Range-Ambiguous Clutter Separation and Suppression in Airborne Bistatic Radar via a Cascaded Blocking Matrix-ZCA Whitening-ABF Architecture

Space-time adaptive processing (STAP) suffers severe performance degradation in airborne bistatic radar, as range-ambiguous clutter exacerbates the inherent clutter non-stationarity. This paper addresses the limitations of conventional beamforming (CBF)-based range-disambiguation methods. We first clarify the core trade-off between range disambiguation accuracy and STAP-accessible degrees of freedom in subarray design. Guided by this, an initial solution utilizing a blocking matrix cascaded with adaptive beamforming (ABF) is proposed. However, in-depth analysis reveals a critical flaw: increasing the subarray size leads to the blocking-matrix-induced noise distortion broadening the mainlobe clutter-suppression notch width. To resolve this, we integrate an innovative zero-phase component analysis (ZCA) whitening technique, developing a blocking matrix-ZCA-ABF joint processing framework. Simulations demonstrate that the proposed method effectively separates range-ambiguous clutter, laying a solid foundation for subsequent non-stationary clutter compensation and STAP suppression. It delivers superior, robust clutter suppression across diverse subarray parameters, narrows the mainlobe clutter-suppression notch, limits the output signal-to-clutter-plus-noise ratio (SCNR) loss to within 3 dB, and maintains target detection power and accuracy simultaneously. Accordingly, it offers reliable technical support for airborne bistatic radar target detection in complex scenarios.