From OPS-SAT to PRETTY Mission: A Second Generation Software Defined Radio Transceiver for Passive Reflectometry

After the successful launch of the ESA OPS-SAT Nanosatellite in December 2019, the Institute of Communication Networks at Graz University of Technology (TUG) has started its work on a new second-generation Software Defined Radio (SDR) transceiver platform for the ESA PRETTY mission. The mission goal of PRETTY is the demonstration of the passive reflectometry concept with an SDR on a 3U Nanosatellite. The PRETTY satellite requires a powerful second-generation SDR receiver that extends the functionality and performance of the first-generation SDR used for OPS-SAT. There are many lessons learned about the first-generation SDR characteristics, the performance, ease of use and the strengths but also the weaknesses of the design during the OPS-SAT environmental and functional testing campaign. The second-generation SDR design considers the experiences from the first-generation SDR and implements several improvements for the thermal behavior, mechanical sustainability, device control and status monitoring in order to achieve higher overall performance and reliability. The second-generation SDR uses an AD9361 radio frequency (RF) frontend chip, that allows the signal reception with two independent receive channels and signal transmission with two independent transmit channels. In particular, the new transmit functionality of the second-generation SDR is a remarkable improvement compared to the first-generation SDR for OPS-SAT, due to its full-duplex, bidirectional communication capabilities. Further improvements provide the possibility, to extend the design with RF mixer boards, to achieve the flexibility required for future applications on higher RF bands.