Summary: On the basis of describing the non- contact-type IC basic structure, introduce the design plan of a kind of high-frequency interface circuit that applies non- contact-type IC card to, analyze the structure of circuit each module of this interface and working course of whole circuit. The fact shows, this high-frequency interface circuit has realized to conversion and rectification steady voltage receiving energy, offer the steady voltage for internal logical circuit, can apply to the non- contact-type IC card chip.

Keyword: The non- contact-type IC card high-frequency interface circuit commutates the module of steady voltage and modulates the module of demodulation

Foreword

? ? With the development of microelectronics and wireless communication, the technology of the non- contact-type IC card grows vigorously too, but China designs the technology not exposed to the IC card not to be ripe enough. It is one of the key technology that a non- contact-type IC card is designed that the circuit of high-frequency interface is designed, the gentle lieutenant general introduces the design of a kind of high-frequency interface circuit.

Basic structure of 1 IC card

Fig. 1 is that one has logic to encrypt the structure block diagram of the non- contact-type IC card of the function. For there is logic that encrypts the non- contact-type IC card of the functioning, generally include IC chip and aerial coil coupling coil . IC chip includes some such as the circuit of high-frequency interface, logic control circuit, memory again.

2 high-frequency interface module is designed

The high-frequency interface circuit in IC chip is that the simulation of the non- contact-type IC card, high frequency transmit a piece of interface between the digital circuit in thorough fare and chip. It gets the electric current of reaction from coupling coil outside the chip, commutates steady voltage, provides the power for chip. High-frequency signal of modulation transmitted out from the reader, construct the digital serial dataflow data entry further processed in the logic control circuit in a production again after the high-frequency interface is through demodulation . The clock pulse produced the circuit and produced the systematic clock used for data carrier from the frequency of signal carrier of the high-frequency field. Fig. 2 is the high-frequency interface block-diagram with load modulating device.

Get back to the reader in order to pass the treated data in the chip, the high-frequency interface includes and supports the wave modulating device or scatter the modulating device backward too. They are controlled by the digitalized data conveyed.

Fig. 3 is the structural block diagram of module of the card. It is mainly the signal carrier receiving the reader and sending to commutate the module of steady voltage, change the signal carrier signal into a direct-flow signal, the power of the chip uses by regarding as contacting within the IC card; Can’t make the power voltage within the chip increase limitlessly because of incessant signal carrier that the reader send at the same time. Modulate the module of demodulation and is mainly taken off the signal carrier signal by the signal sending the reader; Convert the internal digital signal to the analog signal when the IC card sends a message, and upload it in the signal carrier signal in order to transmit to the reader.

1Commutate the design of the module of steady voltage

This module mainly includes source circuit of basis, voltage regulation circuit and power switch circuit. Basis the intersection of source and circuit form by second CMOS differential amplifier circuit and transistor circuit be able to the crack basis source makes up. Its structure. P1, P2 connect to both ends of the coil L0 directly. Couple on P1, P2 through being electromagnetic reaction produces alternating current; After rectification, produced the direct current to press VDD in the electric capacity C0 end of energy storage. Transfer, press the intersection of electric capacity and C5, form, discharge return circuit after it is led openly that N2 is in charge of, make P1, electric current at the P2 begin, charge and stop, charge to C5 to C0, the voltage of C0 both ends remains stable, namely offer the steady power voltage for load circuit.

2Modulate the module of demodulation

The reader is different from code of data transmission between the cards, the modulation and demodulating in the card is different. The transmission agreement between card and reader is half a duplexing mode, the signal received in the card is the signal carrier signal that sends of the reader and ” Miller code out of shape ” 100% of the ASK modulation signals of the signal, so the one that adopted during demodulation just just carried on simple RC demodulation, filter the high-frequency signal carrier signal.

In the modulation, that adopted is that one pair of signal carriers supporting the amplitude key modulated and accusing of is modulated in the agreement. Not only can modulate load by adjusting and controlling the electric capacity, can also modulate load by adjusting and controlling the resistance. Because the electric capacity is relatively large in area compared with resistance, so modulated load by adjusting and controlling the resistance during design, inside, through the code and one pair of signal carriers signal that the figure modulated, through controlling NMOS switch to be in charge of controlling adjusting and controlling the putting through and breaking of resistance, one pair of signal carriers can be sent through aerial when modulating signals like this, such as Fig. 7 b .