Ionospheric phase decontamination based on sparse decomposition for multiple‐input multiple‐output over‐the‐horizon radar

Ionospheric phase contamination deteriorates the coherence of high‐frequency echoes, reducing the detection performance of multiple‐input multiple‐output over‐the‐horizon radar (MIMO‐OTHR) on slow ships. A high‐precision phase decontamination method approximately extracts a single‐frequency reference signal from the echo in advance, called the calibration signal, which is completed in the Doppler domain. When severe ionospheric phase contamination causes the echo Bragg peaks to overlap, this operation is difficult to achieve. To solve this problem, the authors transform calibration signal extraction into a sparse decomposition of a short‐time sequence vector set and solve it by an iterative method. This process is based on the sparsity of the short‐time sequence in the Doppler domain, as well as the reversibility between the original data vector, accumulated after a long coherence time, and its corresponding short‐time sequence vector set, obtained by sliding window segmentation of the original data vector. Then the ionospheric phase contamination is extracted from the calibration signal to compensate for the original echo. Compared with existing methods, the proposed method can adaptively extract a calibration signal to achieve high‐precision phase compensation of a MIMO‐OTHR echo while adding a more robust performance against noise when considering overlapping Bragg peaks formed by serious ionospheric phase contamination.