Waveform shaping circuit after demodulation of card communication in iso/iec 14443 protocol
A waveform shaping and protocol technology, used in pulse shaping and other directions, to solve problems such as inability to decode correctly
Active Publication Date: 2018-08-14
SHANGHAI HUAHONG INTEGRATED CIRCUIT
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Problems solved by technology
[0003] The waveform after analog demodulation, due to the expansion of the signal during the carrier communication transmission process, often demodulates a groove width that is larger than the range of the ISO / IEC 14443 protocol. Digital design may have a certain The margin of the groove can be decoded correctly; but if the groove is too large, it cannot be decoded correctly
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[0016] see figure 1 As shown, in the ISO / IEC 14443 protocol, the waveform shaping circuit after card communication demodulation is in figure 1 In the shown embodiment, it includes: an input synchronous logic unit, which includes a first D flip-flop DCF1, a second D flip-flop DCF2; a shaping logic unit, a groove width counter, and a decoding unit. The input terminal D of the first D flip-flop DCF1 is connected to the analog demodulated signal RF_DIN, the Q terminal of the first D flip-flop DCF1 is connected to the D terminal of the second D flip-flop DCF2, the first D flip-flop DCF1 and the second The clock terminal of the D flip-flop DCF2 is connected to the digital logic working clock RF_CLK_IN. The output terminal of the second D flip-flop DCF2 is connected to the input terminal of the shaping logic unit, and the output terminal of the second D flip-flop DCF2 is simultaneously connected to the input terminal of the groove width counter unit. The output end of the groove wi...
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The invention discloses a waveform shaping circuit after card communication demodulation in an ISO / IEC 14443 protocol. The waveform shaping circuit comprises an input synchronization logic unit which is used for synchronizing analog demodulated signals in a digital logic working clock domain, a groove width counter which is connected with the output end of the input synchronization logic unit and is used for counting synchronized signals output by the input synchronization logic unit and outputting the number of calculated clocks representing the groove width in real time, and a shaping logic unit which is used for setting a value for the number of clocks representing the groove width according to the baud rate of a current received signal, and automatically pulling up the groove signal and generating a groove signal meeting the requirement of the ISO / IEC 14443 protocol when the set number of clocks representing the groove width in the shaping logic unit matches a received number of clocks representing the groove width output by the groove width counter. According to the invention, the success rate of communication can be improved greatly, and the circuit can share analog demodulation pressure.
Description
technical field [0001] The invention relates to the field of digital circuits, in particular to a waveform shaping circuit after card communication demodulation in the ISO / IEC 14443 protocol. Background technique [0002] In the field of contactless cards, the correct demodulation of analog to carrier and the correct decoding of digital circuits often become the key to the design of contactless communication. If the potential problems are underestimated in the design, the probability of successful communication will be greatly reduced. For a digital design engineer, how to correctly deal with the demodulated waveform is a problem that needs serious consideration. [0003] The waveform after analog demodulation, due to the expansion of the signal during the carrier communication transmission process, often demodulates a groove width that is larger than the range of the ISO / IEC 14443 protocol. If the groove is too large, it can be decoded correctly; but if the groove is too l...
Claims
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IPC IPC(8): H03K5/01
Inventor 丁兆健
Owner SHANGHAI HUAHONG INTEGRATED CIRCUIT