After CMA analysis, antenna is fed by coaxial and after simulation getting S11=around -13.82dB at 6.8719 GHz. and after Fairfield monitor analysis of this frequency S-parameter is not getting. Any reason? Both Parameter Image attached. After Field monitor at 6.8719Ghz the parameter changed Why?
I don't know the answer, but I can tell from the top figure that the solver hadn't reached a proper solution. The curve hitting 0 db with a sharp angle and then following the 0 dB line is not a valid result for S11.
Understanding the Change in S-Parameters After Field Monitor Analysis:
- CMA is a method used to analyze the resonant behavior of an antenna structure without considering the excitation. It provides insights into the natural resonant modes of the structure, which can be used to optimize the antenna design. However, the S-parameters, such as S11, are dependent on the excitation and the specific feeding mechanism used in the simulation. When the antenna is fed by a coaxial cable, the S-parameters are calculated based on the input impedance and the reflection at the feed point.
- The field monitor analysis provides a detailed view of the electromagnetic fields at a specific frequency, such as 6.8719 GHz in your case. This analysis can reveal changes in the surface current distribution and the radiation pattern, which might not be captured in the initial S-parameter simulation. If the field monitor analysis shows a different current distribution or radiation pattern, it can lead to changes in the S-parameters because these parameters are sensitive to the exact electromagnetic environment and the excitation conditions.
Possible Reasons for Parameter Change:
- Mode Excitation: The field monitor might reveal that different modes are being excited at 6.8719 GHz, which was not considered in the initial S-parameter simulation. This can lead to a change in the reflection coefficient (S11).
- Simulation Settings: Differences in simulation settings between the initial S-parameter analysis and the field monitor analysis, such as mesh density or boundary conditions, can also affect the results.
- Feed Position and Impedance Matching: The position of the coaxial feed and the impedance matching at the feed point can significantly influence the S-parameters. Any changes in these parameters during the field monitor analysis can lead to different results.
In summary, the change in S-parameters after field monitor analysis at 6.8719 GHz could be due to differences in mode excitation, simulation settings, or feed position and impedance matching. It is important to ensure consistency in simulation parameters and settings to obtain reliable results.
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