power density of the wave (watts per unit area) in free space can be expressed as the product of the E and H fields. Hence, we will have:

PFS = E * H = |E|2 / η

where η is the intrinsic impedance of free space.

The power captured by the antenna from free space can be expressed as follows:

Preceived = PFS * Ae

Where Ae is the antenna aperture, which can be expressed as:

Ae = (λ2 *G) / (4 *π)

At the antenna receiver, the received power can be expressed as follows:

Pr = V2 / Zload

From above, the antenna factor can be expressed in different formulas or equations as below:

Antenna Factor Formula 2

Antenna Factor Formula 3

Antenna Factor Formula 4

The following formula is used for antenna factor to gain conversion as well as for gain to antenna factor conversion.

Antenna Factor to Gain Formula

Antenna Factor Calculator and Conversion

Antenna Factor Calculator and Conversion

Calculate antenna factor and convert between antenna factor and antenna gain using our online calculators. Understand the formulas used in EMC testing.

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