A SiGe Common-Collector-Common-Base Linear Power Amplifier with 17–28-GHz P1dB 3-dB Bandwidth and Enhanced Large-Signal Stability

This paper presents a 17–30GHz SiGe common-collector-common-base (CC-CB) two-stage linear PA with enhanced large-signal stability. Through driving-point admittance analysis, the conventional SiGe cascode PA topology, equipped with a common-emitter device, is shown to be prone to large-signal instability, rendering it unsuitable for broadband PA designs. To address this, the adoption of a CC stage is explained in detail. In addition, a stacked distributed balun is proposed for broadband output matching, accounting for the constraints of limited substrate resistivity. The proposed PA achieves a Psat of 19.3 to 23.3dBm, with a PAEsat of 10.4 to 28.6%. It supports 400-MBd 32-APSK/64-QAM signals. For 64-QAM signals, the PA achieves 14.7–18.9dBm/6.0–15.7% Pavg/PAE at an EVMrms level of -25dB, from 18 to 28GHz.