CN104299024A - Non-contact IC card demodulation circuit - Google Patents
Non-contact IC card demodulation circuit Download PDFInfo
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- CN104299024A CN104299024A CN201310304221.3A CN201310304221A CN104299024A CN 104299024 A CN104299024 A CN 104299024A CN 201310304221 A CN201310304221 A CN 201310304221A CN 104299024 A CN104299024 A CN 104299024A
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- card
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Abstract
The invention discloses a non-contact IC card demodulation circuit. The non-contact IC card demodulation circuit comprises a demodulation unit formed by a diode, a capacitor and a resistor, a high pass filtering unit formed by a resistor and a capacitor which are connected in series, a bias circuit, a comparator and two voltage limit tubes. Amplitude of an antenna signal after demodulation and filtering is controlled through the two voltage limit tubes, and thereby frame time delay can be accurately demodulated and improved.
Description
Technical field
The present invention relates to SIC (semiconductor integrated circuit), refer to a kind of demodulator circuit of contactless IC card especially.
Background technology
Do carrier wave by radiofrequency signal between contactless IC card and card reader and transmit information.Contactless IC card itself does not have power supply, and electric energy during its work is 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 pass data mutually, carrier wave is the radio-frequency carrier of 13.56MHz, and signal transmission rate has 106Kbits/s, 212Kbits/s, 424Kbits/s, 848Kbits/s tetra-kinds respectively.
Wherein, when transmitting data from card reader to contactless IC card, be adopt amplitude-shift keying (ASK:Amplitude-Shift Keying) method to modulate signal, coded system is Miller (miller) coding that is synchronous, that improve.Card reader and contactless ic calorie requirement carry out digital communication that is 0,1 communicate time, the digital signal modulated of card reader to described radio-frequency carrier signal after can form the modulation signal including groove signal (pause), the amplitude of groove signal is less than the amplitude of radio-frequency carrier.Representative digit signal 0 or 1 is carried out, so groove signal is the expression way of data according to the position difference of groove signal in the sequential of modulation signal.Modulation signal is input in contactless IC card by wireless transmission, contactless IC card carries out demodulation by demodulator circuit to this modulation signal after receiving this modulation signal by antenna, demodulating process is divided into analog demodulator and digital demodulation two step, by the analog demodulator of demodulator circuit, the groove signal in modulation signal is demodulated into digital signaling zero or 1, digital signal after demodulation is carried out digital decoding, and digital decoding is data 0 or 1 according to what transmit in the position difference confirmation card reader of 0 in the digital signal of input.
As shown in Figure 1, be the schematic diagram of demodulator circuit of existing contactless IC card; The carrier frequency of the transmission data from card reader to contactless IC card is 13.56MHZ, and demodulator circuit comprises:
Comparer 106, the first input end of described comparer 106 connects the first reference signal VREF1, second input end of described comparer 106 connects input signal VREF3, and this input signal VREF3 is the described contactless IC card signal of the modulated signal of being launched by described card reader after detection and high-pass filtering that ANT receives from antenna and Fig. 1; Described comparer 106 output terminal exports restituted signal DEMOUT.Wherein, detecting circuit unit comprises diode 101, first electric capacity 102 and first resistance 103 of one-way conduction, and described detecting circuit unit is used for the carrier signal in modulated signal described in filtering.Hi-pass filter is made up of the second resistance 104 and the second electric capacity 105.
Biasing circuit 107, the output terminal of this biasing circuit 107 connects the second input end of described comparer 106 and provides a DC offset voltage for described second input end.
As shown in Figure 2, it is the sequential after existing three kinds of analog codecs from card reader to contactless IC card, namely three sequential are comprised after the groove signal in modulation signal being demodulated into the restituted signal DEMOUT of digital signaling zero or 1 also namely in Fig. 1 by the analog demodulator of the demodulator circuit of contactless IC card, each sequential corresponds to the transmission cycle of a data bit, and three sequential of restituted signal DEMOUT are defined as follows respectively:
1, sequential X, this sequential X will produce a groove signal, namely at t at (1/2) × (fc/ transfer rate) × (1/fc) place
xit is t that place starts to produce a width
agroove signal.
2, sequential Y, this sequential Y are t during whole position
bdo not modulate.
