RF MEMS switches and their applications in antenna systems

A novel asymmetric RF MEMS switch, a capacitive RF MEMS switch compatible with microwave laminate and their applications in antenna systems were investigated in detail in this thesis research. A new mode-switching concept (from CPW mode to slotline mode) is introduced into an asymmetric capacitive RF MEMS switch, allowing the traditional capacitive switch extending its operation to low microwave frequencies. It can be easily tuned to operate at the 2--10 GHz frequency range making it suitable for commercial wireless communication systems and diversity antennas. Also, a novel fabrication process is proposed to construct RF MEMS switches directly on the microwave laminate for ready integration with all other RF components. The applications of RF MEMS switches as a signal steering device in multielement antennas (MEAs) system were investigated. The q-dime antenna and cactus antenna were designed, fabricated and measured. A pattern diversity antenna system suitable for switch combining was designed with cactus antenna. The three-element antenna system achieved very low correlation coefficients, low power imbalance, and large diversity gain. Monolithic integration could make RF MEMS a physical part of the antenna resulting in high degree of reconfigurability. A spiral antenna capable of changing its polarization state was designed to develop a polarization diversity antenna.