Introduction

Radio frequency microelectromechanical systems (RF MEMS) can offer unsurpassed RF performance over more conventional solid-state electronic devices and can help to implement advancements within a broad range of applications; from ubiquitous smart sensor networks to mobile handsets. Moreover, they can substantially reduce the size, weight and cost of reconfigurable subsystems; making this an important enabling technology for the twenty-first century.

MEMS technologies are already firmly established within high-volume commercial markets. Examples include inertial sensors/accelerometers (e.g. used in car airbag sensors, gaming accessories and mobile handsets), disk drive read/write heads, ink-jet printer nozzles, microphones and digital light projectors. In contrast, MEMS for RF applications has been relatively slow to move out of the laboratory and into commercial products. Indeed, the first RF MEMS papers started to appear over three decades ago. For example, a truly landmark paper was published on electrostatically actuated cantilever-type ohmic contact switches back in 1979 [1]. Over the past decade, however, a raft of interesting components and circuits has been demonstrated. Some of these developments have been reviewed from the perspective of enabling technologies [2], while the real founding principles have been described in some detail within the established textbooks by Santos [3], Rebeiz [4] and Varadan et al. [5]. More recent articles of noteworthy merit have also appeared on technologies, testing, reliability and applications associated with general RF MEMS [6–8].

Radio frequency microelectromechanical systems (RF MEMS) have just entered a new and exciting era, with this previously elusive technology finally appearing on the open market. In 2008, in the United States and Japan, the first real devices were released and made commercially available to all. Today, there is intense research and development (R&D) activity, and at all levels from concept to manufacture, within North America, Europe and Asia.

The first book to be dedicated to RF MEMS was published in 2002, and two others soon followed in 2003. Within these books, the most recent references to be cited were papers published back in January 2003. Therefore, the motivation for another book on the subject is clear. At this point, I would like to pay homage to the groundbreaking book entitled RF MEMS: Theory, Design and Technology, by Gabriel M. Rebeiz. Indeed, all these books collectively represent a major literary milestone in RF MEMS and could be considered as a springboard for the later activities that led to the first commercially available devices.

Introduction

The past five years have seen a dramatic rise in the number of niche switch technologies being reported in the open literature. These include, but are not limited to, the general areas of latching, multiway and high-power. These niche technologies are covered within the same dedicated chapter, because of the synergy found between them. It should be of no surprise that there is a large overlap between these technologies; with latches being used in both multiway and high-power switches and the need for implementing high-power multiway switches.

Latching switches

For some applications, switches are required that are non-volatile and able to remain in any state after the source of actuation energy has been removed. For example, in certain safety-critical applications it is essential for the state of the system to be preserved in the event of a power failure. In other systems, for example, in portable electronic devices, remote sensors and unmanned aerial (or air or aircraft) vehicles (UAVs) or systems (UASs), the available power is limited and non-volatile switches are attractive because they require zero holding power, regardless of their state.