An Ultra-Compact 34-42GHz Hybrid-Type Phase-Invariant dB-LinearVariable-Gain Amplifier Achieving <1.7° RMS Phase Error

This work proposes a hybrid active-passive variable gain block for Q-band, useful for phased-array beamforming satellite communication (SATCOM) systems and other joint communication-sensing applications. It achieves over 15dB gain control with 0.5dB resolution, low power consumption, and a compact 0.027mm2 footprint. The design combines a phase-invariant active core with binary/unary and fractional Gm-cell slices, passive fine-step attenuators and a two-stage wideband matching network. Measurements demonstrate excellent input/output matching and phase/gain performance: it achieves 18.5% fractional bandwidth, <1.7° RMS phase error and <0.18dB gain error across band, making the block suitable for high-performance beamforming system integration.