CN102750568B - Contactless IC card radio-frequency interface circuit and tuning methods thereof - Google Patents
Contactless IC card radio-frequency interface circuit and tuning methods thereof Download PDFInfo
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Abstract
The present invention relates to a kind of contactless IC card and radio-frequency interface circuit thereof and tuning methods.Wherein, contactless IC card radio-frequency interface circuit comprises: antenna; And radio frequency interface module, comprise tunable capacitor, tuner and adjustable active impedance, wherein: the tuning tunable capacitor of tuner also measures the resistance value of antenna, resistance value is sent to adjustable active impedance; Under the control of the first control signal that adjustable active impedance sends at the modulator of contactless IC card, change in working order and between off working state, wherein, the off working state of adjustable active impedance represents that adjustable active impedance is low-resistance, the duty of adjustable active impedance switches under representing the control of the data-signal that adjustable active impedance exports at modulator between low-resistance and negative resistance, when adjustable active impedance is in negative resistance, the resistance value of adjustable active impedance equals the resistance value of antenna.The present invention can, in weak coupling situation, make the demodulation of read write line become easy, improves the accuracy of read write line.<!--1-->
Description
Technical field
The present invention relates to microelectronic, particularly relate to a kind of contactless IC card radio-frequency interface circuit and tuning methods thereof.
Background technology
(IntegratedCircuit is called for short: IC) be packaged with integrated circuit, in order to Storage and Processing data in card integrated circuit.Since IC-card is born, experienced by and snapped into smart card, evolution from Contact Type Ic Card to contactless IC card from storing.Contactless IC card, also known as radio-frequency card, is the new technology grown up recent years in the world.Contactless IC card is made up of IC chip, antenna, and the IC chip antenna built-in with contactless IC card is connected, and is encapsulated in the PVC card sheet of a standard.Adopt non-contact IC technology, contactless ic is stuck in certain distance scope near read write line surface, is completed the read-write operation of data by the transmission of radiowave.When read write line carries out read-write operation to contactless IC card, read write line sends wireless signal, radio frequency (the RadioFrequency of contactless IC card, be called for short: RF) interface circuit detects the wireless signal that read write line sends, exchanged by RF interface circuit and read write line settling signal under the control of IC chip internal integrated circuit.
As shown in Figure 1, be equivalent circuit theory schematic diagram when read write line in prior art and contactless IC card carry out signal exchange, the circuit that read write line 01 sends wireless signal comprises signal source U
0, electric capacity C
1(resistance R is equivalent to antenna 11
1and inductance L
1), the circuit that read write line 01 receives the wireless signal that contactless IC card 02 sends comprises wave filter, amplifier and detuner.The radio-frequency interface circuit of contactless IC card 02 comprises antenna 12 and (is equivalent to resistance R
2and inductance L
2) and adjustable equivalent load Z
2.
As shown in Figure 2, for read write line in prior art sends data to the circuit theory schematic diagram of contactless IC card, when read write line 01 transmits a signal to contactless IC card 02, the electric current I of antenna 11 is flow through in read write line 01 modulation
1, when passing through inductance L
1electric current I
1during change, the magnetic field that can change around it.When the antenna 12 of contactless IC card 02 enters into by inductance L
1time in the magnetic field of the change produced, can in inductance L
2upper generation induced electromotive force U
q2, wherein, electromotive force U
q2by the mutual inductance M between two antennas and electric current I
1determine:
Wherein, mutual inductance M is by the equivalent inductance L of the coupling coefficient k between two antennas, two antennas
1and L
2determine:
In the inductance L of contactless IC card 02
2the induced electromotive force U of upper generation
q2electric current I can be changed
2, like this through electric current I that read write line 01 is modulated
1change electric current I
2, the detuner 14 of contactless IC card 02, by detecting the change of UQ2, U2 or electric current I 2, can obtain the signal that read write line 01 sends.
