Post processing of Electromagnetic FEM in waveguide

Hello everyone,
I’m trying to finish a FEM procedure in Matlab and the FEM is referred to 《The finite element method in electromagnetics》 written by Jianming Jin. I’ve already finished the Matrix solving but confused by the post processing for getting distribution of electromagnetic field. Especially how to get magnetic field distribution from FEM results? I try to calculate the values in mesh node but they are different in different tetrahedrals. And after I calculate the curl(E) aimed to get H, the plot of H is totally different from simulation sofware. So I’d like to know what the solution of electromagnetic post processing is in FreeFEM?

Thank you for your help!


Could you be a little bit more specific? With the given information, I can only speculate about your problem.

Please supply minimal working example that showcases your problem.

I have access to the second edition of the book by Jin. Please specify the position (chapter, equation or the like) a bit more precisely, the book has >700 pages.

Actually the problem I’d like to solve is the content of Jin’s book in Chapter 8, Section 5 waveguide discontinuity. I’ve finished the matrix assembling and got the right S11 and S21 following his method. That means I have got the solution of whole FEM matrix which are final coefficients of all basis functions. I want to plot the E and H field in waveguide after the FEM process. That’s to say now I want to get the electric and magnetic field distributions based on the previous reults. How can I get the E and H field in all nodes of mesh to plot the picture of E and H vector? Especially I can’t get relatively accurate magnetic field because the variable in FEM is E instead of H. I have to find a method to calculate H field from E field if I don’t want to solve H by FEM again. That’s cofused. I compare my results with COMSOL multiphysics to test whether they are right or not.

I’m not sure whether you can understand my situation. If still not I will send codes and pictures to explain it. Thank you for your answer and look forward to your help.