Demodulator for contactless chip card
First Claim
Patent Images
1. A demodulator of binary data for a contactless chip card with transmission by radio frequency signals, said demodulator comprising:
- a detector for receiving a radio frequency signal and generating a detected signal responsive thereto;
a rectifier for generating a rectified signal based upon the detected signal;
a bandpass filter for generating a first signal at low frequency and a second signal at high frequency based upon the rectified signal;
a comparator stage for comparing the first and second signals; and
a memory for storing a result of a comparing by said comparator stage.
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Abstract
A contactless chip card, receiving binary data transmitted by radio frequency, includes a demodulator for the binary data. The demodulator includes a circuit for the detection of the transmitted signals, a rectifier circuit, a bandpass filter, two comparators and a memory circuit. The bandpass filter provides a low-frequency signal used as a reference for the two comparators and a high-frequency signal that is compared with the references varying with the low frequency signal. As a result, the demodulation is independent of the mean level of the received signal.
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Citations
28 Claims
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1. A demodulator of binary data for a contactless chip card with transmission by radio frequency signals, said demodulator comprising:
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a detector for receiving a radio frequency signal and generating a detected signal responsive thereto; a rectifier for generating a rectified signal based upon the detected signal; a bandpass filter for generating a first signal at low frequency and a second signal at high frequency based upon the rectified signal; a comparator stage for comparing the first and second signals; and a memory for storing a result of a comparing by said comparator stage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A contactless chip card comprising:
a demodulator comprising a detector for receiving a radio frequency signal and generating a detected signal responsive thereto; a rectifier for generating a rectified signal based upon the detected signal; a bandpass filter for generating a first signal at low frequency and a second signal at high frequency based upon the rectified signal; a comparator stage for comparing the first and second signals; and a memory for storing a result of a comparing by said comparator stage. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A demodulator of binary data for a contactless chip card with transmission by radio frequency signals, said demodulator comprising:
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a detector for receiving a radio frequency signal and generating a detected signal responsive thereto; a rectifier for generating a rectified signal based upon the detected signal; a bandpass filter for generating a first signal at low frequency and a second signal at high frequency based upon the rectified signal, said bandpass filter comprising a high-pass filter having cut-off frequency for passing the binary data without substantial attenuation, and a low-pass filter having a cut-off frequency for reducing ripple at a carrier frequency and for determining a DC component of the rectified signal; and a comparator stage for comparing the first and second signals. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A method for demodulating binary data in a contactless chip card receiving transmission by radio frequency signals, the method comprising the steps of:
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receiving a radio frequency signal and generating a detected signal responsive thereto; generating a rectified signal based upon the detected signal; generating a first signal at low frequency and a second signal at high frequency based upon the rectified signal; comparing the first and second signals. - View Dependent Claims (26, 27, 28)
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Specification