A SICL Structure for Eliminating High-modes Interferences in Zero-mode-based mmWave Antenna

In this paper, a Substrate Integrated Coaxial Line (SICL) structure is designed to the mmWave antenna with multilayer configurations for eliminating the high-order interferences. The antenna operates in the first zero-mode generated by shorting pins, hence, to achieve a miniaturized size with 0.15 $\lambda_{0} \times 0.21 \lambda_{0}$ ($\lambda_{0}$ is the free-space wavelength of 28 GHz). However, the multi-layer configurations induce interferences to the mmWave antenna, particularly generates high-mode resonances. The proposed SICL design containing eight via holes resembles the transmission line structures in the substrate, thus, mitigate these interferences and maintain the S11 parameter the same as that of original two-layer design. Moreover, using the miniaturized microstrip patch as antenna element, a $4 \times 1$ array is also constructed and discussed. Good operating performance including 7.2 dBi realized gain and 0.8 GHz impedance bandwidth is obtained, which indicates that the proposed antenna has the advantages of smaller size and potential of assembling array