We consider an application of the orthogonality sampling method (OSM) for a fast identification of a small anomaly from scattering parameter data. In this study, we cannot measure the scattering parameter data when the location of transmitting and receiving antenna is same. Due to this reason, we set the unknown data as a constant and design a new indicator function of the OSM with multiple sources weighted by the incident field data. Based on the simulation results, we confirmed that the designed indicator function improves the imaging quality successfully.