A Wideband Vector-Modulated Variable Gain Phase Shifter for 5G NR FR2 in 40-nm CMOS

This article presents the design of a wideband CMOS vector-modulated variable gain phase shifter (VGPS) for 5G NR FR2. A generation-correction structure, consisting of a differential coupler and a single-stage <tex-math notation="LaTeX">$RC$</tex-math> - <tex-math notation="LaTeX">$CR$</tex-math> poly-phase filter (PPF), is adopted to produce the wideband in-phase and quadrature (IQ) vectors. The PPF with a butterfly layout, featuring symmetric floorplan, low parasitic, and flexible feeding style, is proposed to enhance the IQ balance. The common-source current-steering variable gain amplifiers (VGAs) with tail switches are employed as the vector modulating stage. Orthogonal phase and gain tuning is ensured by the dual-mode control method of the VGA. The proof-of-concept wideband VGPS is implemented in 40-nm CMOS technology, with a core chip area of 0.167 mm <tex-math notation="LaTeX">²</tex-math> . It achieves wideband 6-bit phase tuning across 16.3–43.6 GHz with <tex-math notation="LaTeX">$<$</tex-math> 2.0 <tex-math notation="LaTeX">^∘</tex-math> rms phase error and <tex-math notation="LaTeX">$<$</tex-math> <tex-math notation="LaTeX">±</tex-math> 0.5-dB peak-to-peak gain error. Also, over 6-dB fine gain control is provided by the VGPS, and the related phase error is <tex-math notation="LaTeX">$<$</tex-math> 2.2 <tex-math notation="LaTeX">^∘</tex-math> across 15–45 GHz. The wideband performance, high resolution gain, and phase controls, low power consumption, and compact size make the proposed VGPS suitable for multiband 5G NR applications.