A Ultrawideband Phase-Invariant VGA with Core-Matching Network Co-Design Achieving <1.38° RMS Phase Error

This paper presents a wideband phase-invariant variable gain amplifier (VGA) adopting a gain core and matching network (MN) co-design technique. The core-MN co-design methodology expands the design space by incorporating the phase variation of the MNs, which was often overlooked in conventional designs. This approach enhances design flexibility and enables wideband phase compensation. Specifically, by configuring the gain-dependent phase variation (GDPV) of the MNs and the active gain core to exhibit opposite polarities, the overall GDPV of the VGA is minimized and flattened across a wide frequency range. Implemented in a 28 nm CMOS process, the VGA achieves a peak RMS phase error (RMSPE) of 1.38° and a peak GDPV of 2.78° with a gain tuning range (GTR) of 21 dB within the S21 3-dB bandwidth (10.9–23.6 GHz).