A G-Band 5-Bit Vector-Modulator Phase Shifter With 52-GHz Bandwidth for Phased-Array Systems in 0.13-μm SiGe BiCMOS

This article reports a 5-bit wideband vector-modulator phase shifter (VMPS) for submillimeter-wave (sub-mmW) and terahertz (THz) phased-array systems. To achieve a high-resolution broadband phase-shifting feature, a comb-shaped differential quadrature coupler is proposed to reduce the phase/amplitude imbalances of in-phase and quadrature signals across the broadband frequencies. In addition, to mitigate the impact of the input impedance variations of the variable gain amplifier-based vector modulator (VM) on phase characteristics, fourth-order input matching networks are adopted for the VM modules. Fabricated on a 0.13-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>m SiGe BiCMOS process, the chip occupies a core area of 0.15 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and consumes 25.6 mW. Measured results show that the VMPS achieves 360° coverage with 64 states and provides 5-bit phase accuracy from 184 to 236 GHz, exhibiting near calibration-free characteristics. It features <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$a \lt 7.5^{\circ }$</tex-math> </inline-formula> rms phase error in 190–230 GHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$a \lt 1.5$</tex-math> </inline-formula>-dB rms amplitude error in 180–230 GHz.