CN104518735B - Load modulation module in radio frequency identification - Google Patents
Load modulation module in radio frequency identification Download PDFInfo
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- CN104518735B CN104518735B CN201310447401.7A CN201310447401A CN104518735B CN 104518735 B CN104518735 B CN 104518735B CN 201310447401 A CN201310447401 A CN 201310447401A CN 104518735 B CN104518735 B CN 104518735B
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- nmos pass
- pass transistor
- load modulation
- grid
- variable voltage
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Abstract
The invention discloses the load modulation module in a kind of radio frequency identification, including：One termination power, Card Reader generator terminal is coupled to for coupling a signal to radio frequency identification Card-terminal, or by the load modulation signal of radio frequency identification Card-terminal；One load modulation circuit, be connected with the output end of the termination power, for digital circuit to be handled after data return to card reader；Wherein also include：One amplitude limiter circuit, is connected with the output end of the load modulation circuit, carries out amplitude limit for the output to the load modulation circuit, and provide a variable voltage for the load modulation circuit；The variable voltage follows field strength to change and change, and when field strength increases, the variable voltage also increases, and when field strength is reduced, the variable voltage is also reduced；And load modulation circuit conducting can be controlled in big field strength, complete load modulation.The present invention can preferably improve load modulation waveform and load modulation depth under big field strength, strengthen the compatibility of radio frequency identification card.
Description
Technical field
It is negative in modulation circuit field, more particularly to a kind of radio frequency identification the present invention relates to being loaded in Analogous Integrated Electronic Circuits
Carry modulation module.
Background technology
In radio frequency identification, radio frequency identification card needs to couple the analog signal that card reader is issued, and demodulates Card Reader
The data that machine is sent give digital circuit processing again, and digital circuit returns to the data after processing through overload modulation circuit again
Card reader, this completes whole communication process.The process for returning data to card reader is exactly load modulation, load modulation
Waveform and load modulation depth are bad, can influence demodulation of the card reader to data, therefore load modulation circuit is extremely important and closes
Key.
Referring to Fig. 1, in traditional load modulation circuit, nmos pass transistor MN3 be equivalent to one switch, modulation when
Time is turned on, and is shut off when modulation, and DIN is control signal, is provided by digital circuit and is controlled.MOS transistor is led
Logical and closing can affect the signal on antenna, when MOS transistor is turned on, and the signal on antenna will be pulled down into coming, and be formed
The groove of one, groove signal one by one is exactly to load modulation waveform, data is carried in these waveforms, finally again by reading
Card machine, which is demodulated, to be come.The advantage of this structure is simple, easily realizes, is operated under small field strength, load modulation waveform and load
Modulation depth is all well；Have the disadvantage to be operated under big field strength, load modulation waveform and load modulation depth are all deteriorated, card reader
It is difficult to demodulate, or is easily caused card reader demodulation mistake.If card reader demodulation error, whole communication also just have failed.Cause
All there is preferably load modulation waveform and larger load modulation depth to be all very important under each field strength for this.
The content of the invention
The technical problem to be solved in the present invention is to provide the load modulation module in a kind of radio frequency identification, can preferably it change
The load modulation waveform and load modulation depth being apt under big field strength, strengthen the compatibility of radio frequency identification card.
In order to solve the above technical problems, the load modulation module in the radio frequency identification of the present invention, including：
One termination power, for coupling a signal to radio frequency identification Card-terminal, or by the load of radio frequency identification Card-terminal
Modulated signal is coupled to Card Reader generator terminal；
One load modulation circuit, be connected with the output end of the termination power, for digital circuit to be handled after number
According to returning to card reader；Wherein also include：One amplitude limiter circuit, with it is described load modulation circuit output end be connected, for pair
The output of the load modulation circuit carries out amplitude limit, and provides a variable voltage for the load modulation circuit；The variable voltage with
Change with field strength and change, when field strength increases, the variable voltage also increases, when field strength is reduced, variable voltage is also reduced；And big
Load modulation circuit conducting can be controlled during field strength, load modulation is completed.
