Improving RF Characteristics of MEMS Capacitive Shunt Switches

Yasser Mafinejad(1*), Khalil Mafinezhad(2), Abbas Z. Kouzani(3)

(1) School of Engineering, Deakin University, Australia
(2) Dept. of Electrical Engineering, Ferdowsi University, Iran, Islamic Republic of
(3) School of Engineering, Deakin University, Australia
(*) Corresponding author

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This paper presents a new RF MEMS electrostatic switch with low actuation voltage. Usually, electrostatic switches with low pull-down voltage have large up-state capacitance deteriorating their RF characteristics. The proposed switch enjoys good RF characteristics for a frequency band of larger than one octave, and a low actuation voltage of 9 volts. Low actuation voltage could be achieved by decreasing the gap or increasing the area of the beam. In both cases, the up-state capacitance enlarges deteriorating the RF characteristics. In this work, regardless of the value of Cu, the height of the gap is chosen by considering the reliability and life cycle of the switch. Then, the area is calculated for the chosen gap and the desired actuation voltage. The switch is a π circuit consisting of two shunt switches and a short transmission line in between them. The key aspect of this design is the optimization of the length and the characteristic impedance of the line to suit fabrication constraints and desired frequency band. The switch is simulated and its RF characteristics evaluated. An excellent improvement of the RF characteristics of the up-state position is observed. For the down-state position, a superb isolation is observed.
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Microelectromechanical Systems; RF Characteristics; RF MEMS Switch; Π Matching Circuit; Actuation Voltage

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