singular field+feko

Feko warning 563: The mom matrix is numerically singular, solution very critical.

I try to a patch antenna but at low frequency down to 30-100MHz, the near field (10mm away from patch) is wrong.

Any idea, comments.

DVTsim

The numerically singular warning means your geometry is electrically small. You probably have the patch antenna designed to resonate at 1 GHz+ and now you want to simulate at 30 MHz. That is not going to work.

By default FEKO uses single precision solver as far as I know. This might be not enough for such non-well conditioned simulation. Try to switch to double precision and check if it works.

If you attach your project I can simulate it alternativey with EMC Studio MoM solver.

Yes. You can switch to double precision under Solution settings.