I am simulating image formation for a phantom which is slightly on the deeper side (80mm).
I am using a signal at 5 MHz and what I notice is basically a smooth degradation of the signal from bottom to top i.e. the bottom structures are more easily visible and the signal drops to almost zero from 30-40 mm upwards. I tried to set the focus at various depths but the result is the same.
Additionally, I doubled the PML size in both directions as well.
The focus int he elevation plane is set to the default of 19mm as in the US linear transducer example.
Looking for some advise on trying out things that could help with diagnosing the issue. Similar phantoms at 40 mm depth have all resulted in ok looking images. So, it seems to be a depth issue.