Fabrication of a slotted waveguide array at 94GHz by diffusion bonding of laminated thin plates

We fabricate the single-layer slotted waveguide array antenna in 94GHz band by diffusion bonding. According to the processing conditions, the thickness of slotted plate and that of coupling windows are increased to 0.3mm and 1.0mm, respectively. All these effects of large thickness are precisely evaluated and taken into account during the antenna design. The radiating characteristics of resonant slots are not degenerated much. On the other hand, the frequency characteristics of power dividing and reflection become narrow-band because non-resonant coupling windows are applied in the feed circuit. The designed 18-by-18 elements antenna is trial fabricated by diffusion bonding of laminated thin plates using copper. The antenna efficiency is achieved at 60% for 31.4dBi gain at 93.7GHz in this copper antenna. The material of stainless will provide us with stable process in the tradeoff of large conductor loss. However, the low loss material of copper is indispensable in antenna fabrication. The process of diffusion bonding using copper could result in the misalignment of the thin metal plates, which degrades the aperture efficiency. As the future work, further fabrication is planned to be carried out to enhance the aperture efficiency as well as the antenna efficiency.