Research On Electromagnetic Interference Of Capacitive RF MEMS Shunt Switches

Since RF MEMS devices can meet the requirements of small volume, high reliability and low cost in the wireless communication systems, and have advantages of enhancing robustness and substantially reducing power consumption, they are very compelling for the application of transceiver architectures. The RF MEMS devices are expected to offer switches and filters of greatly improved performance for receiver front-end architectures and offer on-chip integration of high quality for out-put end of the transmitter. Now among the main RF MEMS devices areμmechanical RF switches, tunableμmechanical capacitors,μmachined inductance and vibrating micromechanical resonators.As one of the most important MEMS devices, RF MEMS switches have been applied in front-end circuits of some microwave systems, antenna and phase shift architectures. The more research about RF MEMS switches is needed because many problems need solving before the switches can be applied widely. The research of the electromagnetic interferences(EMI) of the switches to the signals when switching aims to further research the reliability and stability of the RF MEMS switches and try to find a way to enhance the performance of the switches, which enable a MEMS-based system of higher reliability and stability. The following aspects are included in this dissertation.The summary of the latest research development of RF MEMS switches is presented first. Main kinds of MEMS switches are described and compared. Then a typical kind of RF MEMS switches is choosed: RF capacitive MEMS shunt switch as a research example, discussing the structure, the operation characteristics and important parameters of the switch. The MEMS shunt capacitive switches are more suited for higher frequencies (5–100 GHz) compare to other kinds of MEMS switches.Then the paper expatiates on the electromagnetic fields of RF capacitive MEMS shunt switches, elaborates on the characters and modes of electromagnetic interferences and illuminates the necessities of analyzing the electromagnetic interferences which the RF MEMS switches create, including the causes and modes of the interferences. Since the dynamic characteristics of the switch are related to the variation of the electromagnetic field which does create the interferences to the signals, it further researches on the dynamic characteristics of the switch when switching and the switching time and all parameters of the switch are discussed and their influences are simulated.The electromagnetic models of the switch are analyzed and it is concluded that the electromagnetic interferences are mainly produced by the discharge of the switch through the study of the three processes: charging, the movement of the bridge and discharging. The elements which determine the intensities of the interferences are the discharging time, the resistance and the inductance of the switch. The magnitudes of the influences the structure parameters of the switch to the intensities of the electromagnetic interferences are researched on the basis of the analyses of the elements. The results are valuable to the design of RF MEMS switches of high performances.