# Electric field value changing with changing mesh density and not matching to results from FEKO

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• Last Post 11 February 2019
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asimghalib posted this 03 February 2019

Dear all

I want to calculate Electric field at a point in a geometry. For the test case I am just considering a simple conductor sheet and I want to measure the Electric field at the origin, the antenna is excited by a plane wave at an angle of theta=80 deg and phi=60 deg. I am using the field calculator to measure the Electric field at that point.

The Electric field was also calculated in the FEKO but the results from both software's are not matching. Any reason for it? Secondly, in HFSS when I increased the mesh from default settings the Electric field values get changed as well, which is very strange. In the FEKO when i increase the mesh density the results do not change. In the below table you can see how the results are changing for the HFSS simulation...

Ex Ey Ez   Real Imag Real Imag Real Imag FEKO -4.80E-03 3.28E-03 -4.96E-03 4.06E-03 1.30E+00 3.53E-01 HFSS 4.77E-02 3.04E-02 1.22E-01 3.94E-02 3.11E-01 3.71E-01 8.85E-02 2.95E-04 1.54E-01 5.75E-04 -3.10E-01 -3.31E-01 8.85E-02 2.95E-04 1.54E-01 5.75E-04 -3.10E-01 -3.31E-01

The last three rows are for the HFSS case, and we can observe that the values are changing....I am attaching the project file as well as the image of the table at the below link

Attached Files

Peter Serano posted this 04 February 2019

In your solution setup, go to the 'Expression Cache' tab. Here you can set your simulation to converge on any field calculator expression you desire. First, go to the field calculator and create an expression that is the complex magnitude of the E field at your point of interest. Set the simulation to converge on this quantity for more accurate results.

Peter Serano - Senior Application Engineer - High Frequency Products

asimghalib posted this 04 February 2019

Hi Peter

Thanks for your reply. I did the procedure you mentioned but it did not effect any results and they were same as the previous case. Secondly when i follow your procedure I can converge for the complex magnitude of E. So, i went to E field calculator to get the Ex, Ey and Ez component.

Peter Serano posted this 04 February 2019

Please post screenshots of the expression you programmed in the calculator and the expression cache tab of the solution setup...

Peter Serano - Senior Application Engineer - High Frequency Products

asimghalib posted this 11 February 2019

Thank you Peter Serano

I found the answer to the problem. The reason of the difference between the FEKO and the HFSS is that both softwares uses different meshing technique. So for a single point (different w.r.t different meshes) the solution will be different as we are not exactly looking at the same point in the mesh. Remember physically the point is same but with respect to mesh its different.  But if we look at the results for a line or an area the results matches.

The reason of changing electric field in HFSS with varying meshes was that the point changes (the point is located on the mesh) as we change the mesh density. Although physically we are giving the same point but on mesh its different. For a line or area it gives the same result.

Thanks