Design and Analysis of a Wideband 15–35-GHz Quadrature Phase Shifter With Inductive Loading

A Ku-, K-, and Ka-band phase shifter for beamforming applications is presented in this paper. An analysis showing the effect of loading conditions on quadrature phase accuracy in a simple poly-phase filter is carried out. Based on the analysis, a novel quadrature phase shifter (QPS) with inductive load is proposed. Sign-selection and vector addition is performed in two stages to lower supply voltage. The proposed phase shifter is fabricated in a 0.18- μm SiGe BiCMOS process and occupies an area of 520 μm×370 μm. The proposed QPS has a maximum phase error of 6.38
^°
over 15-35 GHz while maintaining an amplitude imbalance less than 2 dB. When combined into a 4-bit phase shifter, the root mean square (rms) gain error is less than 2.2 dB and the rms phase error is less than 13
^°
over 15-35 GHz. The phase shifter thus achieves a full 360
^°
phase-shift range with 22.5
^°
phase resolution. The total power consumption is 14 mA from a 1.8-V power supply. The phase shifter achieves an input P1dB of -6.25 dBm. The measured phase-shifting fractional bandwidth of 87% is the highest reported thus far in the literature for SiGe BiCMOS implementation.