# A New Concept of Reconfigurable Antenna Structure Based on an Array of RF-MEMS Switches
## 3 Development of a 7 \(\times\) 7 Reconfigurable Matrix Structure Prototype
### MEMs Switches Design  
This subsection describes the RF-MEMS switch design and the key components to enable the reconfigurability of the proposed reconfigurable matrix structure. In particular, the following description is a summary for further additional and more detailed considerations about the MEMS design, and characterization can be found in [43]. The considered switch device is a clamped-clamped structure of ohmic type, driven by an electrostatic actuation mechanism. The series connection between the two interrupted sections of the main RF signal line is obtained by utilizing an ohmic metal-to-metal contact between a movable membrane and the underlying contact pads. Figure 4 reports the MEMS switch fabricated prototype.  
The switch dimensions are quite compact, with an overall reduced physical footprint of 430 \(\times\) 170 \(\upmu\)m\({}^{2}\). The switch layout reported in Figure 4 consists of an 8-mask surface micro-machining process developed on a 6-inch silicon support, covered by a basic layer of silicon oxide. The silicon oxide is deposited and used on the different layers to isolate them. Then, it is etched and filled with conductive materials, and an electrical connection must be established between adjacent layers. The fabrication procedure is detailed in [44; 47]; more details concerning the different masks will be summarized in the following subsection to describe the reconfigurable matrix prototype. The scattering parameters (S-parameter) of the considered MEMS switch have been numerically and experimentally assessed. In particular, a comparison between simulated results obtained with commercial software, namely Ansys HFSS, and measurements have been performed with a vectorial network analyzer (VNA) on a broad observation range starting from DC up to 110 GHz. In particular, the on-wafer measurement setup, the MEMS switch prototype, has been characterized using Ground-Signal-Ground (GSG) probes connected to a Vector Network Analyzer (VNA).  
Figure 4: Microphoto details of the single RF-MEMS switch.  
In particular, Figure 5 report the return loss \(S_{11}\) in (a) open (when the membrane is in rest position) and (b) closed (pulled in membrane) conditions, respectively. The insertion loss \(S_{21}\) is reported in Figure 6, also in this case in (a) open and (b) closed switch conditions, respectively. As it can be observed from the data reported in Figures 5 and 6, the agreement between numerical and experimental results is very good. The overall measured return and insertion loss are quite good, especially up to 50 GHz. At higher frequency bands, the performances of such switches are very satisfactory, and they outperform other electronic switches, such as PIN diodes or MOSFET transistors. In light of the considerations and experimental assessment, the RF-MEMS switch proved to be a compact and reliability-oriented device. It provides wideband and remarkable electrical features that make it a suitable building block for the proposed reconfigurable matrix structure.