Passive RFID tag localization has numerous applications, which can benefit from improved accuracy. Ranging methods based on phase difference of arrival become more accurate with higher frequency bandwidth. European regions, following ETSI regulation, historically allowed a single ultra-high fre-quency band (865–868 MHz) with limited accuracy. Recently allowed, the second band (915–921 MHz) increases the fre-quency range from 1.8 MHz to 53 MHz, but with a significant gap between the bands. In a dual-band experiment, distance estimates were obtained between two reader antennas and 17 tags across 6 arrays. The results revealed a new 3.07 m ambi-guity cycle due to the frequency gap, that adds to the existing  0.17 m phase ambiguity. Solving the new ambiguity on 88% of tag-antenna combinations and 100% of the arrays resulted in a maximum error of 0.55 m (median 0.26 m), significantly im-proving accuracy (×6.5) compared to the former single-band ranging. Looking ahead, the adoption of dual-band ranging could enhance the accuracy of various tag localization methods in ETSI-regulated regions.

Passive RFID tags have diverse low-cost sensing applications, with sensors either connected to the tag or the tag antenna acting as a sensor, allowing close-range measurements. However, an emerging approach utilizes wave propagation for remote sensing without physical contact. This study investigates how wave propagation across dense grass alters the phase difference of arrival, enabling the estimation of vegetation volume ratio. A tag positioned 19 meters from the reader is moved vertically into a dense grass medium, then without grass. By analyzing the change in phase meas-urements caused by the wave slowness in the medium, the grass volume ratio can be estimated. The RFID-based estimate of 0.75% aligns with the 0.53% ob-tained from weight measurements. Looking forward, this method might help to monitor crops in agriculture, but also to sense other complex medium.