A novel time misalignment estimation algorithm for envelope tracking (ET) power amplifiers (PA)

In this paper, we present a novel algorithm for estimating the delay (dT) between the RF input of an RF power amplifier (PA) and the modulated supply voltage that is generated by an envelope tracking (ET) power modulator, also known as a power tracker. This algorithm estimates the delay by introducing artificial delays in the acquired baseband output of the RF amplifier and searching for the delay that result in the lowest error vector magnitude (EVM). The proposed algorithm makes only a single acquisition of the RF PA output. A sufficient amount of band limited AWGN is added to the baseband at the input of the RF PA and power supply waveforms. The noise serves to decorrelate the output of the RF PA, improving delay estimation accuracy. The algorithm has the ability to estimate delays in the range of 60nsec and upwards within an error of +/-4nsecs for wideband signals like WCDMA and LTE. Test results using a vector signal generator and analyzer are presented.