An innovative fabrication technique to create nominal height liquid foam substrate layer for integratable antennas is introduced. The liquid foam layer is intended to replace a Rohacell foam or air substrate, especially at millimeter-wave frequencies, where antenna designs require substrate layers less than a millimeter thick. The performance of hi-lo stacked patch antenna with 0.5-mm-thick layer of ECCOSTOCK FPH is presented. The 10-dB return loss bandwidth of the antenna is 18.2%, and the radiation patterns and gain are also presented and discussed.ABSTRACT: This article presents the methods of broadband axial feeding of a Fabry-Perot resonator. The resonator was originally designed with the radial excitation for the absorption measurement in the frequency band ranging from 18 to 80 GHz. If the frequency stays below $26.4 GHz, the excitation of resonator is less satisfactory, since at the frequency in question, the value of Fresnel number of resonator drops to one. For the broadband measurement of gaseous samples' emission spectra, the excitations for frequencies lower than 26.4 GHz were analyzed using the capacitive coupling and two newly proposed couplings.