# A 2-V 1.4-dB NF GaAs MMIC LNA for K-Band Applications
## 4 Simulation Results  
Post-layout scattering (S-parameters) and noise parameters were simulated using Keysight's Advanced Design System software and the Momentum EM simulator at room temperature. The resulting \(\mid\)\(S_{11}\)\(\mid\) and \(\mid\)\(S_{22}\)\(\mid\) as well as the gain and NF are depicted in Figure 5(a),b. The proposed LNA presents an IRL better than 10 dB from 23.5 to 28.5 GHz and an output return loss better than 5 dB. A maximum gain of 34 dB is obtained at 24 GHz, and an NF below 1.4 dB is obtained from 24 GHz to 28 GHz with a minimum value of 1.3 dB at 26.5 GHz.  
Figure 5: Layout and current distribution (**a**), and inductance, and quality factor (**b**) for the inductors employed in stages 3 and 4.  
The value of the Rollet's stability factor \(k\) is shown in Figure 7. As seen, the \(k\)-factor is above one from 0 to 30 GHz, with a minimum of 3.5 at a frequency of 24.3 GHz. Individual stability was also checked for each stage and for the whole four-stage amplifier, concluding that the LNA is unconditionally stable. The NF of the LNA was simulated for different temperature values (-40 \({}^{\circ}\)C, 16.85 \({}^{\circ}\)C and 125 \({}^{\circ}\)C), as shown in Figure 7. As expected, the best results are observed at the lowest temperature, with a minimum NF as good as 1.2 dB at 25.5 GHz. On the other hand, at 125 \({}^{\circ}\)C the LNA presents a minimum NF of 1.6 dB at 26 GHz.  
The results of the single- and two-tone non-linear simulations for the proposed 4-stage GaAs LNA are shown in Figure 8. The gain compression of the LNA at 26 GHz is presented in Figure 8, and the input and output third order intercept points (IIP3 and OIP3) are shown in Figure 8, where two tones with 200 MHz spacing from a central frequency of 26 GHz were used. The GaAs LNA achieves an output power 1 dB-compression point (\(P_{\rm 1 dB}\)) of \(-\)18 dBm, an IIP3 of \(-\)4.5 dBm and an OIP3 of 24.5 dBm.  
Figure 6: Input and output return loss (**a**), and gain and NF (**b**) of the proposed LNA from 20 to 30 GHz.  
Figure 7: Stability factor (**a**), and NF for \(-\)40 \({}^{\circ}\)C, 16.85 \({}^{\circ}\)C and 125 \({}^{\circ}\)C (**b**) of the proposed GaAs LNA.  
A Monte Carlo analysis with 250 samples was also carried out to verify the results vary within an acceptable range. The histograms representing the input return loss, output return loss, gain and NF of the circuit are shown in Figure 9. As seen, the input return loss is better than 10 dB for all the samples, the output return loss is better than 5 dB for most of the samples, the gain is between 32 and 33 dB, and the NF is better than 1.4 dB for most of the samples.  
To better understand how the proposed circuit performs in contrast to other works available in the literature, the small-signal figure of merit (\(FoM_{SS}\)) defined in (12) is introduced [5]. A concise comparison with similar works available in the literature along with the main results of the proposed LNA are given in Table 1. The results of the proposed circuit are superior to most of the GaAs LNAs reported in the literature and are superior to the SOI LNA proposed in [16]. As seen in Table 1, although the 4-stage LNA presents a  
Figure 8: Output 1-dB compression point (\(P_{\rm 1 dB}\)) (**a**), and output third order intercept (OIP3) (**b**) of the proposed GaAs LNA.  
Figure 9: Monte Carlo results for 250 samples of the proposed 4-stage GaAs LNA.  
power consumption and area in line with most of the proposals available in the literature, it achieves one of the highest gains and lowest NFs reported, this combination results in the best \(FoM_{SS}\) compared with the other proposals.  
\[FoM_{SS}=\frac{G}{NF-1} \tag{12}\]