<@U069XNVQM4H>, I am trying to design an LNA at 17...
# qucs-sa
Atif Ali 190021319
12/23/2024, 6:32 AM@Krzysztof Herman, I am trying to design an LNA at 170 GHz frequency using SG13G2. The Problem I am facing is the nan value of the minimum noise figure (min) at certain frequencies after matching input and output. The output side is conjugate-matched, and the input side is matched for minimum noise. I am attaching the figures so you can understand them better. Could you please help me solve these problems?
k
Krzysztof Herman
12/23/2024, 9:08 AMHi @Atif Ali 190021319 could you zip and share your testcase ? Seems to be a simulator problem.
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Atif Ali 190021319
12/23/2024, 9:32 AMThanks @Krzysztof Herman for your prompt reply. I am sharing the zip file here. I am using Ngspice-42 as the simulator. Please let me know if you need any additional information or files.
k
Krzysztof Herman
12/23/2024, 9:43 AMlet me reproduce the case
Krzysztof Herman
12/23/2024, 9:54 AMI have just resimulated using
ngspice 43Krzysztof Herman
12/23/2024, 9:56 AMplease upgrade your ngspice and use the latest version of the PDK
Krzysztof Herman
12/23/2024, 9:57 AMyou could also drop some suggestion about the features Qucs-S is lacking. We are trying to push the development of this tool to be able to design mmWave IC's
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Atif Ali 190021319
12/23/2024, 10:16 AMThanks for your suggestion
Atif Ali 190021319
12/24/2024, 4:30 AMHi @Krzysztof Herman Your suggestion worked perfectly for my circuit. The circuit was built using the inductor. I tried to build the circuit with transmission lines. I have used the s-parameter of transmission lines. Then again I faced the problem of 'nan" in the minimum noise figure (nfmin). This time I am using ngspice-43. Could you please give me some suggestions for this problem?
Atif Ali 190021319
12/24/2024, 4:37 AMI have attached a zip file containing the schematic and S2P files for the transmission lines. The S2P file names are marked in red within the schematic. I would greatly appreciate it if you could provide some insights into them.
k
Krzysztof Herman
12/28/2024, 8:47 AM@Atif Ali 190021319 I was able to reproduce your testcase and indeed got NaN. Please take a look here . The noise data can be implemented in the Touchstone file however I am not sure if ngspice supports this kind of format. I will ask. Anyway you could apply a superposition rule and treat the TL as noiseless components.
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Atif Ali 190021319
12/30/2024, 6:45 AMthanks for your suggestions
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