Measurement samples were prepared to have the same structure dimensions and material properties as the
ones used for the simulation other than the entire board sizes that were 270× 270mm2
(corresponding to 15× 15
units) (see the right of Fig. 2). Compared to our past studies23,26,27, we modified and improved our measurement
system for conducting oblique incidence measurements in an efficient manner. For example, incoming signals
were generated from a vector network analyzer (VNA) (Keysight Technologies N5249A) that, compared to signal
generators (which are used for most conventional pulse measurements), significantly reduced the total measurement
time but still allowed us to tune the pulse width. These signals were then amplified by an amplifier (OPHIR