# High Linearity DC-38 GHz CMOS SPDT Switch
## 3 Results  
On-wafer three-port S-parameters measurement of the SPDT switch was conducted by a Keysight N5245A network analyzer. Figure 4a-c shows the measured S-parameters versus frequency characteristics of the SPDT switch in the condition of P1-to-P2 being on and P1-to-P3 being off. Figure 4a shows the measured \(\rm S_{11}\) and \(\rm S_{22}\) of the SPDT switch. At \(\rm V_{DD}\) (=\(\rm V_{G1}\))/\(\rm V_{SS}\) (=\(\rm V_{G2}\) = \(\rm V_{B}\)) of 2.5 V\(/-\)2.5 V, the SPDT switch achieves \(\rm S_{11}\) of \(-\)12.6\(\sim\)\(-\)26.8 dB for 0.1-6 GHz and \(-\)7.3\(\sim\)\(-\)26.8 dB for 0.1-38 GHz. The result is close to the measured one (\(-\)12.4\(\sim\)\(-\)25.8 dB for 0.1-6 GHz and \(-\)7.2\(\sim\)\(-\)25.8 dB for 0.1-38 GHz) for \(\rm V_{DD}/V_{SS}\) of 1.8 V\(/-\)1.8 V, and the one (\(-\)11.1\(\sim\)\(-\)26.8 dB for 0.1-6 GHz and \(-\)6.1\(\sim\)\(-\)26.8 dB for 0.1-38 GHz) for \(\rm V_{DD}/V_{SS}\) of 1.8 V\(/\)0 V. Moreover, at \(\rm V_{DD}/V_{SS}\) of 2.5 V\(/-\)2.5 V, the SPDT switch achieves \(\rm S_{22}\) of \(-\)12.5\(\sim\)\(-\)25.7 dB for 0.1-6 GHz and \(-\)6.9\(\sim\)\(-\)25.7 dB for 0.1-38 GHz. The result is close to the measured one (\(-\)12.5\(\sim\)\(-\)25.7 dB for 0.1-6 GHz and \(-\)6.9\(\sim\)\(-\)25.7 dB for 0.1-38 GHz) for \(\rm V_{DD}/V_{SS}\) of 1.8 V\(/\)\(-\)1.8 V, and the one (\(-\)12.5\(\sim\)\(-\)25.7 dB for 0.1-6 GHz and \(-\)6.9\(\sim\)\(-\)25.7 dB for 0.1-38 GHz) for \(\rm V_{DD}/V_{SS}\) of 1.8 V\(/\)0 V.  
Figure 4: Measured (**a**) \(\rm S_{11}\) and \(\rm S_{22}\); (**b**) \(\rm S_{21}\) and \(\rm S_{31}\); (**c**) \(\rm S_{33}\) and \(\rm S_{32}\), and (**d**) \(\rm IP_{1 dB}\) of the SPDT switch. Figure 4b shows the measured \(\mathsf{S}_{21}\) and \(\mathsf{S}_{31}\) of the SPDT switch. For \(\mathrm{V}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 2.5 V\(/\)\(-\)2.5 V, the SPDT switch achieves insertion loss of 0.4-1.4 dB for 0.1-6 GHz, 3.6-4.3 dB for 21-29 GHz, and 4.5-5.9 dB for 31-38 GHz. The result is close to the measured one (0.5-1.5 dB for 0.1-6 GHz, 3.8-4.6 dB for 21-29 GHz, and 4.8-6.4 dB for 31-38 GHz) for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V\(/\)\(-\)1.8 V, and better than the one (0.5-1.7 dB for 0.1-6 GHz, 4.5-5.6 dB for 21-29 GHz, and 5.9-7.9 dB for 31-38 GHz) for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V/0 V. Clearly, positive/negative gate-bias and negative body-bias are helpful for insertion-loss reduction, mainly due to the off-state series switch transistor M\({}_{4}\) being more close to being open. Moreover, the SPDT switch achieves isolation of 37.5-59.4 dB for 0.1-6 GHz, 25.7-28.7 dB for 21-29 GHz, and 24.3-25.2 dB for 31-38 GHz. The result is close to the measured one (35.7-60.3 dB for 0.1-6 GHz, 24.2-26.5 dB for 21-29 GHz, and 23-23.7 dB for 31-38 GHz) for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V\(/\)\(-\)1.8 V, and the one (35.6-60.3 dB for 0.1-6 GHz, 25.2-27.4 dB for 21-29 GHz, and 24.4-24.8 dB for 31-38 GHz) for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V/0 V.  
Figure 4c shows the measured \(\mathsf{S}_{33}\) and \(\mathsf{S}_{32}\) of the SPDT switch. For 0-38 GHz, the SPDT switch achieves \(\mathsf{S}_{33}\) of \(-\)1.99\(\dots\)\(-\)3.05 dB for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 2.5 V\(/\)\(-\)2.5 V\(/\)\(-\)2.32\(\dots\)\(-\)3.25 dB for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V\(/\)\(-\)1.8 V, and \(-\)1.84\(\dots\)\(-\)2.87 dB for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V\(/\)0 V, close to the ideal value of 0 dB (i.e., port 3 is short). Compared with V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 1.8 V\(/\)\(-\)1.8 V, better S\({}_{33}\) is achieved for V\({}_{\mathrm{DD}}\)/\(\mathrm{V}_{\mathrm{SS}}\) of 2.5 V\(/\)\(-\)2.5 V because transistors M\({}_{4}\) and M\({}_{5}\)/M\({}_{6}\) are closer to being open and short, respectively.