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[Guilin Sun]

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Total-Field Scattered-Field (TFSF) source - Simulation object

Tips and best practices when using the FDTD TFSF source

 Please set the TFSF XYspan mcuh larger than than the poeriod.

The problem you have is, the substrate should also be modified:
xy span must be expanded to outside of the periodic boundary; and zmin must be outside of PML. Currently you are simulating substrate as cavity since its bottom surface is not expended to outside of PML, which will lead reflection. 

The 2nd one does not have any issue.

Could you please let me know why you want to use TFSF? you can simply use regular plane wave.

For source with circular polarization, you can add two linear polarization, change one of polarization angle to be 90deg. they will be orthogonal. Once you have those two, then follow the common definition eg, same amplitude, phase difference 90deg (can be one is zero, the other is 90deg), it will work as a circular polarized source.  Please refer to  Circular polarization and phase convention

Please focus on one issue. Resolve the problem one by one, and one in one post.