CN104299024B - The demodulator circuit of contactless IC card - Google Patents
The demodulator circuit of contactless IC card Download PDFInfo
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- CN104299024B CN104299024B CN201310304221.3A CN201310304221A CN104299024B CN 104299024 B CN104299024 B CN 104299024B CN 201310304221 A CN201310304221 A CN 201310304221A CN 104299024 B CN104299024 B CN 104299024B
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- pressure limiting
- limiting pipe
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Abstract
The invention discloses a kind of demodulator circuits of contactless IC card, including：The detection unit that one diode, a capacitance and a resistance are constituted；One resistance and capacitance high pass filter unit in series；One biasing circuit；One comparator and two pressure limiting pipes.The amplitude by detection, filtered aerial signal is controlled by two pressure limiting pipes, has the function that correctly to demodulate and improve frame delay time.
Description
Technical field
The present invention relates to semiconductor integrated circuit, particularly relate to a kind of demodulator circuit of contactless IC card.
Background technology
Carrier wave is done to transmit information by radiofrequency signal between contactless IC card and card reader.Contactless IC card itself does not have
Power supply, electric energy when work are provided by the radiofrequency signal of card reader, and wherein the radiofrequency signal of card reader is 13.56MHz.
When card reader and contactless IC card mutually pass data, carrier wave is the radio-frequency carrier of 13.56MHz, and signal transmission rate has respectively
Tetra- kinds of 106Kbits/s, 212Kbits/s, 424Kbits/s, 848Kbits/s.
Wherein, it is to use amplitude-shift keying when transmitting data to contactless IC card from card reader（ASK:Amplitude-
Shift Keying）Method is modulated signal, and coding mode is synchronous, improved Miller（miller）Coding.Card reader
When needing to carry out the communication of digital communication i.e. 0,1 with contactless IC card, the digital signal modulated of card reader to the radio-frequency carrier
It includes groove signal that can be formed after on signal（pause）Modulated signal, the amplitude of groove signal is less than radio-frequency carrier
Amplitude.Digital signaling zero or 1 are indicated according to position difference of the groove signal in the sequential of modulated signal, so groove is believed
Number it is the expression way of data.For modulated signal by being input in contactless IC card, contactless IC card passes through antenna
The modulated signal is demodulated by demodulator circuit after receiving the modulated signal, demodulating process is divided into analog demodulator and number
Two steps are demodulated, the groove signal in modulated signal is demodulated by digital signaling zero or 1 by the analog demodulator of demodulator circuit, it will
Digital signal after demodulation carries out digital decoding, and digital decoding confirms according to the position difference of 0 in the digital signal of input to be read
What is transmitted in card device is data 0 or 1.
As shown in Figure 1, being the schematic diagram of the demodulator circuit of existing contactless IC card；Biography from card reader to contactless IC card
The carrier frequency of transmission of data is 13.56MHZ, and demodulator circuit includes：
The first input end of comparator 106, the comparator 106 connects the first reference signal VREF1, the comparator
106 the second input terminal connects input signal VREF3, and input signal VREF3 is the contactless IC card from antenna, that is, Fig. 1
Signal of the modulated signal launched by the card reader received at ANT after detection and high-pass filtering；The comparator
106 output ends export demodulated signal DEMOUT.Wherein, detecting circuit unit includes the diode 101 of one-way conduction, the first capacitance
102 and first resistor 103, the detecting circuit unit is used to filter out the carrier signal in the modulated signal.High-pass filter
It is made of second resistance 104 and the second capacitance 105.
Biasing circuit 107, the output end of the biasing circuit 107 connect the second input terminal of the comparator 106 and for institutes
It states the second input terminal and one DC offset voltage is provided.
As shown in Fig. 2, being the sequential after existing three kinds of analog codecs from card reader to contactless IC card, i.e., connect by non-
Groove signal in modulated signal is demodulated into digital signaling zero or 1 namely Fig. 1 by the analog demodulator for touching the demodulator circuit of IC card
Demodulated signal DEMOUT after include three sequential, each sequential correspond to a data bit transmission cycle, demodulated signal
Three sequential of DEMOUT are defined respectively as：
1, sequential X, sequential X will (1/2) × (fc/ transmission rates) ×（1/fc）Place generates a groove signal, i.e.,
In txPlace starts to generate a width to be taGroove signal.
