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RF Power Transmission for Self-sustaining Miniaturized IoT Devices

Lukas Schulthess, Federico Villani, Philipp Mayer, Michele Magno

TL;DR

This work addresses reliable RF wireless power transfer for miniaturized IoT by designing a narrow-band, 915 MHz energy-harvesting subsystem composed of an impedance matching network, a RF rectifier, and an energy-storage-based power management circuit. The IMN and a voltage-doubling rectifier employing zero-bias Schottky diodes maximize RF-to-DC conversion efficiency, while the AEM30940 harvesting IC buffers energy to sustain a stable output under fluctuating loads. Experimental results show the system achieving an end-to-end PCE exceeding 30% at -10 dBm and peaking at 57% around 3 dBm, with a cold-start sequence demonstrating wake-up from -15 dBm input within about a minute. The work demonstrates that combining careful RF front-end design with energy storage enables battery-less, self-sustaining IoT operation and provides practical improvements over commercial harvesting solutions.

Abstract

Radio Frequency (RF) wireless power transfer is a promising technology that has the potential to constantly power small Internet of Things (IoT) devices, enabling even battery-less systems and reducing their maintenance requirements. However, to achieve this ambitious goal, carefully designed RF energy harvesting (EH) systems are needed to minimize the conversion losses and the conversion efficiency of the limited power. For intelligent internet of things sensors and devices, which often have non-constant power requirements, an additional power management stage with energy storage is needed to temporarily provide a higher power output than the power being harvested. This paper proposes an RF wireless power energy conversion system for miniaturized IoT composed of an impedance matching network, a rectifier, and power management with energy storage. The proposed sub-system has been experimentally validated and achieved an overall power conversion efficiency (PCE) of over 30 % for an input power of -10 dBm and a peak efficiency of 57 % at 3 dBm.

RF Power Transmission for Self-sustaining Miniaturized IoT Devices

TL;DR

This work addresses reliable RF wireless power transfer for miniaturized IoT by designing a narrow-band, 915 MHz energy-harvesting subsystem composed of an impedance matching network, a RF rectifier, and an energy-storage-based power management circuit. The IMN and a voltage-doubling rectifier employing zero-bias Schottky diodes maximize RF-to-DC conversion efficiency, while the AEM30940 harvesting IC buffers energy to sustain a stable output under fluctuating loads. Experimental results show the system achieving an end-to-end PCE exceeding 30% at -10 dBm and peaking at 57% around 3 dBm, with a cold-start sequence demonstrating wake-up from -15 dBm input within about a minute. The work demonstrates that combining careful RF front-end design with energy storage enables battery-less, self-sustaining IoT operation and provides practical improvements over commercial harvesting solutions.

Abstract

Radio Frequency (RF) wireless power transfer is a promising technology that has the potential to constantly power small Internet of Things (IoT) devices, enabling even battery-less systems and reducing their maintenance requirements. However, to achieve this ambitious goal, carefully designed RF energy harvesting (EH) systems are needed to minimize the conversion losses and the conversion efficiency of the limited power. For intelligent internet of things sensors and devices, which often have non-constant power requirements, an additional power management stage with energy storage is needed to temporarily provide a higher power output than the power being harvested. This paper proposes an RF wireless power energy conversion system for miniaturized IoT composed of an impedance matching network, a rectifier, and power management with energy storage. The proposed sub-system has been experimentally validated and achieved an overall power conversion efficiency (PCE) of over 30 % for an input power of -10 dBm and a peak efficiency of 57 % at 3 dBm.
Paper Structure (10 sections, 3 figures, 1 table)

This paper contains 10 sections, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Architecture
  3. Impedance Matching Network
  4. Rectifier
  5. Power Management with Energy Storage
  6. Experimental Results
  7. Matching Circuit and Rectifier
  8. Wireless Power Conversion Efficiency
  9. Cold Start
  10. Conclusion

Figures (3)

  • Figure 1: (a) High-level circuit block diagram, (b) schematic of the proposed and implemented RF rectifier and matching circuit. Selected components values are listed in Table \ref{['table:selected_components']}.
  • Figure 2: Characterization of the matching and RF rectification circuit. (a) S11 return loss of the three analyzed circuits for 0dBm input power. (b) Rectification efficiency as a function of the input power with optimally matched loads. (c) Optimal maximal power point as a ratio of the open circuit voltage. The inset visualizes the output power for varying load conditions at 0dBm input power.
  • Figure 3: AEM30940 harvesting performance: (a) End-to-end harvesting efficiency for a constant boost converter output voltage of 3.5V. (b) Cold-start sequence of the AEM30940 IC hosting the custom RF frontend at an input power of -15dBm.