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[hola]

Hi,

I have some data from antennas, like S11, S12, S21 ...etc.
each one ex:S11 has 3 columns, now I want to plot the S11(db) versus frequency in Matlab (I mean return loss plot)
How can this be done !?
because every time when I do it I get something unreasonable !!
Is it that the first column is frequency and second is real conductivity and third is imag conductivity ?! I dont know exactly


Thanks in advance for your help !!

[arka]

I am not aware of the EM solver that you are using, but it seems like the three columns are as follows : Frequency, Real part of S11, Imaginary part of S11 (correction- not conductivity as you mentioned).

For each frequency you can take the magnitude of S11 from the real and imaginary parts by (S11_real^2 + S11_imag^2)^0.5 . Then you can find the corresponding value in dB by 20 log10(S11 magnitude) and hence plot.
Thanks.

[hola]

Unfortunately, that is what I did exactly. and got wrong plots

In this link, you can see which plot I need exaclty:
http://www.grc.nasa.gov/WWW/RT/2007/Comm/01-RCA-mueller.html

its the second image (Fig, Return loss (S11) for patch antenna)

thanks alot for your answer [/url]

[arka]

Ya i have seen the second plot. As far as I am aware, the method which I have stated is the one to convert it to dB..No idea why it went wrong, may be somebody else can put some light on it.
Thanks