Enhancement of remote sensing capability of HF skywave radar by correcting the signal for frequency modulations

Ionospherically propagated signals are frequently affected by short-term phase-path variations degrading the remote sensing capabilities of HF skywave radar, in particular for sea state applications. The authors have proposed a method to correct the phase of the signal reflected by the ionosphere and backscattered by the sea surface, based on the derivation of an estimator of the frequency modulation affecting the wave after the double ionospheric transit. This signal processing method has been applied to a large data set and, in the present paper, they study the dependence of the equivalent width of the sea-scatter Bragg line on the coherent integration time. They show that the correction of the phase allows the use of longer coherent integration times and thus improves the detection capabilities of HF radar for targets in sea clutter.<>