Delay Mismatches Analysis for Multi-level Outphasing Digital Transmitters

In this paper, we make the sensitivity analysis on the RF-PWM signal performance metrics with respect to the delay mismatches. First, the delay mismatches in the five-level outphasing digital transmitter architecture are modeled and sorted into three categories. Then, a closed-form expression of the total delay mismatches among random outphasing outputs is proposed, in terms of the outphasing RF-PWM principle and digital delay line characteristic. Finally, numerical simulations in MATLAB were used to analyze the EVM, ACPR and harmonics elimination performances affected by delay mismatches in three different scenarios. We find the EVM and the third-harmonic are very sensitive to delay mismatches, while ACPRs even perform better. Besides, we make a brief discussion on the observed asymmetry and periodicity of the simulation results in all scenes.