Jo Bito

Ambient RF Energy-Harvesting Technologies for Self-Sustainable Standalone Wireless Sensor Platforms

In this paper, various ambient energy-harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed. Specifically, far-field low-power-density energy-harvesting technology is thoroughly investigated and a benchmarking prototype of an embedded microcontroller-enabled sensor platform has been successfully powered by an ambient ultrahigh-frequency (UHF) digital TV signal (512-566 MHz) where a broadcasting antenna is 6.3 km away from the proposed wireless energy-harvesting device. A high-efficiency dual-band ambient energy harvester at 915 MHz and 2.45 GHz and an energy harvester for on-body application at 460 MHz are also presented to verify the capabilities of ambient UHF/RF energy harvesting as an enabling technology for Internet of Things and smart skins applications.

Additively Manufactured Nanotechnology and Origami-Enabled Flexible Microwave Electronics

Inkjet printing on flexible paper and additive manufacturing technologies (AMT) are introduced for the sustainable ultra-low-cost fabrication of flexible radio frequency (RF)/microwave electronics and sensors. This paper covers examples of state-of-the-art integrated wireless sensor modules on paper or flexible polymers and shows numerous inkjet-printed passives, sensors, origami, and microfluidics topologies. It also demonstrates additively manufactured antennas that could potentially set the foundation for the truly convergent wireless sensor ad-hoc networks of the future with enhanced cognitive intelligence and “zero-power” operability through ambient energy harvesting and wireless power transfer. The paper also discusses the major challenges for the realization of inkjet-printed/3-D printed high-complexity flexible modules as well as future directions in the area of environmentally-friendly “Green”) RF electronics and “Smart-House” conformal sensors.

Fully inkjet-printed multilayer microstrip and T-resonator structures for the RF characterization of printable materials and interconnects

A vertically-integrated, fully inkjet-printed microwave structure is demonstrated for the first time, where both the metallic elements and the platform substrate are completely fabricated with the additive inkjet printing process. The surface uniformity of SU-8 polymer ink is outlined as a function of layer deposition to provide a desirable profile for a thick RF substrate application. Inkjet-printed vias are demonstrated and realized as microwave substrate interconnects within SU-8. Microstrip and T-resonator structures are developed to demonstrate the application of these inkjet-printed platforms for the RF characterization of a printable material, where the relative permittivity of the substrate is extracted as a function of frequency from 1-30 GHz.

Ambient RF Energy Harvesting From a Two-Way Talk Radio for Flexible Wearable Wireless Sensor Devices Utilizing Inkjet Printing Technologies

A complete design and additive fabrication process of flexible wearable radio-frequency (RF) energy harvesters for off-the-shelf 2 W two-way talk radios utilizing inkjet printing technology is discussed in this paper. As a result of numerous output dc power measurements of fabricated proof-of-concept prototypes, a maximum output power of 146.9 mW and 43.2 mW was achieved with an H-field and E-field harvester, respectively. Also, the effect of misalignment between receiver and hand-held radio on harvesting performance is discussed in detail. To verify their potential in real-world wearable autonomous RF modules, the operation of E- and H-field energy harvesters was verified by utilizing an LED and a microcontroller communication module under on-body and on-bottle conditions, and the effect of the energy harvesters on the performance of the harvested communication systems was inspected through received power measurements in an anechoic chamber.

A Real-Time Electrically Controlled Active Matching Circuit Utilizing Genetic Algorithms for Wireless Power Transfer to Biomedical Implants

This paper discusses the feasibility of a real-time active matching circuit (MC) for wireless power transfer applications, especially for biomedical systems. One prototype of low-cost real-time automatic MC, utilizing a variable circuit topology, including discrete passives and p-i-n diodes, has been implemented and the principle has been verified by measurements. One genetic algorithm was introduced to optimize the design over a wide range of impedances to match. As a result of preliminary operation verification tests, the proposed real-time MC system results in improving the transfer coefficient in the range of 10-16-cm coil separation distance a maximum of 3.2 dB automatically in about 64 ms. Similar performance improvement results were observed in additional tests under misaligned conditions, as well as for nonsymmetrical Tx-Rx coil configurations further verifying the potential applicability of the proposed system to practical biomedical devices.