2, sequential Y, sequential Y are t during entire positionbIt does not modulate.
3, at the beginning of during sequential Z, sequential Z are in place, it is t to generate a widthaGroove signal.
For 848Kbits/s, 424Kbits/s, 212Kbits/s and 106Kbits/s transmission rate when, a data
The transmission time Tbit of position, respectively 16,32,64 and 128 clock cycle（clk）, wherein 1clk=1/13.56MHz=
73.746nS, transmission time Tbit are shown as t in Fig. 1b。
As shown in figure 3, being the frame delay time FDT (FDT from card reader to card:Frame Delay Time).Due to reading
Card device and card need to carry out data exchange, therefore also have strict demand to the sequential of every frame data, if timing error, can cause
Decoding error.According to agreement, the FDT of non-contact card demodulation is to be overturn to comparator 0 μ of μ s~0.4 s, that is, groove signal end time
Time only has 0 μ of μ s~0.4 s.
As shown in Figure 1, the second input terminal of the comparator 106 is biased by biasing circuit 107, work as input
Modulated signal in groove signal when arriving, input signal VREF3 needs are pulled low, and at the end of groove signal, VREF3 is needed
Normal current potential is reverted to from the current potential being pulled low just now, and is charged to capacitor charging 105, due in " pause " duration
Interior, VREF3 is necessarily less than VREF1, therefore the driving current of biasing circuit 107 must be smaller, for different field strength, transmission speed
Rate, when card reader, at the end of groove signal, VREF3 is likely to be at lower level, causes to be restored to normal current potential
Overlong time, and come then in next groove signal, VREF3, which was likely to be at, is flushed to higher level, causes to be restored to
The overlong time of normal current potential, to affect the correctness of demodulation output or influence the FDT times.
Invention content
Technical problem to be solved by the invention is to provide a kind of demodulator circuits of contactless IC card, correctly demodulate and improve
Frame delay.
To solve the above problems, a kind of demodulator circuit of contactless IC card of the present invention, including a diode, first
The high pass filter unit that the detection unit that capacitance and first resistor are constituted, second resistance and the second capacitance are constituted, a biasing circuit,
One comparator；Also include first and second two pressure limiting pipes, the connection relation of the demodulator circuit is：
Detection unit, the anode of diode connect antenna, after the first capacitance and first resistor parallel connection, a terminating diode
Cathode, other end ground connection；
High pass filter unit, second resistance and the series connection of the second capacitance, the cathode of one terminating diode of residue of second resistance,
The residue one of second capacitance terminates the output end of biasing circuit, and the input of biasing circuit terminates the second reference voltage；
Comparator, output end are demodulator circuit output end, and the output end of the second input termination biasing circuit, first is defeated
Enter the first reference voltage of termination；
First pressure limiting pipe leaks termination power, and source connects the second input terminal of comparator, and grid connects the first limitation voltage；
Second pressure limiting pipe, drain terminal ground connection, source connect the second input terminal of comparator, and grid connects the second limitation voltage.
Further, first pressure limiting pipe is NMOS, and the second pressure limiting pipe is PMOS.
The demodulator circuit of contactless IC card of the present invention is controlled by the first, second two pressure limiting pipes by inspection
The amplitude of wave, filtered aerial signal has the function that correctly to demodulate and improve FDT.
Description of the drawings
Fig. 1 is existing contactless IC card demodulator circuit；
Fig. 2 is existing three kinds of analog codec sequential from card reader to contactless IC card；
Fig. 3 is the frame delay time from card reader to contactless IC card；
Fig. 4 is the demodulator circuit of contactless IC card of the present invention.
Reference sign
1,101 be diode, and 2,102 be the first capacitance, and 3,103 be first resistor, and 4,104 be second resistance, and 5,105 are
Second capacitance, 6,106 be comparator, and 7,107 be biasing circuit, and 8 be the second pressure limiting pipe, and 9 be the first pressure limiting pipe.
