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LNA Design with Cadence
Dec 08^th, 2007, 12:38pm

In my thesis (that I just began), I must design a chip wich contains a Filter + LNA. I�m new to Cadence (also to LNA) . After 1 Week of reading Tutorials, I have some Questions for experts.
lets begin with this Questions:
1- there are many possible simulations in Cadence, so which I will probably need exactly for LNA
2- is a Simulation with Spectre sufficient or first after simulating a Layout you can make solid conclusions

thank you!

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didac

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Re: LNA Design with Cadence
Reply #1 - Dec 8^th, 2007, 1:02pm

Hi,
1)You will need: DC(for operating points,biasings...),AC(voltage gain),PSS(for CP1dB,IIP3-PSS+PAC or QPSS-),noise(for NF), SP(input matching,stability,also can be used for transducer gain,NF...), and I don't know if I forgot anything.
2)My experience say that if the models of the library are good silicon and a full simulation of the extracted circuit with parasitics after the layout match pretty well.
PS:check http://www.cadence.co.in/community/virtuoso/resources/SpectreRF_LNA533AN.pdf as reference.
Hope it helps,

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RadioFreeq

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Re: LNA Design with Cadence
Reply #2 - Dec 8^th, 2007, 1:23pm

thanks for the link.

I�m working in a company which has good modles surely.. there is a multichip package with 1 Filter and 1 LNA in it, and they are matched with external passives. Filter output is matched to 50 Ohm and so the input for LNA and the Chip has NF: 1.9 and Gain>19dB.... So my job is to change the Filter and the LNA and match them in a way (not 50 OHM) to have the best performance (NF, GAIN, Linearity, Consumption..) without much external elements. My supervisor says, I must simulate, play with the different configurations...

How can you estimate the complexity of this task, and what do you think are the appropriate tools (if cadence is essential or just ADS)?

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didac

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Re: LNA Design with Cadence
Reply #3 - Dec 8^th, 2007, 1:35pm

Hi,
I think that both ADS and Cadence are suitable for this job, although for what I understand you have a System in Package so maybe ADS it's a little bit more suitable for the transmission line modelling between filter and LNA, depending on the frequency you should be able to eliminate completely external components using transmission lines for the matching network. I think that in your case I will start plotting the NF,stability and gain circles of the LNA and find the trade-off between them, this can be done with S-parameters only, for the linearity you need the LNA spice model(that can be used in ADS and Cadence).
Hope it helps,

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Jess Chen Community Fellow Offline Posts: 380 California Bay Area	Re: LNA Design with Cadence Reply #4 - Dec 9^th, 2007, 3:33pm RadioFreeq, Cool username and picture. I love it!! -Jess
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