As shown in Figure 3, for contactless IC card in prior art sends data to the equivalent radio frequency interface circuit principle schematic of read write line, when contactless IC card 02 transmits a signal to read write line 01, the data-signal that contactless IC card 02 exports according to its modulator 13 changes equivalent load Z
2thus antenna (inductance L is flow through in modulation
2) electric current I
2, based on mutual inductance principle, can in antenna (inductance L
1) on produce induced electromotive force, this induced electromotive force is with equiva lent impedance Z '
tAGrepresent, equiva lent impedance Z '
tAGdetermined by following formula:
As can be seen from the above equation, the data-signal exported according to the modulator of contactless IC card changes the equivalent load Z on contactless IC card 02
2, the electric current I on read write line 01 can be changed
1, the detuner of read write line 01 is by detecting electric current I
1change, can obtain contactless IC card 02 send signal.
The signal exchange of both direction shown in Fig. 2 and Fig. 3 be all by antenna (inductance) between coupling carry out, without the need to by Line Contacts, the principle of work of Here it is contactless IC card.
As shown in Figure 4, be the equivalent load Z of contactless IC card in prior art
2equivalent circuit theory schematic diagram, equivalent load Z
2be equivalent to variable capacitance C in parallel
2with variable resistor R
l,on contactless IC card 02, integrated circuit changes Z
2mode have two kinds: change variable capacitance C
2and variable resistor R
l.To change variable resistor R
lfor example, according to the data-signal that the modulator of contactless IC card exports, variable resistor R
lcan switch between low-resistance and high resistant two resistances.Wherein, as variable resistor R
lwhen low-resistance place, variable resistor R can be thought
lresistance be 0, be equivalent to short circuit, as variable resistor R
lwhen high resistant place, variable resistor R can be thought
lresistance be ∞, be equivalent to open circuit.Such as, when modulator exports data " 0 ", variable resistor R
lat low-resistance place, when modulator exports data " 1 ", variable resistor R
lat high resistant place.
As variable resistor R
lwhen low-resistance place, equiva lent impedance Z '
tAGcan be expressed as:
As variable resistor R
lwhen high resistant place, equiva lent impedance Z '
tAGcan be expressed as:
At the frequency of carrier signal that contactless IC card 02 works, there is following relation:
Therefore, at the detuner of read write line 01, as variable resistor R
lwhen low-resistance, equiva lent impedance Z '
tAGimpedance minimum; As variable resistor R
lwhen high resistant, equiva lent impedance Z '
tAGimpedance maximum.The scope of the coupling coefficient k between contactless IC card 02 antenna (inductance L 2) and read write line 01 antenna (inductance L 1) is: 0≤k≤1.Wherein, as k=0, be not coupled completely corresponding between two antennas.Work as k=1, be coupled completely corresponding between two antennas, completely the same by the magnetic flux of two antennas.And in actual use, coupling coefficient k is far smaller than 1.Due to by between the physical size of two antennas, relative position, antenna and the impact of the many factors such as physical shielding around, coupling coefficient k can be reduced to only has 1%.Again see Fig. 3, the detuner of read write line 01 needs to detect equiva lent impedance Z '
tAGchange.Equiva lent impedance Z '
tAGbe and square being directly proportional, even if as variable resistor R of coupling coefficient k
lat high resistant place, equiva lent impedance Z '
tAGimpedance maximum time, because coupling coefficient k is very little, cause variable resistor R
lat the equiva lent impedance Z ' at high resistant place
tAGrelative to variable resistor R
lat the equiva lent impedance Z ' at low-resistance place
tAGchange very faint, cause when coupling coefficient k is very little, the demodulation of read write line 01 is very difficult, easily makes mistakes, thus causes the accuracy of read write line 01 lower.
Summary of the invention
The invention provides a kind of contactless IC card and radio-frequency interface circuit thereof and tuning methods, in order to realize in weak coupling situation, make the demodulation of read write line become easy, improve the accuracy of read write line.