The load modulation module of the present invention, controls to load modulation circuit by a variable voltage changed with field strength,
When being operated in small field strength, the magnitude of voltage of variable voltage less, can be very good to control and complete the load modulation of signal；Work as work
Make in big field strength, its magnitude of voltage can pull down antenna waveform than larger, can equally form preferably load modulating wave
Shape and larger load modulation depth.Therefore the load modulation circuit load modulation waveform not only under small field strength of the present invention with
Load modulation depth is good, and the load modulation waveform and load modulation depth under big field strength can also better meet card reader very well
Demodulation；Radio frequency identification card can preferably compatible various card readers, so as to ensure the normal communication of radio frequency identification card, strengthen
The compatibility of radio frequency identification card.
Brief description of the drawings
The present invention is further detailed explanation with embodiment below in conjunction with the accompanying drawings：
Fig. 1 is existing load modulation circuit schematic diagram；
Fig. 2 is the embodiment schematic diagram of load modulation module one in the radio frequency identification.
Embodiment
Fig. 2 is one embodiment of the invention, the load modulation module in the radio frequency identification, including：One termination power, with
The load modulation circuit that the output end of the termination power is connected, is connected with the output end of the load modulation circuit
One amplitude limiter circuit.In order to improve the load modulation waveform under big field strength and load modulation depth, strengthen the simultaneous of radio frequency identification card
Capacitive, the load modulation circuit is by a variable voltage, the NMOS crystal in control load modulation circuit under big field strength
Pipe MN1 and MN2 unlatching, so as to realize load modulation.
The termination power, is made up of inductance L1, inductance L2 and electric capacity C1.Electric capacity C1 is connected in parallel on inductance L2 two ends.It is defeated
Enter signal IN and radio frequency identification Card-terminal is coupled to by inductance L1 and L2, occur resonance with electric capacity C1；Meanwhile, data-signal is defeated
Enter to radio circuit, radio circuit demodulates data signal and sends digital circuit to, digital circuit returns the data after processing again
Back to card reader.The data returned after digital circuit processing are returned in the way of loading modulation, i.e., digital circuit passes through control figure 2
The load modulation signal DIN at the load modulation signal end of middle load modulation circuit magnitude of voltage loads modulation to realize.Load is adjusted
Signal DIN processed is provided and controlled by digital circuit.
The load modulation circuit is by nmos pass transistor MN1, MN2 and MN3, PMOS transistor MP1, phase inverter INV1 and anti-
Phase device INV2 is constituted.
Nmos pass transistor MN1 drain electrode is connected with the inductance L2 of termination power one end, and the node of the connection is used as day
One connection end ANT1 ends of line；Nmos pass transistor MN2 drain electrode is connected with the inductance L2 of the termination power other end, the connection
Node as antenna another connection end ANT2 ends；The source electrode of nmos pass transistor MN1 source electrode and nmos pass transistor MN2 connects
Ground.Nmos pass transistor MN1 grid is connected with nmos pass transistor MN2 grid, and its node connected is set to A.
Phase inverter INV1 output end is connected with phase inverter INV2 input, phase inverter INV2 output end and PMOS
Transistor MP1 grid is connected；Phase inverter INV1 input is inputted as the load modulation signal end of load modulation circuit
Load modulation signal DIN, and be connected with nmos pass transistor MN3 grid；PMOS transistor MP1 source electrode is variable as inputting
Voltage end input variable voltage VLIM.Nmos pass transistor MN3 source ground.PMOS transistor MP1 drain electrode and NMOS crystal
Pipe MN3 drain electrode is connected with node A.
The amplitude limiter circuit is made up of nmos pass transistor MN4, MN5, MN6, MN7, MN8, MN9 and MN10, and resistance R1.
Nmos pass transistor MN4 grid and drain electrode are connected with the ANT1 ends, nmos pass transistor MN5 grid and drain electrode
It is connected with the ANT2 ends, nmos pass transistor MN4 source electrode is connected with nmos pass transistor MN5 source electrode, its section connected
Point is set to B.
Nmos pass transistor MN6 source electrode, the drain electrode of nmos pass transistor MN9 source electrode and nmos pass transistor MN10 and the B
Point is connected.Nmos pass transistor MN6 grid and drain electrode are connected with nmos pass transistor MN7 source electrode, nmos pass transistor MN7's
Grid and drain electrode are connected with nmos pass transistor MN8 source electrode, nmos pass transistor MN8 grid and grounded drain.
Nmos pass transistor MN9 grid is connected with nmos pass transistor MN6 grid, nmos pass transistor MN9 drain electrode with
Resistance R1 one end is connected, resistance R1 other end ground connection.Nmos pass transistor MN9 drain electrode and resistance the R1 section being connected
Point is used as the output end of variable voltage, output variable voltage VLIM.
