WR-3.4 Band Waveguide and Bandpass Filters Using Copper Additive Manufacturing

This article presents a waveguide with a pair of
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-plane bends and two waveguide bandpass filters (BPFs) which operate in WR-3.4 band (220–330 GHz). These devices are fabricated by a micro metal additive manufacturing (M-MAM) technology on copper in one piece. Both filters are fifth order and operate at a center frequency of 280 GHz with a bandwidth of 8 GHz. Cylindrical resonators are employed for filter design. The standard feed waveguides are designed in bend structures, facilitating the measurements. The M-MAM technology is a layer-by-layer additive manufacturing process constructing the waveguide devices in five layers. Since the layout of the devices has a strong impact on the electrostatic field distributions and hence the electroforming quality, both full-wave electromagnetic (EM) simulations and electrostatic analysis are simultaneously considered in the device design. It eases the subsequent electroforming and polishing processes, effectively improving the performance of the devices. The insertion losses and return losses of the measured filters are lower than 1.65 dB and better than 15 dB. The center frequency shifts are less than 0.3%. The excellent results attribute to the delicate co-design method between EM and electrostatic analyses encountered both in the filter design and in the additive manufacturing process.