Signal processing techniques for phase-coded HF-VHF radars

HF-VHF radar techniques are easy to employ and commonly used in geophysical applications. They include deep
radio soundings, used for probing the ionosphere, stratosphere-mesosphere measurement, weather forecast and
radio-glaciology. Fast algorithms and powerful processors facilitate the development of several kinds of low power
radars, but the reduction of the transmitted power has to be compensated by on-line processing of an encoded
signal to maintain a favorable signal-to-noise ratio suitable for detection. Moreover, radars have to reconstruct
return echoes with different travel times due to various origins (multi-path, adjacent objects, etc.). Such needs
can be accomplished by means of signal phase coding and one of the most attractive is the reversal phase code.
The composite echo signal must be processed to extract the physical information useful for the measurement
considered. In this paper some algorithms used for on-line processing of phase-coded signals will be described,
both in time and frequency domain.