Retrieving the refractive index

[tungsin]

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?

Hi Gong,

I dont think the robust method proposed by X. Chen deals with number of resonance. It works for both single or multi resonance structures.

For data flip, in my opinion, it can be explained by the accuracy of 2nd-order iterative method. When the retrieval values of Re are in range of between 2 roots, there may happen data flip as you saw. For this problem, I suggest that your code should control this point, and then you can shift the border of choosing correct root. Another way, you can try for new input data with smaller step of frequency. Hope these are useful for you.

Best

 

[SAJ25]

hi tungstin
i uploaded my code
please modify it with regards to your opinion.

 

[sangwoo]

Hi everyone,
I have the same problems as Gong, but I also find a data flip in Imaginary part of mue and epsilon. If anyone can manage this problem, please tell me too.

 

[joyhappy84]

Hi all,
I have redo the same work reported in this article "Electromagnetic parameter retrieval from inhomogeneous metamaterials" published in PRL by Smith in 2005. The results are the same. but the probleme is when I change the excitation (the wave propagation now is perpendicualr the particle plane under study) this method doesn't work anymore.So I moved to another method.
For people who used CST I would like to mention that they have to deembed Sij in order to get correct results. if the results are not deembed the retrieval method gives wrong results.

best wishes.

Hey,
It seems that the deembed is not used for unit cell boundary condition. Does that mean I can not based on the S-parameter to retrieval eps and mu??
Thanks,
Joy

 

[yairhol]

Hello all,
This is my first post here.
For retrieval of the metamaterial parameters you can look at my published work here:
https://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4396063

Also may I suggest that you simulate 2 similar structured models, one with several material periods in the propagation vector (k) direction (I simulated mine with 9 periods) and the other model with somewhat less or more periods. Compare your retrieval results for the 2 models. This is what I called the "set method" in my work. For every frequency point you can get an infinite number of (eps, mu) sets since the retrieval process uses exponents which are periodc functions (hence "branches" as someone didn't understand the term from a few posts up). Since eps and mu do not change as a function of material thickness, the 'set' that has the same (eps,mu) values in the two models I described above are the correct extracted parameters. The other sets will be different for the two models and must be disregarded.
Hope this helps.

Yair

 

[sandeep_voore21]

Hi guys,
Please any1, who have information and idea baout my project . please help ne out .....

My project 'ELECTROMANETIC INDUCTION IN METAMATERIALS'

To integrate Helmholtz equation in meta-material waveguide using PDE tool solver using MATLAB software.
Considering the Snell’s law for an electromagnetic wave propagating from air to a meta-material.
Calculating the refracted beam angle with respect from normal to the surface.
Using Simulation in MATLAB,
Observing the design and propagation of EM wave in normal and concave meta-material.
Calculating the focal length, its spot size.

 

[sandeep_voore21]

Hi guys,
Please any1, who have information and idea baout my project . please help ne out .....

My project 'ELECTROMANETIC INDUCTION IN METAMATERIALS'

To integrate Helmholtz equation in meta-material waveguide using PDE tool solver using MATLAB software.
Considering the Snell’s law for an electromagnetic wave propagating from air to a meta-material.
Calculating the refracted beam angle with respect from normal to the surface.
Using Simulation in MATLAB,
Observing the design and propagation of EM wave in normal and concave meta-material.
Calculating the focal length, its spot size.

 

[mordakhay]

Dear all,

If anyone get the correct code for retriving the parameters ( muo and epslon) . the only data available is the S11,S21 and thier phases. how we can overcome the Data flip due to infinite number of solution for the inverse cosine.
Thanks in advane
Yours,

 

[bzai]

I've been struggling with this problem for quite some time as well.

Can't seem to get the right answers with CST results.


Would someone kindly describe the de-embbeding process?

Thanks!

 

[katko]

Mordakhay, the answer is in the Robust paper (Chen). Enforce continuity of real. That also describes how to choose the branch at a particular point, which is all you need then.

bzai, I'm not sure how to do it in CST. I can tell you how to de-embed in HFSS or describe what the concept is but not the details in CST.

 

[yairhol]

In CST de-embedding is done in "ports" found in the menu on the left side.
enter the ports and choose Zin (input port), then enter a negative number which is the de-embedding distance. Do the same for Zout (output port).

Added after 2 minutes:

Also, it has been shown in several papers already that taking only a single unit cell along the propagation axis does not yield accurate results for the extracted parameters. You need at least a couple of periods.

 

[bitele]

Re: matlab code+refractive

ok i am going to upload some papers which i think to be important

first is robust method paper, second one is another paper that mentioned about the different calculation in homo and inhomogeneous structure. I think you can verify ur code by using data from second paper (both cases: homo and inhomogeneous structures).

how to chose the best branch of imaginary part of n?

 

[myebook]

I got the results. refer to:

 

[ylzhang508]

hi all,

Can somebody explain more on de-dembedded process with CST MWS. I'm trying to simulate left handed metamaterials with the transient solver.

thanks in advance

 

[chinmoy_rpe]

I am working in SRR of different geometrical shapes. So far I have simulated SRR in HFSS. Now I need to extract µ using S11 and S12 in some code. Can anyone share the MATLAB code for retrieval. It will be of graet help. Plese mail the code in chinmoy_rpe@yahoo.com[/code]

 

[SAJ25]

hi all
To correct the ambiguity in m based on IEEE MTT and AP papers you have to choose m=-1, 0 or 1
then for a single frequency, calculate the S11 of the extracted material and compare it with CST simulation!
regards

 

[raihanreza]

hi saj25 , can you give some refereence for checking the result in this procedure

 

[behnam_zr]

Hi
Did you write the Robust code to retrieve mu and epsilon from s parameters for DNG metamaterials? If yes, please upload your code.
Thank you so much

Group,

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.

Thanks!!
-Tip

 

[lostinsocorro]

Dude, your results were deleted from the post you are referring! Can you please post your results to this blog post? I would greatly appreciate your support. Thanks.

 

[hanyahmedeg]

Re: forum smith robust retrieval technique code

many thanks rrumpf kindly i need your dissertation the link not work