The invention provides a kind of contactless IC card radio-frequency interface circuit, comprising:
Antenna, for being coupled with read write line; And
Radio frequency interface module, comprises tunable capacitor, tuner and adjustable active impedance, wherein:
Described tuner is connected in the two ends of described antenna in parallel, measures the resistance value of described antenna, described resistance value is sent to described adjustable active impedance for tuning described tunable capacitor;
Described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described tunable capacitor and described adjustable active impedance are formed is connected in the two ends of described antenna in parallel, under the control of the first control signal that described adjustable active impedance sends at the modulator of described contactless IC card, change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
The present invention also provides a kind of contactless IC card, comprises radio-frequency interface circuit and logic processing circuit, and described radio-frequency interface circuit comprises:
Antenna, for being coupled with read write line; And
Radio frequency interface module, comprises tunable capacitor, tuner and adjustable active impedance, wherein:
Described tuner is connected in the two ends of described antenna in parallel, measures the resistance value of described antenna, described resistance value is sent to described adjustable active impedance for tuning described tunable capacitor;
Described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described tunable capacitor and described adjustable active impedance are formed is connected in the two ends of described antenna in parallel, under the control of the first control signal that described adjustable active impedance sends at the modulator of described contactless IC card, change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
The present invention also provides a kind of noncontact near field communication system, comprises read write line and contactless IC card, and described contactless IC card comprises radio-frequency interface circuit and logic processing circuit, and described radio-frequency interface circuit comprises:
Antenna, for being coupled with read write line; And
Radio frequency interface module, comprises tunable capacitor, tuner and adjustable active impedance, wherein:
Described tuner is connected in the two ends of described antenna in parallel, measures the resistance value of described antenna, described resistance value is sent to described adjustable active impedance for tuning described tunable capacitor;
Described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described tunable capacitor and described adjustable active impedance are formed is connected in the two ends of described antenna in parallel, under the control of the first control signal that described adjustable active impedance sends at the modulator of described contactless IC card, change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
The present invention also provides a kind of tuning methods of contactless IC card radio-frequency interface circuit, described contactless IC card radio-frequency interface circuit comprises antenna, tunable capacitor, tuner and adjustable active impedance, described tuner is connected in the two ends of described antenna in parallel, described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described adjustable active impedance and described tunable capacitor are formed is connected in the two ends of described antenna in parallel, and described method comprises:
Adopt described tuner, tuning described tunable capacitor also measures the resistance value of described antenna, and described resistance value is sent to described adjustable active impedance;
Adopt the first control signal that the modulator of described contactless IC card exports, control described adjustable active impedance to change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
In embodiments of the present invention, relative to prior art, when adjustable active impedance in running order and be negative resistance time, greatly improve the equiva lent impedance Z ' of read write line end
tAGimpedance, like this, when contactless IC card to read write line send signal time, even if coupling coefficient k is very little, but the detuner of read write line still can see enough large equiva lent impedance Z '
tAGchange, thus can correctly demodulation, achieving when not changing the design of read write line, making the demodulation of read write line become easy, improve the accuracy of read write line.
Accompanying drawing explanation
Fig. 1 is equivalent circuit theory schematic diagram when read write line and contactless IC card carry out signal exchange in prior art;
Fig. 2 is the equivalent radio frequency interface circuit principle schematic that in prior art, read write line sends data to contactless IC card;
Fig. 3 is the equivalent radio frequency interface circuit principle schematic that in prior art, contactless IC card sends data to read write line;
Fig. 4 is the equivalent load Z of contactless IC card in prior art
2equivalent circuit theory schematic diagram;
Fig. 5 is the circuit theory schematic diagram of noncontact near field communication system first embodiment of the present invention;
Fig. 6 is the circuit theory schematic diagram of noncontact near field communication system second embodiment of the present invention;
Fig. 7 is the schematic flow sheet of tuning methods first embodiment of contactless IC card radio-frequency interface circuit of the present invention;
Fig. 8 is the schematic flow sheet of tuning methods second embodiment of contactless IC card radio-frequency interface circuit of the present invention.
Embodiment
Below in conjunction with specification drawings and specific embodiments, the invention will be further described.
As shown in Figure 5, for the circuit theory schematic diagram of noncontact near field communication system first embodiment of the present invention, this noncontact near field communication system can comprise read write line 01 and contactless IC card 02, and wherein, contactless IC card 02 can comprise radio-frequency interface circuit 51 and logic processing circuit 53.Wherein, radio-frequency interface circuit 51 can comprise antenna 12 and radio frequency interface module 52, and radio frequency interface module 52 can comprise tunable capacitor C
2, tuner 521 and adjustable active impedance N
z2.Antenna 12 is equivalent to resistance R
2and inductance L
2.Tuner 521 is connected in the two ends of antenna 12 in parallel, adjustable active impedance N
z2with tunable capacitor C
2be connected in series, adjustable active impedance N
z2with tunable capacitor C
2the series arm formed is connected in the two ends of antenna 12 in parallel.
