The application of Micro-Electro-Mechanical-Systems (MEMS) in the fields of radio frequency and microwave is offensively spreading. Nowadays a large amount of scientists and research centers worldwide are involved with development, design, and fabrication of MEMS components for RF applications. RF-MEMS show numerous capabilities for improving the performance of RF transceivers. Their excellent features such as extremely low power consumption, low loss, simple and cheap fabrication process, the ability to work at UHF and SHF frequencies, and compatibility with standard CMOS process make them ideal devices replacing the bulky off-chip components and enhancing the performance of on-chip circuits of transceivers. Therefore they can realize the idea of a transceiver on a chip. The aim of this chapter is to provide a reader with deep information in the field of RF-MEMS, covering their current and possible applications, design, modeling, and simulation. Also their problems such as power handling, packaging, frequency extension, et cetera, are discussed. In addition, this chapter will introduce case studies in RF-MEMS area for researchers.
TopIntroduction
Nowadays MEMS technology finds numerous applications in technology and science. These applications spread from everyday supplies such as toys, civil engineering monitoring, automotive industries, biotechnology, medical, energy conservation, and etc. to military and aerospace applications as both sensors and actuators. MEMS is an enabling technology for smaller device sizes, batch processing for low cost and uniform productions, distributed device placement and more precise sensing and actuating.
One of the most important research areas in the field of wireless RF transceivers is miniaturization. Miniaturization (integration) has significant benefits such as lightness, reducing the costs and improving the shape factors. For example, in the last decades, communication systems were bulky, heavy and without suitable shape and also required large batteries. But nowadays, they become small and light systems with wide variety of abilities with tiny and rechargeable batteries. These tremendous progresses are as the result of integration. But, nevertheless, there are some barriers against fully miniaturization of RF transceivers on a single chip. There are many off-chip components on the transceiver board which cannot be integrated alongside the state of the art CMOS technology, such as high Q off-chip crystals and quartz filters, high Q inductors and capacitors.
RF-MEMS is an advanced branch of MEMS technology which can provide necessary components for RF transceiver’s integration. This technology introduces very high performance components such as filters, switches, inductors and varactors which all are capable of integration alongside CMOS transistors and hence can realize monolithic RF transceivers.
This chapter is organized as follows; the next section introduces RF-MEMS components where the most important components such as resonators, switches, inductors and varactors are discussed. The third section is concerning RF-MEMS applications in wireless transceivers and describes some RF building blocks realizable by MEMS technology such as filters, mixer-filters, oscillators and VCOs, switchable filters and duplexers followed by a conclusion in the last section.