Gain-Enhanced On-Chip Folded Dipole Antenna Utilizing Artificial Magnetic Conductor at 94 GHz

On-chip antennas suffer from low gain values and distorted radiation patterns due to the lossy and high permittivity Si substrate. An ideal solution would be to isolate the lossy Si substrate from the antenna through a perfect electric conductor ground plane. However, the typical CMOS stack up that has multiple metal layers embedded in a thin oxide layer does not permit this. In this letter, an artificial magnetic conductor (AMC) reflecting surface has been utilized to isolate the Si substrate from the antenna. Contrary to the previous reports, the AMC structure is completely embedded in the thin oxide layer with the ground plane above the Si substrate. In this approach, the AMC surface acts for the first time as both a reflector and a silicon shield. As a result, the antenna radiation pattern is not distorted and its gain is improved by 8 dB. The fabricated prototype demonstrates good impedance and radiation characteristics.