Bistatic Ground-Wave Over-The-Horizon Radar (GWOTHR) uses an array located on a coast to transmit orthogonal frequency coded signals, and a single antenna to receive the returns. The direct-path-interference suppression methods such as transmit nulling and sidelobe cancellation are inapplicable because the energy is radiated isotropiclly and the receive platform is moving. The method of subspace-projection based direct-path-interference suppression is presented in this paper with the characters of this radar and the interference nulling technique considered, followed by the anlysis of the technqiues performance. The orthogonal projection matrix to the direct-path subspace is formulated using the received signals which are then projected to the null space and the direct-path interference are suppressed. Both the simulated and the real data prove the validity of the method.
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