## 4 Experimental Result  
The proposed 26-30 GHz GaN HEMT LNA MMIC that adopts the series inductor-based stability enhancement technique was fabricated using 0.15-\(\upmu\)m GaN-on-SiC technology, and its performance was demonstrated from bare-die measurements. Figure 8 shows a die microphotograph of the implemented design, which occupies an active area of 2.61 mm \(\times\) 1.02 mm (2.66 mm\({}^{2}\)), including bonding pads. All test measurements were conducted using a single die via on-wafer probing. RF signals were injected externally and measured at the RF input and output ports, respectively, using GSG-type probes, whereas the required gate and drain bias voltages were supplied through GPPPG-type DC probes. The overall insertion loss arising from the cables and probes was measured at the desired frequencies and used to compensate for the measured results. Figure 9 shows the measurement setups for the S-parameter, NF, and linearity performance characterization, focusing on band n257 and band n261 of the 5G NR FR2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Components** & **Values** & **Components** & **Values** \\ \hline L\({}_{\text{SE}}\) & 510 pH & C\({}_{\text{B1}}\) & 3.16 pF \\ \hline R\({}_{\text{G}}\) & 202 \(\Omega\) & C\({}_{\text{B2}}\) & 0.56 pF \\ \hline R\({}_{\text{B}}\) & 202 \(\Omega\) & C\({}_{\text{BLK}}\) & 0.36 pF \\ \hline W\({}_{\text{TL}}\) & 15 \(\upmu\)m & L\({}_{\text{S1}}\), L\({}_{\text{S2}}\), L\({}_{\text{S3}}\) & 130 \(\upmu\)m \\ \hline L\({}_{\text{IN1}}\) & 250 \(\upmu\)m & L\({}_{\text{IN2}}\) & 280 \(\upmu\)m \\ \hline L\({}_{\text{INT1}}\) & 160 \(\upmu\)m & L\({}_{\text{INT2}}\) & 240 \(\upmu\)m \\ \hline L\({}_{\text{INT3}}\) & 176 \(\upmu\)m & L\({}_{\text{INT4}}\) & 860 \(\upmu\)m \\ \hline L\({}_{\text{OUT1}}\) & 120 \(\upmu\)m & L\({}_{\text{OUT2}}\) & 459 \(\upmu\)m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values of the utilized components. Figure 8: Die microphotograph of the implemented GaN HEMT-based low-noise amplifier. Figure 10 shows the measured and simulated S-parameter results, which include the small-signal gains (S21s) and input and output return losses (S11s and S22s). The designed LNA achieves a maximum small-signal gain of 20.2 dB with a 1-dB bandwidth of approximately 7 GHz (23.6-30.3 GHz). As is also seen from Figure 10, a gain degradation of 2-3 dB is observed in comparison with the simulation results. This is mainly caused by a slight deviation from the optimal matching condition. The attained return loss results are less than -10 dB over the 26-30 GHz frequency range. Figure 9: Measurement configurations: (**a**) a block diagram of the S-parameter, noise figure, P1 dB, and IIP3 performance measurements and (**b**) a probe station setup. To primarily validate the stability performance improvement of the designed LNA over the frequency range, \(\mu\) values were calculated from the measured S-parameter values, and the results are presented in Figure 11 along with the simulated \(\mu\) values. It is noted that \(\mu\) enhancement is achieved with the peak value of \(\mu\) = 7.68 at 27.6 GHz, even if the peak frequency is slightly shifted to a lower frequency in comparison with the simulated stability results. Moreover, the designed LNA with the stability enhancement technique achieves an unconditionally solid stable condition, where \(\mu\) is greater than 1 over the frequency range of 20-35 GHz. The measured and simulated NFs of the designed LNA, shown in Figure 12, range from 2.42 to 2.56 and 1.5 to 1.6 dB, respectively, in the operating frequency. The measured NFs of the implemented design are approximately 0.9 dB higher than the simulated NFs owing to the degraded small-signal gain and deviated noise-matching condition. Figure 11: Measured and simulated stability \(\mu\) values of the LNA. Figure 10: Measured and simulated small signal gains, \(S11\)s and \(S22\)s of the LNA.