6.1 Introduction

This chapter is exclusively dedicated to radio frequency (RF)/microwave microelectromechanical system (MEMS) phase shifters. Phase shifters can be classified into two categories: absorption types and reflection types. An absorption-type phase shifter is widely used for RF and microwave frequencies, whereas a reflection-type phase shifter is best suited for higher microwave and mm-wave frequency applications. A phase shifter is the most critical component of an electronically scanning-phased array antenna, widely deployed in electronic warfare (EW) systems, missile tracking radar, forwarding looking radar used by airborne fighter/bomber aircraft, communications systems, and space-based surveillance and reconnaissance sensors. MM-wave phase shifters using conventional field-effect transistors (FETs) and PIN-diodes suffer from excessive insertion loss (IL), high power consumption, and poor reliability. It is important to mention that the dominant IL of a phase shifter demands excessive power consumption, which is not easily available in airborne systems or satellite-based sensors because of stringent requirements for power consumption, weight, and size. Current research and development activities on MEMS and nanotechnologies (NTs) reveal that integration of MEMS-based switches, tuning capacitors and air gap 3 dB coplanar waveguide (CPW) couplers will lead to successful design and development of MEMS phase shifters operating at microwave and mm-wave frequencies with low IL, high switching speeds, minimum power consumption, higher reliability, and life cycles exceeding ten billions. The activities further reveal that mm-wave phase shifters using MEMS technology will not only offer low IL and minimum power consumption but also provide ultrawide bandwidth and reduced intermodulation (IM) distortion...