Symmetrical Doherty power amplifier design via continuous harmonic-tuned Class-J mode

Abstract

This paper proposes bandwidth and efficiency improvements of symmetrical Doherty power amplifiers (SDPAs) using continuous harmonic-tuned Class-J mode (CHTCJM). By this approach, the effects of the CHTCJM on the impedance inverter network and post-matching network in SDPAs are reanalysed using formulated mathematical equations. In this way, to recover and further improve the bandwidth and efficiency performances in the conventional SDPA. The term recovery as proposed in this context is to redefine, reanalyse, retrieve and further enhance the output-power-back-off efficiency and bandwidth performances lost in the conventional SDPAs using an alternative theoretical methodology based on the CHTCJM. Based on the findings, the proposed technique can substantially recover and enhance the bandwidth and efficiency of SDPAs at the desired output-power-back-off level. According to the measurement results, the fabricated SDPA model operates within 1.45–2.45 GHz frequency band with more than 50% peak drain efficiency at 6 dB output-power-back-off. Furthermore, more than 60% drain efficiency, 12 dB gain and 43 dBm output power are delivered at saturation. Using digital predistortion with a 20-MHz long-term evolution signal in testing the linearity of the implemented SDPA, the SDPA’s adjacent channel leakage ratio is less than −45 dBc at an average output power of 36 dBm.