Specific implementation mode
The demodulator circuit of contactless IC card of the present invention a kind of is as shown in figure 4, from card reader to contactless IC card
The carrier frequency of transmission data is 13.56MHZ, and demodulator circuit includes：
Comparator 6, the first input end of the comparator 6 connect the first reference signal VREF1, and the of the comparator 6
Two input terminals connect input signal VREF3, input signal VREF3 be the contactless IC card received from antenna ANT by
The modulated signal that the card reader is launched passes through detection unit and the filtered signal of high pass filter unit；The comparator 6
Output end exports demodulated signal DEMOUT.Wherein, detecting circuit unit includes the diode 1 of one-way conduction, the first capacitance 2 and
One resistance 3, the cathode of one terminating diode 1 after 3 parallel connection of the first capacitance 2 and first resistor, other end ground connection, 1 sun of diode
Pole connects antenna.The detecting circuit unit is used to filter out the carrier signal in the modulated signal.High-pass filter is by the second electricity
Resistance 4 and the second capacitance 5 are composed in series, the cathode of another terminating diode 1 of second resistance 4, another termination ratio of the second capacitance 5
Compared with the second input terminal of device 6.Second and first pressure limiting pipe 8 and 9, first pressure limiting pipe 9 are a NMOS tube MNA, drain electrode
Supply voltage is connect, grid meets limitation voltage VCLAMPL, and source electrode meets VREF3；Second pressure limiting pipe 8 is a PMOS tube MPA,
Its source electrode meets VREF3, and grid connects limitation voltage VCLAMPH, grounded drain.
The input of biasing circuit 7 terminates the second reference voltage VREF2, the second input terminal of output termination comparator 6.Compare
The first input end of device 6 meets the first reference voltage VREF1, and the output end of comparator 6 is the output DEMOUT of demodulator circuit.
When this demodulator circuit works, VREF3 provides direct current biasing by biasing circuit 107, by antenna after detection, filtering
Signal provide AC signal.And in a data bit transmission time, VREF3 needs to revert to the offset signal of VREF2, this
Sample will not have an impact next data bit.When for different field strength, transmission rate, card reader, the signal amplitude on antenna
Also it differs, it is excessive by detection, the possible amplitude of filtered AC signal so that VREF3 is in a data bit transmission time
At the end of, have little time to revert to bias voltage, causes next data decoding errors.Therefore two pressure limitings are added on VREF3
Pipe MNA and MPA.When the difference of the threshold voltage of grid voltage VCLAMPLs and pressure limiting pipe MNA of the voltage VREF3 less than pressure limiting pipe MNA
When, supply voltage is charged by pressure limiting pipe MNA toward VREF3, to prevent voltage VREF3 reductions.Similarly, when voltage VREF3 is higher than
When the grid voltage VCLAMPH of the threshold voltage of pressure limiting pipe MPA and pressure limiting pipe MPA, VREF3 by pressure limiting pipe MPA it is past discharge, with resistance
Only voltage VREF3 is increased.In this way so that the voltage fluctuation of VREF3 always in a certain range, and when a data bit is transmitted
Between at the end of, bias voltage can be restored to, next data decoding correctness is ensure that, also reduce FDT simultaneously.
It these are only the preferred embodiment of the present invention, be not intended to limit the present invention.Those skilled in the art is come
It says, the invention may be variously modified and varied.All within the spirits and principles of the present invention, any modification made by is equal
Replace, improve etc., it should all be included in the protection scope of the present invention.
