Imaging quality of optically transparent antennas on shared apertures

Silva, Zachary J.; Valenta, Christopher R.

doi:10.1117/12.2603967

Cited by 2 publications

(3 citation statements)

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“…1. The pitch (p) and width (w) of the metal strips determine the transparency of the structure and it can be calculated by [13]:…”

Section: A Transparent Conductive Metal Meshmentioning

confidence: 99%

Optically Transparent Beam-Steering Reflectarray Antennas Based on a Liquid Crystal for Millimeter-Wave Applications

Aghabeyki,

de la Rosa,

Caño-García

et al. 2024

IEEE Trans. Antennas Propagat.

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This study presents a method to realize an optically transparent beam-steering antenna. The RF and optical features of Liquid Crystal (LC) technology are used in combination with transparent metal mesh to realize the first optically transparent reconfigurable reflectarray (RA). Since the electric field of bias and Radio Frequency (RF) signals are highly non-uniform, the LC permittivity is both anisotropic and inhomogeneous thus the behavior of LC molecules needs to be obtained for accurate modeling prior to antenna design. A unit cell consisting of metallic mesh and LC is analyzed and LC director distribution is obtained. The director data are transformed into permittivity tensors in the entire LC volume and the LC is discretized in electromagnetic simulation software to perform full-wave periodic boundary simulation to model the anisotropy and inhomogeneity. The discretized model is approximated by a single dielectric block with a new permittivity range for GT7 LC material. A 10×10 RA is fabricated and measured in terms of optical and RF performance. The measured phase shift of the unit cell is 260˚ when the voltage is increased from 0 V to 40 V. The measured beam scans from -10˚ to 50˚ in the E-plane and from -50 to +50 in the H-plane with a 14.35 dBi maximum gain. The prototype optical performance is also measured. The benefits and drawbacks of current RF LC mixtures are discussed. It shows that with an appropriate LC mixture optimized for both RF and optical transmission, the LC-based optically transparent antennas are a viable solution for various new applications.

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“…1. The pitch (p) and width (w) of the metal strips determine the transparency of the structure and it can be calculated by [13]:…”

Section: A Transparent Conductive Metal Meshmentioning

confidence: 99%

Optically Transparent Beam-Steering Reflectarray Antennas Based on a Liquid Crystal for Millimeter-Wave Applications

Aghabeyki,

de la Rosa,

Caño-García

et al. 2024

IEEE Trans. Antennas Propagat.

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“…As shown in [22], periodic mesh gratings over an optical aperture induce degradation to the optical performance of the aperture in terms of not only transparency, but optical resolution. The degradation in optical performance has an inverse relationship to the conductor or antenna performance such that when the antenna conductor is not transparent, an ideal case for an antenna, the worst optical performance is obtained.…”

Section: Diffraction and Its Effect On Imaging Qualitymentioning

confidence: 99%

“…The periodic square unit cell is the most common transparent conductor used for antenna and other RF applications due to its design and manufacturing simplicity [4,23,24]. In general, the periodic square unit cell has a well-known diffraction pattern that is a 2-D sinc function through both the vertical and horizontal planes (as shown on the left side of Figure 1).…”

Section: Periodic Square Unit Cellmentioning

confidence: 99%

Ultra-uniform diffraction patterns in meshed optically transparent antennas

Silva,

Van Zyl,

Luk

et al. 2023

SPIE Future Sensing Technologies 2023

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State-of-the-art optically transparent antennas used for shared RF/EO/IR apertures typically utilize mesh conductors to simultaneously achieve high optical transmission and low RF resistivity compared to that of transparent conducting oxides (TCOs). Unlike TCOs, however, mesh conductors need to be patterned in a geometric shape – most commonly a square or rectangular periodic grid. As a result, this grid can introduce a diffraction pattern which can degrade the imaging quality of the optical system. It is shown that transmission decreases according to the geometric area covered by the mesh at normal incidence and that transmitted energy is pushed into higher diffractive orders, as expected. These effects are ultimately summarized as a decrease in the signal-to-noise and signal-to-background ratios. Performance tradeoffs in varying the line width and line spacing of a rectangular grid are shown whereas the smaller the line width and spacing, the smaller effects there are from the grid. Furthermore, methods to reduce diffractive effects –improving imaging quality - in structures by randomizing the substructure in which light interacts are presented. Randomizing tiled mesh substructures reduces periodicity to generate ultra-uniform diffraction, while maximizing conductivity of the structure. Increased randomization of a meshed aperture allows for a reduction in higher diffraction orders by 99%. By leveraging the results of this study, shared RF/EO/IR apertures can maximize their performance across the electromagnetic spectrum.

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Imaging quality of optically transparent antennas on shared apertures

Cited by 2 publications

References 0 publications

Optically Transparent Beam-Steering Reflectarray Antennas Based on a Liquid Crystal for Millimeter-Wave Applications

Optically Transparent Beam-Steering Reflectarray Antennas Based on a Liquid Crystal for Millimeter-Wave Applications

Ultra-uniform diffraction patterns in meshed optically transparent antennas

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