Doherty Power Amplifiers Using 2nd Generation HVHBT Technology for High Efficiency Basestation Applications

Abstract

Second generation HVHBT GaAs technology developed for use in wireless basestation applications is shown to be suitable for use in symmetric and asymmetric Doherty efficiency enhancement solutions. Each solution demonstrates the unique high efficiency characteristic of HVHBT GaAs technology where average power efficiencies approaching 60% have been achieved in both configurations. This paper will review recent results achieved using second generation HVHBT technology in two Doherty configurations operating at 28V. First, a symmetric Doherty amplifier exhibiting 350W (55.5dBm) of saturated power with greater than 57% efficiency at 74W (48.7dBm) average output power while achieving -55dBc linearized IM3 products using a two-carrier 101 WCDMA 6.5dB PAR signal. When cascaded with an LDMOS driver, lineup efficiency of 48% was achieved with 46dB gain at 74W (48.7dBm) average output power while maintaining linearity of -55dBc. Second, a symmetric Doherty amplifier exhibiting 550W (57.5dBm) of saturated power achieving greater than 55% efficiency at 128W (51.1dBm) average output power while achieving -55dBc linearized IM3 products using a two-carrier 101 WCDMA 6.5dB PAR signal. Finally, an asymmetric Doherty amplifier exhibiting 425W (56.3dBm) of saturated power with greater than 54% efficiency at 65W (48.2dBm) average output power while achieving -56dBc linearized IM3 products using a two-carrier 101 WCDMA 8.0dB PAR signal.