Liquid-Crystal-Embedded Aperture-Coupled Microstrip Antenna for 5G Applications

This letter presents a novel reconfigurable microstrip antenna with a frequency of 28 GHz and an embedded liquid crystal (LC). First, a novel fabrication process that employs a heat press machine is developed. This allows for the successful creation of thin substrates with thicknesses ranging between 0.13 and 0.25 mm. It is validated that the proposed stacked topology achieves a wide tunable range of resonant frequency. In addition, a simple bias configuration is achieved by connecting the bias position to the middle of the patch, where radio frequency (RF) potential is zero. The proposed antenna adopts a three-layer stacked printed circuit board (PCB) structure to render a cavity in which the LC is injected. The bottom patch of the top substrate is designed to contact the LC, and thus, it simultaneously functions as a dc bias electrode and a radiating element. In addition, unlike conventional stacked patch antennas, the additional patch on the top of the PCB structure is tuned to enhance gain. Compared with the simulated performance of a prior LC-based antenna, the tunable range of the resonant frequency of the proposed antenna is improved by more than three times at a center frequency of 28 GHz and the peak radiation efficiency is improved by up to 17%. Furthermore, the area (252 mm(2)) of the proposed LC-based antenna is 40% of the area of the prior LC-based antenna (625 mm(2)).