Realization of optically transparent and broadband frequency selective rasorber using thin copper wire

Abstract

Numerous studies have been made to design broadband frequency selective rasorber (FSR). However, it is still a challenge to realize optically transparent FSR, due to the difficulty in realizing high transparency, high-quality factor(Q) parallel resonance, and low-Q series resonance simultaneously. Here, we propose a new method to design transparent FSR for the first time. To break through the technical barrier, a thin copper wire with a different configuration method is utilized to design lossy layer, which can realize high transparency, in-band transmission, and out-of-band absorption concurrently. The proposed FSR is configured by cascading a transparent lossy layer above a transparent frequency selective layer with an air space to separate them. We adopt the equivalent circuit model, electric field distribution, and loss distribution to reveal the physical mechanism of the FSR. The simulation results show that the transmission loss is 1 dB at 8.3 GHz, and the reflection amplitude is less than −10 dB in 2.7–8.9 GHz. The FSR can achieve 96.3% optical transparency theoretically. A prototype is fabricated and measured to validate the proposed design. The measured results achieve good agreement with the simulated results. The proposed FSR can act as a stealth radome for transparent components of ships and aircrafts. The application scenarios can be extended to communication and imaging systems.