Load modulating module in radio-frequency identification (RFID)

Abstract

The invention discloses a load modulating module in RFID. The load modulating module comprises a coupling circuit, which is used to couple the signals to the RFID card terminal or couple the load modulating signals of the RFID card terminal to the card reader terminal; and a load modulating circuit, which is connected to the output terminal of the coupling circuit and is used to return the data processed by the digital circuit to the card reader; and further comprises an amplitude limiting circuit, which is connected to the output terminal of the load modulating circuit and is used to limit the amplitude of the output of the load modulating circuit and provide a variable voltage to the load modulating circuit; wherein the variable voltage changes with the change of field strength: when the field strength increases, the variable voltage increases, when the field strength decreases, the variable voltage decreases too; and moreover, the amplitude limiting circuit can conduct the load modulating circuit under a large field strength to finish the load modulation. The provided load modulating module can improve the load modulation waveform and load modulation depth under a large field strength so as to improve the compatibility of RFID cards.

Description

technical field [0001] The invention relates to the field of load modulation circuits in analog integrated circuits, in particular to a load modulation module in radio frequency identification. Background technique [0002] In radio frequency identification, the radio frequency identification card needs to couple the analog signal sent by the card reader, and demodulate the data sent by the card reader and then send it to the digital circuit for processing. The digital circuit returns the processed data to the reader through the load modulation circuit. Card machine, this completes the entire communication process. The process of returning data to the card reader is load modulation. If the waveform and depth of load modulation are not good, it will affect the demodulation of the data by the card reader. Therefore, the load modulation circuit is very important and critical. [0003] see figure 1 , in a traditional load modulation circuit, the NMOS transistor MN3 is equivale...

AI Technical Summary

Problems solved by technology

The advantage of this structure is that it is simple and easy to implement. When working in a small field strength, the load modulation waveform and load modulation depth are not bad; the disadvantage is that working in a large field strength, the load modulation waveform and load modulation depth are both worse The card machine is difficult to demodulate, or it is easy to cause the demodulation error of the card reader

If the card reader demodulation error, the entire communication will fail

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