Correction of ionosphere phase contamination of high-frequency hybrid sky-surface wave radar using wavelet transform

Ionospheric phase contamination (IPC) is a major contributor to the imprecise retrieval of ocean dynamics parameters by the high-frequency hybrid sky-surface wave radar (HFHSSW). Since the direct wave and sea echo of HFHSSW have comparable IPC, the information of ocean dynamics parameters can be preserved by using the IPC extracted from the direct waves to correct the sea echoes. In this article, a wavelet transform (WT) algorithm for HFHSSW sea echo correction is proposed. The direct waves are decomposed using a series of wavelet functions constructed with complex Morlet wavelets in order to extract the IPC and correct the sea echoes. The authors enumerated two examples and counted the correction results for 50 echoes to validate the performance of the WT algorithm. The results demonstrate that the WT algorithm enhances the signal-to-noise ratio (SNR) of the sea echoes and suppresses the broadening of the sea echoes. The 6-dB bandwidth of the positive and negative first-order Bragg peaks (B+, B-) decreases by 32.96% and 35.04% respectively, while the SNR increases by 1.16 and 1.21 dB respectively. In comparison to the generalised S-transform (GST algorithm), the computation speed of the WT algorithm is approximately 3.2 times that of the GST algorithm, making it more suitable for practical operation.