## 3 Results and Discussion of SPDT SW1
SPDT SW1 achieves a measured S\({}_{12}\) of \(-0.67\) dB at a low P\({}_{\text{in}}\) of 0 dBm and an S\({}_{12}\) of \(-1.67\) dB at a high P\({}_{\text{in}}\) of 28.5 dBm. The corresponding P\({}_{\text{1 dB}}\) is 28.5 dBm. This result is consistent with the simulated one, i.e., an S\({}_{12}\) of \(-0.52\) dB at a low P\({}_{\text{in}}\) of 0 dBm and an S\({}_{12}\) of \(-1.52\) dB at a high P\({}_{\text{in}}\) of 30.6 dBm, corresponding to simulated P\({}_{\text{1 dB}}\) of 30.6 dBm. The decent P\({}_{\text{1 dB}}\) performance of SPDT SW1 in the TX mode is mainly attributed to the novel SPDT switch topology and the adoption of DTMOS-R switch transistors. This can be explained in more detail as follows. In contrast to the traditional common-source (CS) switch transistors using a V\({}_{\text{sw1}}\) / V\({}_{\text{sw2}}\) of 0/V\({}_{\text{DD}}\) and a body voltage of 0 V, DTMOS-R M\({}_{1}\) and M\({}_{2}\) achieve a better off-states due to higher off-state channel/substrate resistance (R\({}_{\text{off,ch}}\)/R\({}_{\text{off,sub}}\)) because of a higher threshold voltage (V\({}_{\text{th}}\)) and the suppression of substrate leakage (I\({}_{\text{B}}\)). Moreover, DTMOS-R M\({}_{3}\) achieves a better on-state due to lower on-state channel/substrate resistance (R\({}_{\text{on,ch}}\)/R\({}_{\text{on,sub}}\)) because of a lower V\({}_{\text{th}}\), i.e., a higher over-drive voltage V\({}_{\text{ov}}\) (=V\({}_{\text{gs}}\)\(-\)V\({}_{\text{th}}\)). In other words, a higher P\({}_{\text{in}}\) (with a more negative peak voltage) is required to conduct the off-state shunt/series M\({}_{1}\)/M\({}_{2}\). This leads to a high P\({}_{\text{1 dB}}\) in the TX mode. Moreover, the high P\({}_{\text{1 dB}}\) of 28.5 dBm is partly due to the prominent TX-to-RX isolation of 62.3 dB (see Figure 8a). Figure 8: Measured and simulated (**a**) IL and isolation and (**b**) S\({}_{11}\) and S\({}_{22}\) of SPDT SW1 in the TX mode. Measured and simulated (**c**) IL and isolation and (**d**) S\({}_{11}\) and S\({}_{33}\) of SPDT SW1 in the RX mode. Figure 9b shows the measured and simulated power gain \(S_{31}\) against \(P_{in}\) the characteristics of SPDT SW1 at 28 GHz in the RX mode. That is, DTMOS-R \(M_{1}\) and \(M_{2}\) are in the on-state and \(M_{3}\) is in the off-state. SPDT SW1 achieves a measured \(S_{31}\) of \(-1.9\) dB at a low \(P_{in}\) of 0 dBm and \(-2.9\) dB at a high \(P_{in}\) of 24 dBm. The corresponding \(P_{1\mathrm{dB}}\) is 24 dBm. This result is consistent with the simulated one, i.e., an \(S_{12}\) of \(-1.91\) dB at a low \(P_{in}\) of 0 dBm and an \(S_{12}\) of \(-2.91\) dB at a high \(P_{in}\) of 25.4 dBm, corresponding to a simulated \(P_{1\mathrm{dB}}\) of 25.4 dBm. This decent \(P_{1\mathrm{dB}}\) performance of the SPDT switch in the RX mode is also attributed to the novel SPDT switch topology and the adoption of DTMOS-R switch transistors. Figure 10a shows the measured fundamental (\(P_{out}\)) and third-order intermodulation output power (IM3) versus the \(P_{in}\) characteristics of SPDT SW1 in the TX mode at 28 GHz. SPDT SW1 achieves an excellent IIP3 of 38.5 dBm. Figure 10b shows the measured P1 dB and IIP3 versus the frequency characteristics of SPDT SW1 over the 24.25-29.5 GHz (N257/N258) 5G mm wave band. SPDT SW1 achieves a \(P_{1\mathrm{dB}}\) of 28-29 dBm and an IIP3 of 38.1-39 dBm in the TX mode, and a \(P_{1\mathrm{dB}}\) of 24-24.8 dBm and an IIP3 of 34.1-35 dBm in the RX mode. This result is reasonable since it is consistent with the theoretical analysis, i.e., IIP3 is about 9.6 dBm larger than \(P_{1\mathrm{dB}}\)[17].