G Band H-Plane Diplexer Manufactured by SU8 Micromachining

A G-band waveguide diplexer, designed and fabricated by SU8 micromachining to obtain high precision dimensions and measured, is presented in this paper. The designed diplexer is composed of a common non-resonant (NRN) cavity junction and rectangular dual-mode resonators, which have two cross-coupled dual-mode cavities employing the TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">102</inf> and TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">301</inf> modes. It operates at 215-218 GHz and 221-224 GHz respectively. The entire device in the SU8 chips consists of the designed diplexer and three bends for measuring. The entire device has a total of three layers, and his entire circuit can be completed by two SU8 chips spliced together, in which SU8 chip I contains only one layer structure of the input standard waveguide port I, while SU8 chip II contains two layers structure for the designed diplexer at the top layer, the output waveguide port II and port III at the bottom layer. Between them, the use of copper as a masking layer solves the requirement of the SU8 micromachining that the top structure is larger than the bottom structure. In the two bands, the measured return loss (RL) is about 10.5 dB, the insert loss (IL) of the fabricated designed diplexer is about 1dB, their center frequency shift are approximately 0.92% in the lower bandpass and 1.12% for the high bandpass, respectively.