Design and Fabrication of a Ternary Switch for MEMS-Controlled Reflectarray Elements

For a digitally controlled reflectarray consisting of many elements, the cost and complexity increase considerably with every additional control line in each element. A ternary design for controlling microelectromechanical systems (MEMS) capacitive switches is proposed to reduce the number of lines required without decreasing the number of states realized. Three distinct capacitance states are realized with custom-fabricated shunt switches having different pull-in voltages. To increase the versatility of the concept, the capability of designing the pull-in voltage and the capacitance of a switch independently of each other is also demonstrated. This design can be applied to any digital tuning circuit involving MEMS switches for the reduction of biasing layout complexity.