A Novel Solar and Electromagnetic Energy Harvesting System With a 3-D Printed Package for Energy Efficient Internet-of-Things Wireless Sensors

This paper discusses the design of a novel dual (solar + electromagnetic) energy harvesting powered communication system, which operates at 2.4 GHz ISM band, enabling the autonomous operation of a low power consumption power management circuit for a wireless sensor, while featuring a very good “cold start” capability. The proposed harvester consists of a dual port rectangular slot antenna, a 3-D printed package, a solar cell, an RF-dc converter, a power management unit (PMU), a microcontroller unit, and an RF transceiver. Each designed component was characterized through simulation and measurements. As a result, the antenna exhibited a performance satisfying the design goals in the frequency range of 2.4–2.5 GHz. Similarly, the designed miniaturized RF-dc conversion circuit generated a sufficient voltage and power to support the autonomous operation of the bq25504 PMU for RF input power levels as low as −12.6 and −15.6 dBm at the “cold start” and “hot start” condition, respectively. The experimental testing of the PMU utilizing the proposed hybrid energy harvester confirmed the reduction of the capacitor charging time by 40% and the reduction of the minimum required RF input power level by 50% compared with the one required for the individual RF and solar harvester under the room light irradiation condition of 334 lx.

Fully inkjet-printed multilayer microstrip patch antenna for Ku-band applications

A fully inkjet-printed multi-layer microstrip patch antenna with a CPW to microstrip line transition is designed and demonstrated for the first time in this paper. Both metallic layers and SU-8 substrate are fabricated with an additive inkjet printing process. The patch antenna is designed to operate at 14 GHz, and the operation of the antenna is confirmed in measurement validating that fully additively-processed RF devices are a new option for post processing RF devices with substrate independence.

Additively Manufactured RF Components and Modules: Toward Empowering the Birth of Cost-Efficient Dense and Ubiquitous IoT Implementations

In this review, the particular importance and associated opportunities of additively manufactured radiofrequency (RF) components and modules for Internet of Things (IoT) and millimeter-wave ubiquitous sensing applications is thoroughly discussed. First, the current advances and capabilities of additive manufacturing (AM) tools are presented. Then, completely printed chipless radio-frequency identification (RFID) systems, and their current capabilities and limitations are reported. The focus is then shifted toward more complex backscattering energy autonomous RF structures. For each of the essential components of these structures, that encompass energy harvesting and storage, backscattering front ends, passive components, interconnects, packaging, shape-chaging (4-D printed) topologies and sensing elements, current trends are described and representative stateof- the-art examples reported. Finally, the results of this analysis are used to argue for the unique appeal of AM RF components and systems toward empowering a technological revolution of costefficient dense and ubiquitous IoT implementations.

A Novel Ultra-Lightweight Multiband Rectenna on Paper for RF Energy Harvesting in the Next Generation LTE Bands

This paper introduces a novel compact ultralightweight multiband RF energy harvester fabricated on a paper substrate. The proposed rectenna is designed to operate in all recently released LTE bands (range 0.79–0.96 GHz; 1.71–2.17 GHz; and 2.5–2.69 GHz). High compactness and ease of integration between antenna and rectifier are achieved by using a topology of nested annular slots. The proposed rectifier features an RF-to-dc conversion efficiency in the range of 5%–16% for an available input power of −20 dBm in all bands of interest, which increases up to 11%–30% at −15 dBm. The rectenna has been finally tested both in laboratory and in realistic scenarios featuring a superior performance to other state-of-the-art RF harvesters on flexible substrates.

Ambient energy harvesting from a two-way talk radio for flexible wearable devices utilizing inkjet printing masking

In this paper, the design, on a flexible LCP substrate, and fabrication process of a wearable circuit harvesting the ambient energy emitted from a two-way radio is discussed in detail.The circuit is fabricated through the combination of circuit traces made with masking utilizing inkjet printing technology and lumped circuit components. The input power for the RF-DC conversion circuit is analytically computed from the measured S-parameters of the Tx-Rx propagation channel. A maximum output power of 43.2mW with the RF-DC conversion efficiency of 82.5% and open- circuit voltage of 17.87 V is achieved with an E-field energy harvester placed 7cm away from an off-the-shelf 1W two-way talk radio.