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A cost-effective integration of passive UHF RFID tags and sensors is still a challenge. In such a field, authors have already proposed a label-type multi-antenna Sensor-Tag, an RFID device accepting as input a generic sensor and allowing the transmission of the measured data towards a standard RFID reader. In this work a new enhanced version of Sensor-Tag is presented. It is based on optimized tag antennas designed by taking into account both size constraints and coupling effects. Compared with the old version, an appreciable size reduction is obtained and the working distance doubled, being now as good as a long range passive UHF tag.