A Transparent SIWS LOT Antenna for KA-Band Applications

This study addresses the challenge of developing high-performance, aesthetically integrated antennas for Ka-band (24.31–27.81 GHz) applications, essential in 5G networks and automotive systems where transparency is advantageous. We propose a novel transparent substrate-integrated waveguide (SIW) slot antenna that utilizes a polyethylene terephthalate (PET) substrate integrated with a conductive mesh, achieving high optical transparency (approximately 71%) alongside superior electrical conductivity. The antenna's SIW structure is modified by selectively omitting specific metallic vias and incorporating resonant I-shaped and U-shaped slots to enhance hybrid resonance generation, broadening operational bandwidth significantly. Our design exhibits a peak gain of 7.8 dBi at 26.5 GHz and maintains a front-to-back ratio and cross-polarization ratio exceeding 20 dB, making it highly suitable for millimeter-wave applications. Empirical validation demonstrates a measured impedance bandwidth from 24 to 28.55 GHz with a fractional bandwidth of 17.3%, surpassing simulated predictions due to minor design optimizations. Despite slight manufacturing discrepancies, the agreement between simulated and measured results confirms the design's robustness and reliability. This research underscores the potential of transparent antennas in next-generation communication systems, offering a functional solution that merges transparency with high-frequency performance, paving the way for seamless integration in modern, visually sensitive applications.