Antenna 12 is for being coupled with read write line 01.Tuner 521 is for tuning tunable capacitor C
2, measure the resistance R of antenna 12
2resistance value, this resistance value is sent to adjustable active impedance N
z2.Adjustable active impedance N
z2under the control of the first control signal sent at the modulator 13 of contactless IC card 02, change in working order and between off working state, wherein, the first control signal represents whether modulator 13 works; Wherein, adjustable active impedance N
z2off working state represent adjustable active impedance N
z2for low-resistance, adjustable active impedance N
z2duty represent adjustable active impedance N
z2switch between low-resistance and negative resistance, as adjustable active impedance N under the control of the data-signal of modulator 13 output
z2when being in negative resistance, adjustable active impedance N
z2resistance value equal the resistance R of antenna 12
2resistance value, as adjustable active impedance N
z2when being in low-resistance, adjustable active impedance N
z2the lower or short circuit of resistance value.
Further, radio-frequency interface circuit 51 can comprise following two states:
First state, when modulator 13 does not work, adjustable active impedance N
z2be in off working state;
Second state, when modulator 13 works, adjustable active impedance N
z2in running order.
In the present embodiment, the principle of work of radio-frequency interface circuit 51 is as follows: the tuning tunable capacitor C of tuner 521
2, by the radio-frequency interface circuit of contactless IC card 02 be tuned to need resonance frequency on, complete resistance R simultaneously
2measurement.When contactless IC card 02 needs to send a signal to read write line 01, modulator 13 works, and modulator 13 is to adjustable active impedance N
z2send the first control signal representing that modulator 13 works, this first control signal is by adjustable active impedance N
z2be set to duty, when tuner 521 carry out tuning or contactless IC card 02 need to receive the signal that read write line 01 sends time, modulator 13 does not work, and modulator 13 is to adjustable active impedance N
z2send and represent idle first control signal of modulator 13, this first control signal is by adjustable active impedance N
z2be set to off working state.
As shown in Figure 6, be the circuit theory schematic diagram of noncontact near field communication system second embodiment of the present invention, be with the difference of schematic diagram shown in Fig. 5, radio frequency interface module 52 can also comprise variable resistor R
lwith field intensity testing circuit 522, variable resistor R
lwith tunable capacitor C
2be connected in parallel and with adjustable active impedance N
z2be connected in series, adjustable active impedance N
z2also be connected with field intensity testing circuit 522, variable resistor R
lbe connected with modulator 13 and field intensity testing circuit 522.
In the present embodiment, coupling coefficient k and predetermined threshold value, for estimating the coupling coefficient k of antenna, compare by field intensity testing circuit 522, generate the second control signal according to comparative result.Variable resistor R
lmodulator 13 send the first control signal and field intensity testing circuit 522 send the second control signal jointly controlling under, change in working order and between off working state, wherein, variable resistor R
loff working state represent that variable resistor is high resistant, variable resistor R
lduty represent that the data-signal that variable resistor exports according to modulator 13 switches between low-resistance and high resistant.Adjustable active impedance N
z2modulator 13 send the first control signal and field intensity testing circuit 522 send the second control signal jointly controlling under, change in working order and between off working state.
In the present embodiment, field intensity testing circuit 522 is by detecting the induced voltage U of antenna 12
2, thus estimation coupling coefficient k.
In the present embodiment, radio-frequency interface circuit 51 can comprise following three states:
First state, when modulator 13 does not work, adjustable active impedance N
z2be in off working state, variable resistor R
lbe in off working state;
Second state, when coupling coefficient k is more than or equal to predetermined threshold value and modulator 13 works, adjustable active impedance N
z2be in off working state, variable resistor R
lin running order;
The third state, when coupling coefficient k is less than predetermined threshold value and modulator 13 works, adjustable active impedance N
z2in running order, variable resistor R
lbe in off working state.
