A Doherty power amplifier with extended resonance power divider for linearity improvement

A Doherty power amplifier using an extended resonance power divider is designed for linearity improvement. Taking advantage of the class C amplifier input admittance variations as a function of input power level, the extended resonance power divider is designed to provide proper power-dependent power division ratio for improving the linearity of the Doherty amplifier. This kind of power divider acts like a pre-distorter. To verify the proposed method, an extended resonance Doherty and a conventional Doherty power amplifier are designed and fabricated for comparison. The proposed technique shows considerable improvement in linearity without compromising the efficiency. An improvement of 5-16 dB in IM3R over a wide range of output power is achieved. Furthermore, it is shown that this method can be used to improve the phase nonlinearity of the amplifiers.