This paper presents a multi-antenna approach of the phase-based SARFID method to locate static tags by employing two UHF-RFID reader antennas installed on an Unmanned Grounded Vehicle (UGV). The UGV is remotecontrolled and equipped with Laser Range Finder sensors to move inside an indoor environment, and the knowledge of its trajectory is achieved through a Simultaneous Localization And Mapping procedure. By processing the phase data collected from each reader antenna, different matching functions can be obtained and combined to improve the estimation of the bidimensional tag position. Differently from other localization techniques, neither reference tags (anchor tags), nor large phased array antennas are required.