During the beginning of 3, sequential Z, this sequential Z period in place, producing a width is t
agroove signal.
During transfer rate for 848Kbits/s, 424Kbits/s, 212Kbits/s and 106Kbits/s, the transmission time Tbit of a data position, be respectively 16,32,64 and 128 clock period (clk), wherein 1clk=1/13.56MHz=73.746nS, the transmission time, Tbit was shown as t at Fig. 1
b.
As shown in Figure 3, be frame delay time FDT (FDT:Frame Delay Time) from card reader to card.Because card reader and calorie requirement carry out exchanges data, therefore also there is strict demand to the sequential of every frame data, if timing error, can decoding error be caused.According to agreement, the FDT of non-contact card demodulation only has 0 μ s ~ 0.4 μ s to comparer flip-flop transition at 0 μ s ~ 0.4 μ s and groove signal end time.
As shown in Figure 1, second input end of described comparer 106 is biased by biasing circuit 107, when the groove signal in the modulated signal inputted arrives, input signal VREF3 needs to be dragged down, at the end of groove signal, VREF3 needs from just now being reverted to normal current potential by the current potential dragged down, and charge to capacitor charging 105, due at " pause " in the duration, VREF3 must be less than VREF1, therefore the drive current of biasing circuit 107 must be smaller, for different field intensity, transfer rate, in the situations such as card reader, at the end of groove signal, VREF3 may be in lower level, cause the overlong time returning to normal current potential, and come then in next groove signal, VREF3 may be in and be flushed to higher level, cause the overlong time returning to normal current potential, thus have impact on the correctness of demodulation output or affect the FDT time.
Summary of the invention
Technical matters to be solved by this invention is to provide a kind of demodulator circuit of contactless IC card, and correct demodulation also improves frame delay.
For solving the problem, the demodulator circuit of a kind of contactless IC card of the present invention, comprises the detection unit that a diode, the first electric capacity and the first resistance are formed, the high pass filter unit that the second resistance and the second electric capacity are formed, a biasing circuit, a comparer; Also comprise first and second two pressure limiting pipes, the annexation of described demodulator circuit is:
Detection unit, the positive pole of its diode connects antenna, after the first electric capacity and the first resistor coupled in parallel, the negative pole of a terminating diode, other end ground connection;
High pass filter unit, the second resistance and the second capacitances in series, the negative pole of residue one terminating diode of the second resistance, the output terminal of the residue one termination biasing circuit of the second electric capacity, input termination second reference voltage of biasing circuit;
Comparer, its output terminal is demodulator circuit output terminal, the output terminal of its second input termination biasing circuit, and first input end connects the first reference voltage;
First pressure limiting pipe, it leaks termination power, and source connects the second input end of comparer, and grid connects the first deboost;
Second pressure limiting pipe, its drain terminal ground connection, source connects the second input end of comparer, and grid connects the second deboost.
Further, described 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, controls the amplitude through detection, filtered aerial signal by first, second two pressure limiting pipes, reaches correct demodulation and improves the effect of FDT.
Accompanying drawing explanation
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.
Description of reference numerals
1,101 is diodes, and 2,102 is the first electric capacity, and 3,103 is the first resistance, and 4,104 is the second resistance, and 5,105 is the second electric capacity, and 6,106 is comparers, and 7,107 is biasing circuits, and 8 is second pressure limiting pipes, and 9 is first pressure limiting pipes.
Embodiment
As shown in Figure 4, the carrier frequency of the transmission data from card reader to contactless IC card is 13.56MHZ to the demodulator circuit of a kind of contactless IC card of the present invention, and demodulator circuit comprises:
Comparer 6, the first input end of described comparer 6 connects the first reference signal VREF1, second input end of described comparer 6 connects input signal VREF3, and this input signal VREF3 modulated signal of being launched by described card reader that to be described contactless IC card receive from antenna ANT is through detection unit and the filtered signal of high pass filter unit; Described comparer 6 output terminal exports restituted signal DEMOUT.Wherein, detecting circuit unit comprises diode 1, first electric capacity 2 of one-way conduction and the negative electrode of the first resistance 3, first electric capacity 2 and the first resistance 3 rear one terminating diode 1 in parallel, and other end ground connection, diode 1 anode connects antenna.Described detecting circuit unit is used for the carrier signal in modulated signal described in filtering.Hi-pass filter is composed in series by the second resistance 4 and the second electric capacity 5, the negative electrode of another terminating diode 1 of the second resistance 4, the second input end of another termination comparer 6 of the second electric capacity 5.Second and first pressure limiting pipe 8 and 9, described first pressure limiting pipe 9 is a NMOS tube MNA, and its drain electrode connects supply voltage, and grid meets deboost VCLAMPL, and source electrode meets VREF3; Described second pressure limiting pipe 8 is a PMOS MPA, and its source electrode meets VREF3, and grid meets deboost VCLAMPH, grounded drain.