Claims (1)
1. a kind of demodulator circuit of contactless IC card, including the detection unit that a diode, the first capacitance and first resistor are constituted,
Second resistance and the second capacitance high pass filter unit in series, a biasing circuit, a comparator；It is characterized in that：Also wrap
Containing first and second two pressure limiting pipes, the connection relation of the demodulator circuit is：
Detection unit, the anode of diode connect antenna, after the first capacitance and first resistor parallel connection, a terminating diode it is negative
Pole, other end ground connection；
High pass filter unit, second resistance and the series connection of the second capacitance, the cathode of one terminating diode of residue of second resistance, second
The residue one of capacitance terminates the output end of biasing circuit, and the input of biasing circuit terminates the second reference voltage；
Comparator, output end are demodulator circuit output end, the output end of the second input termination biasing circuit, first input end
Connect the first reference voltage；
First pressure limiting pipe leaks termination power, and source connects the second input terminal of comparator, and grid connects the first limitation voltage；
Second pressure limiting pipe, drain terminal ground connection, source connect the second input terminal of comparator, and grid connects the second limitation voltage；
First pressure limiting pipe is NMOS, and the second pressure limiting pipe is PMOS；
When the source voltage terminal of the first pressure limiting pipe is less than the difference of the first limitation voltage and the threshold voltage of the first pressure limiting pipe, power supply
Voltage is charged by the source of the first pressure limiting pipe toward the first pressure limiting pipe, to prevent the source voltage terminal of the first pressure limiting pipe from reducing；Similarly,
When the source voltage terminal of the first pressure limiting pipe is higher than the threshold voltage of the second pressure limiting pipe and the second limitation voltage, the source of the second pressure limiting pipe
Terminal voltage by pressure limiting pipe it is past discharge, with prevent the second pressure limiting pipe source voltage terminal increase.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310304221.3A CN104299024B (en) | 2013-07-19 | 2013-07-19 | The demodulator circuit of contactless IC card |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310304221.3A CN104299024B (en) | 2013-07-19 | 2013-07-19 | The demodulator circuit of contactless IC card |
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| Publication Number | Publication Date |
|---|---|
| CN104299024A CN104299024A (en) | 2015-01-21 |
| CN104299024B true CN104299024B (en) | 2018-08-21 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201310304221.3A Active CN104299024B (en) | 2013-07-19 | 2013-07-19 | The demodulator circuit of contactless IC card |
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Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110135206B (en) * | 2018-02-09 | 2022-05-31 | 博通集成电路（上海）股份有限公司 | Card detector and card detection method |
Citations (7)
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|---|---|---|---|---|
| EP1136940A1 (en) * | 2000-03-22 | 2001-09-26 | Infineon Technologies AG | Chip card |
| CN1433151A (en) * | 2001-11-14 | 2003-07-30 | 夏普公司 | Comparator circuit and infrared signal receiver |
| CN1805416A (en) * | 2006-01-20 | 2006-07-19 | 清华大学 | Comparison and decision circuit in amplitude keying signal demodulation circuit module |
| EP1748613A2 (en) * | 2005-07-27 | 2007-01-31 | Fujitsu Limited | Demodulator |
| CN101019308A (en) * | 2004-07-13 | 2007-08-15 | 皇家飞利浦电子股份有限公司 | Demodulator for amplitude-modulated signals |
| CN101957926A (en) * | 2010-09-09 | 2011-01-26 | 扬州恒信仪表有限公司 | Radio-frequency card reading and writing circuit controlled and formed by MCU supporting nanoWatt technology |
| CN102968657A (en) * | 2011-08-31 | 2013-03-13 | 北京中电华大电子设计有限责任公司 | Circuit for achieving frame delay time (FDT) precise timing in high frequency smart card |
-
2013
- 2013-07-19 CN CN201310304221.3A patent/CN104299024B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1136940A1 (en) * | 2000-03-22 | 2001-09-26 | Infineon Technologies AG | Chip card |
| CN1433151A (en) * | 2001-11-14 | 2003-07-30 | 夏普公司 | Comparator circuit and infrared signal receiver |
| CN101019308A (en) * | 2004-07-13 | 2007-08-15 | 皇家飞利浦电子股份有限公司 | Demodulator for amplitude-modulated signals |
| EP1748613A2 (en) * | 2005-07-27 | 2007-01-31 | Fujitsu Limited | Demodulator |
| CN1805416A (en) * | 2006-01-20 | 2006-07-19 | 清华大学 | Comparison and decision circuit in amplitude keying signal demodulation circuit module |
| CN101957926A (en) * | 2010-09-09 | 2011-01-26 | 扬州恒信仪表有限公司 | Radio-frequency card reading and writing circuit controlled and formed by MCU supporting nanoWatt technology |
| CN102968657A (en) * | 2011-08-31 | 2013-03-13 | 北京中电华大电子设计有限责任公司 | Circuit for achieving frame delay time (FDT) precise timing in high frequency smart card |
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| CN104299024A (en) | 2015-01-21 |
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