This method is from TRANSMISSION LINE – PERIODIC CIRCUIT REPRESENTATION OF PLANAR MICROWAVE PHOTONIC BANDGAP STRUCTURES （https://doi.org/10.1002/mop.1207 ）.

Following formulas is needed for the calculation of the dispersion diagram.

But the result is totally different from Figure 3(a) in the paper.

Has anyone ever found a similar problem?

Attachments are the procedures and the MATLAB code I used for the calculations.

I would be appreciated if you could give me some advice.