Envelope Tracking

Hello!

Envelope Tracking is a technique used to enhance the efficiency of a power amplifier used in wireless systems. In this technique, the amplitude envelope of the RF signal is tracked and the bias voltage is adjusted accordingly to ensure that the PA operates with maximum efficiency at any instantaneous power level.

An RF Power Amplifier operates most efficiently when it is operated at peak output power, where the gain enters compression. Envelope Tracking takes advantage of this principle, it ensures that the amplifier operates at a point close to compression as often as possible by regulating the supply/bias voltage. So, if the amplifier is required to operate at a lower power level, the supply voltage is adjusted to lower the compression point of the amplifier which makes it more efficient for low power levels. The alternative to this would be to let the amplifier operate at a constant power level with a static supply voltage in all cases, however in this scenario the efficiency of the amplifier for low power levels will be very low. And thus if used in a battery operated device, would drain the battery very quickly.

Thanks!