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Research in the Design of Transparent RF Circuits

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Design and Characterization of Meshed Microstrip Transmission Lines
Zachary J. Silva ; Christopher R. Valenta ; Gregory D. Durgin
2019 IEEE MTT-S International Microwave Symposium (IMS) Year: 2019

Advancements in manufacturing techniques have enabled the ability to create micro-mesh conductive structures which have applications in a variety of electrical engineering technologies. This paper presents the theoretical analysis verified with simulated results and laboratory measurements of a 2.4 GHz micro-mesh transmission line over a solid ground plane. As expected, the reduction in conductive area results in a decrease in capacitance per unit length, and the mesh structure results in an increase in inductance per unit length leading to an overall increase in characteristic impedance and increase in electrical length. Results show that the mesh implementation to reduce the conductive material to 16% on a microstrip transmission line using FR-4 must get 44% wider than its solid metal counterpart to maintain 50 Ω impedance. Length must be similarly increased by a factor of 4% to maintain the same electrical length.

Journal Article on the Reader Used in RFTsat

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Low-Power and Compact Frequency Hopping RFID Reader at 5.8 GHz for Sensing Applications in Space
Cheng Qi ; Robert W. Corless ; Joshua D. Griffin ; Gregory D. Durgin
IEEE Journal of Radio Frequency Identification
Year: 2019 | Volume: 3, Issue: 3

Radio frequency identification (RFID) is the driving technology behind many compelling applications, such as Internet-of-Things, smart cities, and inventory tracking. However, it is always challenging to make a small, low-cost transceiver with little power consumption. This paper presents the design and characterization of a low-power, compact frequency hopping RFID reader that has great potential for use in space-based sensing applications including structural health monitoring, tracking inventory, and sensitive field measurements. This RFID reader will be launched into low-earth orbit aboard the radio frequency tag satellite (RFTSat), a nanosatellite developed at Northwest Nazarene University, and serves as a demonstration of backscatter communications in space. This reader is capable of operating in the 5725–5850 MHz frequency industrial scientific medical band with up to 31 dBm equivalent isotropically radiated power (EIRP) and −58 dBm to −82 dBm sensitivity in different conditions.

Finishing up at the ISS

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The CubeSat slingshot dispenser holding RFTSat will be installed on the Cygnus hatch today, while docked at the International Space Station.  Cygnus will then undock from the ISS Tuesday (tomorrow) at noon EDT, which will be live-streamed on NASA TV.  The CubeSats will deploy at the first signals from RFTSat will send on-orbit data sometime Wednesday afternoon.

Third Time’s a Charm

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After a couple of delays, the SpX-18 (Dragon) launched successfully on a Falcon 9 SpaceX rocket on Thursday, 26 July 2019, at 6:01pm.  The entire video of the launch, as well as the first stage recovery, is shown below.  Included on this space mission is a small satellite — RFTsat — that contains a special passive microwave sensing system designed and built by a team of Northwest Nazarene University and the GTPG.  The low-powered microwave reader converts solar power to a microwave beam that energizes a rectenna at distance, which powers a sensor platform at distance.  Among other things, this is a history-making piece of hardware — the first demonstration of a 5.8 GHz solar-to-microwave-to-DC wireless power conversion in space.  Read more about reader and tag system here.