Dual‐mode band‐pass filters made by SU‐8 micromachining technology for terahertz region

Abstract

Two four-order dual-mode rectangular waveguide filters centred at 100 GHZ with return loss all better than −19 dB are presented. The filters consist of two cascade resonant cavities suppose TE102/TE301 degenerate modes and three pairs of round corner inductive irises symmetrical with waveguide. Since the introduction of round corner irises and dual-mode cavities, the filter structures have lower aspect ratio and less resonant cavities, thus the difficulty of fabrication sharply reduced. Single zero exists at the one side of pass-band because of the same width of two resonant cavities. All the other parameters constant except for the widths of two cavities slightly unequal, two distinct transmission zeros can generate at the same side of pass-band. UV lithography technology with SU-8 photo-resist is used for the fabrication of filters. On the whole, results from measurement are in good agreement with simulation, which fully confirm the validity of design and fabrication methods.