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1. A Single-Aperture, Single-Pixel Reader for Optical Frequency Identification

   https://doi.org/10.1109/ISCAS51556.2021.9401470  

   Fan, Xiaozhe; Hidalgo, James; Leon-Salas, Walter D. (May 2021, 2021 IEEE International Symposium on Circuits and Systems (ISCAS))

   null (Ed.)

   This paper presents a single-aperture, single-pixel reader for communication with Optical Frequency Identification (OFID) tags. OFID tags use solar cells to transmit and receive information wirelessly as well as to harvest radiant energy. Due to its single-aperture architecture, the reader's optical system provides a shared optical path for reception and transmission. Also, physical alignment between the reader and an OFID tag is visually guided using the reader's emitted light, securing a robust data link as long as the OFID tag is illuminated. In this paper, a description of the reader's optical and electronic sub-systems are presented. The transmitter and receiver circuits are described in detail. The transmitter, built with a linear LED driver, achieves a power efficiency of nearly 87%. The receiver, featuring a third-order bandpass filter, reduces both low-frequency and high-frequency ambient noise. A prototype of the reader was fabricated and housed in a custom 3D-printed enclosure. Test results show that the reader is able to receive modulated luminescent signals from an OFID tag at a distance of 1 m and at a data rate of 3 kbps. 

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2. Discrete Time Synchronization Modeling for Active Rectifiers in Wireless Power Transfer Systems

   https://doi.org/10.1109/COMPEL.2019.8769717  

   Cochran, Spencer; Costinett, Daniel (June 2019, IEEE Workshop on Control and Modeling for Power Electronics (COMPEL))

   Active rectifiers in wireless power transfer systems exhibit many benefits compared to diode rectifiers, including increased efficiency, controllable impedance, and regulation capability. To achieve these benefits, the receivers must synchronize their switching frequency to the transmitter to avoid sub-fundamental beat frequency oscillations. Without additional communication, the receiver must synchronize to locally-sensed signals, such as voltages and currents induced in the power stage by the transmitter. However, the waveforms in the receiver are dependent on both the transmitter and receiver operation, resulting in an internal feedback between sensing and synchronization which prohibits the use of traditional phase-locked-loop design techniques. In this digest, a discrete time state space model is developed and used to derive a small signal model of these interactions for the purpose of designing stable closed-loop synchronization control. A prototype 150 kHz wireless power transfer converter is used to experimentally validate the modeling, showcasing stable synchronization. 

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3. Backscatter Communications with Passive Receivers: From Fundamentals to Applications

   Stanacevic, M.; Athalye, A.; Haas, Z.J.; Das, S.R; Djuric, P.M. (December 2020, ITU Journal)

   null (Ed.)

   The principle of backscattering has the potential to enable a full realization of the Internet of Things. This paradigm subsumes massively deployed things that have the capability to communicate directly with each other. Based on the types of excitation and receivers, we discriminate four types of backscattering systems: (i) Dedicated Exciter Active Receiver systems, (ii) Ambient Exciter Active Receiver systems, (iii) Dedicated Exciter Passive Receiver systems, and (iv) Ambient Exciter Passive Receiver systems. In this paper, we present an overview of bacskscattering systems with passive receivers which form the foundation for Backscattering Tag-to-Tag Networks (BTTNs). This is a technology that allows tiny batteryless RF tags attached to various objects to communicate directly with each other and to perform RF-based sensing of the communication link. We present an overview of recent innovations in hardware architectures for backscatter modulation, passive demodulation, and energy harvesting that overcome design challenges for passive tag-to-tag communication. We further describe the challenges in scaling up the architecture from a single link to a distributed network. We provide some examples of application scenarios enabled by BTTNs involving object-to-object communication and inter-object or human-object dynamic interactions. Finally, we discuss key challenges in present-day BTTN technology and future research directions. 

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4. Factors Influencing in-situ Detection of PIT-tagged Hellbenders (Cryptobranchus alleganiensis) Occupying Artificial Shelters Using a Submersible Antenna

   Connock, John R; Case, Brian F; Button, Sky T; Groffen, Jordy; Galligan, Thomas M; Hopkins, William A. (August 2020, Herpetological conservation and biology)

   Secretive species are difficult to study and often of conservation concern, as exemplified by the Eastern Hellbender (Cryptobranchus alleganiensis). Traditional methods for sampling Hellbenders involves moving rocks, which damages essential habitat. Use and installation of artificial shelters has made studying Hellbenders less dangerous for the animal and less disruptive to stream habitat; however, researchers using shelters generally capture occupying animals to identify them. We tested the ability of a submersible portable Passive Integrated Transponder (PIT) antenna to accurately detect PIT-tagged Hellbenders in shelters. We tested the effects of the presence and depth of cover rocks on top of shelters, PIT tag location within the shelter, and tag orientation on detection efficiency of Hellbenders. For the 32 shelters occupied by a tagged individual with cover rocks in place, the scanner accurately detected 31% of the animals versus 88% when cover rocks were removed. The detection efficiency of the scanner dropped below 50% once cover rock depth exceeded 11 cm. Tags placed near the interface of the entrance tunnel and chamber, or along the chamber walls, had higher detection efficiencies than those in other locations within the shelter. Vertically oriented tags were 18% more likely to be detected than horizontally oriented tags. Our study demonstrates that while this technology has certain limitations, it shows potent 

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5. Passive metamaterial-based acoustic holograms in ultrasound energy transfer systems

   https://doi.org/10.1117/12.2296741  

   Bakhtiari Nejad, Marjan; Elnahhas, Ahmed; Hajj, Muhammad R.; Shahab, Shima (March 2018, Passive metamaterial-based acoustic holograms in ultrasound energy transfer systems)

   Contactless energy transfer (CET) is a technology that is particularly relevant in applications where wired electrical contact is dangerous or impractical. Furthermore, it would enhance the development, use, and reliability of low-power sensors in applications where changing batteries is not practical or may not be a viable option. One CET method that has recently attracted interest is the ultrasonic acoustic energy transfer, which is based on the reception of acoustic waves at ultrasonic frequencies by a piezoelectric receiver. Patterning and focusing the transmitted acoustic energy in space is one of the challenges for enhancing the power transmission and locally charging sensors or devices. We use a mathematically designed passive metamaterial-based acoustic hologram to selectively power an array of piezoelectric receivers using an unfocused transmitter. The acoustic hologram is employed to create a multifocal pressure pattern in the target plane where the receivers are located inside focal regions. We conduct multiphysics simulations in which a single transmitter is used to power multiple receivers with an arbitrary two-dimensional spatial pattern via wave controlling and manipulation, using the hologram. We show that the multi-focal pressure pattern created by the passive acoustic hologram will enhance the power transmission for most receivers. 

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