How to get Characteristic modes

Hi;

I want to replicate results from this paper : 'Characteristic-Mode-Based Improvement of Circularly Polarized U-Slot and E-Shaped Patch Antennas' by using Feko. Unfortunately, i can't get no satisfactory tracked characteristic modes when simulating the U-shaped patch antenna. In fact, some errors appear as 37561 and 37591. The structure is simulated from 2 GHz to 2.7 GHz. Number of frequency points is set to 200. I've chosen finer mesh. Any idea to mesh correctly the antenna and to get good tracked modes and compare it to those in figure 2 in the paper. Thanks.

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