Space-time focusing of HF skywave radar signals with application to nonlinear scattering phenomenology

Increasing the power density incident on a target without raising the radiated power may offer a number of benefits to HF skywave radar systems. Among these is the prospect of detecting nonlinear echoes, which could greatly enhance detection in sea clutter. Other prospects include improved detection of low RCS targets and more effective use of sub-apertures for multiple simultaneous task operations. In this paper we review the physics underlying these missions and assess the potential of various approaches to concentrating energy in localized regions within the illuminated zone.