An Improved Wideband All-Pass I/Q Network for Millimeter-Wave Phase Shifters

This paper presents the design and analysis of an improved wideband in-phase/quadrature (I/Q) network and its implementation in a wideband phased-array front-end. It is found that the addition of two resistors $(R_{s})$ in the all-pass I/Q network results in improved amplitude and phase performance versus capacitance loading and frequency, which is essential for wideband millimeter-wave applications. A prototype 60–80-GHz phased-array front-end based on 0.13-$\mu{\hbox {m}}$ SiGe BiCMOS is demonstrated using the improved quadrature all-pass filter and with 4-bit phase-shifting performance at 55–80 GHz. Application areas are in wideband millimeter-wave systems.