In recent years, radio frequency identification (RFID) microwave technology receives great attention because of its advantages, e.g. long identification distance, small size of antenna, high identification speed and strong anti-collision ability. RFID tag plays one of the most important roles in logistics, and therefore special attention should be paid to tag design. In this paper, we present a 2.45G semi-active tag design, which is compatible with ISO 18000-4. The proposed tag can switch the manners of working between active and passive. When the generated RF-power is sufficient to operate, the tag works as a passive tag, and low noise amplifier (LNA), oscillator (OSC) and power amplifier (PA) are cut off to save the whole chip power consumption mostly. Otherwise it operates in active mode using battery power, and the working distance is greatly increased as a result of using PA.

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This paper proposes a new approach to the multi-robot map fusion algorithm that enables a team of robots to build a joint map without initial knowledge of their relative pose. First, the relative distance and bearing measurements between two robots are fused together by the covariance intersection method after they detect each other. Second, the transformation equations among multi robots coordinates are derived based on their relative distance and bearing measurements. Third, all the multi robots local maps are merged into one global map by unscented transform based on the transformation equations. Fourth, the possible duplicate features are filtered out by the robots maximal detection area and the features coordinate range, then the Mahalanobis distance is computed to decide the duplicate features correspondence through unscented transform, and the Kalman Filter is used while fusing the duplicate features information. As a means of validation for the proposed method, experimental results obtained from the two robots are presented.