如何在ADS中自由修改基板？

我真的需要修改基板的尺寸，但不能这样做。
我在互联网上找到了三维设计基板的文章。
例如：“基板尺寸：26x45x1 mm”。
但是，当我单击EM Simulation Setup，然后在基板中，我创建了一个新的基板。
例如，默认为Alumina，然后单击图层，然后我只有“厚度”选项。
如何设置三维基板？



     以下为原文

  I really need to modify the dimensions of the substrate, but can not do it. I find articles on the Internet to design substrates with three dimensions. For example: "Substrate Dimensions: 26x45x1 mm". But when I click EM Simulation Setup, and then in substrate, I create a new substrate. For example, the default is Alumina, then click on the layer, and then I have just the "Thickness" option. How can I set a substrate in three dimensions as well?