Software Defined Radio for Time and Frequency Applications: Example of Passive Monitoring of TWSTFT and other Timing Signals: (Invited Paper)

Software Defined Radio (SDR) is a paradigm aimed at minimizing the contribution of hardware and maximizing the contribution of software when processing radiofrequency signals. While the concept is mostly used in the context of digital communication for agile systems flexible enough to adapt to unexpected conditions, accessing the raw samples right after the digitization of the radiofrequency wave provides opportunities for benefiting from information on the physical system before the signal has been processed. Not only does this access to the physical layer provide security, e.g. G NSS anti-spoofing and anti-jamming using null steering, but also the opportunity to finely recover timestamps in the context of time and frequency transfer. Free, opensource software is readily distributed for reproduction of the experiment at the Oscillator Instability Measurement Platform (OscIMP) Digital repository at https://github.com/oscimp/gr-satre for SATRE TWSTFT signal reception or https://github.com/oscimp/gnss-sdr-lpps/ for GNSS-controlled 1 PPS generation, and repetition of the measurements at remote sites, a core requirement of a scientific endeavor.