The separation of multipath signal components by spatial filtering in a narrowband antenna array is addressed for cases where diffuse scattering and array calibration errors may cause the spatial signatures of the received propagation modes to deviate significantly from the plane-wave array manifold. The distorted wavefronts may have complex spatial signatures that are difficult to accurately characterize and mutually resolve on the basis of array manifold models described by few parameters. Furthermore, the temporal signature of the source waveform may also be quite arbitrary, with no known deterministic or statistical properties that can be utilized for multipath separation. This problem calls for blind waveform estimation methods that rely on relatively mild assumptions. An alternative blind spatial filtering technique referred to as the Generalized Estimation of Multipath Signals algorithm, or GEMS, is introduced for this purpose and tested on experimental data provided by the high frequency (HF) radar program of the Defence Science and Technology Organization (DSTO), Australia.
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