# Research and Analysis of MEMS Switches in Different Frequency Bands
## 3 The Research Status of MEMS Switches in Different Frequencies
### Research Regarding Insertion Loss and Isolation of MEMS Switches in Different Bands
#### MEMS Switches Based on Combinations of Several Switches in Series in Different Frequency Bands  
Some MEMS switches were designed based on combinations of several switches in series to achieve high isolation. A RF signal can be isolated several times by this combination; therefore, the isolation of the MEMS switch is greatly improved. Table 2 summarizes the performance parameters of MEMS switches using this type of combination in different frequency bands.  
Both capacitive MEMS switches presented in [25; 33] achieved high isolation in the centimeter band by using two identical bridges in series. Comparing the switches with the single bridges in Table 1, the isolation of the switch with double bridges was almost doubled. The dual- bridge structure was used by [PERSON] et al. [25] to improve isolation while sacrificing insertion loss. A high-impedance transmission line was designed by [PERSON] et al. [33], and the thickness of the CPW was more than two times the skin depth. As a result, the switch achieved a low insertion loss of 0.15 dB at 20 GHz and a high isolation of 60 dB at 12 GHz. [PERSON] et al. [34] achieved a high isolation of 40 dB at 25 GHz using a double-arm cantilever and a low insertion loss of 0.2 dB at 20 GHz by optimizing the dimensions of the cantilever in a DC-contact MEMS switch. The SP4T MEMS switch designed by [PERSON] et al. [35] achieved a high isolation of 51 dB at 20 GHz and a low insertion loss of 0.04 dB at 20 GHz using a structure with a shunt capacitive switch and an ohmic contact switch in series. The capacitive MEMS switches designed in [25; 33; 35] achieved low-actuation voltages by using serpentine flexure structures.  
High isolation was achieved by using combinations of several switches in series in [36; 37; 38] in the millimeter-wave band. The MEMS switch proposed by [PERSON] [36] achieved a high isolation of  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Band** & **Insertion Loss** & **Isolation** & **Actual Voltage** & **Reference** \\ \hline \multirow{4}{*}{centimeter} & 0.6 dB@13 GHz & 50 dB@9 GHz & 3.6 V & [25] \\  & 0.15 dB@12 GHz & 60 dB@12 GHz & 7.5 V & [33] \\  & 0.2 dB@25 GHz & 40 dB@25 GHz & 10 V & [34] \\  & 0.04 dB@20 GHz & 51 dB@20 GHz & 7.19 V & [35] \\ \hline \multirow{2}{*}{Q} & 0.1–0.19 dB & 57 dB@36 GHz & - & [36] \\ \cline{2-5}  & 0.14 dB@32 GHz & 70 dB@32 GHz & 22.5 V & [37] \\ \hline V & 0.1–0.19 dB & 30–36 dB & - & [36] \\ \hline W & 0.3–1.3 dB & 30–50 dB & 30 V & [38] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of MEMS switches using combinations of several switches in series in different bands.  
better than 30 dB through secondary isolation by using a combination of two bridges in series and a low insertion of 0.1-0.19 dB by covering a metal layer on the dielectric layer in the Q and V bands. The MEMS switch designed by [PERSON] (2016) achieved low insertion loss of 0.14 dB at 32 GHz and high isolation of 70 dB at 32 GHz based on a series-shunt configuration. The MEMS switch designed by [PERSON] et al. [PERSON] _et al._ (2017) achieved high isolation and low insertion loss in the W band using \(\pi\)-match with two bridges in series.