60-GHz air-cavity-fed slot antenna array using modified silicon micromachining process

This paper presents an air-cavity-fed four-element slot antenna array, which is fabricated using a modified silicon micromachining process. Different from traditional silicon micromachining process, the silicon dielectric is fully plated with gold without any silicon being exposed to the electromagnetic environment. In this modified silicon micromachining process, air cavities can be easily obtained to avoid substrate loss, with the merit of low loss. This new silicon micromachining process is recently introduced to the millimeter-wave antenna design, with the basic procedures of through-silicon-wafer dry etching and gold plating. An example of a four-element slot antenna array is constructed, characterized, and tested at 60 GHz. The proposed slot array is inspired by breaking the field symmetry of the channelized coplanar waveguide. By alternatively and periodically arranging the shielding blocks, a four-element slot array is achieved and fed by an air cavity, which is easily achieved using the modified process. A prototype is fabricated with the measured results including an impedance bandwidth of 10.1% from 57.15 to 63.23 GHz and a fan-shaped beam with a peak broadside gain of 12.1 dBi.