## 4 Simulations and Measurements
For 5G communication systems, the LO frequency is often changed, rather than working at a fixed frequency. Therefore, within the design range, we simulated and measured the LO frequencies from 16 GHz to 24 GHz in steps of 1 GHz. When the LO frequency is 16 GHz, the IF band is 8-11 GHz, and the CG is \(-\)2.3 \(\pm\) 1.5 dB; when the LO frequency is 17 GHz, the IF band is 7-11 GHz, and the CG is \(-\)2.5 \(\pm\) 1.5 dB; when the LO frequency is 18 GHz, the IF band is 6-10 GHz, and the CG is \(-\)2.7 \(\pm\) 1.6 dB; when the LO frequency is 19 GHz, the IF band is 5-10.5 GHz, and the CG is \(-\)2.7 \(\pm\) 1.6 dB; when the LO frequency is 20 GHz, the IF band is 4-9.5 GHz, and the CG is \(-\)2.7 \(\pm\) 1.6 dB; when the LO frequency is 21 GHz, the IF band is 3-8.5 GHz, and the CG is \(-\)2.8 \(\pm\) 1.6 dB; when the frequency is 22 GHz, the IF band is 3-7.5 GHz, and the CG is \(-\)3.0 \(\pm\) 1.5 dB; when the LO frequency is 23 GHz, the IF band is 3-6.5 GHz, and the CG is \(-\)2.9 \(\pm\) 1.3 dB; when the LO frequency is 24 GHz, the IF band is 3-5.5 GHz, and the CG is \(-\)3.4 \(\pm\) 0.9 dB. The results show that the mixers all show good CG performance under different LO frequencies without large loss, and the flatness is acceptable within a certain frequency range. Figure 16: Simulated and measured return losses of (**a**) RF port (S\({}_{11}\)), (**b**) LO port (S\({}_{22}\)) and (**c**) IF port (S\({}_{33}\)). (**d**) Simulated and measured CG versus LO power while RF frequency and LO frequency are 27 GHz and 20 GHz, respectively. The effect of the linearity improvement is shown in Table 3. To demonstrate the effectiveness of this method, we selected different frequency combinations to simulate and measure the CG curves. Under nine different operating frequencies, the mixer's simulation and measurement compression curves are displayed. As the input RF power increases, \"reverse uplift\" appears before gain compression, which aligns with the aforementioned theoretical analysis. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**LO Frequency** & **16 GHz** & **17 GHz** & **18 GHz** \\ \hline
**Simulated and measured CG versus** & & & \\
**RF frequency** & & & \\ \hline
**LO Frequency** & & & \\ \hline
**Simulated and measured CG versus** & & & \\
**RF frequency** & & & \\ \hline
**LO Frequency** & & & \\ \hline
**Simulated and measured CG versus** & & & \\ \hline
**LO Frequency** & & & \\ \hline
**Simulated and measured CG versus** & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulated and measured CG versus RF frequency under different LO frequencies. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Frequency** & **RF: 24 GHz; LO:** & **RF: 24 GHz; LO:** & **RF: 24 GHz; LO:** \\
**17 GHz; IF: 7 GHz** & & **18 GHz; IF: 6 GHz** & **19 GHz; IF: 5 GHz** \\ \hline
**Simulated and measured CG versus** & & & \\ \hline
**RF power** & & & \\ \hline
**Frequency** & & & \\ \hline
**Simulated and measured CG versus** & & & \\ \hline
**RF power** & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulated and measured CG versus input power under nine different RF/LO/IF frequencies. The IP1 dB simulation and measurement results are shown in Table 4. Under the condition that the LO frequency is from 16 to approximately 24 GHz and the step is 1 GHz, the results show the high linearity of the proposed mixer. The measurement results show that this new linearization method improved the IP1 dB effectively. In the IF range of 3-11 GHz, an IP1 dB of + 7.2\(\sim\)+10.7 dBm is achieved. At the same time, an ultra-high OP1 dB is achieved, far exceeding other similar works under the silicon-based process because this linearization does not reduce the conversion gain significantly, and an average OP1 dB can reach +5.4 dBm. The simulated curves of fundamental and third-order products are shown in Figure 17a, and the simulated IIP3 versus RF power is shown in Figure 17b.