A 220-320-GHz vector-sum phase shifter using single Gilbert-cell structure with lossy output matching

This paper presents a wideband vector-sum phase shifter (VSPS) that operates over the entire WR-3 band (220-320 GHz). Compared to conventional VSPSs with double Gilbert cells, the proposed phase shifter employs a single Gilbert-cell structure for vector modulation. This reduces the output current combining ratio from 8:2 to 4:2, and boosts the impedance at the combining node, thus facilitating wideband output matching at upper millimeter-wave and terahertz bands. The simplified structure leads to a reduction in dc power consumption and chip area without sacrificing the 360° phase-shifting property. Lossy matching is applied at the Gilbert-cell output to further increase bandwidth and stability at the expense of relatively high loss. The phase shifter is implemented using a 250-nm InP DHBT technology that provides f_T and f_max exceeding 370 and 650 GHz, respectively. The measurements exhibit a wideband phase shift with continuous 360° coverage and average insertion loss ranging from 11.8 to 15.6 dB for the entire WR-3 band. The root mean square amplitude and phase error among different phase states are less than 1.2 dB and 10.2°, respectively. The input-referred 1-dB compression is measured at 0.7 dBm on average. The dc power consumption is 21.8-42.0 mW at different phase states.