For HF ground-wave OTH radar to detect ship targets in the shipboard environment is faced with a range of technical challenges.One of them is that the spreading of the first order Bragg lines will obscure targets with Doppler frequencies within the range of this spreading.In this paper

the properties of the spreading are firstly analyzed with the aid of the synthetic aperture theory.On this basis

the feasibility of canceling sea-clutter and retaining target returns by the space filtering is proved.The experimental results presented in the end further demonstrate the effectiveness of the technique put forward in this paper.