An 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) that adopts a gain core and matching network (MN) co-design technique to enable wideband phase compensation. Conventional phase-invariant VGA approaches typically overlook the MNs’ gain-dependent phase variation (GDPV). In contrast, this work fully integrates both the gain cores and MNs into a unified phase-compensation scheme, allowing their respective GDPV responses to compensate for each other, thereby minimizing the overall VGA GDPV. The holistic design effectively minimizes phase error over a wide bandwidth. Implemented in a 28-nm CMOS process, the proposed VGA achieves a measured peak RMS phase error (RMSPE) of 1.38° along with a 21 dB gain tuning range across 10.9–30 GHz (93.4%).