some doubt in using CST MWS 5.0 ，thank you !

I have some doubt In using CST MWS 5.0 doubt:

1 When i choose a “transient solver” to solve an antenna, the original bounding box is antenna structure size, after I set the “frequency range”, however , the bounding box was expanded from antenna structure size to a larger size. And the bounding box varies when I modify the “frequency range”. but I do not know why and what had happened to the added size or the added size is controlled by the program automatically . I have been told that bounding box = original structure size + surrounding space, but I find the surrounding space in my problem is zero as the lower /upper x/y/z distance is zero even after I change “frequency range”. So how to explain that , any help will be appretiated!

2 when I start to solve an antenna , it is noted that”18 critical cells have been expanded to full size”, so what had happened?

Best regards!

Don't worry about the black-wire box. It's adjusted automatically. Click on Sover/Boundary to see more details

because the λ varies.

Your boundary set to open. Go to boundary then you can change it to open add space

For the cells you have to refine your mesh. to prevent it