Abstract: Ionospheric frequency modulation causes spreading of the surface clutter in Doppler domain which greatly limits the detection performance of HF sky-wave radars. This paper proposes a cascaded approach to correct the ionospheric frequency modulation. This approach consists of two correction steps. At the first step, time-frequency distribution (spectrogram or pseudo Wigner-Ville distribution) of the time-varying signal is adopted and a peak-tracking scheme is designed to obtain a coarse ionosperic modulation estimation from the time-frequency distribution. At the second correction step, a parametric method based on piecewise polynomial phase model is exploited to eliminate the residual contamination. Simulation results show the effectiveness of this cascaded approach even for very serious cases where broadened Bragg lines are overlapped.