The purpose of this master thesis was to study if the drain efficiency of power amplifiers can be maintained at power back off using a technique called load modulation.

The amplifier classes studied are E, F and D-1. The target figure was to obtain a 10 to 12 dB dynamic range of amplitude with reasonable efficiency. Studies of power amplifiers have been made to understand how power is generated. Several different load modulation networks have been evaluated. Attempts to derive design equations for the modulation networks have also been done.

The thesis work was carried out with simulations in ADS 2006. As active devices commercially available bare-die transistor models have been used. The power rating of the dies are 15 W.

A dynamic range of amplitude of over 15 dB has been achieved with drain efficiency greater than 60 percent. The peak output power is in the 40 – 45 dBm range.