  We developed a wideband quasi-optical band-pass filter covering 170-520 GHz
by exploiting the recent advancements in commercially available flexible
printed circuit (FPC) fabrication technologies. We designed and fabricated a
three-layered stack of loaded hexagonal grid metal meshes using a copper
pattern with a narrowest linewidth of $50~\mu\mathrm{m}$ on a polyimide
substrate. The measured frequency pass-band shape was successfully reproduced
through a numerical simulation using a set of parameters consistent with the
dimensions of the fabricated metal meshes. FPC-based metal mesh filters will
provide a new pathway toward the on-demand development of
millimeter/submillimeter-wave quasi-optical filters at low cost and with a
short turnaround time.
