Reliability of passive RFID of multiple objects using folded microstrip patch-type tag antenna

We have used a novel folded microstrip patch-type tag antenna in RFID of cigarette cartons, which contain highly conductive aluminium foil. Identification of multiple cartons and the effect of conductive material are studied with read range measurements and the results are compared and analyzed. The folded microstrip patch-type tag antenna is shown to be capable of identifying objects containing high quantities of reflecting materials. Furthermore, tagged objects located behind large quantities of reflective materials can be identified when the tagged objects are configured in their typical case configuration. Read ranges are shorter when multiple objects are identified. Two tagged cartons with foils inside the individual packs can be identified on top of each other. If the conductive foils are removed from the cigarette packs, three tagged cartons on top of each other can be identified. This indicates that the tag antenna is very suitable for packages not containing any conductive material. The tests showed also that identification is more reliable when the cartons are in motion. This indicates that the tag antenna can be used in reading multiple objects on a conveyor belt.