An Ultra-Wideband Circularly Polarized Optically Transparent Antenna Using ITO Film

This paper presents a novel broadband circularly polarized optically transparent monopole antenna using indium tin oxide (ITO) and PMMA. The proposed design successfully integrates ultra-wideband circular polarization characteristics with exceptional optical transparency. The antenna, constructed with a three-layer configuration utilizing ITO films as both the radiating patch and ground plane, along with transparent PMMA serving as the substrate, features compact dimensions of 40 × 40 × 1 mm³. By leveraging a co-optimized design incorporating a slotted hexagonal-ring radiating patch, triangular perturbation ground plane, and stepped-impedance feeding structure, the antenna achieves a circularly polarized operating bandwidth of 2.8-6.6 GHz (fractional bandwidth of 77.9%), with an axial ratio < 3 dB and return loss < -15 dB. The experimental findings exhibit strong consistency with the simulations, illustrating a high level of visible-light transmittance and radiation patterns characterized by right-hand circular polarization in the positive <i>z</i>-axis direction (+z) and left-hand circular polarization in the negative <i>z</i>-axis direction (-z). This innovative antenna shows great potential for applications in smart windows, display integration, and 5G communication systems.