Asymmetric Capacitor-Loaded Marchand Balun-Based Four-Stacked Power Amplifier Utilized C-Band Stimulus Source in SOI CMOS

This letter presents a novel stimulation source with a four-stack power amplifier (PA) based on an asymmetric capacitor-loaded Marchand balun. The stimulus source comprises a cross-coupled voltage-controlled oscillator (VCO), common-source buffer, and two-stage four-stacked PA. The target power level of the PA was specified by performing an analysis assuming a realistic far-field stimulation environment. Loading two capacitors with different capacitances onto the OFF-chip Marchand balun eliminates the imbalance between the two balun nodes. Improvements in magnitude and phase balance show an enhanced performance and are also robust against fabrication errors. A stimulus source was designed and fabricated at 6.5 GHz using 0.28- $\mu \text{m}$ silicon on insulator complementary metal–oxide–semiconductor (CMOS) process for validation. The measured maximum output power and peak drain efficiency (DE) were 33.4 dBm and 28.3%, respectively. The proposed stimulus source is the first-of-a-kind system with a watt-level output for behavioral experiments in the $C$ -band.