A highly efficient Doherty power amplifier based on class AB and class C at 2.6 ghz

This thesis presents a highly efficinet Doherty type high power amplifier appropriate for various WiMAX applications. The power amplifier consists of a Class AB type main amplifier which operates linearly and efficiently at low power levels and a Class C auxillary amplifier which starts to operate at high input power levels. The gain compression behaviour shown by Class AB type power amplifier is suppressed by the gain expansion behaviour of Class C type power amplifier at high power levels by adjusting the third order products of each amplifier outphased. Therefore, more linear power amplifier can be obtained even at high power levels.First an unequal wilkinson power divider designed to divide power at 1:2 ratio for both amplification parts. That lets the whole amplifier transmit maximum output power at maximum input power. Then for the choosen LDMOS amplifier, optimum input and output matched amplification stage prototype designed carefully using loadpull simulations. Finally Doherty amplifier operating at 2.6GHz designed and simulated. Operated at 25V power supply, is 46.6dBm and gain at this input power is nearly 9dB. The Power Added Efficiency (PAE) corresponding to is 51.1% and at 6dB backoff is 40%.