A fast and accurate forward scattering algorithm is described for near-field microwave imaging and sensing problems, such as, dielectric parameter estimation, inverse scattering, microwave imaging etc. This algorithm incorporates a variation on the Method of Moments (MOM) simulation technique with antenna calibration measurements. The result is a forward scattering algorithm which accurately caters for antenna-target interactions. Promising preliminary results are given for an Ultra Wide Band (UWB) Ground Penetrating Radar (GPR) antenna.