Distortion free LINC amplifier with chireix- outphasing combiner using phase-only predistortion

A LlNC amplifier with perfectly balanced branches and a Chireir-outphasing combiner is studied and the sources of its nonlinearity are identified. A phase-only predistortion function is derived in explicit form and used to linearize this amplifier. The predistortion function preserves constant envelope operation of the amplifiers. The impact of the predistortion function on the combiner efficiency is also investigated. It is found, through simulation with a CDMA signal that the predistortion function linearizes perfectly the amplifier. It is also shown, that with perfect linearity, the efficiency of Chireix-outphasing amplifier reduces to that of the LINC amplifier with a resistive combiner.