## 3 Results and Discussion of SPDT SW1  
The on-wafer S-parameter measurements of SPDT SW1 and SW2 were performed using a Keysight NS227B PNA microwave network analyzer, as shown in Figure 7. Figure 8a shows the measured and simulated IL (i.e., \(\mathrm{IS_{21}}\)l) and isolation (i.e., \(\mathrm{IS_{32}}\)l) of SPDT SW1 in the TX mode. SPDT SW1 achieves a measured minimum IL (\(\mathrm{IL_{min}}\)) of 0.58 dB at 24.8 GHz and an IL better than 1 dB for 17-34.9 GHz, corresponding to a 1 dB bandwidth (\(\mathrm{f_{1 dB}}\)) of 17.9 GHz. This result is close to the simulated one, i.e., an \(\mathrm{IL_{min}}\) of 0.47 dB at 25 GHz and an IL lower than 1 dB for 15.1-39.4 GHz, corresponding to an \(\mathrm{f_{1 dB}}\) of 24.3 GHz. This decent IL is attributed to the low loss of the equivalent \(\lambda\)/4-TL, the good TX-RX isolation, and the high impedance of the off-state DTMOS-R M\({}_{1}\). Moreover, SPDT SW1 achieves a measured maximum isolation (\(\mathrm{IS_{32}}\mathrm{l_{max}}\)) of 62.3 dB at 31.4 GHz and isolation of 25.6-62.3 dB for 17-34.9 GHz. This result is close to the simulated one, i.e., an \(\mathrm{IS_{32}}\mathrm{l_{max}}\) of 59.5 dB at 31.7 GHz and isolation of 27.7-59.5 dB for 17-34.9 GHz. Figure 8b shows the measured and simulated \(\mathrm{S_{11}}\) and \(\mathrm{S_{22}}\) of SPDT SW1 in the TX mode. SPDT SW1 achieves a measured minimum \(\mathrm{S_{11}}\) (\(\mathrm{S_{11,min}}\)) of \(-\)21.9 dB at 23.7 GHz and \(\mathrm{S_{11}}\) better than \(-\)15 dB for 18.4-31.4 GHz, equivalent to a \(-\)15 dB input matching bandwidth (\(\mathrm{f_{15 dB}}\)) of 13 GHz. This result is close to the simulated one, i.e., an \(\mathrm{S_{11,min}}\) of \(-\)37.6 dB at 25.9 GHz and an \(\mathrm{f_{15 dB}}\) of 16.4 GHz (18.8-35.2 GHz). Moreover, SPDT SW1 achieves a measured minimum \(\mathrm{S_{22}}\) (\(\mathrm{S_{22,min}}\)) of \(-\)30.6 dB at 26.8 GHz and an \(\mathrm{S_{22}}\) better than \(-\)15 dB for 18.9-39.2 GHz, equivalent to an \(\mathrm{f_{15 dB}}\) of 20.3 GHz. This result is close to the simulated one, i.e., an \(\mathrm{S_{22,min}}\) of \(-\)43.5 dB at 26.8 GHz and an \(\mathrm{f_{15 dB}}\) of 18.9 GHz (18.8-37.7 GHz). Figure 8c shows the measured and simulated IL (i.e., \(\mathrm{IS_{31}}\)l) and isolation (i.e., \(\mathrm{IS_{21}}\)l) of SPDT SW1 in the RX mode. SPDT SW1 achieves a measured \(\mathrm{IL_{min}}\) of 1.83 dB at 30.9 GHz and an IL of 1.83-2.1 dB for 25-38.3 GHz. This result is close to the simulated one, i.e., an \(\mathrm{IL_{min}}\) of 1.33 dB at 38.4 GHz and an IL of 1.33-2.1 dB from 26.6 GHz to over 50 GHz. Moreover, SPDT SW1 achieves a measured isolation of 24.5-27 dB for 25-38.3 GHz. This result is close to the simulated one, i.e., an isolation of 22.2-25.1 dB for 25-38.3 GHz. Figure 7: Measurement setup of SPDT SW1 and SW2. Figure 8d shows the measured and simulated S\({}_{11}\) and S\({}_{33}\) of SPDT SW1 in the RX mode. SPDT SW1 achieves a measured S\({}_{11,\min}\) of \(-14.7\) dB at 30.9 GHz and an S\({}_{11}\) better than \(-10\) dB for 20.7-50 GHz, corresponding to an f\({}_{10\text{dB}}\) of 29.3 GHz. This result is consistent with the simulated one, i.e., an S\({}_{11,\min}\) of \(-12.7\) dB at 36.8 GHz and an f\({}_{10\text{dB}}\) of 17.7 GHz (29.1-46.8 GHz). Moreover, SPDT SW1 achieves a measured minimum S\({}_{33}\) (S\({}_{33,\min}\)) of \(-30.4\) dB at 29 GHz and an S\({}_{33}\) better than \(-10\) dB for 18.1-44.9 GHz, equivalent to f\({}_{10\text{dB}}\) of 26.8 GHz. This result is consistent with the simulated one, i.e., an S\({}_{33,\min}\) of \(-31.1\) dB at 32.4 GHz and an f\({}_{10\text{dB}}\) of 25.6 GHz (20.9-46.5 GHz). Figure 9a shows the measured and simulated power gain S\({}_{12}\) (i.e., P\({}_{\text{out}}\)\(-\)P\({}_{\text{in}}\) in dBm) against the input power (P\({}_{\text{in}}\)) characteristics of SPDT SW1 at 28 GHz in the TX mode. That is, DTMOS-R M\({}_{1}\) and M\({}_{2}\) (controlled by V\({}_{\text{sw1}}\)) are in the off-state and M\({}_{3}\) (controlled by V\({}_{\text{sw2}}\)) is in the on-state.