32.9 An Ultra-Compact 28GHz Doherty Power Amplifier with an Asymmetrically-Coupled-Transformer Output Combiner

Mm-wave wireless communication and sensing heavily rely on phased arrays to compensate for high path losses and meet link-budget targets. Recent mm-wave arrays have grown increasingly complex, often with many parallel RF paths integrated on a single front-end/beamformer chip [1]. Dual-polarization and multiband operation further multiply the number of RF front-end paths. Consequently, one technology trend of array front-end chips is to aggressively miniaturize RF building blocks for integration and cost saving, while simultaneously achieving higher energy efficiency to maintain the thermal density and ease the packaging.