Ultra-Thin Artificial Magnetic Conductor for Gain Enhancement of Antenna-on-Chip

Abstract

System-on-Chip (SoC) has become an attractive solution to achieve highly integrated wireless systems. However, the Antenna-on-Chip (AoC) suffers from poor radiation due to the lossy silicon substrate in standard CMOS processes. Artificial Magnetic Conductors (AMC) with the ground plane above the silicon can enhance the radiation, however, fitting the AMC completely in the thin stack-up (~10-15 μm) is extremely challenging, particularly for frequencies below 100 GHz. In this paper, Metallic Posts (MP) and Embedded Guiding Structures (EGS) have been investigated to reduce the AMC thickness by employing the available vias and metal layers in the stack-up. An in-house CMOS-compatible process has been used to realize the AoC, where typical low-conductivity adhesion layers have been avoided to reduce the undesired losses by using the surface roughness in a unique fashion. With MP and EGS approaches, AMC thickness can be reduced by 33% and 41% respectively. The AMC with EGS fits within an oxide of a thickness of 16 μm. A monopole antenna, backed by this AMC, demonstrates a gain of 5.85 dBi and radiation efficiency of 57% at 94 GHz, bettering the gain and radiation efficiency by 9.15 dB and 42% respectively as compared to the case without AMC.

Improving the Performance of Antenna-on-Chip by Effectively Illuminating the Artificial Magnetic Conductors Through Coupling Enhancement Structures

“…This configuration has previously only been possible with a thick dielectric layer [23], which is not suitable for conventional CMOS processes. In our previous work, we showed that a specially designed thickness reduction structure (TRS) could reduce the AMC thickness by 41% [24].…”

“…In addition to the thickness issue that was tackled in [24], the ineffective illumination of the AMC by AoC is another essential issue that affects the performance of the AMC and antenna combination significantly. Theoretically, the AMC must be an infinitely large periodic surface.…”

“…Therefore, it is important that every AMC unit cell is effectively illuminated in order to benefit from the limited available space. Owing to ineffective illumination, the AMC-backed antenna gain curve reaches the saturation point early [15,23,24,26,27].…”

An Improved Path-Loss Model for Reconfigurable-Intelligent-Surface-Aided Wireless Communications and Experimental Validation

“…can provide an improved end-user experience with enhanced 29 coverage and spectral efficiency. Therefore, numerous studies 30 have been conducted on mmWave beamforming systems [1], 31 [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. 32 However, the coverage hole problem in a non-line-of-33 sight (NLOS) environment remains difficult to solve, even 34 with the advanced beamforming technologies of 5G FR2 35 bands, as explained below.…”

“…However, this beam pattern is impractical because it represents an ideal rectangular beam, which assumes that the antenna radiates equally in the rectangular area. In [49], the beam efficiency is applied in (7) to calculate the practical case, as…”