Metal-dielectric patterned metasurfaces based on fishnet unit cells have been recently proposed as promising platforms for terahertz (THz) Fabry-Perot cavity leaky wave antennas (FPC-LWAs). Still, their experimental validation in the THz range is lacking. In this work, we design several layouts of such metasurfaces at a working frequency of 300 GHz, by varying the geometrical parameters of the unit cell. This variation allows for achieving different electromagnetic responses that in turn provide for different radiating performances when used in a Fabry-Perot cavity environment. For this purpose, we microfabricated eight different demonstrators by patterning a 200-nm aluminum film over a silica substrate through a low-cost, large-area, photolithographic process. The design flexibility of this kind of metasurfaces is then experimentally validated through THz time-domain spectroscopy (TDS) measurements in the …