Method for transmitting data between a terminal and a portable data carrier over a wireless electromagnetic transmission link

摘要

A method for transmitting data between a terminal and a portable data carrier over a wire-free electromagnetic transmission link using a carrier signal which is 100% ASK-modulated in accordance with the data. The carrier signal serving as a clock signal for the portable the data carrier. The significance of an item of data is determined by a position of a shift keying point in the carrier signal within a time slot. The information content of the shift keying point corresponds to a number of N bits, N being greater than or equal to 2. The significance of the N bits is defined by a position of the shift keying point within 2. sup.N possible positions within the time slot. At the start or at the end of a time slot there is a zero time period in which no shift keying point which is assigned to the data to be transmitted occurs, in order to avoid an unacceptably long loss of the carrier signal.