Ahsan Halimi

RF energy harvesting (RF-EH) technology has emerged as a key research direction driven by the increasing demand for sustainable power solutions in applications such as low-power wireless sensors, radio frequency identification (RFID) tags, IoT, and biotelemetry. The need to eliminate frequent battery replacements in large-scale sensor deployments has made RF-EH a promising alternative. At the core of these systems is the rectenna, a key component responsible for capturing and converting ambient RF energy into usable DC power. Research efforts have primarily focused on enhancing power conversion efficiency, ensuring compatibility with various sensors, and maximizing harvested power. Multi-band rectennas have gained significant attention for their ability to capture RF energy across multiple frequency bands, enabling higher overall power generation compared to narrowband counterparts. Consequently, multi-band rectifier circuits play a critical role in RF-EH systems. This paper presents a comprehensive review and performance analysis of multi-band rectifier designs, encompassing over 110 research studies published in the last decade. To enable objective comparison, we propose a novel power/frequency-weighted efficiency (PFE) metric, which accounts for operating frequency, input power, and the number of bands. This metric provides valuable insights into the efficiency of various rectifier architectures and serves as a benchmark for future advancements in RF energy harvesting.

The microwave energy-harvesting (MEH) and microwave power transfer (MPT) technologies have become the most emerging areas of research nowadays. The microwave rectifier circuit is the bottleneck of both the MEH and MPT systems. The efficiency of the system depends on the power conversion efficiency (PCE) of the rectifier. Due to the recent advancement of the fifth-generation communication system, it is desirable to propose an efficient rectifier operating at sub-6 GHz 5G bands. A dual-band rectifier circuit is designed and demonstrated for MEH/MPT purposes, specifically at sub-6 GHz 5G frequency bands. The dual-band matching is achieved by using a stepped impedance transmission line. The rectifier covers N78 (3.3–3.6 GHz) and N79 (4.8–5.0 GHz) bands. Peak PCE of 67.6% @ 3.5 GHz and 56.8% @ 4.9 GHz are achieved. For validation purpose, the rectifier is fabricated and characterized and measured results show good agreement with simulated results.

RF-based wireless energy harvesting (WEH) and wireless power transfer (WPT) are gaining attention due to their capability of powering various sensors and devices. A low-power device can be fed wirelessly by capturing ambient RF energy through a WEH system. In the case of a high-power device, a WPT system can provide the required amount of power using intentional RF sources.

This article presents an overview of dielectric resonator (DR)-based sensing elements and their applications in RF energy-harvesting (RFEH) and wireless power transmission (WPT) systems. With increased wireless applications, the demand for electrical energy goes up, thereby enabling the development of various energy sources. RF energy is widely available and the most efficient energy source. Although DR antennas (DRAs) have been studied extensively in the last few decades, they have not been employed in RFEH and WPT applications. The intention of the proposed article is 1) to provide an overview of the DRA for RFEH and WPT applications; 2) to accommodate various performance enhancement approaches for the DRA; and 3) to highlight the research gap for developing a complete rectenna system that helps future researchers. We believe that this survey may help the DRA.

In this paper, the characteristics of four spiral-facet structures are studied for RF energy harvesting (RFEH) applications for increasing the harvesting power from the surrounding atmosphere. A rectangular dielectric resonance antenna (RDRA) is selected and placed above an FR4-epoxy substrate. Metallic rectangular spirals are then placed on the dielectric resonator (DR) surface to create resonances with insensitive polarization characteristics. The proposed spirals help provide wideband/ multiband characteristics at 4.85, 5.0, 5.5, 5.8, and 6.25 GHz that covers 5G 4.9, WLAN 5.0, WLAN 5.5, Wi-Fi 5.8, and Wi-Fi 6E bands. The minimum gain achieved is 5 dBi in all possible configurations. A broadband rectifier circuit (4.67-7.0 GHz) with a staircase multistage transmission line matching network covering all resonant frequencies in various facet-loaded antenna configurations is proposed for RF-to-DC conversion purposes. The rectifier’s maximum power conversion efficiency (PCE) is achieved as 77.3% at a 13.5 dBm input power level, and the corresponding output voltage is 4.92 V.

In this article, we present an overview of the 5G rectifying antenna and its primary elements for applications in millimeter-wave (mm-wave) energy harvesting (EH) and wireless power transmission (WPT). The wide spectrum available for 5G communication bands have attracted significant attention for extensive applications. The power received by the harvesting antenna relies on the size of the antenna. Hence, the realization of antenna and rectenna systems with good efficiency at 5G mm-wave is a challenge. This review article highlights the recent advances in 5G rectenna systems for different applications at the component and structure levels. The primary objectives of the article are 1) to explore the potential advances of mm-wave rectenna systems and the feasibility of their designs to attain desired characteristics and 2) to present a comparative assessment of performance parameters of existing rectenna systems.

RF energy harvesting (RFEH) is an emerging technique in the field of wireless technology. The key components of this system are receiving antenna, matching network, and rectifier circuit. A rectifier circuit based on a tuned matching circuit is demonstrated in this paper for RFEH applications. The topology of this rectifier circuit is suitable for selecting a wide range of operating frequency bands, realized by changing the value of the inductor in the matching network. For validation purpose, a rectifier has been designed, developed, and tested at 2.45 GHz. The rectifier achieved peak power conversion efficiency (PCE) of 64.5% at 0 dBm. The PCE is higher than 50% for input power in the range of −8.5–2 dBm. The proposed rectifier has a compact size of 20 × 15 × 1.524 mm³. By changing the value of the inductor in the matching network this rectifier can be redesigned for any other operating frequency in the range of 0.6–2.6 GHz.

A dual-band rectifier is presented for RF energy harvesting (RFEH) and microwave power transfer (MPT) applications. Starting with a single-band rectifier, the second band is added by utilizing a half-wavelength transmission line (HWTL) in the matching network (MN). A series diode topology using HSMS-2860 Schottky diode is used for power conversion. The rectifier simultaneously harvests the RF energy with power conversion efficiency (PCE) of 54.9% and 42.3% and output voltage of 1.4 and 1.242 V at 0-dBm input power for 3.5-GHz 5G band and 5.8-GHz Wi-Fi band, respectively.