System Design Issues in a HQPM-Based Transmitter

This paper presents the analysis of signal quality and the efficiency performance in an RF transmitter using hybrid quadrature polar modulation (HQPM) scheme. The measurement results of the Class-ii power amplifier and Class-5 modulator are applied in this analysis. The path-delay difference between the envelope and the phase signal is also considered. Output spectra with and without predistortion are both shown to demonstrate improvement from the predistortion function. The simulated and experimental results have validated the key feature of the HQPM architecture, that its adjacent channel power ratio and DC-to-RF efficiency are not sensitive to the output power level.