A Transparent Ultra-wideband Antenna Fed by CPW Based on Characteristic Mode Theory

This paper proposes a high isolation transparent ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna based on characteristic mode theory. The antenna consists of four coplanar waveguide (CPW)-fed UWB monopoles, each of which is hollowed out into a mesh structure guided by feature mode theory with metal and substrates, with an excitation added at the feed point to successfully excite modes 1, 3, 5, and 7. These excited modes cover a frequency range of 1.7-13 GHz. An orthogonal layout is adopted to make the antenna structure more compact. Ultimately, a transparency of 76.3% and a radiation efficiency of over 85% are achieved, with an effective frequency band coverage of 1.32-12.15 GHz. A fan-shaped metal mesh (MM) decoupling structure is printed on the mesh structure of the antenna substrate, achieving isolation greater than 20 dB between any two components without reducing the antenna’s transparency. Across the entire operating frequency band, the gain of the antenna varies from 1.3 to 5.5 dBi within the effective bandwidth, and the envelope correlation coefficient (ECC) is less than 0.001. Additionally, the antenna exhibits good radiation characteristics. It can be easily manufactured at a low cost using traditional printed circuit board (PCB) and laser cutting techniques.