# Broadband Millimeter-Wave 5G Power Amplifier Design in 22 nm CMOS FD-SOI and 40 nm GaN HEMT
## 3 Results
### Differential Cascode CMOS PA Measurement Results  
Figure 12 presents the schematic of the differential cascode CMOS PA designed in the 22 FDX technology and the small-signal _S-parameter_ measurement data compared to post-layout PEX simulations of this PA. Layout parasitic elements for this design were extracted using Mentor Graphic's Calibre \(R+C+CC\) extraction. Small-signal measurement data agree well with the PEX simulations, exhibiting excellent broadband performance. PEX simulations achieve a maximum \(S_{21}\) small-signal gain of 17.4 dB with 3-dB BW of 20.5-47.4 GHz (or an absolute BW of 79.2%), while measurement achieves a 3-dB BW of 19.1-46.5 GHz and a maximum \(S_{21}=16.4\) dB (absolute BW of 83.5%). The RC feedback network allows for adequate input matching with \(S_{11}<-5.5\) dB across the entire \(\sim\)27 GHz band in both simulation and measurement values. Thus, measurement data display virtually no degradation on the targeted small-signal broadband BW to cover the entire key 5G FR2 band of 24.25-43.5 GHz, as indicated by the PEX simulations, and only minimal degradation in measured vs. the simulated values of small-signal gain. The effect of the RC feedback on this differential CMOS SOI PA design is also simulated here in post-layout PEX simulations in Figure 12d, where the original design is compared to the same design with the only change being that the RC feedback is removed (and the PA layout is re-extracted and re-simulated). Here, it shows that the overall gain is reduced by \(\sim\)2 dB when RC feedback is added, as this PA without the RC feedback achieves a maximum \(S_{21}=19.6\) dB. However, the BW is increased when RC feedback is added, as, without it, the 3-dB BW decreases to 20.9-39.6 GHz (or an absolute BW of 61.8%). Thus, the absolute BW is degraded by \(\sim\)15% without the RC feedback, and the input/output matching worsened considerably as well. Figure 11: EM PEX simulated maximum PAE, \(S_{21}\), and \(P_{OUT,SAT}\) vs. frequency of the broadband differential GaN PA.  
Figure 10: Large-signal EM PEX simulations of the broadband differential GaN PA for CW inputs at (a) 24, (b) 28, and (c) 44 GHz. The large-signal measured data vs. PEX simulation results at 24/28/44 GHz are shown in Figure 13, where degradation in the large-signal measurement data from simulations is seen, likely due to inaccuracies in the large-signal transistor modeling. These figures show that at 44 GHz, the measured gain is 3 dB higher than those of the PEX EM simulations. The measured gain values are usually reduced by 1-2 dBs from the simulated data at 24-39 GHz, while at 24/28/44 GHz this broadband PA achieves measured \(OP_{1 dB}\) of 11.5/9.2/7.4 dBm with PAE@\(OP_{1 dB}\) of 18.6%/11.2%/9.3%, \(P_{SAT}\) of 14.6/14.0/10.9 dBm, and maximum PAE of 26.1%/19.9%/12.5 %, respectively. Figure 12: (**a**) Simplified schematics and (**b**) micrograph of the broadband 22 nm CMOS FD-SOI PA (620 \(\upmu\)m \(\times\) 500 \(\upmu\)m with pads); (**c**) its _S-Parameter_ post-layout PEX simulations vs. measurement; and (**d**) a comparison of its PEX _S-parameters_ simulations with and without the RC feedback. Figure 13: _Cont._  
Figure 14 plots the measured maximum PAE, \(S_{21}\), and \(P_{OUT,SAT}\) vs. the frequency from 20-44 GHz, which shows this PA maintains a maximum PAE \(\geq\) 12.5% and \(P_{OUT,SAT}\)\(\geq\) 11 dBm across this frequency range.