The principle of work of the present embodiment is as follows: the tuning tunable capacitor C of tuner 521
2, by the radio-frequency interface circuit on contactless IC card 02 be tuned to need resonance frequency on, complete the measurement to resistance R2 simultaneously.When tuner 521 carry out tuning or contactless IC card 02 need to receive the signal that read write line 01 sends time, modulator 13 does not work, variable resistor R
lwith adjustable active impedance N
z2off working state is under the control of the first control signal of modulator 13 transmission.When contactless IC card 02 sends signal to read write line 01, modulator 13 works.At modulator 13 duration of work, if field intensity testing circuit 522 judges that coupling coefficient k is more than or equal to predetermined threshold value, modulator 13 send the first control signal and field intensity testing circuit 522 send the second control signal jointly controlling under, adjustable active impedance N
z2be in off working state, variable resistor R
lin running order.At modulator 13 duration of work, if field intensity circuit 522 judges that coupling coefficient k is less than predetermined threshold value, modulator 13 send the first control signal and field intensity testing circuit 522 send the second control signal jointly controlling under, adjustable active impedance N
z2in running order, variable resistor R
lbe in off working state.
As shown in Figure 7, be the schematic flow sheet of tuning methods first embodiment of contactless IC card radio-frequency interface circuit of the present invention, the method can be applied to the radio-frequency interface circuit 51 in schematic diagram shown in Fig. 5, and the method can comprise the steps:
Step 71, employing tuner 521, tuning tunable capacitor C
2and measure the resistance value of antenna 12, this resistance value is sent to adjustable active impedance N
z2;
Step 72, the first control signal adopting the modulator 13 of contactless IC card 02 to export, control adjustable active impedance N
z2change in working order and between off working state;
Wherein, the first control signal represents whether modulator works, adjustable active impedance N
z2off working state represent adjustable active impedance N
z2for low-resistance, adjustable active impedance N
z2duty represent adjustable active impedance N
z2switch between low-resistance and negative resistance, as adjustable active impedance N under the control of the data-signal of modulator 13 output
z2when being in negative resistance, adjustable active impedance N
z2resistance value equal the resistance value of antenna 12;
In step 72., when contactless IC card 02 receives the signal of read write line 01 transmission or tuner 521 carries out tuning, modulator 13 does not work, and adopts the first control signal that modulator 13 exports, and controls adjustable active impedance N
z2be in off working state; When contactless IC card 02 sends signal to read write line 01, modulator 13 works, and adopts the first control signal that modulator 13 exports, and controls adjustable active impedance N
z2in running order.
As shown in Figure 8, be the schematic flow sheet of tuning methods second embodiment of contactless IC card radio-frequency interface circuit of the present invention, the method can be applied to the radio-frequency interface circuit 51 in schematic diagram shown in Fig. 6, and the method can comprise the steps:
Step 81, employing tuner 521, tuning tunable capacitor C
2and measure the resistance value of antenna 12, this resistance value is sent to adjustable active impedance N
z2;
Step 82, employing field intensity testing circuit 522, estimate the coupling coefficient of antenna 12, coupling coefficient and predetermined threshold value compared, generate the second control signal according to comparative result;
The second control signal that step 83, the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls adjustable active impedance N
z2change in working order and between off working state;
In a step 83, when coupling coefficient is less than predetermined threshold value and modulator 13 works, the second control signal that the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls adjustable active impedance N
z2in running order; When coupling coefficient is more than or equal to predetermined threshold value or modulator 13 does not work, the second control signal that the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls adjustable active impedance N
z2be in off working state;
The second control signal that step 84, the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls variable resistor R
lchange in working order and between off working state;
Wherein, variable resistor R
loff working state represent variable resistor R
lfor high resistant, variable resistor R
lduty represent variable resistor R
lswitch between low-resistance and high resistant according to the data-signal that modulator 13 exports.
In step 84, when coupling coefficient is more than or equal to predetermined threshold value and modulator 13 works, the second control signal that the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls variable resistor R
lin running order; When coupling coefficient is less than predetermined threshold value or modulator does not work, the second control signal that the first control signal adopting modulator 13 to export and field intensity testing circuit 522 export, controls variable resistor R
lbe in off working state.
