Satisfying the complex NxNxM requirement in s2rlgc function

Hello world,

I am trying to convert some s-parameters to the RLGC values using matlabs s2rlgc function. (It comes with the RF toolbox). However so far it has been able to do so for one individual value of s parameters. For example, I run the following script.

 S_11 = 2.80007716585167 - 194.777061344490i;
S_12 = 1.01738305506126 + 0.00852418806674031i;
S_21 = 1.00027791458013 + 6.81079834005747e-07i;
S_22 = 10.1134655629712 + 0.881321459087057i;
 freq = 40000000000;
% put the 4 s-parameters in a matrix
 s_params = [S_11,S_12; S_21,S_22];
 length = 4.5;
 z0 =50;
sparams_passive = makepassive(all_s_params);
rlgc_params = s2rlgc(sparams_passive,length,freq,z0);
disp(rlgc_params)

and it will output

        R: -9.3154
        L: -2.5604e-10
        G: 0.0036
        C: 9.9513e-14
    alpha: 1.2686
     beta: -0.1837
       Zc: 0.0012 -50.7238i

into the command window. The problem is that I have a 3202x2 complex double of s paramters since I took them in from a VNA(vector network analyzer; equipment from lab) As you can see from the line of code above, the S parameters form in 4 complex numbers, and so in the s_params matrix, they come out as a 3202x2 complex double. I also have a frequency 1601x1 double that corresponds with each set of s parameters.

I would love to run them all at once. When I try to do so I get error messages that say "S_PARAMS must be a complex NxNxM array."

I am not sure what is meant by NxNxM array. Does anyone have an idea?

[David Goodmanson]

Hi Jesus,

Take a look at 'doc s2rlgc'. You have 1601 frequencies, and you need to make a 2x2x1601 array S, each layer of which is a 2x2 matrix [S11 S12; S21 S22] for that frequency. The 3202x2 array (call it A) has the values and it's just a question of how it is organized. For example if it looks like

S11 S12   freq 1
S21 S22   freq 1
S11 S12   freq 2
S21 S22   freq 2
...
then each layer of S is constructed from two rows of A, which can be accomplished with a for loop or otherwise.

[Jesus Perez]

Hi David,

Thank you for the reply and help. The 3202x2 matrix is organized like this;

      A = 1st value of array :[ S11 S12 ]
                                .     .
                                .     .
                                .     .
           the 1602nd value    S21  S22 
                                .     .
                                .     .
                                .     .
      3202 value of the array [ S21  S22 ]

So the corresponding S21 and S22 values for the first frequency are found in the 1602 spot of array A. Also the frequency is in a separate 1601x1 array.

I'm guessing it is still possible to make the 2x2x1601 array, I'll just have to extract them from the two arrays?

Its been a while since I've delt with 2d(/3d) array loops but I'll give it a try.

[David Goodmanson]

Hi Jesus,

This looks like a favorable situation, where for loops are not necessary. If you preallocate S as zeros(2,2,1601) then for example for S11,

S(1,1,:) = A(1:1601,1). And so forth.

[Jesus Perez]

Hi David,

I understand and it seems like this should work. The attached picture shows S11 successfully placed in the matrix(although the value are being multiplied by some factor of 10 and I don't know why) Although I am trying to complete transferring the values this way;

    S(1,1,:) = A(1:1601,1);     %S11
    S(1,2,:) = A(1,1:1601);     %S12
   % S(2,1,:) = A(1602:3202,1);  %S21
   % S(1,2,:) = A(2,1601:3202);  %S22

Just by running the second line I get this error:

    Index in position 2 exceeds array bounds (must not exceed 2).
    Error in matlab_code_testing (line 60)

   S(1,2,:) = A(1,1:1601); %S12

Is the syntax wrong?

[David Goodmanson]

Hi Jesus,

S12 is in the second column of A, which is A(1:1601,2) and similarly S22 is in the second column which is A(1602:3202,2). Also there is a mistake on your last line where you meant S(2,2,:).

[Jesus Perez]

Just saw the comment above, thank you I will try it that way to make sure it works out.Compared to me getting the S values into the 2x2x1601 array using the slightly different method, but now I have stumbled across another problem. This is the error message I now see,

   Operands to the || and && operators must be convertible to logical scalar values.
Error in s2rlgc (line 129)
    if any(isnan(R) || isnan(L) || isnan(G) || isnan(C))
Error in matlab_code_testing (line 68)
rlgc_params = s2rlgc(sparams_passive,length,F,z0);

I have attached a screenshot of it as well.

[David Goodmanson]

I don't have the RF toolbox so I can't say much. I guess all I could suggest is

plot(abs(S(1,1,:)))
and
plot(angle(S(1,1,:)))

just to see if they make sense. And similarly for S(1,2,:) etc.

[Jesus Perez]

Thanks David,

You helped get a passed some hurdles. I am still working this code but working on another module first. I'll get back to this one sooner rather than later hopefully

Answer 1

[Martin]

Hi,

with the data in the following form

      A = 1st value of array :[ S11 S12 ]
                                .     .
           the 1602nd value    S21  S22 
                                .     .
      3202 value of the array [ S21  S22 ]

I would use reshape like this

     M = 1601;                                               % size() or length() would be better
     B = [A(1:M,1),A(M+1:end,1),A(1:M,2),A(M+1:end,2)].';    % Creates a Matrix of row vectors [s11;s21;s12;s22]
     S = reshape(B,[2,2,M]);                                 % creates NxNxM matrix from B

this should work as input for s2rlgc.