Coherent Signal Angle Estimation With Circular Array Rotational Motion

Estimating angles for coherent signals remains a critical challenge in array signal processing. Traditional spatial smoothing techniques can recover the rank loss caused by signal coherence, but they inevitably lead to a reduction in array aperture. Circular arrays provide uniform beam response in all directions, enabling omnidirectional coverage, and have received considerable attention in practice. This study shows that the rotational motion of circular array enables accurate coherent signal estimation without aperture loss, an aspect that has been scarcely explored in previous studies. First, the signal model of the circular array under rotational motion is derived, which contain the phase modulation introduced by rotational motion of array. Second, using the signal model, we constructed a decoherence matrix capable of recovering the covariance rank loss induced by coherent signals. Subsequently, we apply beamspace processing to transform the decorrelated covariance matrix, thereby obtaining a manipulable Vandermonde structure from the circular array's output and search for angle estimates of the coherent signals. Finally, to mitigate the bias introduced by both beamspace transformation and search grid mismatch, we propose a subspace compensation approach that ultimately achieves precise angle estimation. The proposed method effectively alleviates the aperture loss associated with traditional coherent signal angle estimation using spatial smoothing and provides more accurate angle estimates. Simulation results validate the effectiveness of the presented approach.