The input termination second reference voltage VREF2 of biasing circuit 7, exports the second input end of termination comparer 6.The first input end of comparer 6 meets the first reference voltage VREF1, and the output terminal of comparer 6 is the output DEMOUT of demodulator circuit.
During the work of this demodulator circuit, VREF3 provides direct current biasing by biasing circuit 107, provides AC signal by antenna through detection, filtered signal.And within a data bit transmission time, VREF3 needs the offset signal reverting to VREF2, can not have an impact to next data bit like this.During for different field intensity, transfer rate, card reader, signal amplitude on antenna is not identical yet, through detection, filtered AC signal may amplitude excessive, make VREF3 at the end of a data bit transmission time, have little time to revert to bias voltage, cause next data decoding errors.Therefore on VREF3, add two pressure limiting pipe MNA and MPA.When the difference of voltage VREF3 lower than the grid voltage VCLAMPL of pressure limiting pipe MNA and the threshold voltage of pressure limiting pipe MNA, supply voltage is charged toward VREF3 by pressure limiting pipe MNA, reduces to stop voltage VREF3.In like manner, as the grid voltage VCLAMPH of voltage VREF3 higher than the threshold voltage of pressure limiting pipe MPA and pressure limiting pipe MPA, VREF3 by pressure limiting pipe MPA past discharge, raise to stop voltage VREF3.Make the voltage fluctuation of VREF3 so all the time within the specific limits, and at the end of a data bit transmission time, can bias voltage be returned to, ensure that next data decode correctness, also reduce FDT simultaneously.
These are only the preferred embodiments of the present invention, be not intended to limit the present invention.For a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (2)
1. a demodulator circuit for contactless IC card, comprises the detection unit that a diode, the first electric capacity and the first resistance are formed, the high pass filter unit that the second resistance and the second capacitances in series are formed, a biasing circuit, a comparer; It is characterized in that: also comprise first and second two pressure limiting pipes, the annexation of described demodulator circuit is:
Detection unit, the positive pole of its diode connects antenna, after the first electric capacity and the first resistor coupled in parallel, the negative pole of a terminating diode, other end ground connection;
High pass filter unit, the second resistance and the second capacitances in series, the negative pole of residue one terminating diode of the second resistance, the output terminal of the residue one termination biasing circuit of the second electric capacity, input termination second reference voltage of biasing circuit;
Comparer, its output terminal is demodulator circuit output terminal, the output terminal of its second input termination biasing circuit, and first input end connects the first reference voltage;
First pressure limiting pipe, it leaks termination power, and source connects the second input end of comparer, and grid connects the first deboost;
Second pressure limiting pipe, its drain terminal ground connection, source connects the second input end of comparer, and grid connects the second deboost.
2. the demodulator circuit of contactless IC card as claimed in claim 1, is characterized in that: described first pressure limiting pipe is NMOS, and the second pressure limiting pipe is PMOS.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201310304221.3A CN104299024B (en) | 2013-07-19 | 2013-07-19 | The demodulator circuit of contactless IC card |
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| 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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| CN104299024A true CN104299024A (en) | 2015-01-21 |
| CN104299024B CN104299024B (en) | 2018-08-21 |
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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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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110135206A (en) * | 2018-02-09 | 2019-08-16 | 博通集成电路（上海）股份有限公司 | Card detector and card test method |
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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 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110135206A (en) * | 2018-02-09 | 2019-08-16 | 博通集成电路（上海）股份有限公司 | Card detector and card test method |
| 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 |
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| CN104299024B (en) | 2018-08-21 |
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