Efficient inverse sources solutions above lossy dielectric halfspace

Near-field (NF) measurements of automobile antennas are preferably performed in an as realistic as possible environment, which is still reproducible and easy to handle. Measurements above a dielectric, possibly lossy halfspace appear to be a good compromise in this respect. We present an efficient inverse equivalent sources solver for the NF farfield (FF) transformation of NF measurements in such an environment. The solver starts from the radiation integrals in free-space with multilevel propagating plane-wave representation of the Green's function and is extended by an appropriate Green's function representation for a halfspace of infinite extent. In order to avoid the cumbersome Sommerfeld integral representation, a very good approximation of the Green's function is utilized, which is shown to exhibit sufficiently good accuracy for the necessary field transformations. The approach is demonstrated by transformation results based on synthetically generated data.