S-parameters peaks and bandwidth

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mikeeee
mikeeee 2019-12-30
回答： Deepak Kumar 2020-1-9
Hey guys
I have a S-parameter touchstone file with such a characteristic:
I want to use findpeaks function for determination of the width and central frequency of each peak, but I get an error.
  2 个评论
Deepak Kumar
Deepak Kumar 2020-1-2
What is the error you are getting ? can you share the data ?
You can refer the below documentation link to know more about "findpeaks" function
https://in.mathworks.com/help/signal/ref/findpeaks.html
mikeeee
mikeeee 2020-1-8
Dear Deepak,
I have attached the data-file. The error that I get is:
Attempt to execute SCRIPT findpeaks as a function:
C:\Users\.....\findpeaks.m
Error in findpeaks_sparam (line 3)
peaks = findpeaks(S_ML,freq_sim)
Code is:
S_ML = sparameters('file.s2p');
freq_sim = S_ML.Frequencies;
peaks = findpeaks(S_ML,freq_sim

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采纳的回答

Deepak Kumar
Deepak Kumar 2020-1-9
Couple of points that I noticed in your code:
S_ML is S-parameter object
>> S_ML
S_ML =
sparameters: S-parameters object
NumPorts: 2
Frequencies: [10000×1 double]
Parameters: [2×2×10000 double]
Impedance: 50
rfparam(obj,i,j) returns S-parameter Sij
The input data to “findpeaks” function must be a vector,real and of the type ‘single’ or ‘double’. So, you cannot give S_ML directly as input to the “findpeaks” functions as the S_ML is neither ‘single’ nor ‘double’.
Refer the below documentation for details:
https://in.mathworks.com/help/signal/ref/findpeaks.html
You can extract the parameter values like below
>>x= S_ML. Parameters;
But I noticed that, x= S_ML. Parameters, is of the size and it has complex values. Since 'x' is not a vector rather 3-D data (It’s because it is representing all the S parameters for (S11,S12,S21,S22) for a two port network and 10000 is the number of frequency values at which the S-Parameters are calculated).
Please refer the below documentation for more details:
https://in.mathworks.com/help/rf/ug/s-parameter-notation.html
you can try to extract the individual S values, something like below
>>k1=x(1,1,:) %for S11
and, reshape it to make it a vector
>> k1=reshape(k1,10000,1)
Then, take only the magnitude values,
>>k1=abs(k1);
Now, you will be able to use “findpeaks” function.
Hope this helps!

更多回答（1 个）

Deepak Kumar
Deepak Kumar 2020-1-8
Can you try to rename your script file (findpeaks.m) and check if it resolves your issue ?

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