Design of a Double-Layer Slotted Waveguide Array with a Partially Corporate Feed Circuit Installed in the Bottom Layer and its Fabrication by Diffusion Bonding of Laminated Thin Plates in 38GHz Band

This paper is to demonstrate the potential and realizability of a high-performance waveguide slot antenna. A double-layer slotted waveguide array with a partially corporate feed circuit installed in the bottom layer is proposed and designed in 38GHz band to realize broadband characteristics. For the antenna realization, a diffusion bonding of laminated thin plates is introduced as the fabrication technique of low-cost and high mass-productivity. Previously, a single-layer slotted waveguide array [1, 2] has been developed for commercial use. It is an attractive candidate for high-efficiency and high-gain planar antennas because of its negligible transmission loss and simple structure. As show in Fig. 1 where the feed waveguide is placed at the end of antenna, the slot array cut in each radiating waveguide is fed in series. The bandwidth of antenna gain is restricted due to long line effect in radiating waveguide. And the mainbeam direction will also tilt a lot according to the frequency divergence of propagation coefficient in waveguide. In order to realize a wideband antenna in single-layer, the center feed [3] and the partially-corporate feed [4] structures have been investigated. The bandwidth is enhanced by reducing the long line effect to a certain fraction. However, the increase of blocking area with no radiating elements leads to the degradation of sidelobe level (SLL). Furthermore, the embedded feed circuits with more complexity than the series feed also lead to the difficulty in antenna realization using present fabrication technique. In this study, a double-layer configuration is adopted: the partially-corporate feed circuit in the bottom layer and the radiating waveguides in the top layer. The etching of thin metal plates has high-precision and low-cost as a feature. The number of etching patterns for this double-layer antenna is only five. A proper number of etched metal plates are laminated together by diffusion bonding [5]. It is a process where the diffusion motions of atoms happen under the condition of high-temperature and high-pressure. In addition, a large number of antennas can be fabricated at one time for reduction in cost.