Analysis and Compensation of Temporal Mismatch between Input Signals of Envelope-Tracking Amplifiers

PAs with constant power supply exhibit only high efficiency at high output power level. In other words, conventional PAs only work effectively in saturation region. However, PAs are seldom operated in saturation region, because the proportion of the high power signal is very low in the signal of Gauss distribution function and hence PAs are usually operated with a huge back-off for the input signal of dynamic amplitude. The fundamental idea of Envelope-Tracking (ET) technique is to dynamically adapt the PA power supply voltage to the envelope of the input RF signal by a highly efficient supply voltage modulator [1], [2]. Thus, PAs in ET system are always operated close to their saturation region, i.e. in high efficiency region. In practice, a digital predistortion (DPD) technique alone cannot sufficiently compensate the nonlinearities generated in an ET