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i write a matlab code for extraction the permitivity and permeability based on smith paper. i upload it, if you write the matlab code of rebust method i hope to upload that that we both investigate the codes and solve their problems.
in this code first i enter the hfss output for s-parameters in : S11 and S21 in dB, phase in Rad
regards
There is a rather new but complicated retrieval technique in:
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 56, NO. 6, JUNE 2008
"Determining the Effective Constitutive Parameters of Finite Periodic Structures: Photonic Crystals and Metamaterials" **broken link removed**
As far as I can see, the method can be applied to 3D metamaterials with SRRs and wires. I think it is a more robust method, but costly, you need to implement a GPOF code or something, (and of course you need more and bigger simulations)...
As mentioned above, the Sij( phase) from CST shoulb be deembed in order to get correct results . Could anyone give more detail how to deembed Sij from CST? Thanks very much.
Hi all,
this topic is very useful for me
now I m doing this work (Retrieving the refractive index) follow smith's paper SAJ25, I want to ask you for decribtion in your matlab code :
for gh=1:length-1
n(gh)=n(gh)*sign(imag(alpha(gh)));
end
Thanks you very much
After inspecting the codes uploaded to this discussion, neither seem to implement the algorithms correctly. An important thing to consider here is the "branching." In the Smith code for example there is an inverse cosine function. There are an infinite number of answers here because
cos(a + 2*pi*m) = cos(a) m=...,-2,-1,0,1,2,...
The uploaded code assumes m=0, which is not a correct assumption.
In the "Robust" code, the branching problem is handled through continuity of the material functions. This feature is not present in the uploaded code and again the m=0 assumption was made. The algorithm also defines a procedure for determining the correct thickness of the slab that does not seem to be part of the uploaded code.
These codes are a great start, but they are incomplete and will likely only give correct results for thin slabs and at frequencies away from resonance.
Unfortunately, I have not written these algorithms myself, but I may have a need for them in a few months. If I do, and I get them working correctly , I will certainly share with the group. I actually hope somebody will make the modifications and share their code before then.
Based on the idea in Part C of paper "Robust method to retrieve the constitutive effective parameters of metamaterials", i've got stable and continuous effective impedance just as shown in Fig.3. The structure i simulated is the microstrip with csrr etched in ground plane and gap in the strip---resonant type composite right/left-handed transmission line unit cell. Furthermore, from equation (6) and (4), the imaginary part of the refractive index n can be determined. Without considering the branching choice problem first, there exists data filp in the real part of n, espcially in the transmission zero (with small s21) and transmisson pole (with small s11). Up to now, i have not seen any paper has mentioned or studied such a phenomenon.Anyone has any idea?
Hi, SAJ25
What do you mean by multi resonance structures? Don't you mean the SRR/Wire structure studied most belongs to the single resonance structure? So why the retrieval method in the paper "Robust method" can only deal with the single resonance structure rather than the multi resonance structure?
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