An envelope shaper for a tracking power supply, the shaper pr oviding RF signal compression at high output signal amplitudes

摘要

The power supply for an envelope-tracking amplifier provides a voltage resulting in controlled amplitude compression at high instantaneous output powers, thereby improving efficiency at the expense of reduced linearity. The amount of crest factor reduction and the shape of the clipping characteristic can be set to maximise the efficiency obtainable while meeting spectral emission requirements. The detected signal envelope 86 is input to a shaping table block 108 which provides an output to the envelope-modulated power supply 110. The RF power to supply voltage characteristic (figure 5) to be used in the shaping block 108 may be selected by control signal 107 in dependence on the average signal power so that improved efficiency may be obtained at lower power levels.