A New GaN HEMT Small-Signal Model Considering Source via Effects for 5G Millimeter-Wave Power Amplifier Design
Round 1
Reviewer 1 Report
Dear Author,
this paper introduces a new small-signal model that predicts with very high accuracy S-parameters, MAG and stability factor of GaN HEMTs. The model is verified with the simulation for three different bias points, with good results. I really liked the results obtained, and have some few concerns:
1) In Introduction, line 31, you miss other state-of-the-art publications for MMIC GaN power amplifiers for very high frequencies, such as: "D-Band and G-Band High performance GaN Power Amplifier MMICs" DOI:10.1109/TMTT.2019.2936558
2) For the Smith-Charts it would be good to indicate the direction of the increment in the frequency, for example with an arrow, so that readers know where 1 GHz begins (right in the Smith-Chart) and which point corresponds to 120 GHz. Also it would be good to indicate the port numbers in Figs. 6 and Fig. 5 (it helps for better clarification in the S, Z and Y parameters).
3) Regarding the Smith-Chart and Phase EM Simulations in Figs. 4 and 10. it looks like ideal simulations were performed, as no losses in S11 parameters are appreciated. How is this possible if they were EM simulations (for example in Figs 11-14 in contrast we can appreciate the expected insertion losses)? Why is the change in Phase from -180° to +180° at around 45 GHz produced (phase S11 in Fig. 10), and why is this phase change not seen in the smith-chart?
4) In the measurement setup it would be interesting to mention how the measurements of the stability factor and MAG were performed. Measurements of S-parameters are very well know, but few researchers measure K and MAG.
Author Response
I am appreciate your valuable comments. Thanks to your comments, I responded to all comments as sincerely as possible and were able to further develop the insufficient paper. I hope that my research will be published in this journal.
Thank you so much again.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper proposed a new GaN HEMT small-signal model considering source-via effects. However, some data should be further clarified or demonstrated.
Here are the comments:
- From Fig. 2, the Cds1 and Lds branch should connects to the external source terminal, not the internal source as shown in Fig. 5(b). Please explain it and indicate Cds1, Lds, Cds2, Rs, and Ls components in Fig. 2, which consist with the small-signal equivalent circuit in Fig. 5(b).
- In page 6, the author mentions that the layers constituting the gate part are not included in the EM substrate setup, but in Fig 7, we can see the gate part in the EM simulation structure. Please give a more clear demonstration.
Author Response
Dear reviewers,
I am appreciate your valuable comments. Thanks to your comments, I responded to all comments as sincerely as possible and were able to further develop the insufficient paper. I hope that my research will be published in this journal.
Thank you so much again.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
This revised version could be published.
