Browse Prior Art Database

PEAK TRACK DATA RECOVERY DEMODULATOR

IP.com Disclosure Number: IPCOM000009519D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-29
Document File: 2 page(s) / 87K

Publishing Venue

Motorola

Related People

Michel Burri: AUTHOR [+3]

Abstract

The problem relates generally to detecting data in an electronic reader interface, received from a contact less smart card or tag transponder, in which the reader supplies power to the contact less card or transponder via a radio frequency transmit loop antenna. The same transmit antenna is also used to receive a back-scattered signal from the smart card or tag device which is performed with an admittance load switching device inside the card/tag circuit. The problem arises in that the received data signal developed at the transmitter coil is very small in comparison with the radio frequency transmit signal requiring high carrier rejection filtering prior to signal detection. The solution proposed is a peak track demodulator capable of detecting low-level signals in a large signal environment such as card/tag reader.

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Technical MOTOROLA @ Developments

PEAK TRACK DATA RECOVERY DEMODULATOR

by Michel Burri, Hans Staufer and Tony Newton

PROBLEM

  The problem relates generally to detecting data in an electronic reader interface, received from a contact less smart card or tag transponder, in which the reader supplies power to the contact less card or transponder via a radio frequency transmit loop antenna. The same transmit antenna is also used to receive a back-scattered signal from the smart card or tag device which is performed with an admittance load switching device inside the card/tag circuit. The problem arises in that the received data signal developed at the transmitter coil is very small in comparison with the radio frequency transmit signal requiring high carrier rejection filtering prior to signal detection. The solution proposed is a peak track demodulator capable of detecting low-level signals in a large signal environment such as card/tag reader.

SOLUTION

  Figure 1 shows an electrical diagram of the pro- posed Peak Track and Hold demodulator and the corresponding signal diagram of the different wave- forms. A low-level amplitude modulated (AM) data signal (ASK) is presented to the base of transistor Tl (See Ref 1 in the Timing Diagram of Figure 2). At the emitter of Tl the signal appears half wave rectified. The half wave rectified signal is then fed

to the non-inverting input of the comparator 10. The inverting comparator input is controlled by the time constant of RI and Cl. The discharge rate of this time constant has been chosen for an optimum decay rate of t...