Enhancement of RF Tag Backscatter Efficiency With Low-Power Reflection Amplifiers

Increasing backscatter tag communication ranges is crucial for the development of low-power long-range wireless sensor networks. A major limitation for increasing the signal-to-noise ratio (SNR) for RF identification tags lies in the fact that tag antennas are terminated with passive loads for modulation, which yields reflection-coefficient values less than unity. Recent work in the field has exploited reflection amplifiers that achieve reflection-coefficient values larger than unity to increase the communication range. However, most of these systems rely on increasing the reflection coefficient at one modulation state only, which is suboptimal. In this paper, an analysis is given for the optimal way to utilize a reflection amplifier and how this compares to suboptimal practices. To demonstrate the concept, a tag is designed that achieves reflection-coefficient values higher than unity for both states in the 900-930-MHz band. The two values are antipodal, thus maximizing the tag SNR for a given amplifier. The system comprises of an ultra-low-power reflection amplifier with up to 10.2-dB gain and sub-milliwatt power consumption, and a phase-shift modulator that selectively alternates the phase of the backscatter signal between 0 ° and 180 °. The reflection amplifier-phase modulator system is experimentally characterized in terms of gain, power consumption, and backscatter efficiency.Grant numbers : This work was supported by the Spanish Ministry of Economy and Competitiveness, by FEDER funds under Project TEC2012-39143, by the COST Action IC1301 "Wireless Power Transmission for Sustainable Electronics (WIPE)," and by the Generalitat de Catalunya under Grant 2014 SGR 1551.© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

3DlInkjet-printed Origami Antennas for Multi-direction RF Harvesting

A system design is presented for radio frequency (RF) energy harvesting on wireless sensor network (WSN) nodes, where all electronics reside inside a 3D structure and the antennas lie on the surfaces of it. Additive manufacturing techniques are used for the packaging and antenna fabrication: A 3D-printed cross-shaped structure is built that folds to a cuboid in an “origami” fashion and retains its shape at room temperature. Inkjet printing is used to directly fabricate antennas on the surfaces of the 3D-printed plastic, enabling a fully additive manufacturing of the structure. Multiple antennas on the cube's surfaces can be used for RF energy harvesting of signals arriving from totally orthogonal directions, with the use of an appropriate harvester. The system modules (cube, antenna, harvester) are described and characterized, offering a proof-of-concept for the combination of fabrication techniques to build systems for demanding RF applications.Grant numbers : This work was supported by the Generalitat de Catalunya under grant 2014 SGR 1551, and the Spanish Ministry of Economy and Competitiveness and FEDER funds through the project TEC2012-39143 (SOSRAD). The authors would also like to acknowledge EU COST Action IC1301 "Wireless Power Transmission for Sustainable Electronics (WIPE).© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

3D-Printed Origami Packaging With Inkjet-Printed Antennas for RF Harvesting Sensors

This paper demonstrates the combination of additive manufacturing techniques for realizing complex 3D origami structures for high frequency applications. A 3D-printed compact package for enclosing radio frequency (RF) electronics is built, that features on-package antennas for RF signal reception (for harvesting or communication) at orthogonal orientations. Conventional 3D printing technologies often require significant amounts of time and supporting material to realize certain structures, such as hollow packages. In this work, instead of fabricating the package in its final 3D form, it is 3D-printed as a planar structure with “smart” shape-memory hinges that allow origami folding to a 3D shape after heating. This significantly reduces fabrication time and effectively eliminates the need for supporting material, thus minimizing the overall manufacturing cost. Metallization on the package is performed by directly inkjet printing conductive inks on top of the 3D-printed surface with a modified inkjet-printed process without the need for surface treatment or processing. Inkjet-printed on-package conductive features are successfully fabricated, that are combined with RF energy harvesting electronics to showcase the proof-of-concept of utilizing origami techniques to build fully 3D RF systems. The methodologies presented in this paper will be enabling the manufacturing of numerous real-time shape-changing 3D complex structures for electromagnetic applications.Grant numbers > This work was supported by the Generalitat de Catalunyaunder grant 2014SGR 1551.© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

3D/Inkjet-printed Origami Antennas for Multi-direction RF Harvesting

A system design is presented for radio frequency (RF) energy harvesting on wireless sensor network (WSN) nodes, where all electronics reside inside a 3D structure and the antennas lie on the surfaces of it. Additive manufacturing techniques are used for the packaging and antenna fabrication: A 3D-printed cross-shaped structure is built that folds to a cuboid in an “origami” fashion and retains its shape at room temperature. Inkjet printing is used to directly fabricate antennas on the surfaces of the 3D-printed plastic, enabling a fully additive manufacturing of the structure. Multiple antennas on the cube's surfaces can be used for RF energy harvesting of signals arriving from totally orthogonal directions, with the use of an appropriate harvester. The system modules (cube, antenna, harvester) are described and characterized, offering a proof-of-concept for the combination of fabrication techniques to build systems for demanding RF applications.Grant numbers : This work was supported by the Generalitat de Catalunya under grant 2014 SGR 1551, and the Spanish Ministry of Economy and Competitiveness and FEDER funds through the project TEC2012-39143 (SOSRAD). The authors would also like to acknowledge EU COST Action IC1301 "Wireless Power Transmission for Sustainable Electronics (WIPE).© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

An Enhanced-range RFID Tag Using an Ambient Energy Powered Reflection Amplifier

A great challenge in UHF RFID systems consists of increasing their operating range. In this work, a circuit topology consisting of a reflection amplifier and a passive coupler is proposed to both amplify the input signal to the tag as well as the backscattered signal towards the reader. System analysis is provided to estimate the performance requirements of the proposed circuit. The amplifier is optimized in order to maximize its gain while minimizing its dissipated power, thus allowing for low-power operation by using ambient energy harvesting devices such as solar cells. The circuit is compatible with commercial UHF RFID tags and is implemented using low-cost inkjet printing fabrication. Prototypes of the various circuit components are fabricated and evaluated demonstrating the feasibility of the proposed system. Interesting results are showcased for tag efficiency improvement through such non-conventional front-end designs