For schematic flow sheet shown in the schematic diagram of circuit theory shown in Fig. 5 and Fig. 6 and Fig. 7 and Fig. 8, as adjustable active impedance N
z2in running order and be negative resistance time, the equiva lent impedance Z ' in read write line 01
tAGcan be expressed as:
See above formula, when antenna 12 be tuned to read write line 01 send carrier frequency time, have ω
2l
2c
2=1, as adjustable active impedance N
z2during for negative resistance, adjustable active impedance N
z2resistance equal resistance R
2resistance value, therefore, the denominator in above formula levels off to 0, thus greatly improves equiva lent impedance Z '
tAGimpedance, like this, when contactless IC card 02 sends signal to read write line 01, even if the coupling coefficient k in above formula molecule is very little, but due to denominator simultaneously also very little, therefore the detuner of read write line 01 still can see enough large equiva lent impedance Z '
tAGchange, thus can correctly demodulation, achieving when not changing the design of read write line 01, making the demodulation of read write line 01 become easy, improve the accuracy of read write line 01.
Last it is noted that above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to technical scheme of the present invention or equivalent replacement, and not depart from the spirit and scope of technical solution of the present invention.
Claims (10)
1. a contactless IC card radio-frequency interface circuit, is characterized in that, comprising:
Antenna, for being coupled with read write line; And
Radio frequency interface module, comprises tunable capacitor, tuner and adjustable active impedance, wherein:
Described tuner is connected in the two ends of described antenna in parallel, measures the resistance value of described antenna, described resistance value is sent to described adjustable active impedance for tuning described tunable capacitor;
Described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described tunable capacitor and described adjustable active impedance are formed is connected in the two ends of described antenna in parallel, under the control of the first control signal that described adjustable active impedance sends at the modulator of described contactless IC card, change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
2. contactless IC card radio-frequency interface circuit according to claim 1, is characterized in that, described radio-frequency interface circuit comprises:
First state, when described modulator does not work, described adjustable active impedance is in off working state;
Second state, when described modulator work, described adjustable active impedance is in running order.
3. contactless IC card radio-frequency interface circuit according to claim 1, is characterized in that, described radio frequency interface module also comprises:
Field intensity testing circuit, for estimating the coupling coefficient of described antenna, compares described coupling coefficient and predetermined threshold value, according to comparative result, generates the second control signal;
Variable resistor, be connected in parallel with described tunable capacitor and connect with described adjustable active impedance, described variable resistor is under the jointly controlling of described first control signal and described second control signal, change in working order and between off working state, wherein, described variable-resistance off working state represents that described variable resistor is high resistant, described high resistant represents that described variable resistor is opened a way, described variable-resistance duty represents that the data-signal that described variable resistor exports according to described modulator switches between low-resistance and high resistant, described low-resistance represents described variable resistor short circuit,
Described adjustable active impedance, under the jointly controlling of described first control signal and described second control signal, changes in working order and between off working state.
4. contactless IC card radio-frequency interface circuit according to claim 3, is characterized in that, described radio-frequency interface circuit comprises:
First state, when described modulator does not work, described adjustable active impedance is in off working state, and described variable resistor is in off working state;
Second state, when described coupling coefficient is more than or equal to predetermined threshold value and described modulator works, described adjustable active impedance is in off working state, and described variable resistor is in running order;
The third state, when described coupling coefficient is less than predetermined threshold value and described modulator works, described adjustable active impedance is in running order, and described variable resistor is in off working state.
5. a contactless IC card, comprises radio-frequency interface circuit and logic processing circuit, it is characterized in that, described radio-frequency interface circuit comprises the arbitrary described contactless IC card radio-frequency interface circuit of claim 1-4.
6. a noncontact near field communication system, comprise read write line and contactless IC card, described contactless IC card comprises radio-frequency interface circuit and logic processing circuit, it is characterized in that, described radio-frequency interface circuit comprises the arbitrary described contactless IC card radio-frequency interface circuit of claim 1-4.
7. the tuning methods of a contactless IC card radio-frequency interface circuit, it is characterized in that, described contactless IC card radio-frequency interface circuit comprises antenna, tunable capacitor, tuner and adjustable active impedance, described tuner is connected in the two ends of described antenna in parallel, described adjustable active impedance and described tunable capacitor are connected in series, the series arm that described adjustable active impedance and described tunable capacitor are formed is connected in the two ends of described antenna in parallel, and described method comprises:
Adopt described tuner, tuning described tunable capacitor also measures the resistance value of described antenna, and described resistance value is sent to described adjustable active impedance;
Adopt the first control signal that the modulator of described contactless IC card exports, control described adjustable active impedance to change in working order and between off working state, wherein, described first control signal represents whether described modulator works, the off working state of described adjustable active impedance represents that described adjustable active impedance is low-resistance, described low-resistance represents described adjustable active impedance short circuit, the duty of described adjustable active impedance switches under representing the control of the data-signal that described adjustable active impedance exports at described modulator between low-resistance and negative resistance, when described adjustable active impedance is in negative resistance, the resistance value of described adjustable active impedance equals the resistance value of described antenna.
