A Miniaturized Marchand Balun-Based Broadband Vector Sum Phase Shifter with 0.49° RMS Phase Error

This paper presents a miniaturized Marchand balun-based passive vector sum phase shifter (P-VSPS) for millimeter-wave phased-array systems. By implementing miniaturized Marchand balun structures as matching networks, the proposed P-VSPS achieves broadband performance with low RMS phase/gain errors. The P-VSPS also functions as an attenuator and can replace all phase shifters and attenuators in both the receive (RX) and transmit (TX) channels, reducing die area and simplifying beamforming. The phase shifter is fabricated in 28-nm CMOS technology with a core size of 0.15 mm$^2$ excluding pads. From 64.7 to 93.3 GHz, the proposed P-VSPS achieves the lowest RMS phase error of 0.49$^{\circ}$ to 2$^{\circ}$ and the lowest RMS gain error of 0.12 to 0.33 dB among reported VSPSs. The measured insertion loss is 11.8 $\pm$ 0.25 dB at 75 GHz, which is the lowest among reported P-VSPSs.