A 60-GHz SiGe Power Amplifier With Three-Conductor Transmission-Line-Based Wilkinson Baluns and Asymmetric Directional Couplers

A compact, 60-GHz high-power, wideband balanced power amplifier, implemented in a 90-nm SiGe BiCMOS technology, is demonstrated. A three-conductor transmission-line-based asymmetric coupled-line directional coupler is used to achieve impedance transformation and quadrature power combining simultaneously. A Wilkinson balun based on a three-conductor transmission line structure is implemented to achieve a four-way series-parallel power combining. Analyses of the three-conductor asymmetric coupler and the Wilkinson balun combiner are provided in this article. The design achieved 17.3-dB small-signal gain, with 41.8-GHz 3-dB bandwidth, from 28.1 to 69.9 GHz. A 24.4-dBm saturated output power (PSAT) was measured at 60 GHz with a 22-GHz 1-dB P
_SAT
bandwidth, covering 45-67 GHz. The circuit showed a peak power-added efficiency (PAE) of 14.2% at 60 GHz, and the peak PAE is above 11.5% across the 1-dB P
_SAT
bandwidth. The proposed eight-way power combining scheme achieves 0.077-mm2 per-way area consumption and 449-mW/mm
²
power density.