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 degrees/180 degrees) 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 degrees 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 mm(2) and manufactured with IHP 0.25 mu m 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.