Hello, I’m a graduate student currently studying EMC (Electromagnetic Compatibility).

At the moment, I’m working on a project comparing shielding effectiveness when using a fixed-size pipe to create 1, 2, or 4 holes in a shielding box.

A problem I encountered is that, with the pipe length and its diameter (both width and height) kept constant, the S21 results for 1 hole and 2 holes are nearly identical.

Interestingly, when two holes are used, I found that a 1-row, 2-column arrangement provides better shielding than a 2-row, 1-column configuration.

When I compared the result of the 2-row, 1-column configuration with that of a single hole, they turned out to be very similar.

Additionally, when I measured S21 with only one hole—while keeping the vertical dimension constant and increasing the horizontal dimension—I observed very little change in the result.

Could this be related to the behavior I’m seeing?

I also tested using circular pipes, and in that case, the results for both the 1-row, 2-column and 2-row, 1-column configurations were almost the same.
I’m wondering if this outcome also makes sense.

Thank you very much for your time and help.