SiGe process integrated full-360° microelectromechanical systems-based active phase shifter for W-band automotive radar

This study presents the implementation of a microelectromechanical systems (MEMS)-based active phase shifter (APS) by using vector sum method. The proposed phase shifter comprises of two variable gain amplifiers (VGAs), a Wilkinson power divider with 90° phase shift lines, a Wilkinson power combiner and two 1-bit (0°/180°) MEMS phase shifters. First, all the components were designed and fabricated individually to check for their proper functionality, then they were brought together in a novel vector sum topology to work as a full-360° span phase shifter. Fabricated VGAs function properly at designed frequency (77 GHz) with gain variation from 0 to 14 dB with the tuned base voltages from 1.8 to 2.3 V. The VGAs not only serve for providing the weighted amplitudes but also compensate 4.3 dB loss from 1-bit MEMS phase shifter and 0.8 dB loss from each power divider and combiner. Active/passive components and MEMS switches are all integrated at one single chip of 3.74 mm² and manufactured with IHP 0.25 μm SiGe BiCMOS technology. As to the author´s knowledge, this is the first demonstration of an APS using integrated active components and MEMS technology. Presented phase shifting mechanism can be used at automotive radar system for beam steering purpose.