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Jun 19th, 2019, 10:12am
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NF simulation using out-of-band blocker (SpectreRF) (Read 116 times)
Guilherme Theis
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NF simulation using out-of-band blocker (SpectreRF)
May 21st, 2019, 6:56am
 
Hello,

I should start saying I know basics from SpectreRF simulations. I am simulating a wideband LNA with a switched capacitor filter. While I can see my harmonic response, NF, S11, IIP3 using PSS+PSP simulation I would like to know how I can properly simulate my circuit to see how a 0 dBm blocker at 20 MHz can affect it (GSM).

My circuit uses a Sine Port in the input and a DC port in the output (I can draw you the schematic if you need it but I can't get the pictures/data because of security constraints in the lab I am doing my master's thesis).

I have see this tutorial, but is about mixers and I don't know how to translate it to my circuit. https://filebox.ece.vt.edu/~symort/rfworkshop/Mixer_workshop_instruction.pdf
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Ken Kundert
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Re: NF simulation using out-of-band blocker (SpectreRF)
Reply #1 - May 21st, 2019, 6:52pm
 
Switched capacitor filter? I have no idea why you would have a switched capacitor filter in this simulation, but its clock will cause a lot of problems. You should eliminate it if you can.

Conceptually an LNA with a blocker is very much like a mixer where you are interested in the direct transmission path (no frequency conversion). In this case the blocker plays the role of the LO.  So apply the blocker as a large sinusoid on the input. Apply the input signal as a small stimulus (using pacmag), also on the input.  Run PSS at the blocker frequency. Run PAC at the input frequency and set the sideband to 0.

-Ken
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