# 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
#### 3.1.1 MEMS Switches with Serpentine Flexure Structures in Different Frequency Bands  
Serpentine flexure structures reduce the spring constant and increase the series inductance of the MEMS bridge, thereby achieving high isolation and low-actuation voltage. Table 1 summarizes the performance parameters of MEMS switches using the bridges with serpentine flexure structures in different frequency bands recently.  
MEMS switches with serpentine flexure structures in centimeter band have been reported in [25; 26; 27; 28]. [PERSON] et al. [25] designed a single-bridge MEMS capacitive switch and a double-bridge MEMS capacitive switch with serpentine folded suspensions to achieve higher isolation at X-band frequencies, and the measurement results presented an isolation of 16.5-28 dB for the single-bridge switch and 25-35 dB  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Band** & **Insertion Loss** & **Isolation** & **Actuation Voltage** & **Reference** \\ \hline \multirow{4}{*}{centimeter} & 0.35 dB@13 GHz & 37 dB@10 GHz & 3.6 V & [25] \\ \cline{2-5}  & 0.2 dB@15 GHz & 23.57 dB@15 GHz & 10 V & [26] \\ \cline{2-5}  & 0.4 dB@10 GHz & 28 dB@10 GHz & - & [27] \\ \cline{2-5}  & 0.4 dB@20 GHz & 80 dB@20 GHz & 2.45 V & [28] \\ \hline \multirow{2}{*}{Q} & 0.82 dB@40 GHz & 70 dB@40 GHz & 6.25 V & [29] \\ \cline{2-5}  & 0.29 dB@35 GHz & 20.5 dB@35 GHz & 18.3 V & [30] \\ \hline \multirow{2}{*}{V} & 9.2 dB@55 GHz & 23 dB@55 GHz & 2.9 V & [31] \\ \cline{2-5}  & 7.25 dB@60 GHz & 27.29 dB@60 GHz & 3.53 V & [32] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of MEMS switches with serpentine flexure structures in different bands.  
Figure 1: The schematics of typical microelectromechanical systems (MEMS) switches: (**a**) shunt capacitive MEMS switch; (**b**) DC contact switch. Coplanar waveguide (CPW) = coplanar waveguide.  
for the double-bridge switch at 10-13 GH. [PERSON] et al. [26] designed a MEMS switch with a bridge supported by four springs, and it achieved an insertion loss of 0.19 dB at 10 GHz and 0.2 dB at 15 GHz and an isolation of 27.17 dB at 10 GHz and 23.57 dB at 15 GHz. [PERSON] et al. [27] designed a MEMS switch with four folded springs. The isolation was 28 dB at 10 GHz, and the insertion loss was 0.4 dB at 10G Hz. High isolation of 80 dB at 20 GHz, low insertion loss of 0.4 dB, and low-driving voltage of 2.45 V were achieved in the capacitive MEMS switch designed using serpentine flexure bridge with holes and a dielectric layer made of HfO\({}_{2}\) with a spring constant of 25 [28].  
Bridges with low elastic constant were designed in [29; 30; 31; 32] to realize the low-actuation voltage and high isolation of MEMS capacitive switches using folded beams in the millimeter-wave band.  
A serpentine flexure structure with a large series inductance in a MEMS switch was designed by [PERSON] et al. [29], leading to a low-driving voltage of 6.25 V and a high isolation of 70 dB at 40 GHz. A novel capacitive MEMS switch with low insertion loss of 0.29 dB@35 GHz was presented by [PERSON] et al. [30] in which the utilizing membrane was connected to the anchors by four springs. Both MEMS capacitive switches proposed by [PERSON] et al. [31; 32] achieved high isolation and low-actuation voltage using folded beams in the V band, but due to the small air gaps and small thickness of the CPW line, the switches had excessive insertion loss, which was caused by the conductor and microbridge. Detailed results are shown in Table 1.