Limiting amplitude protection circuit used in non-contact IC card and radio frequency identification label

Abstract

The invention discloses an amplitude-limiting circuit used for the non-contact type IC card and the radio frequency identified tag chip comprising a bypass grounding transistor being paralleled to therectified filter circuit of the chip radio frequency interface, a high voltage and a low voltage detection circuits for detecting the output signal from the rectified filter circuit, wherein the highvoltage and low voltage circuit controls the opening of a charging current source for charging a capacitor and a discharging current source, the capacitor forms an amplitude-limiting signal by discharging, and the amplitude-limiting signal controls the opening of the bypass grounding transistor. The invention can implement amplitude-limiting function without affecting the posterior demodulation,voltage stabilization, and normal operation of the clock and the reset circuit.

Description

technical field [0001] The invention relates to a limit protection circuit, in particular to a limit protection circuit for a non-contact IC card and a radio frequency identification tag chip. Background technique [0002] At present, non-contact IC cards or radio frequency identification tags commonly used in subways, public transportation, identity authentication, logistics and other industries are gradually replacing traditional paper tickets and have more and more applications. [0003] Schematic block diagram of contactless IC card or radio frequency identification tag system, such as figure 1 As shown, it includes two parts: reader and non-contact IC card or radio frequency identification tag chip. [0004] The reader loads the data to be sent on the high-frequency carrier wave and then transmits it to the space. The non-contact IC card or radio frequency identification tag within the effective range of the reader's emission field strength receives the signal through ...

AI Technical Summary

Problems solved by technology

[0007] As mentioned above, the non-contact IC card or RFID tag needs to be able to respond to the signal sent by the reader within a certain range of field strength, so the limiter circuit must be able to couple the non-contact IC card or RFID tag The energy is limited within an acceptable range, and at the same time, it cannot affect the normal operation of subsequent demodulation, voltage stabilization, clock, and reset circuits

However, if you use a limiter circuit without bandwidth control, it will affect the envelope of the modulated signal, thereby affecting the normal operation of subsequent demodulation, voltage stabilization, and reset circuits

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