In a non-contacting smart card interrogator ( 1 ) a first end (A) of an eighth-wave transmission line ( 13 ) is connected to a terminal connecting a first receiver ( 16 ) to a transmission line ( 14 ), and to a second end (B) of the transmission line ( 14 ) the carrier wave generator ( 11 ) is connected. To the first end (A) of the eighth-wave transmission line ( 13 ) the first amplitude demodulation receiver ( 16 ) and to the second end (B) thereof a second amplitude demodulation receiver ( 16 ') are connected. In the non-contacting smart card interrogator of the invention an effective use of amplitude demodulation is made possible by changing the phase modulation into an amplitude one by means of a passive element, whereby, however, no noise source has been introduced into the system.
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