Innovative Adaptive Processing Techniques for Wideband and Multi-Band Conformal Arrays

Multi-mission airborne radars of the future will require larger transmit and receive apertures to meet challenging surveillance requirements in the presence of severe clutter, ECM and RFI. Large planar arrays mounted on either the side, top or bottom of current airframes are impractical, if not aerodynamically unstable. Consequently, the Air Force is investing in new RF technologies to support lightweight large conformal apertures designs and is investigating approaches for mounting/integrating them into a variety of conventional, and future air vehicles including UAV¡_s (e.g. SensorCraft) and mini-UAV¡_s. To meet mission objectives, these radars are expected to rely on space-time adaptive processing (STAP) techniques to achieve the interference suppression performance required. These non-conventional conformal array radar systems, however, will face unique signal processing challenges. Many simplifying assumptions made by planar array adaptive processing approaches will be violated by conformal aperture designs. The desire for high range resolution capabilities for ground target feature extraction and identification provides additional design challenges. These requirements drive the design to wideband STAP where the narrowband assumptions implied in most STAP approaches lead to spatial and Doppler dispersion effects and potential degradation in STAP performance. One approach for handling these effects is to decompose the wideband signal into smaller subbands, each with sufficiently small bandwidth such that narrowband STAP processing can be employed. The narrowband outputs are recombined to reconstruct the full bandwidth, high-resolution signal with the clutter interference suppressed.