# A New Concept of Reconfigurable Antenna Structure Based on an Array of RF-MEMS Switches
## 4 Numerical and Experimental Assessment
### Numerical Assessment  
Let us start with the first experiment. The matrix has been set as a microstrip line of different widths by activating rows of the matrix. In particular, we increased the microstrip width by adding different rows. The simulation was carried out using the ADS electromagnetic simulator (from Keysight, Santa Rosa, CA, USA). The whole CAD structure has been imported into the simulator, and for the sake of accuracy, the disconnected gold patches (with the surrounding MEMS switches in an open state) are considered in the simulation. In the first simulation, only one activated row is considered. This configuration represents a microstrip of thickness \(t_{m}=430\)\(\upmu\)m with an impedance of about \(Z_{m}=54.75\)\(\Omega\). Then, different rows have been added by properly activating the MEMS switch (up to six rows) in order to increase the microstrip width and consequently decrease the microstrip impedance. The microstrip width ranges from \(t_{m}=43\)\(\upmu\)m up to \(t_{m}=3430\)\(\upmu\)m. The obtained results are summarized in Table 1; the fourth column reports the microstrip impedance; as expected, the microstrip impedance decreases with the width starting from \(Z_{m}=54.75\)\(\Omega\) for a single activated row, and for six activated rows, the impedance decreases up to \(Z_{m}=10.34\)\(\Omega\). Despite the simplicity of this first set of experiments, it is worth noticing that the capability to implement microstrip segments with different widths permits the fabrication of quarter wavelength transformers, broadband impedance transformers, and other fundamental radio frequency or microwave components.  
In the second set of numerical experiments, a more complex geometry consisting of a reconfigurable patch antenna has been considered. In these experiments, different columns are activated in order to modify the length and, consequently, the resonant frequency of a rectangular patch antenna, obtaining an electronic reconfigurable antenna able to operate in different frequency bands. The simulations were done with the ADS software, and also, in this case, to simulate realistic scenarios, the disconnected gold patches (with all the surrounding MEMS in an open state) were considered in the simulation. The obtained results are reported in Figure 10. As can be noticed from the data reported in Figure 10, the patch obtained with all the seven columns activated represents a \(5230\times 5230\)\(\upmu\)m\({}^{2}\) square patch antenna with a resonance frequency of about \(f_{7\times 7}=8.0\) GHz as indicated by the yellow curve of Figure 10. Then, as can be observed by reducing the column number from seven to two, the resonance frequency decreases consequently due to the antenna length reduction. The following resonance frequencies, with reference to Figure 10 have been obtained for the different configuration: \(f_{7\times 6}=10.5\) GHz (black line), \(f_{7\times 5}=14.5\) GHz (cyan line), \(f_{7\times 4}=17.0\) GHz (green line), \(f_{7\times 3}=22.5\) GHz (blue line), and \(f_{7\times 3}=30.0\) GHz (red line).  
Figure 9: High-resolution photo of the \(7\times 7\) matrix prototype made with an optical microscope.