High frequency surface wave radar (HFSWR) has the capability of detecting vessels and low-altitude aircrafts over the horizon,but the performance is affected by the ionospheric clutter.In order to detect the targets in ionospheric clutter, the detection characteristics of ionospheric clutter was researched based on multiple signal classification (MUSIC) scheme,and it was indicated that most ionospheric clutter has apparent directivity. The directivity was used as known information for the ionospheric clutter with directivity, and then the targets in the range-Doppler resolution cells, which were polluted by the ionospheric clutter,was detected based on the Constrained-MUSIC scheme.The real data analysis showed that the method is effective to restrain ionospheric clutter with directivity,and detect targets in the ionospheric clutter.The scheme achieved angle supper resolution in HFSWR, and the range-Doppler-azimuth three-dimension detection background was given.
