Very low-loss distributed X-band and Ka-band MEMS phase shifters using metal-air-metal capacitors

Abstract

2-bit wide-band distributed coplanar-waveguide phase shifters have been developed on a 500-/spl mu/m quartz substrate for X- and Ka-band operation. The designs utilize microelectromechanical system (MEMS) switches in a distributed MEMS transmission line periodically loaded by MEMS switches and high Q (/spl ges/250 at 30 GHz) metal-air-metal capacitors. The MEMS switches are actuated by a /spl plusmn/20-V voltage waveform using a high-resistance bias line. Estimated spring constant and switching time is 30 N/m and 9 /spl mu/s, respectively. The Ka-band 2-bit design results in a reflection coefficient better than -11.5 dB, an average insertion loss of -1.5 dB and phase shifts of 0/spl deg/, 89/spl deg/, 180/spl deg/, and 270/spl deg/ at 37.7 GHz. The X-band 2-bit design results in a reflection coefficient better than -12.5 dB, an average insertion loss of -1.2 dB and phase shifts of 0/spl deg/, 94/spl deg/, 176/spl deg/, and 270/spl deg/ at 13.6 GHz. These results are very competitive with switched transmission-line and reflection-based phase shifters. The distributed design can be easily scaled to V- and W-band frequencies for wide-band low-loss performance.