An easy way to add loss/conductivity to the walls of a waveguide structure in Microwave CST
Step 1: Create the geometry and set the ports for
your particular structure. For example, I show below an extracted pole bandpass filter. As it stands, the waveguide walls
are perfect conductors (
Step 2: Select the structure from the project tree
Step 3: Copy and paste the structure right over itself.
You should now have two identical structures which lay right on top of each other. The project tree should reflect this:
Step 4: Select the duplicate from the project tree. Then, in the main drawing window, select the duplicates faces which lay on top of the ports. These are the surfaces where there will be no conductive wall; they shall be left alone as ports instead.
Step 5: Select the Shell Solid or Thicken Sheet option in the Objects dropdown menu. In the Shell dialog box that appears, change Direction to Outside. Enter a value for thickness that is much larger than the skin depth of the conducting walls (five or six skin depths is plenty). For example, this particular design has silver walls (the conductivity of silver = 6.173E7 S/m) and operates around 18 GHz. At 18 GHz, the skin depth of silver is 4.77E-7 meters, or 1.878E-5 inches. As you can see in the figure below, I set the thickness to 0.017 inches. This value is ridiculously larger than a skin depth, which is fine. Click OK.
Once you click Ok, your duplicate should now have transformed into a shell with some small thickness which completely surrounds your original structure except for the ports.
Step 6: Change the shells conductivity to that of your walls (in my case, I simply change the shells material itself to silver), and there you have it! A silver shell with a thickness much greater than a skin depth surrounding your structure perfectly models a silver wall.
