Advances in non-linear apodization for irregularly shaped and sparse two dimensional apertures

Presented in this paper are selected new methods and applications of non-linear apodization for irregularly-shaped and sparse coherent apertures and arrays. The benefits include improved impulse response performance, i.e. reduced peak sidelobes and integrated sidelobe power, along with improved mainlobe resolution, compared to classic windowing techniques. Non-linear apodization (NLA) techniques can also serve as powerful engines for effective superresolution and bandwidth extrapolation of coherent data for filling sparse apertures. The sparse aperture filling property of superresolution algorithms for radar data forms the basis for a new concept which is introduced here: synthetic multiple aperture radar technology (SMART). Increased swath and/or reduced antenna size are some of the benefits postulated for SMART applied to synthetic aperture radar (SAR) systems. The benefits of these new methods and applications for nonlinear apodization are then demonstrated for two specific applications: 1) side lobe control for Y-type synthetic aperture radiometers, such as the European soil moisture and ocean salinity (SMOS) system [12] and JPL´s proposed GeoSTAR [13] concept; and, 2) filling of sparse synthetic aperture radar data by exploiting the bandwidth extrapolation properties of non-linear apodization based superresolution techniques. The methods that have been developed and demonstrated here have potential application to a wide range of passive and e microwave remote sensing and radar systems.