Gielen, SenneSenneGielenGungor, BerkeBerkeGungorZhang, YangYangZhangIngels, MarkMarkIngelsReynaert, PatrickPatrickReynaert2026-09-092026-09-0920260018-9480https://imec-publications.be/handle/20.500.12860/60288This article presents a Guanella transformer-based stacked Doherty power amplifier (PA) operating in D-band frequencies (110–170 GHz) in a 250-nm InP DHBT process. The Doherty PA is implemented using amplifier stages consisting of stacked common-emitter and common-base pairs with DC-coupled 1:4 Guanella transformer-based interstage matching networks. An in-depth analysis is conducted on 1:4 on-chip Guanella transformers, providing insight into the presented design. A wide instantaneous bandwidth adaptive bias network (ABN) together with a power detector is implemented to improve the linearity and back-off efficiency of the designed PA. 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 PA has a saturated output power of 20.3 dBm. The amplifier achieves a maximum power-added efficiency (PAE) of 21.4% and 11.5% at 6-dB power back-off. The performance of the amplifier is verified with modulated measurements up to 24 Gb/s.engJournal article10.1109/tmtt.2026.3673014WOS:0017275288000011557-9670