## 4 Simulation Results
### Large-Signal Characterization  
Figure 10a demonstrates that P1 dB lies between 30.5 dBm and 31.8 dBm, peaking at 27 GHz, with the corresponding PAE ranging from 31.3% to 37.6% over the 24-31 GHz band. Both of them follow the trend of higher values near the band center and lower values at the band edges. By contrast, P4 dB exceeds 32.3 dBm, with a maximum in-band fluctuation of only 0.4 dB, and the associated PAE increases to a range of 35.5-37.8%. Figure 10b presents the power sweep characteristics of the PA, showing that the best performance is achieved at the center frequency, where the peak PAE approaches 40% at an input power (P\({}_{\text{in}}\)) of 15 dBm, corresponding to P2 dB. The responses at low and high frequencies are similar, with the PA reaching a saturation state and the maximum PAE as P\({}_{\text{in}}\) nears the 4 dB compression point.  
Under the preset bias conditions, the quiescent current of the two-stage PA is 179 mA, as described in Figure 11a. The total DC consumption rises markedly as P\({}_{\text{out}}\) increases beyond 25 dBm, especially in the saturation region, where it peaks at nearly 450 mA. Similar current profiles are obtained at the three representative frequencies, indicating consistent power consumption over the band of interest. Figure 11b displays the IMD3 performance of the PA under two-tone power sweep simulations at 24 GHz, 27.5 GHz, and 31 GHz. The best overall linearity occurs at the center frequency, where the single-tone P\({}_{\text{out}}\) at an IMD3 of \(-\)25 dB is about 25.6 dBm.  
Figure 9: The simulated (a) S\({}_{21}\), (b) S\({}_{11}\), and (c) S\({}_{22}\) at different temperatures.  
Table 4 summarizes the performance of this work and compares it with recently reported GaAs and GaN PAs operating in similar frequency bands. To enable a comprehensive and relatively robust and fair assessment, a figure of merit (FoM) is introduced, which incorporates all of the parameters listed in the table and considers both high performance and consistency. The FoM is defined as follows:  
\[\text{FoM}=\frac{\text{FBW}(\%)\times\overline{\text{P}_{\text{out}}}(\text{W} )\times\overline{\text{P}\text{A}\text{E}}(\%)}{\text{Area}(\text{mm}^{2}) \times V_{\text{DD}}(\text{V})\times\prod_{\text{i}}\left(1+\frac{\Delta x_{ \text{i}}}{\overline{x_{\text{i}}}}\right)} \tag{21}\]  
where FBW is the fractional bandwidth, \(V_{\text{DD}}\) denotes the supply voltage, and \(\Delta x_{\text{i}}\) and \(\overline{x_{\text{i}}}\) refer to the in-band fluctuation and the mean of each metric (\(\text{P}_{\text{out}}\), PAE, and gain), respectively. Note that the gain must be converted from its logarithmic ratio into a linear value before being used in calculations. In contrast to conventional FoM formulas, the cumulative multiplication term added to the denominator serves for evaluating the overall flatness of both large- and small-signal responses, while the use of the average rather than the maximum values for \(\text{P}_{\text{out}}\) and PAE in the numerator underscores the importance of a balanced broadband performance. The inclusion of the \(V_{\text{DD}}\) product term in the denomi  
Figure 11: The simulated (**a**) total DC consumption versus \(\text{P}_{\text{out}}\); (**b**) two-tone power sweep with a 100 MHz frequency spacing.  
Figure 10: The simulated (**a**) \(\text{P}_{\text{out}}\) and PAE at 1 dB and 4 dB compression points; (**b**) \(\text{P}_{\text{out}}\), PAE, and gain behaviors with respect to \(\text{P}_{\text{in}}\).  
nator improves the comparability among varying technologies and supply voltages. As evidenced in Table 4, the proposed mmWave PA demonstrates a superior FoM, achieving the smallest chip size and excellent frequency consistency under similar conditions, reflecting its advanced comprehensive performance.