8. method according to claim 7, is characterized in that, the first control signal that the described modulator of described employing exports, control described adjustable active impedance in working order and between off working state change comprise:
When described modulator does not work, adopt the first control signal that described modulator exports, control described adjustable active impedance and be in off working state;
When described modulator work, adopt the first control signal that described modulator exports, control described adjustable active impedance in running order.
9. method according to claim 7, is characterized in that, described radio-frequency interface circuit also comprises variable resistor and field intensity testing circuit, and described variable resistor and described tunable capacitor are connected in parallel;
Described method also comprises: adopt described field intensity testing circuit, estimate the coupling coefficient of described antenna, described coupling coefficient and predetermined threshold value are compared, generate the second control signal according to comparative result;
The first control signal that the described modulator of described employing exports control described adjustable active impedance in working order and between off working state change be specially: the first control signal adopting described modulator to export and described second control signal, control described adjustable active impedance and change in working order and between off working state;
Described method also comprises: the second control signal that the first control signal adopting described modulator to export and described field intensity testing circuit export, control described variable resistor to change in working order and between off working state, wherein, described variable-resistance off working state represents that described variable resistor is high resistant, described high resistant represents that described variable resistor is opened a way, described variable-resistance duty represents that the data-signal that described variable resistor exports according to described modulator switches between low-resistance and high resistant, and described low-resistance represents described variable resistor short circuit.
10. method according to claim 9, it is characterized in that, the first control signal that the described modulator of described employing exports and the second control signal that described field intensity testing circuit exports, control described adjustable active impedance in working order and between off working state change comprise:
When described coupling coefficient is less than predetermined threshold value and described modulator works, the second control signal that the first control signal adopting described modulator to export and described field intensity testing circuit export, controls described adjustable active impedance in running order;
When described coupling coefficient is more than or equal to predetermined threshold value or described modulator does not work, the second control signal that the first control signal adopting described modulator to export and described field intensity testing circuit export, controls described adjustable active impedance and is in off working state;
The first control signal that the described modulator of described employing exports and the second control signal that described field intensity testing circuit exports, control described variable resistor in working order and between off working state change comprise:
When described coupling coefficient is more than or equal to predetermined threshold value and described modulator works, the second control signal that the first control signal adopting described modulator to export and described field intensity testing circuit export, controls described variable resistor in running order;
When described coupling coefficient is less than predetermined threshold value or described modulator does not work, the second control signal that the first control signal adopting described modulator to export and described field intensity testing circuit export, controls described variable resistor and is in off working state.
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| CN1359198A (en) * | 2000-11-30 | 2002-07-17 | 超传感器（私有）有限公司 | Input impedance match for RF repeater |
| CN101501991A (en) * | 2006-06-27 | 2009-08-05 | 传感电子公司 | Resonant circuit tuning system with dynamic impedance matching |
| CN202771460U (en) * | 2012-06-01 | 2013-03-06 | 北京昆腾微电子有限公司 | Non-contact IC card radio-frequency interface circuit, non-contact IC card and non-contact near field communication system |
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| JP2009302953A (en) * | 2008-06-13 | 2009-12-24 | Toshiba Corp | Noncontact data communications device |
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| CN1359198A (en) * | 2000-11-30 | 2002-07-17 | 超传感器（私有）有限公司 | Input impedance match for RF repeater |
| CN101501991A (en) * | 2006-06-27 | 2009-08-05 | 传感电子公司 | Resonant circuit tuning system with dynamic impedance matching |
| CN202771460U (en) * | 2012-06-01 | 2013-03-06 | 北京昆腾微电子有限公司 | Non-contact IC card radio-frequency interface circuit, non-contact IC card and non-contact near field communication system |
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