# MEMS-Switched Triangular and U-Shaped Band-Stop Resonators for K-Band Operation
## 2 SPDT Design, Technology, and Test
Finally, the isolation between the disconnected ports, parameters S\({}_{31}\) and S\({}_{32}\), was from \(-30\) dB to \(-20\) dB at the upper band, a rather good value expected for the isolation, since it was obtained using only one not actuated switch. On the other hand, a complete analysis of this device should include a deformed bridge, electromechanically simulated to give a more realistic result. At the same time, most of the simulations in the literature have estimated the electrical response with a rigid ON-OFF functionality, moving the entire beam up or down with respect to the contact position. This gives back a normally underestimated performance depending on the operative frequency, because parasitic contributions cannot be correctly predicted. The situation is clarified in Figure 4, where the simulation is compared with the experimental result for the transmission parameter S\({}_{21}\). The parasitic effects in the electrical response of the MEMS SPDT and the CPW lines were considered, including the material properties and thickness in the electromagnetic simulations. The dielectric loss contributions and the transmission lines' losses are defined in terms of tan\(\delta\) and bulk resistivity for the materials and the resistivity of the thick metal used to simulate the CPW lines. Of course, as discussed above, a complete analysis of the parasitics should include the deformed shape of the bridge and not simply a comparison between the up and down state as a rigid metal beam, but,  
Figure 3: Simulated results of the SPDT configuration when the switch at port 3 is considered not actuated. Results are shown in terms of matching at the input port (S\({}_{11}\)), transmission to actuated branch (S\({}_{21}\)), isolation between ports 1 and 3 and ports 2 and 3 (S\({}_{31}\) and S\({}_{32}\), respectively), and reflection from port 3 (S\({}_{33}\)). in most cases, this approximation is valid for obtaining a reasonable agreement between a simulation and experiment [26]. Accounting for additional details is probably more critical for miniaturized RF MEMS switches, like those designed for higher frequencies [27]. Concerning the mechanical response and its latency, the MEMS devices were not minded for fast switching, but for providing response times in the order of tens of \(\upmu\)s down to 1 \(\upmu\)s, depending on the actuation procedure and the mechanical structure, and their utilization in redundancy and reconfiguration applications does not imply a fast electronic solution since the beginning [28]. Good reflection and insertion loss performances were obtained from an experimental point of view, as shown in the plot exhibiting the S\({}_{11}\) and S\({}_{21}\) parameters of the measured SPDT device in Figure 5, compared to the simulation. As expected from an ohmic switch, a wideband response was also achieved. Some boundary disturbances affected the measurement, which was noisy, still maintaining an acceptable value of the reflection coefficient S\({}_{11}\) that was comparable to the expected values. In addition, multiple reflections caused notches in the S\({}_{11}\) response, and this could be a sign that, when the switch was actuated, the non-flat metal beam was affected by local discontinuities that were not entirely considered. Other factors influencing the reflection could have been the right-angle, non-optimized CPWs transmitting the signal towards the resonators. The actuation voltage for the first actuation was high, close to 80-90 V, but was reduced to 60-65 V after exercising the switch with more actuations, also contributing to removing some minor residuals that could still be present after the etching of the sacrificial layer. Figure 4: Comparison between the expected and the experimental S\({}_{21}\) parameter, in dB scale, for the SPDT configuration used in this work. The losses are underestimated, especially below 30 GHz.