Design and Implementation of a D-Band Guanella Transformer-Based Stacked Doherty Power Amplifier in 250-nm InP DHBT

Abstract

This 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.