Scattering parameters improvement in CPW MEMS shunt switches

This paper presents a CPW micromachined shunt switch. The structure improves S parameters in up state and down state positions. In the proposed structure two additional plates are placed in CPW gap under the beam. These plates increase down state capacitance and hence increase the down state isolation. By adding these extra plates the area of the electrostatic field is increased and therefore the actuation voltage decreased. Another plate is placed over the beam. When the voltage is applied to this plate, the beam moves up, hence the up state capacitance is decreased and the S parameters in up state are improved. The proposed structure was simulated using ANSYS7and HFSS 5.4 software. For a CPW line with dimensions of G/W/G 60/100/60 (50Ω), the obtained results indicate that isolation in the down state position is increased thirty five percent at 10 GHz, and return loss is decreased fifty percent. In the up state, return loss and insulation loss are improved fifty percent and twenty five percent respectively. Actuation voltage is decreased approximately fifteen percent. The obtained results are due to structural modification without losing any other micromachined microwave switch parameters, which is an advantage.