Nmos pass transistor MN10 grid is connected with the output end of variable voltage, its source ground.
The amplitude limiter circuit also provides a variable voltage in addition to amplitude limit function in itself for load modulation circuit
VLIM.Variable voltage VLIM changes with the change of field strength.When the load modulation module in the radio frequency identification is operated in
During small field strength, variable voltage VLIM magnitude of voltage is relatively low, with field strength increase variable voltage VLIM magnitude of voltage also with
Increase.When the load modulation module in the radio frequency identification is operated under big field strength, variable voltage VLIM magnitude of voltage also compared with
Greatly.
When B point voltages are raised and are more than nmos pass transistor MN6, MN7 and MN8 threshold voltage sum, variable voltage
VLIM magnitude of voltage is just raised, and is gradually opened nmos pass transistor MN10 and is released unwanted currents；B points voltage will be reduced therewith, most
Stablize afterwards on the magnitude of voltage of three nmos pass transistors MN6, MN7 and MN8 threshold voltage sum.Therefore, variable voltage VLIM
Magnitude of voltage be with field strength change and change, field strength is small, variable voltage VLIM values just it is small, field strength greatly, variable voltage VLIM
Value just becomes big.The present invention passes through VLIM magnitudes of voltage control load modulation waveform and load modulation depth.
When load modulation signal DIN is low level, it is meant that load modulation circuit is started working.Nmos pass transistor
MN3 is closed first, and PMOS transistor MP1 pipes turn on and variable voltage VLIM is transferred into A points therewith, and A points once have voltage
Afterwards, nmos pass transistor MN1 and MN2 are turned on, and can pull down the signal at antenna ends ANT1 and ANT2 ends, are formed recessed
Groove, also just realizes and completes the load modulation of signal.A point voltage swings directly decide opening for nmos pass transistor MN1 and MN2
Degree of leaving.Under small field strength, antenna ends magnitude of voltage is smaller, and A point voltages are also small, and nmos pass transistor MN1 and MN2 are opened
Small, the waveform of antenna end is also easier to be pulled down into forming groove, therefore the effect of load modulation waveform and load modulation depth
Fruit all can be with.With the increase of field strength, A points voltage will also be raised, and nmos pass transistor MN1 and MN2 opening degree also increase, and be born
Carry modulation waveform and load modulation depth is also not bad.Under big field strength, although antenna ends voltage is than larger, A point voltages
Compare high, nmos pass transistor MN1 and MN2 unlatching are just very abundant, therefore antenna ends waveform is easily formed groove, therefore
Load modulation waveform and load modulation depth are also preferable under big field strength.
Load modulation is main to be completed by nmos pass transistor MN1 and MN2, and variable voltage VLIM is anti-phase by phase inverter INV1
Device INV2, PMOS transistor MP1 and nmos pass transistor MN3 are smoothly transferred to A points during modulation is loaded, and coordinate nmos pass transistor
MN1 and MN2 completes load modulation.
The work field strength of radio frequency identification card is usually 1.5A/m~7.5A/m.For different types of radio-frequency identification card
Piece, the possible difference of its big field strength defined is very big, generally may be considered big field strength when field strength is more than 6A/m, or
Person may be considered big field strength when field strength is more than 7A/m.
Be similarly for different types of radio frequency identification card, its define small field strength may also difference it is very big.
Although the present invention is illustrated using specific embodiment, the explanation to embodiment is not intended to limit the present invention's
Scope.One skilled in the art is by reference to explanation of the invention, without departing substantially from the spirit and scope of the present invention
In the case of, easily carry out various modifications or embodiment can be combined.
