Study on detection and recognition of phase contamination and multimode propagation in ionosphere for OTHR

Recognition of ionosphere phase contamination and multimode propagation is an important step in rejection of clutter spectrum spread for OTHR. Based on the algorithm of time reversibility, this paper proposes a method based on eigenvalue decomposition to detect multimode propagation. Besides, a cascaded technique composed of the two methods above is proposed to recognise contaminations. Another detection algorithm based on time series Hankel matrix is proposed, which will be suitable for more widely application. For the first time, the method based on backscatter sounding is also proposed for multimode recognition, and a hybrid method based on time reversibility and Hankel matrix is also proposed to distinguish phase contamination and multimode propagation.