Space-frequency joint processing method for platform-interference-resilient tonal detection in underwater acoustic signals

When a compact underwater platform carries a passive acoustic payload for detecting non-cooperative signals, platform-related interference often manifests as a set of narrowband spectral lines within the operating band—comprising both stationary and nonstationary components. These components may exhibit slow drifts in frequency and amplitude under varying operating conditions, thereby degrading the salience of weak tonal components, impairing near-frequency parameter estimation, and complicating false-alarm control. To address these challenges, this paper proposes a space–frequency joint detection framework tailored to platform-interference backgrounds. In the frequency domain, an adaptive interference representation is constructed by exploiting the quasi-harmonic consistency and clustered structure of interference line sets; line-level suppression is then applied to mitigate masking of candidate tonal components. In the spatial domain, a weakly frequency-coupled discriminant is designed by leveraging differences in spatial coherence between the desired signal and near-field platform interference across array observations—thereby enhancing resolvability under co-frequency or near-frequency conditions. Simulation and experimental results demonstrate that the proposed space–frequency joint strategy remains robust in the presence of platform interference with fluctuating statistical characteristics and provides a generalized solution for real-time detection in practical engineering scenarios.