A D-Band Waveguide Diplexer Based on Copper Additive Manufacturing

This article presents a D-band waveguide diplexer fabricated using micro metal additive manufacturing (M-MAM) technology. The diplexer features two sixth-order filters with passbands of 130–134 GHz and 141–148.5 GHz, respectively, for a crucial RF application band. Cylindrical resonators were employed in the filter design, and a nine-layer process was developed specifically for this frequency band, allowing the diplexer to be manufactured as a single piece. The process was optimized to minimize photoresist deformation during repeated thermal cycles, so a larger waveguide can be fabricated. To ensure accurate measurements, a fixture equipped with a straight-through calibration channel was also designed and manufactured. The measured insertion losses and return losses of both channels are less than 2 dB and greater than 15 dB, respectively, and the center frequency shifts are negligible at less than 0.15%. The excellent correlation between simulations and measurements is a result of the carefully designed process and its high level of accuracy.