A 2–24 GHz SiGe HBT Cascode Non-uniform Distributed Power Amplifier Using A Compact, Wideband Two-Section Lumped Element Output Impedance Transformer

This paper presents a 2–24 GHz SiGe HBT cascode, non-uniform distributed power amplifier (NDPA). Optimum impedances at each SiGe HBT cascode are obtained by simultaneous characteristic impedance scaling of the collector transmission lines (TLs) and SiGe HBT emitter area tapering. To further boost output power (Pout), a compact, wideband two-section lumped-element output impedance transformer is proposed, which lowers a load impedance from 50 to 25 Ω. Each λ/4 transformer is realized by four cascaded C-L-C π-networks integrated into a single symmetric inductor, for its compact size and high passive efficiency. The proposed SiGe HBT cascode NDPA achieves a saturated Pout of 21.3 dBm at 8 GHz and peak power added efficiency (PAE) of 21.7% at 4 GHz, with its 3 dB bandwidth and PAE higher than 12.2% from 2 to 24 GHz.