Mike Varner recently returned from Kalamata, Greece, where he presented original research on the use of perfect pulses for scattering low-powered digital signals onto existing radio transmissions (often referred to as ambient communications or ambient scatter in the research literature; we like the term ReMoRa — Reflection of Modulated Radio — since it conjures up the analogous image of a “suckerfish” signal). Perfect pulses are signal components with remarkable DC-nulling properties; from these primitive signal constructs, a radio can construct informative digital signals that enable a number of applications, from clandestine signal transmission to low-power/batteryless sensors that “piggy-back” their information onto FM, TV, or cellular transmissions. Download his poster presentation here.
If all goes well, the NNU team that brought us MakerSat will be launching a new satellite mission early next year as part of a new NASA-funded project. The new satellite experiment, called RFsat, will have a unique RF energy-harvesting radio designed and built by the Georgia Tech Propagation Group. PhD student researcher Cheng Qi has built a one-of-a-kind microwave backscatter reader and tag-sensor combo that will drive the mission package.
The low-powered reader designed by our team deploys a sensor that unfurls a distance away from the spacecraft. The reader then energizes and receives backscatter information from the device using a 5.8 GHz transmission. Complete with generator, retrodirective antenna, and rectenna harvester, the radio package qualifies as the first microwave space-based solar power satellite ever tested — despite the somewhat limited 1m range. You have to start somewhere.
Check out the story of the November 2017 MakerSat launch by the NNU team here.
Inventors at Georgia Tech have developed techniques that can extend the range and the potential data rate of low-power communication. These techniques use multiple antennas at the transmitter, receiver, and RF tag and will soon allow the exchange of low data rates over long distances. The techniques have the capability to allow RF tags to return high powered signals with higher data rates back to a reader unit. This allows for the sweeping of an RF waveform through space so that passive radio devices may more effectively harvest energy and boost the collection of microwave power by an energy-harvesting RF tag using multiple antennas. Collectively, these techniques work together to enhance the range and reliability of RF tags.
Download the summary at 5147.
Some of the best tunneling diode work from Francesco Amato’s PhD research will appear in the IEEE Journal on RFID this year. This paper contains a comprehensive early survey of long-range communications with extraordinarily low power levels.