Tunable liquid crystal metamaterial filter with polarization-insensitive characteristic

ABSTRACT

In this paper, a systematic design method for polarization-insensitive tunable liquid crystal (LC)-based metamaterial filter with the passband of flat-top and sharp roll-off is proposed. A compact LC-based bandpass metamaterial filter unit cell with a dimension of 0.09 λ × 0.09 λ is designed. The metamaterial filter element consists of a pair of planar pinwheel-shaped metallic structures with four symmetrically distributed isosceles triangular patches. LC is sandwiched in this pair of metallic structures. The metal pattern on each layer is 90° rotationally symmetrical leading that the LC-based metamaterial filter is insensitive to the polarization of incident waves. In order to obtain the transmission characteristics of flat top and sharp roll-off, a double-layer LC-based metamaterial filter structure is proposed. Full-wave simulations show that the central frequency of the metamaterial filter is tuned from 10.88 GHz to 11.78 GHz, and the tuning range reaches up to 7.9%. Meanwhile, under TE and TM polarizations, the double-layer LC-based metamaterial filter structure achieves filtering characteristics with a flat-top passband of not less than 997 MHz and sharp roll-off for arbitrary LC states. Moreover a prototype sample is designed, fabricated, and measured to verify the proposed design method.      

Graphical abstractSchematic of the LC-based metamaterial filter. (a) Three-dimensional expansion view. (b) The unit cell structure. (c) Metal resonant structure

KEYWORDS:

• Polarisation-insensitive
• tunable
• liquid crystal
• metamaterial filter

Acknowledgments

The authors would thank the support from the National Natural Science Foundation of China (Grant No. 61971160).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Grant No. 61971160].