A D-band Guanella Transformer Based Stacked Doherty Power Amplifier with Adaptive Bias Network in 250-nm InP DHBT

This paper presents a compact D-band Doherty power amplifier (PA) in 250-nm InP DHBT. The power amplifier core consists of a stacked common-emitter and common-base pair and utilizes an integrated 1:4 Guanella transformer for interstage matching. A power detector as well as an adaptive bias network are also implemented to boost the linearity and efficiency of the amplifier. The PA achieves a small-signal gain of 17.8 dB and a small-signal bandwidth of 14.7 GHz. In continuous-wave measurements, the power amplifier has a saturated output power of 20.3 dBm. The amplifier achieves a maximum power-added efficiency (PAE) of 21.4% and 11.5% with 6-dB power backoff. The performance of the amplifier is verified with modulated measurements up to 24 Gb/s.