A Compact, Highly Linear Ku-Band SiGe HBT Power Amplifier Using Shared Single Center-Tap Four-Way Output Transformer Balun for Emerging Low Earth Orbit SATCOM Phased-Array Transmitter

This paper presents a compact, highly linear Ku-band SiGe HBT PA for Low Earth orbit (LEO) satellite communication (SATCOM). A four-way output transformer (TF) balun with a shared single center-tap (SSCT) is proposed not only for simplifying signal routing for compact chip size, but also obtaining high power combining efficiency. A prototype Ku-band SiGe PA, which merely occupies a core area of 0.21 mm
²
, attains measured peak output power (POUT) and power added efficiency (PAE) of 24.4 dBm and 32.1% at 11.7 GHz, respectively, with the highest power density of 1311.5 mW/mm
²
. The PA also delivers average POUT (Pavg) of 18.6/16.6 dBm with average PAE (PAEavg) of 16.0/12.6% at 250 MHz symbol rate DVB-S2X 64/256 APSK modulation.