In this paper, an optically transparent metamaterial with broadband absorption is presented theoretically and demonstrated experimentally. The design comprises of structures made of resistive films of indium-tin-oxide and the metamaterial exhibits over 10 dB absorption in the frequency range of 6.06–14.66 GHz. The novelty of the structure lies in its large absorption bandwidth along with a reduced thickness and optical transparency compared to broadband absorbers reported earlier. Besides, the proposed design is polarization-insensitive and gives rise to angular independent absorption for both transverse electric and transverse magnetic polarizations. The absorption mechanism in the structure has been studied by deriving an equivalent circuit model as well as analyzing several design parameters. Finally, a prototype of the proposed structure has been fabricated and measured, which shows good agreement with the simulated results.

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In this letter, a polarization‐insensitive broadband rasorber structure with in‐band transmission response has been presented. The proposed structure comprises a periodic arrangement of convoluted cross‐dipole pattern in the top layer and square slot geometry in the bottom layer. Lumped resistors are symmetrically mounted across the top pattern to result in wideband absorption, whereas in‐band transmission is obtained by careful design of the square slot in the bottom layer. The overall structure exhibits a broad absorption band (having reflection coefficient below −10 dB) in the range of 2.18 to 9.80 GHz, and the transmission band appears at 6 GHz with an insertion loss of 0.56 dB. The novelty of the proposed design lies in its compact topology, polarization‐insensitivity, angular stability, and in‐band transmission response unlike the existing rasorber structures. Surface current distribution, equivalent circuit model, and several parametric variations have also been illustrated for in‐depth analysis. A sample prototype has been fabricated and the measured results show a good agreement with the simulated responses, under normal as well as oblique incidence.

In this article, an optically transparent and flexible microwave absorber for X and Ku bands application has been presented. The proposed absorber uses optically transparent ITO coated PET sheet for creating ohmic loss and polydimethylsiloxane has been used as a dielectric substrate for optical transparency and flexibility. The novelty of the structure lies in its optical transparency and flexible with increased absorption bandwidth and minimum thickness in comparison to previously reported state of the art absorbers. The proposed absorber exhibits absorptivity (above 90%) in the frequency range from 8.00 to 20.70 GHz under normal incidence. The thickness of the absorber is 0.196λg (where λg correspond to guided wavelength with respect to dielectric constant εr). An equivalent circuit model has been proposed which shows good match with the full wave model.

A switchable wideband reflective metamaterial polarisation rotator based on plasmon resonances has been presented. The proposed design comprises of periodically arranged split rings on which PIN diodes are mounted to demonstrate switching operation. By controlling the bias voltage of the PIN diodes, the polarisation of the reflected wave can be controlled over a broad frequency range. The simulated result shows that over 90% cross-polarised reflection is observed in 2.42-3.52 GHz under OFF state, whereas co-polarised reflection is exhibited under ON state. Polarisation rotation has also been explained using two plasmon resonances in terms of electromagnetic responses. Finally the structure has been fabricated, whose measured results agree well with simulated responses, thus validating the concept behind switchable polarisation rotator.

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