# Design and Implementation of a Flexible Chipless RFID Coding Tag Based on Eyeball Structure

## TL;DR

A bio-inspired chipless RFID tag with an eyeball-like structure is developed, offering high coding capacity and flexibility for wearable applications.

## Contribution

A novel bio-inspired chipless RFID tag design with joint frequency-shift and graphic coding is introduced.

## Key findings

- The tag achieves an encoding capacity exceeding 45 bits within a 4–12 GHz frequency range.
- The design maintains performance under bending and rotation, suitable for flexible applications.

## Abstract

What are the main findings?
A bio-inspired chipless RFID tag based on an eyeball-like multi-ring resonant structure is proposed, enabling joint frequency-shift and graphic coding through branch modulation.Within the effective operating bandwidth, the designed flexible tag achieves an encoding capacity exceeding 45 bits while maintaining a compact structure on a polyimide substrate.

A bio-inspired chipless RFID tag based on an eyeball-like multi-ring resonant structure is proposed, enabling joint frequency-shift and graphic coding through branch modulation.

Within the effective operating bandwidth, the designed flexible tag achieves an encoding capacity exceeding 45 bits while maintaining a compact structure on a polyimide substrate.

What are the implications of the main findings?
The eyeball-inspired hierarchical resonator architecture provides a new design paradigm for high-density chipless RFID encoding under limited spectral resources.The demonstrated bending and rotation tolerance indicates suitability for flexible and wearable identification applications where mechanical deformation is unavoidable.

The eyeball-inspired hierarchical resonator architecture provides a new design paradigm for high-density chipless RFID encoding under limited spectral resources.

The demonstrated bending and rotation tolerance indicates suitability for flexible and wearable identification applications where mechanical deformation is unavoidable.

In this paper, inspired by the structural characteristics of the human eyeball, a bionically designed circular resonant structure is proposed, and a flexible chipless radio frequency identification (RFID) tag based on this concept is developed. By selectively adding or removing branch structures, the proposed tag achieves controllable resonant frequency shifts and distinguishable geometric pattern variations. Fabricated on a polyimide substrate with a compact size of 20 × 26 × 0.2 mm3, the tag achieves a coding capacity exceeding 45 bits while operating within an effective frequency bandwidth in 4–12 GHz, realizing a synergistic improvement in coding capacity and structural compactness under limited spectrum constraints. Simulation analyses are performed to investigate the encoding stability of the tag under various bending and rotational conditions relevant to flexible applications. Experimental results obtained under the unbent condition are consistent with the simulations, demonstrating the feasibility of the proposed chipless RFID tag.