Four-port circularly polarized antenna array with enhanced isolation and polarization conversion using metasurface for 5G communications

This study presents a four-port sequentially rotated circular polarized (SRCP) low-profile antenna array with enhanced isolation through a dual-layer, double-sided metasurface-based decoupling (DSMD) structure for 5G communications. The dual-layer DSMD structure is placed over the SRCP antenna array. The DSDM, with positive permeability and epsilon-negative properties, improves the isolation in an SRCP antenna array by manipulating electromagnetic wave behavior. Its band-stop characteristics attenuate 3.5 GHz within the CP antenna's bandwidth, minimizing interference between closely spaced CP antennas. The dual-layer DSDM has achieved a polarization conversation ratio (PCR) of 92% at 3.5 GHz and 90% at 3.1 to 3.7 GHz. To validate our simulation results, a prototype of the SRCP antenna array with dimensions 0.92λo × 0.92λo × 0.0281λo at 3.5 GHz is fabricated, along with the proposed decoupling DSMD with dimensions of 1.03λo × 1.03λo × 0.0409λo at 3.5 GHz. The measurements show that integrating a DSMD substantially enhances inter-port isolation, realized gain, and efficiency. The measured isolation between the SRCP antenna array elements is increased by over 25 dB across the frequency band of 3.3 GHz to 3.7 GHz. At the 3.5 GHz, the measured isolation reaches 27 dB. Additionally, a 3 dB axial ratio and envelope correlation coefficient <0.0004 are achieved across the operating band, with a peak realized gain of 8.20 dBic and 76% total efficiency obtained at 3.5 GHz. The CP antenna generates a broadside radiation pattern at 45° and 135° in the azimuth plane. These advancements position it as a promising solution for 5G communication applications.