Theoretical Investigation of the Ultrawideband FMCW Signal Propagation Through Ionospheric Radiochannel

A theoretical description is given to the chirpsounder operation configuration in the mode of sounding the ionospheric radiochannel by the ultrawideband frequency-modulated continuous wave (FMCW) signal. A preprocessing of the received signal is carried out using the frequency-compression method. It is shown that the result derived from processing an individual time sample is mathematically equivalent to a sounding of the radio channel by a complex-valued narrow-band impulse signal. Analysis of both in-phase and quadrature components of received FMCW signal at the output of intermediate frequency (IF) band-pass filter of the chirpsounder demonstrates a new possibility of recovering the transfer function of the HF radiochannel within the band of operating frequencies and the interval of time delays that are defined by the IF filter characteristics