A method to correct HF skywave backscattered signals for ionospheric frequency modulation

A method is described to correct HF signals reflected by the ionosphere and backscattered by the sea surface for ionospheric frequency modulation, which produces spectral-line smearing. The statistical mean of the time derivative of the phase of the signal, weighted by the signal energy, is proposed as an estimator of this modulation. The accuracy of the estimator is measured and the efficiency of the signal processing is tested by synthetically contaminating high-quality signals obtained via sporadic E-layer propagation. Examples of data corrected for F2-layer ionospheric perturbations are shown