3-D Monostatic RCS Determination From Multistatic Near-Field Measurements by Plane-Wave Field Synthesis

A fully polarimetric plane-wave field synthesis-based approach is presented to accurately determine the 3-D monostatic radar cross section (RCS) of an object under test from a set of bistatic near-field (NF) measurements. It allows the use of small scan surfaces around the transmitting antenna to acquire the scattered field, thus significantly reducing the required number of measurements compared to a full bistatic approach. At the same time, and unlike image-based approaches, it does not suffer from inaccuracies due to multiple interactions at the object. The method solves a series of inverse source problems for all NF illuminations and computes the monostatic RCS by a subsequent plane-wave synthesis of the incident field. Great flexibility and computational efficiency are achieved by working with a hierarchical multilevel propagating plane-wave expansion of the incident and scattered field. This allows almost arbitrarily shaped scan surfaces and arbitrary measurement probes to be processed very efficiently. The theory of the algorithm is outlined in detail and its performance is assessed by considering numerical studies as well as experimental data from measurements. It is shown that the overall accuracy mainly depends on the quality of the synthesized plane-wave field, which is controlled by adapting the angular range spanned by the locations of the transmitting antenna.