RF Power Density

Calculate the RF power density at a given distance from an antenna.

RF Power Density refers to the amount of electromagnetic radiation power per unit area, commonly expressed in watts per square meter (W/m²). It serves to quantify the strength of radiofrequency (RF) signals.

Key Concepts

Concept	Description
Units	RF Power Density is quantified in W/m², denoting electromagnetic radiation power per unit area
Distance	Signal intensity diminishes with distance, adhering to the inverse square law (1/r²) — intensity reduces fourfold when distance is doubled
Obstacles	The presence of barriers can additionally weaken the RF signal, further diminishing its power intensity
FCC Guidelines	The FCC outlines regulations for maximum permissible power density thresholds across different frequency ranges — e.g. FCC Rule §1.1307(b)(3) dictates that in public areas, UHF channel power density must not surpass 5% of the prescribed exposure limit
Applications	RF Power Density is applied across wireless communication, radar technology, and medical equipment — playing a pivotal role in guaranteeing safety and efficiency

Conclusion

RF Power Density represents the power per unit area of electromagnetic radiation. Its significance lies in:

Assessing the safety of exposure to electromagnetic radiation
Evaluating antenna performance
Determining the coverage range of wireless communication setups

About This Calculator

This online calculator computes the RF power density using the input power, antenna gain, and distance to the center of the antenna.

Formula

$S = \frac{P \times G}{4 \times \pi \times R^2}$

where:

$S$ = Power Density (W/m²)
$P$ = Power Input (W)
$G$ = Power Gain
$R$ = Distance to the Center of Antenna (m)
$\pi$ = 3.14159...

Inputs

Input Power(mW)

Transmit power fed to the antenna in milliwatts

Power Gain(dB)

Antenna power gain in decibels — converted to linear via G = 10^(dB/10)

Distance to Centre of Antenna(cm)

Distance from the antenna centre to the point of measurement in centimetres

Results

⚠Distance must be greater than zero

Power Density—mW/cm²RF power density at the given distance in milliwatts per square centimetre