Abstract: An antenna system (20) in transponder article surveillance and identification system (10) employs a separate interrogating transmitting antenna (31) and interrogating receiving antenna (41) both of which are circularly polarized in opposite hand senses whereby very little of a transmitted electromagnetic interrogation signal is coupled to the interrogation receiving antenna (41) and reflections from nearby surfaces are transparent, significantly improving system performance. Interrogating transmitting antenna (31) and interrogating receiving antenna (41) are cavity-backed, crossed-dipole-fed antennas producing a substantially hemispherical radiation pattern. Transponder (11) is mounted together with a dipole antenna (50) on a tag (13) carried on each article to be identified.