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docs:become [2020/04/22 23:01] pklapetek |
docs:become [2020/04/22 23:06] pklapetek |
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//periodic NFFF// in the next text. | //periodic NFFF// in the next text. | ||
In most of the graphs here we show complete diffraction pattern. | In most of the graphs here we show complete diffraction pattern. | ||
- | However, if we are interested in the maximum in some diffraction order direction, it is much simpler and it seems that this is the preferably used approach - we calculate the far field value only at the diffraction order maximum. Luckily enough, this value is dependent on the aperture only, which constructs the envelope for the diffraction pattern, so in this case one could work only with a single aperture. However, to construct the diffraction pattern is a good way how to debug the problem. The schematics of | + | However, if we are interested in the maximum in some diffraction order direction, it is much simpler and it seems that this is the preferably used approach - we calculate the far field value only at the diffraction order maximum. Luckily enough, this value is dependent on the aperture only, which constructs the envelope for the diffraction pattern, so in this case one could work only with a single aperture. However, to calculate the whole diffraction pattern is a good way how to debug the problem. The schematics of |
the calculations is here: | the calculations is here: | ||
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An important message is that | An important message is that | ||
- | using the periodic approach for only a small number of repetitions does not work as it does not take into account the field on sides of the computational domain. For large number of periodic approach repetitions we get results that are same as analytical results. | + | using the periodic approach with only a small number of repetitions does not work as it does not take into account the field on sides of the computational domain. For large number of periodic repetitions we get results that are same as analytical results. |
If we manually extend the computational domain and include all the apertures, results agree with the analytical results also for small number of apertures. See the technical explanation listed below for our reference. | If we manually extend the computational domain and include all the apertures, results agree with the analytical results also for small number of apertures. See the technical explanation listed below for our reference. | ||
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This uses very similar geometry to our calculation (TSF source, periodic and CPML boundaries), | This uses very similar geometry to our calculation (TSF source, periodic and CPML boundaries), | ||
so we can expect that there are not many additional potential error sources when comparing to our calculation. | so we can expect that there are not many additional potential error sources when comparing to our calculation. | ||
- | |||
- | First of all, error in the reference value (PEC reflection) is below 0.001 percent. This certainly | ||
- | cannot affect our results. | ||
Reflectance of the default metal for this particular voxel spacing and other settings is 0.983 | Reflectance of the default metal for this particular voxel spacing and other settings is 0.983 | ||
Reflectanceof the fitted metal model is 0.9587. | Reflectanceof the fitted metal model is 0.9587. | ||
Result from the Filmmetrics reflectance calculator is 0.9678, which is something in between. | Result from the Filmmetrics reflectance calculator is 0.9678, which is something in between. | ||
- | This is probably also not the source of problem (however might be compared to reflectance | + | Finally, error in the reference value (PEC reflection) is below 0.001 percent. This certainly |
+ | cannot affect our results. | ||
+ | So, this all is probably also not the source of problem (however might be compared to reflectance | ||
coming from FEM). | coming from FEM). | ||