Harnessing Ambient Energy: A Review of Spiral Antenna Designs for IoT-Driven Rectenna Systems

Abstract

The Internet of Things (IoT) represents a global network of interconnected devices capable of sensing, communicating, and acting upon their environment. Within this ecosystem, sensors serve as the fundamental components that bridge the physical and digital worlds by detecting parameters such as temperature, humidity, pressure, motion, and pollution levels, and converting them into digital signals for decision-making. Sensors and actuators embedded in physical objects form the interface through which real-world information is acquired and controlled. However, one of the major challenges in deploying large-scale IoT systems lies in providing a continuous and sustainable power supply to numerous sensors, especially flexible or wearable ones. To overcome this limitation, energy harvesting technologies have emerged as a promising solution by capturing and converting energy from ambient sources such as solar radiation, infrared (IR) light, and radio frequency (RF) signals. This enables self-powered operation in diverse applications ranging from wearable and textile-based electronics to medical implants and environmental monitoring systems. In such systems, the rectenna—a combination of a receiving antenna and a rectifying circuit—is often employed to convert ambient electromagnetic energy into direct current (DC) power. The antenna plays a crucial role as the primary energy collector, and its geometry directly affects the harvesting efficiency. Among the various geometries explored, this paper discusses how spiral antenna structures fulfill these design requirements and contribute to efficient multi-source energy harvesting systems.

Introduction

The Internet of Things (IoT) is an interconnected ecosystem of smart devices—sensors, actuators, wearables, and machines—that continuously sense environmental parameters and transmit data for real-time analysis, enabling automation, remote monitoring, and intelligent responses. However, powering autonomous, low-power IoT devices remains a major challenge, as traditional batteries are often impractical for large-scale deployments.

Energy harvesting (EH), particularly RF energy harvesting (RFEH), offers a solution by converting ambient electromagnetic waves—from Wi-Fi, cellular networks, Bluetooth, and broadcasts—into usable electrical power for IoT sensors, wearable electronics, and biomedical implants. RFEH reduces maintenance, extends device lifetimes, and supports sustainable operation in remote areas.

The working principle relies on a rectenna system:

1. Antenna captures ambient RF waves.

2. Impedance matching network maximizes power transfer.

3. Rectifier converts AC to DC.

4. Energy storage supplies continuous or intermittent power to devices.

Key antenna requirements include broadband/multiband operation, high efficiency, compact size, polarization insensitivity, and integration suitability for wearables and IoT devices. Spiral antennas (e.g., Archimedean, logarithmic, Fibonacci) are particularly suitable due to their broadband performance, compact planar structure, and adaptable radiation characteristics, making them ideal for real-world RF energy harvesting applications.

RFEH thus bridges the gap between low-power electronics and sustainable, autonomous operation, supporting the next generation of IoT, wearable, and biomedical devices.

Conclusion

Energy-harvesting antennas hold great potential for powering low-energy electronics, sensors, and wearable or implantable devices. Among the various designs, spiral and fractal geometries have proven especially effective for broadband RF harvesting, while nano-antennas are opening new avenues for capturing energy from infrared and visible light. To translate these technologies into practical applications, it is essential to overcome material limitations, enhance conversion efficiency, and ensure seamless integration with existing systems. Ongoing research into hybrid harvesting techniques, circuit-level optimization, and novel antenna geometries is paving the way towards reliable, efficient, and scalable energy-harvesting solutions.

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Copyright

Copyright © 2025 M L Sharma, Sunil Kumar, K C Tripathi, Vartika Bhujel , Piyush Dahiya . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.