RF

Power Density

What is Power Density ? As it name implies.. it is "Density of Power"? So simple ? -:)

You may vaguely understand what 'Power' is even though you may not be able to describe it clearly and you may vaguely understand what 'Density' means. All of these came from what you learned in high school physics class.

Power indicates the rate over energy transfer over a certain time.

Density indicates 'something measured (or contained) per unit volume (or per unit surface)'.

Just combining these two definition, you can get the definition of Power Density. Power Density is 'Power per unit volume'. and it would indicate 'how much energy transfer happens over a specific time within a predefined unit volume'.

Over the course and your experience, you might have seen many different form of 'Power', such as mechanical power, electrical power etc.

Since this page is about RF, the Power in this context is most likely mean 'the rate of RF energy transfer over a certain period'. If we confine this to more specific application, like Antenna, the power can mean 'Transmitter Power (energy over a certain time period) from an antenna'.

For example, let's suppose we have two antenna showing the propagation pattern as shown below. You picked the three locations for power density measurement. In left pattern (omni directional antenna), the power density is same all over the place. In right pattern, the power density gets different depending on which point you pick. As seen in this example, Power density can be a good indicator when you comparing the energry transfer rate (Transmitted power in case of Antenna) among multiple different locations.