A High Efficiency Outphasing Transmitter Structure for Wireless Communications

An outphasing radio transmitter can provide high linearity. The overall system efficiency for an outphasing transmitter is constrained by the combiner at the output stage. The combiner efficiency can be as low as 20% for an OFDM signal due to its high peak-to-average power ratio (PAPR). We propose a digital signal processing approach to improve the average system efficiency of an outphasing transmitter from 20% to about 80%. The efficiency improvement is achieved by combining PAPR reduction technique with the outphasing transmitter structure. The efficiency achieved by this approach can be optimized according to the probability density functions of the input signals. This new approach is insensitive to the mismatch of the two branches in the outphasing structure.