Low-Cost mmWave Metallic Waveguide Based on Multilayer Integrated Vertical-EBG Structure and its Application to Slot Array Antenna Design

A novel methodology to create metallic waveguides with multilayer integrated vertical-electromagnetic bandgap (EBG) structure is proposed in this article, and the structure realizes low-cost millimeter-wave (mmWave) slot array antennas. A multilayer stack of easy-to-process thin metallic etching plates is introduced to design mmWave waveguide using compression fit instead of diffusion bonding and welding assembly process. The electromagnetic (EM) wave leakage from the gaps between the metallic plates is suppressed using the vertical-EBG structure and antiphasing feeding. The dispersion diagrams of the vertical-EBG unit cell are investigated to illustrate the suppression of leakage. Another leakage wave intercepting methodology is adopted by antiphase feeding to prevent leakage wave from the adjacent slot subarrays. Finally, two examples of 2 $\times $ 8 and 8 $\times $ 8 slot array antennas are presented to verify our design concept. The measured impedance bandwidths of the two antennas are 77.1-84.6 GHz (9.3%) and 78.6-84.9 GHz (7.7%). In addition, the 3 dB broadside gain bandwidths are 73.1-85.3 GHz (15.1%) and 76.8-84.4 GHz (9.4%). The results show the aperture efficiencies up to 56.4%.