This article presents a compact, efficient, and linear Q-/V-band silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) cascode power amplifier (PA) for emerging very low-Earth-orbit (VLEO) satellite communication (SATCOM). A novel four-way Wilkinson combiner balun (WCB), realized by two coupled line impedance inverting baluns (ZIBs) and isolation (ISO) resistors (RISOS), is proposed. The design procedure of the proposed four-way WCB, specifically focused on reducing electrical length (θ < 45°) and extending bandwidth (BW) of coupled line ZIBs, is revealed in detail and their associated design parameters are subsequently obtained using the so-called graphical extraction method. With this intuitive approach, the four-way WCB is synthesized fast to improve BW, passive efficiency, and signal balance simultaneously, within a compact chip size. Also, the impact of an on-chip ground (GND) parasitic inductance on the PA is studied, where a co-design of layout and schematic is explored to decide an optimal differential SiGe HBT cascode output stage. Fabricated in 0.13-µm SiGe HBT BiCMOS, the PA obtains measured peak output power (Pout), power added efficiency (PAE), and gain of 24.1 dBm, 35.3%, and 23.0 dB at 43.0 GHz, respectively, with a power density of 1295.6 mW/mm2. The 1-dB Pout BW ranges from 39 to 51 GHz, covering both up- and down-links of VLEO SATCOM. It delivers the linear Pout(Pavg) of 17.9/15.5 dBm with an average PAE (PAEavg) of 19.0%/14.5% at 250-/ 400-MHz symbol rate Direct Video Broadcasting-Second Generation Satellite Extension (DVB-S2X 64) amplitude phase shift keying (APSK) signals. To the best of the author’s knowledge, this SiGe PA attains the highest gain/peak PAE/ Pavg/PAEavg/power density at the Q-/V-band, enabling for low-cost, highly integrated VLEO SATCOM TX beamformer ICs (BFICs).
This work was supported in part by the Ministry of Trade, Industry and Energy (MOTIE), South Korea, through the Technology Innovation Program, Development of Q/V-Band RF Components and Reconfigurable Active Antenna Components, under Grant RS-2024-00452149; in part by the New Faculty Research Fund of Ajou University; and in part by Korea Basic Science Institute (National Research Facilities and Equipment Center) Grant funded by Korean Government [Ministry of Science and ICT (MSIT)] under Grant RS-2024-00399663. The authors are grateful to the SiGe Team, GlobalFoundries, for chip fabrication. They also thank the Integrated Circuit Design Education Center (IDEC), Daejeon, Republic of Korea, for providing Electronic Design Automation (EDA) tools.
