A highly efficient chireix amplifier using adaptive power combining

A novel, highly efficient out-phasing amplifier with adaptive power combiner is presented. Saturated class-F operation is used for the amplifier cells. Varactor tuning is applied to make the output power combining network adaptive. Use of optimum input drive conditions and output varactor tuning, to eliminate imaginary loading introduced by the out-phasing principle, yields an amplifier efficiency of more than 50% over a 9 dB power back-off range.