Transparent Saltwater in Glass Structure: Simultaneous Tunable UHF Antenna and EMI Shielding Window

This paper presents a transparent saltwater in glass structure working simultaneously as a tunable UHF antenna and EMI shielding window. The proposed structure has high transparency (
$\!>91$
%), which is achieved through its use of salty water as a conductive medium held within a clear and hollow glass rectangular prism, allowing its use as an optical window. On one hand, the saltwater in glass structure plays a role as an EMI shielding window with a shielding effectiveness (SE) above 20 dB in the C-band. On the other hand, the proposed structure works as a frequency-and beam-tunable UHF antenna by using dual-port feeding configurations. Experimental results show that for a basic configuration using single-port feeding, the antenna has a −6 dB bandwidth ranging from 350 to 680 MHz and efficient radiation efficiency (
$\!>60$
%) over the band. For advanced configurations, a tunable frequency and directional radiation pattern can be achieved with enhancing gain compared to the basic configuration. These results demonstrate the proposed antenna can be used as a bi-functional device, i.e., as a tunable antenna and EMI shielding window. To the best of our knowledge, this is the first demonstration of such a bi-functional device with transparent performance.