Time alignment in a dynamic load modulation transmitter architecture

A time alignment algorithm is proposed for a dynamic load modulation transmitter architecture. The effect of time mismatch between the RF input and baseband control signal is investigated by experiments, and it is shown that unsynchronized signals can result in severe distortion of the output signal. In this paper, cross correlation and sinc interpolation techniques are applied to estimate and compensate for the sub-sample delay between the RF signal path and the baseband control signal path in the measurement system. The performance of the dynamic load modulation transmitter architecture with accurate time alignment is shown by experimental results. The measurement shows that, the efficiency is greatly affected by time alignment and the spectral regrowth is suppressed by more than 10 dB.