Claims (2)
1. the load modulation module in a kind of radio frequency identification, including：
One termination power, is modulated for coupling a signal to radio frequency identification Card-terminal, or by the load of radio frequency identification Card-terminal
Signal is coupled to Card Reader generator terminal；
One load modulation circuit, be connected with the output end of the termination power, for digital circuit to be handled after data return
Back to card reader；Characterized in that, also including：
One amplitude limiter circuit, is connected with the output end of the load modulation circuit, for the output to the load modulation circuit
Amplitude limit is carried out, and a variable voltage is provided for the load modulation circuit；The variable voltage follows field strength to change and change, and field strength increases
When big, the variable voltage also increases, and when field strength is reduced, variable voltage is also reduced；And load modulation electricity can be controlled in big field strength
Road is turned on, and completes load modulation；
The load modulation circuit is by the first nmos pass transistor, the second nmos pass transistor and the 3rd nmos pass transistor, the first PMOS
Transistor, the first phase inverter and the second phase inverter composition；
The drain electrode of first nmos pass transistor is connected with one end of the second inductance of termination power, and the node of the connection is used as antenna
A connection end, be set to ANT1 ends；The drain electrode of second nmos pass transistor is connected with the other end of the second inductance of termination power,
The node of the connection is set to ANT2 ends as another connection end of antenna；The source electrode of first nmos pass transistor and the 2nd NMOS are brilliant
The source ground of body pipe；The grid of first nmos pass transistor is connected with the grid of the second nmos pass transistor, its node connected
It is set to A；
The output end of first phase inverter is connected with the input of the second phase inverter, the output end of the second phase inverter and the first PMOS
The grid of transistor is connected；The input of first phase inverter is used as the load modulation signal end input load for loading modulation circuit
Modulated signal DIN, and be connected with the grid of the 3rd nmos pass transistor；The source electrode of first PMOS transistor can power transformation as input
Pressure side inputs variable voltage VLIM, the source ground of the 3rd nmos pass transistor；The drain electrode of first PMOS transistor and the 3rd NMOS
The drain electrode of transistor is connected with node A；
The amplitude limiter circuit is by the nmos pass transistor of the 4th nmos pass transistor~the tenth, and resistance composition；
The grid of 4th nmos pass transistor and drain electrode are connected with the ANT1 ends, the grid of the 5th nmos pass transistor and drain electrode with
The ANT2 ends are connected, and the source electrode of the 4th nmos pass transistor is connected with the source electrode of the 5th nmos pass transistor, its section connected
Point is set to B；
The source electrode of 6th nmos pass transistor, the drain electrode of the source electrode and the tenth nmos pass transistor of the 9th nmos pass transistor and the B points
It is connected；The grid of 6th nmos pass transistor and drain electrode are connected with the source electrode of the 7th nmos pass transistor, the 7th nmos pass transistor
Grid and drain electrode be connected with the source electrode of the 8th nmos pass transistor, the grid and grounded drain of the 8th nmos pass transistor；
The grid of 9th nmos pass transistor is connected with the grid of the 6th nmos pass transistor, the drain electrode of the 9th nmos pass transistor and institute
The one end for stating resistance is connected, the other end ground connection of the resistance；What the drain electrode of the 9th nmos pass transistor was connected with the resistance
Node is used as the output end of variable voltage, output variable voltage VLIM；
The grid of tenth nmos pass transistor is connected with variable voltage VLIM output end, its source ground.
2. modulation module is loaded as claimed in claim 1, it is characterised in that：
The termination power, by the first inductance, the second inductance and electric capacity composition, the electric capacity are connected in parallel on the two of the second inductance
End；Input signal is inductively coupled to radio frequency identification Card-terminal by the first inductance and second, occurs resonance with the electric capacity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310447401.7A CN104518735B (en) | 2013-09-26 | 2013-09-26 | Load modulation module in radio frequency identification |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310447401.7A CN104518735B (en) | 2013-09-26 | 2013-09-26 | Load modulation module in radio frequency identification |
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| Publication Number | Publication Date |
|---|---|
| CN104518735A CN104518735A (en) | 2015-04-15 |
| CN104518735B true CN104518735B (en) | 2017-09-15 |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101145188A (en) * | 2006-09-12 | 2008-03-19 | 盛群半导体股份有限公司 | Wireless radio frequency identification responder |
| CN102244502A (en) * | 2011-04-25 | 2011-11-16 | 胡建国 | Automatic Q value adjustment amplitude limiting circuit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4355711B2 (en) * | 2006-04-20 | 2009-11-04 | フェリカネットワークス株式会社 | Information processing terminal, IC card, portable communication device, wireless communication method, and program |
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2013
- 2013-09-26 CN CN201310447401.7A patent/CN104518735B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101145188A (en) * | 2006-09-12 | 2008-03-19 | 盛群半导体股份有限公司 | Wireless radio frequency identification responder |
| CN102244502A (en) * | 2011-04-25 | 2011-11-16 | 胡建国 | Automatic Q value adjustment amplitude limiting circuit |
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| Publication number | Publication date |
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| CN104518735A (en) | 2015-04-15 |
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