RFID Reader Transmitter Power

[Catalyst]

Howdy,

I've been looking at the following RFID reader. On the datasheet (see link below) tt states the power to the transmitter/antenna can be adjusted from 0.5 Watts to 10 Watts.

**broken link removed**

In the case for inductive coupling RFID applications, why would you want to increase the power?

Wouldn't that mean that there was less current flowing through the antenna? meaning less energy available for the tag?

I'm not totally sure what is involved when changing the power...... is it the resistance or voltage that is modified?


I think I am missing something very fundamental here.

Can anyone shed light on this?


Kind Regards

Cat

 

[rautio]

The resistance of the reader coil does not change (unless you see smoke and flames coming out of it!). When you increase the power, both the voltage and the current increase. For example, if the voltage doubles, then the current also doubles (by Ohm's Law). Then you have four times the power. Power = V*I = (V**2)/R = (I**2) * R.