Radar imaging, as understood here, involves target recognition, i.e. the
determination of the detailed properties of an object (size, shape,
structure and composition, and also location and speed) from radar
echoes returned by it. Advanced approaches are required for this, and
several of recent interest are discussed in this book. They include
mathematical inverse-scattering techniques based on the solution of
integral equations; use of the singularity expansion method (SEM),
related to the resonance scattering theory (RST), in which the pattern
of resonance-frequency location in the complex frequency plane can be
employed to characterize a given radar target; and the use of
polarization information. Finally, the measurement of radar
cross-sections is described.