Device for securely exchanging data without contact between a card reader and a card

摘要

The transponder has a reception and transmission unit for reception and transmission of data. The reception and transmission unit is provided with primary antenna loops and secondary antenna loops that are coupled with a card reader. Demodulators (224a, 224b) are arranged to allow or prevent transmission of the data based on phase displacement function between the signals received by the antenna loops. The antenna loops comprise resonant circuits (210a, 210b).