Sounding the ionosphere using software define radio (SDR)
This project will involve evaluating the concept in the laboratory, and then utilising sounder transmissions from the Defence Science & Technology Group (DST) Murray Bridge field site to evaluate the concept experimentally.
The ionosphere is the shell of electrons and charged particles surrounding the Earth, extending from a height of 50 km to beyond 1000 km. The ionosphere supports propagation of high-frequency (HF) radio signals over long distances, allowing applications such as communications and over-the-horizon radar, such as those comprising Australia’s Jindalee Operational Radar Network (JORN).
The ionosphere also affects propagation of global positioning systems (GPS) satellite signals, reducing position accuracy through signal absorption, scintillation, Faraday rotation & decoherence.
Ionospheric sounders (or Ionosondes) are instruments which characterise the ionosphere by measuring the time delay of ionospherically propagated HF signals across a wide frequency range. Ionospheric sounder measurements allow the development of real-time ionospheric models (RTIM), which are critical for the successful operation of JORN.
Software defined radio (SDR) provides the potential for development of low-cost ionospheric sounder receivers. This may provide an economical means for increasing the number of deployable ionospheric sounder receivers, potentially increasing the spatial and temporal fidelity of the JORN RTIM.
However, to achieve these outcomes, the SDRs and any subsequent signal processing need to be able to operate in the highly dynamic HF interference and noise environment.