The Research Of RFID Tag Orientation Based On Dual-frequency Carrier Phase Positioning

RFID technology is accompanied by the development of embedded and wirelesscommunications and then becoming of a new technology, now, it is becoming a hottopic and mainly used in the field of automatic identification. Among them, radiofrequency identification (RFID) systems for its low-power, low-cost, non-line,non-contact, wide transmission distance, etc., are widely used in large warehousestores and vehicles, railway automatic identification system and indoor positioning.First, this article summarizes the research status of RFID-based indoorpositioning, analysis describes the most commonly used indoor positioning algorithmand three-dimensional localization algorithm, analyze and compare their advantagesand disadvantages.On this basis， researching on get the value of pahse through the IQdemodulator.Then by studying the phase difference ranging principle,proposed the useof single-frequency wave phase difference to get the distance.In order to avoid thismethod brings positive cycle ambiguity. Proposed a new method that based on the useof dual-frequency carrier phase difference to get the distance between reader and tagand to get the position of the tag. The algorithm that currently used methods based ondifferent with that based on RSSI, First, no need to create energy attenuationmodel,second,if the energy that tag in the RFID system reflect is low,this method willbe better. Considering the tag’s internal circuit will impact the carrier signal phase,therefore, by simulation, select the frequency of the carrier within a reasonable range,so that the effects due to the internal circuit caused by tags or may ignore thelowest.After get the phase, proposed the use of least squares estimation method toobtain phase information.Then,according the dual-frequency carrier ranging method,design an experimentthat use two antennas to locate the posion of the target tag.Through getting thedistance between tag and reader to locate the tag.Finally,through the experiment verificate that the dual-band frequency wavealgorithm is reasonable,and make a comparison with the method that based onRSSI.From the results of the experiment this method can get the distance between tagand reader.