Antenna Power Density Calculator

What is RF power density of an antenna?

The power density of an antenna is the measure of power/square cm (in space) from the center of the antenna. The space can be represented as a sphere having a radius “R” (distance from the center of the antenna). In other words, power density can also be defined as the product of the power density of an isotropic antenna and its gain. Unit of power density is usually represented in mW/cm2.  

How is RF Power density calculated?

An isotropic antenna is a theoretical antenna (i.e., practically not exist) that would radiate out RF waves equally in all directions with the same intensity. 

The power density at a distance “R” from an isotropic antenna is defined as the ratio of the transmitted power to the surface area of a sphere (4πR2) at that distance.

Power density from an isotropic antenna (at distance R) P D =   P / 4πR2 

Where, P = Transmitted power/power input in Watts

R = Distance to the center of the antenna (i.e., radius of the sphere)

The gain (G) of the practical antenna represents the maximum radiation intensity in a given direction (or absorbs incident power from that direction) when compared with a theoretical isotropic antenna. 

The power density at a distant point (R) from a practical antenna with a gain of G is the power density from an isotropic antenna multiplied by the practical antenna gain. Usually, the power density is measured in mW/cm2.

The formula for calculating Power density of a practical antenna:

Where,

S = Power density in mw/cm2

P = transmitted power from antenna/power input to the antenna in watts/mw

G = Power gain of the antenna in linear/dB (decibels)

R = Distance to the centre of the antenna in cm/Feet