The effects of timing skew in envelope tracking and EER type transmitters

摘要

Two supply modulated transmitter techniques, envelope tracking (ET) and envelope elimination and restoration (EER) are studied when timing skew between the RF carrier and supply signal is introduced. Measurements with digital modulations show that the spectrum asymmetry is mostly affected by the VDD/PM distortion of the amplifier and it can be reduced by careful timing. Higher timing accuracy is needed to optimize EER, but in return the VDD/PM distortion is smaller in average and linearity can be achieved with less effort. ACPR of 50 dB is reached with VDD/AM, VDD/PM, timing and IQ-modulator error corrections.