# Broadband Millimeter-Wave 5G Power Amplifier Design in 22 nm CMOS FD-SOI and 40 nm GaN HEMT
## 3 Results
### Single-Ended GaN (GaN #1) PA Measurement Results  
Figure 4 shows the final schematic of the single-ended broadband GaN PA as well as the _S-Parameter_ measurement vs. post-layout EM simulation. The EM simulations for the HRL GaN PDK are performed using Cadence's AXIEM in AWR to include all layout parasitic elements. This PA achieves maximum \(S_{2I}\) of 12.5 dB and a small-signal 3-dB BW of 18-38.7 GHz (absolute BW = 73.0%) at \(V_{DD}\) = 6 V, and \(S_{2I}\) = 10.3 dB with BW = 18-40.3 GHz (or an absolute BW = 76.5%) at \(V_{DD}\) = 4 V. Although not plotted here, _S-Parameter_ measurements with \(V_{DD}\) = 12 V shown in [13] achieved maximum \(S_{2I}\) = 13.0 dB with BW = 18.3-32.7 GHz (absolute BW = 56.5%). Thus, as the load-pull EM simulations had suggested, lowering the drain voltage makes this design more broadband. The \(S_{2I}\) modeling at \(V_{DD}\) = 4 V is not as accurate vs. \(V_{DD}\) = 6 V, which may be due to the 4 V model being constructed from  
Figure 3: Load-pull simulations of the (**a**) single-ended cascode device pair (with a 427 fF cap on the cascode gate) at (**b**) 24 GHz and (**c**) 37 GHz; and of the (**d**) differential cascode device pair with neutralization capacitors at (**e**) 24 GHz and (**f**) 37 GHz all at around \(OP_{1 dB}\). extrapolation whereas the 6 V models are directly from measurements. However, we do see that the \(S_{11}\) and \(S_{22}\) do match well with simulations for both supply voltages of 4 V and 6 V.  
The large-signal measurement results vs. post-layout EM simulations are shown in Figure 5 for \(V_{DD}\) = 4 and 6 V at 24, 28, and 44 GHz. This PA achieves a maximum \(\text{PAE}/P_{SAT}\) of 34.0%/18.6 dBm at 24 GHz, 42.1%/18.6 dBm at 28 GHz, and 21.6%/17.8 dBm at 44 GHz. With a 6 V supply, there is once again good agreement between the measurement and simulation data, and the PA achieves maximum \(\text{PAE}/P_{SAT}\) of 28.9%/20.1 dBm at 24 GHz, 34.6%/20.3 dBm at 28 GHz, and 19.1%/19.3 dBm at 44 GHz. Figure 6 shows the measured \(P_{OUT,SAT}\) and maximum PAE plotted across the frequency, which highlights the broadband performance of this PA as it is able to maintain greater than \(\sim\)20% PAE across the entire band of 18-40 GHz for \(V_{DD}\) = 4 V and greater than 14% PAE with \(V_{DD}\) = 6 V. The peak PAE for \(V_{DD}\) = 4 V is much higher at above 42% at 28 GHz. Figure 4: (**a**) Simplified schematics and the (**b**) micrograph of the broadband single-ended GaN PA (2.1 \(\times\) 0.88 mm\({}^{2}\) with pads) and its _S-Parameter_ EM PEX simulations vs. measurement with (**c**) \(V_{DD}\) = 4 V; and (**d**) \(V_{DD}\) = 6 V.  
Figure 5: Large-signal EM PEX simulation vs. CW measurement of the broadband single-ended GaN, PA with \(V_{DD}\) = 4 V at (**a**) 24, (**b**) 28, and (**c**) 44 GHz and \(V_{DD}\) = 6 V at (**d**) 24, (**e**) 28, and (**f**) 44 GHz. PA Linearity is then tested with 50, 100, 400, and 9 \(\times\) 100 MHz 256-QAM-modulated 5G NR inputs at PAPR (peak-to-average-power ratio) = 8.0 dB at 24 GHz and V\({}_{DD}\) = 4 V (Figure 7). With \(P_{OUT,AVE}\) = -11 dBm, this PA achieves ACLR \(-/+\) (adjacent channel leakage ratio) of \(-27.6/-27.0\) dBc with BW = 50 MHz (\(PAE_{AVE}\) = 13.3%), \(-27.4/-27.2\) dBc with BW = 100 MHz (\(PAE_{AVE}\) = 12.1%), \(-26.7/-26.8\) dBc with BW = 400 MHz (\(PAE_{AVE}\) = 11.8%), and \(-25.5/-26.0\) dBc with BW = 9 \(\times\) 100 MHz (\(PAE_{AVE}\) = 12.0%). The signal BW is varied from 50-900 MHz at 24, 28, 37, and 39 GHz, and the measured ACLR vs. BW is plotted in Figure 8 all at \(P_{OUT,AVE}\) -11 dBm when \(V_{DD}\) = 4 V, and \(P_{OUT,AVE}\) = -12 dBm with \(V_{DD}\) = 6 V. Figure 8 shows that there is not a significant degradation in the PA linearity increasing the 5G NR signal BW from 50 MHz to 9 \(\times\) 100 MHz at 28, 37, and 39 GHz, and only a slight degradation (\(\sim\)2 dBc) in the measured ACLR at 24 GHz for both \(V_{DD}\) = 4 V and 6 V. Additionally, there is minimal degradation on the linear output power, increasing from 24/28 GHz to 37/39 GHz.