The discrete Fourier transform (DFT) of observation sequence is usually used in the detection of tonal signal. A tone without any prior information cannot be guaranteed to lie exactly on the discrete DFT frequency bin, which will degrade the performance of the tonal detector based on DFT. In this work, the authors study the detection problem for a tone deviated from the discrete frequency bin. A generalised likelihood ratio detector utilising the information of adjacent frequency bins is designed. Theoretical analysis, computer simulations, and lake experiment show that the proposed detector is robust against the deviation and is more suitable for the tone detection in practical circumstances. * , then Δ = k 0 * − k 0 , Δ ∈ [ − 0.5, 0.5). If M = N, exp(j2πk 0 * Ml/N) = exp(j2πΔl) and
We present an efficient approach for the sub-regional multiple-source detection. The essence of this approach is to extract the characteristic components of the signals of interest (SOIs) from the estimated signal-plus-interference subspace by a matrix filter. Compared with some other spatial filtering-based approaches, it has two significant advantages. First, since the power of each source in the signal-plus-interference subspace is normalized, the proposed approach is effective to filter out interferences regardless of their strengths. Second, the matrix filter would not reduce the dimension of SOIs, thus, the proposed approach is able to distinguish multiple SOIs from the output of the matrix filter.Index Terms-Matrix filter, multiple-source detection, signal-plus-interference subspace.
Direction of arrival (DOA) estimation is of great interest due to its wide applications in sonar, radar and many other areas. However, the near-field interference is always presented in the received data, which may result in degradation of DOA estimation. An approach which can suppress the near-field interference and preserve the far-field signal desired by using a spatial matrix filter is proposed in this paper and some typical DOA estimation algorithms are adjusted to match the filtered data. Simulation results show that the approach can improve capability of DOA estimation under near-field inference efficiently.
A spatial rotation technique in application to unmanned underwater vehicle (UUV) sonar arrays is proposed. The essence of the technique is to rotate the signals of interest from the array coordinates to geodetic coordinates while providing robustness against interferences and preserving the white noise property at the output. Convex formulation of the rotation matrix design problem is derived using the semi-definite relaxation technique and the optimal solution is obtained by rank-one decomposition theorems. Using the authors' technique, the subspacebased direction of arrival estimation methods can get large snapshot support for weak sources in the UUV motion-case.
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