Abstract
Introducing diffusion bonding of laminated thin metal plates to the fabrication of slotted waveguide arrays enlightens the high potential and the feasibility of multi-layer antennas with high-performance. It is a promising process with low cost even for a double-layer antenna, because the number of etching patterns for thin metal plates is only five. In this paper, a double-layer antenna for broadband characteristics is designed in 39GHz band as demonstration. A 20 × 20-element antenna is composed of 2 × 2 sub-arrays by installing a partially-corporate feed circuit in the bottom layer underneath radiating waveguides in the top layer. The five-element sub-arrays in both the feeding and radiating parts are designed first. A new structure for the last slot coupler with shortened termination is also proposed to avoid an extra slot-free region when assembling the neighbor sub-arrays. As the simulation results by HFSS, the maximum gain of 34.55dBi with the antenna efficiency of 85.5% is estimated at 38.5GHz. The test antenna is fabricated by the diffusion bonding of thin copper plates. As the measurement results, a very high aperture efficiency of 83.2% with the directivity of 34.5dBi is realized at the center frequency of 38.75GHz, where the antenna gain of 34.4dBi with the high antenna efficiency of 81.4% is achieved. The bandwidth of 5.0% defined as 1dB down from the maximum gain is achieved.
