Simultaneous Gain and Bandwidth Enhancement of an AMC-Backed Antenna-on-Chip Through Magnetic Coupling Structures

Antenna-on-Chip (AoC) is one of the most promising solutions in the upcoming 6G era. However, AoC radiates often inefficiently due to the highly conductive silicon substrate of standard complementary metal-oxide–semiconductor (CMOS) processes. Artificial magnetic conductors (AMCs) embedded within the CMOS stack-up have been shown to enhance the gain by providing in-phase reflection and isolating the AoC from the Si substrate. However, due to the proximity of AoC to the AMC, only the nearby AMC cells get properly illuminated. Thus, the outermost cells do not contribute to the in-phase reflection. Additionally, a typical AMC-backed AoC suffers from narrow bandwidth because of the ultrathin CMOS stack-up. To address these issues, this communication proposes magnetic coupling structures based on metallic patches (H-CES-M), which can not only improve the illumination of the AMC by coupling the energy from well-illuminated unit cells to the outermost unit cells but also enhance the bandwidth by introducing additional resonances. Compared to the conventional AMC, the antenna gain can be improved by 4.5 dB through H-CES-M, and the impedance bandwidth can be enhanced by six times. Finally, the proposed AMC-backed AoC with H-CES-M achieved an impedance bandwidth of 14.8 GHz (an improvement of 12.7 GHz over standard AMC), a boresight gain of 10.4 dBi, a radiation efficiency of 62% at 94 GHz, and 3-dB gain bandwidth of 9.6%.