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TwoPort BLKBOX2 - noise figure simulation looks wierd

Question asked by CYBERPHOX on Jun 24, 2011
Latest reply on Jun 27, 2011 by CYBERPHOX
Hi All,

I am trying to use this simple 2 port model to help me understand things but have found some odd results from it.

If I set the following parameters in BLKBOX2

S21 = dbpolar(-1.1,0)
S12 = dbpolar(-1.1,0)
S11 = X
S22 = X
ZRef = 50 ohm

then if I sweep X from 0 to 1 and then plot the NF for this the NF drops from 1.1dB gradually to zero when X = 0.473

if I make S22 = 0 but only sweep S11 from 0 to 1 then the NF stays flat at 1.1dB and then drops 'digitally' to 0 when X= 0.473.

This is not making sense to me. Please help

kind regards
marino  

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