Graphene-based Programmable Dual Dipole Antenna

Academic Background

The terahertz (THz) band (0.1 to 10 THz) has garnered significant attention in fields such as wireless communication, high-resolution imaging, and body-centric communication due to its distinctive characteristics. However, a major drawback of terahertz waves is the substantial propagation loss in the atmosphere, leading to short-range communication. Additionally, designing and manufacturing devices for terahertz applications encounter challenges, particularly regarding the robustness of signal sources capable of delivering high gain and adequate coverage. Despite these challenges, the sub-terahertz range offers unprecedented opportunities for next-generation wireless communication systems, including channel capacities with theoretical data rates exceeding 100 Gbps, significant miniaturization of antenna geometries, and improved spatial resolution.

To overcome these limitations, reconfigurable antennas (RAs) have become a hot topic in wireless communication research. Traditional reconfigurable antennas typically use PIN diodes, micro-electromechanical system (MEMS) switches, etc., but these technologies are not suitable for the terahertz band. Graphene, as a two-dimensional material, has become an ideal choice for developing tunable electromagnetic devices due to its tunable surface conductivity and seamless integration capabilities with other components. However, graphene-based reconfigurable antennas still face issues with radiation efficiency, especially when the chemical potential approaches 0 eV.

Additionally, optically transparent antennas have gained increasing attention in recent years because they enable new functionalities such as transparent displays with embedded antennas and hidden base stations. However, existing transparent antenna models suffer from issues such as frequency offset, low gain, low efficiency, and reconfigurability. Therefore, developing a transparent antenna with both transparency and high performance in the sub-terahertz range has become an urgent problem to solve.

Paper Source

This paper, titled “Graphene-based programmable dual dipole antenna with parasitic elements,” was co-authored by Sana Ullah, Ilaria Marasco, Antonella D’Orazio, and Giovanni Magno from the Department of Electrical and Information Engineering at the Polytechnic University of Bari, Italy. It was published in the journal Optical and Quantum Electronics in 2025, with the DOI: 10.1007/s11082-025-08050-1.

Research Details

a) Research Process

This study designed a transparent programmable dual-dipole antenna based on graphene to achieve beamforming in the sub-terahertz band. The research process includes the following steps:

1. Antenna Design
   The antenna uses a polyimide substrate with two orthogonal graphene dipoles and eight fan-shaped graphene parasitic elements. By adjusting the chemical potential of graphene, the current distribution of the antenna can be changed to form different radiation patterns (such as single beam, dual beam, and quad beam).

   • Experimental Object: The design parameters of the antenna structure include the length ((l)), width ((w)), gap ((g)) of the dipole arms, the inner and outer radii ((r_i, r_o)) of the parasitic elements, and the angular width ((\theta)).
     
   • Experimental Method: Electromagnetic simulations were performed using CST Microwave Studio software, and the optimal parameter combination was determined through iterative optimization.
     
   • Innovation Point: Coplanar side-gate technology was used to adjust the chemical potential of graphene to achieve dynamic switching.

2. Parameter Optimization
   The research team systematically optimized multiple geometric parameters, including the frequency range (180 GHz to 220 GHz), dipole dimensions ((l = 135-160 \mu m, w = 15-35 \mu m)), inner and outer radii of the parasitic elements ((r_i = 220-260 \mu m, r_o = 600-680 \mu m)), and angular width ((\theta = 10^\circ-60^\circ)). The final optimized parameters were: (r = 680 \mu m, r_i = 240 \mu m, r_o = 610 \mu m, l = 155 \mu m, w = 27 \mu m, g = 25 \mu m, h = 150 \mu m, \theta = 40^\circ).

3. Radiation Pattern Analysis
   The research team generated various radiation patterns by changing the coding pattern (i.e., activating specific parasitic elements). These included single-beam, dual-beam, and quad-beam modes, and analyzed the directivity, gain, and bandwidth of each mode.

b) Main Results

1. Impedance Matching and Spectral Response
   The study showed that different coding patterns have little impact on the impedance matching and spectral response of the antenna. The -10 dB impedance bandwidth of the antenna ranges from 187 GHz to 214 GHz, with the resonant frequency varying slightly between 196 GHz and 203 GHz.

2. Gain and Efficiency
   Within the -10 dB impedance bandwidth, the antenna’s gain ranges from -1.2 dBi to 2.3 dBi. For single-beam, dual-beam, and quad-beam configurations, the maximum realized gains are 2 dBi, 1.3 dBi, and 0.7 dBi, respectively. The total efficiency exceeds 27% and reaches over 45% near the impedance matching frequency.

3. Symmetry of Radiation Patterns
   The study found that flexible control of radiation patterns can be achieved by rotating or reflecting the coding patterns. For example, coding patterns “h15”, “h35”, and “h345” can generate complete 360° beam scanning through symmetry operations.

c) Conclusions and Significance

This study successfully designed a transparent dual-dipole antenna based on graphene that can achieve programmable beamforming in the sub-terahertz band. The main feature of this antenna is its transparency and high performance, making it suitable for applications in indoor communications, smart buildings, transportation, flexible electronics, and wearable technology. Additionally, this design demonstrates the potential of graphene in high-frequency antennas, providing important references for future research.

d) Research Highlights

1. Innovative Design: First realization of a transparent antenna with 360° beam scanning capability in the terahertz band.
   
2. Versatility: Dynamic adjustment of graphene’s chemical potential to switch between single-beam, dual-beam, and quad-beam modes.
   
3. Efficiency: Optimized antenna exhibits high efficiency and high gain at the impedance matching frequency.
   
4. Transparency: Use of polyimide substrate and graphene materials ensures optical transparency of the antenna.

e) Other Valuable Information

The research team noted that future work will focus on exploring more coding schemes to generate more complex radiation patterns. Additionally, the study will also examine the interference effects between horizontal and vertical dipoles to further expand the functionality of the antenna.

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Summary

This paper proposes a transparent dual-dipole antenna based on graphene, addressing the shortcomings of existing antennas in terms of transparency, reconfigurability, and performance. Through detailed parameter optimization and radiation pattern analysis, the research team demonstrated the wide application potential of this antenna in the sub-terahertz band. This research achievement not only advances the development of transparent antenna technology but also provides new solutions for future wireless communication systems.