Design and Optimization of Transparent Antennas for Repeater-Assisted MIMO Systems for Solar Panel Integration

Abstract

Antennas are fundamental components in the evolution of wireless communication systems, including current 5G networks and emerging 6G technologies. This thesis presents the design, simulation, and experimental validation of two antennas specifically developed for integration into repeater-assisted MIMO (Multiple Input Multiple Output) systems. These systems aim to enhance spatial multiplexing and coverage by employing distributed, low-complexity repeater nodes that act as active scatterers, retransmitting signals with minimal latency and without relying on dedicated backhaul connections.

The proposed antennas are designed for conformal deployment on cylindrical solar panel surfaces, enabling compact, energy-autonomous communication nodes. This integration supports flexible and cost-effective deployment of repeater-assisted MIMO in scenarios where conventional infrastructure is impractical, such as in coverage holes, indoor or obstructed environments, or locations lacking reliable backhaul connectivity.

This work investigates two complementary antenna designs: a directive equiangular spiral antenna array for focused backhaul communication, and a transparent omnidirectional antenna array for uniform azimuthal coverage. Both designs are optimized for conformal integration, with special attention to minimizing mutual coupling, achieving impedance matching, maintaining high radiation efficiency, and preserving polarization purity.

The proposed antennas are evaluated through comprehensive full-wave electromagnetic simulations and validated via experimental measurements. Key performance metrics such as gain, bandwidth, impedance matching, polarization, and isolation are assessed under realistic conformal mounting conditions. The results confirm that both antennas exhibit robust performance when integrated onto curved photovoltaic surfaces, supporting their suitability for next-generation solar-powered repeater nodes.

By enabling efficient, low-profile, and scalable antenna solutions, this thesis advances the development of repeater-assisted MIMO architectures, offering a promising foundation for sustainable and flexible wireless infrastructure in future 5G and 6G networks.

Popular Abstract

As mobile networks evolve toward 5G and 6G, they demand faster data rates, broader coverage, and greater energy efficiency. However, traditional base stations are not always viable due to size, power, or cost constraints. One solution is to use compact, solar-powered wireless repeaters that relay signals without needing fixed infrastructure.

This work focuses on the design and optimization of two antennas for direct integration onto curved solar panels. The goal is to create self-powered communication nodes that can be seamlessly embedded into urban furniture such as rooftops.

Two types of antennas were developed: an omnidirectional antenna, based on a transparent metal mesh structure, which radiates uniformly in all horizontal directions to ensure local coverage and a directive spiral antenna, optimized for circular polarization and focused radiation, ideal for long-range backhaul communication.

Both antennas were designed using full-wave electromagnetic simulations and were tested under conformal (curved) conditions. The omnidirectional design maintains high optical transparency and structural integrity, enabling its integration over photovoltaic surfaces without reducing energy harvesting. The spiral antenna preserves directional performance and circular polarization even when conformed to cylindrical geometries.

Simulation and experimental results confirm that the antennas achieve good impedance matching, isolation, and gain in the 3–5 GHz band, even when mounted on curved surfaces.

By integrating renewable energy and wireless communication into a single platform, this project contributes to the development of sustainable and scalable network infrastructure. It lays the groundwork for future multifunctional systems where structures such as solar poles or external walls serve as both energy sources and wireless relays.

• author: Bocigas Iglesias, Julia Patricia
• supervisor: Anders J. Johansson; Sara Willhammar
• organization: Department of Electrical and Information Technology
• course: EITM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Directive antenna, Omnidirectional antenna, Repeater-assisted MIMO, Conformal antenna, Cylindrical integration, Solar-powered repeater, Electromagnetic simulation.
• report number: LU/LTH-EIT 2025-1099
• language: English
• id: 9213508
• date added to LUP: 2025-10-08 13:34:37
• date last changed: 2025-10-08 13:34:37