CN103606001A - Adaptive threshold adjusting method for non-contact intelligent card demodulation system - Google Patents
Adaptive threshold adjusting method for non-contact intelligent card demodulation system Download PDFInfo
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- CN103606001A CN103606001A CN201310586002.9A CN201310586002A CN103606001A CN 103606001 A CN103606001 A CN 103606001A CN 201310586002 A CN201310586002 A CN 201310586002A CN 103606001 A CN103606001 A CN 103606001A
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Abstract
The invention discloses an adaptive threshold adjusting method for a non-contact intelligent card demodulation system. An additionally-arranged adaptive threshold adjusting circuit in a non-contact IC card is utilized for accomplishment. The adaptive threshold adjusting circuit determines whether a threshold is appropriate according to the number of zeros in a zero number counter. After stabilization of a power-on simulation front end circuit, adjustment is carried out from a greatest threshold downwards, the great number of the zeros means that the threshold is too great, burr generation occurs, a fixed threshold step length is subtracted from a present threshold, after accomplishment of threshold switching of the simulation circuit, next determination is carried out continuously, till the number of the zeros reaches a prescribed range, the threshold reaches an optimum one, or demodulation for a smallest threshold is carried out. According to the adaptive threshold adjusting method, in a field intensity range of 1.5A/m-7.5A/m, for multiple antenna waveforms prescribed in an ISO/IEC14443TypeA protocol, a comparator threshold can be automatically selected, and demodulation data with pause width close to 3mus is outputted.
Description
Technical field
The present invention relates to meet adaptive threshold control method in the demodulating system of non-contact IC card of ISO/IEC14443Type A agreement.For different field intensity different antennae waveforms, select adaptively best compare threshold, make demodulating system obtain the demodulating data of standard.
Background technology
The concept of IC-card was to put forward early 1970s, and first French boolean (BULL) company createed smart card sample in 1976, and this technology was applied to a plurality of industries such as finance, traffic, medical treatment and proof of identification.The form transmitting according to card and extraneous data, IC-card can be divided into Contact Type Ic Card and non-contact IC card.According to ISO/IEC14443-2A agreement regulation, smart card reader produces the RF electromagnetic field that is coupled to IC-card, in order to transmit energy and two-way communication.The field strength range of RF field is 1.5A/m～7.5A/m, carrier frequency f
cfor 13.56MHz ± 7kHz.Data transmission rate=13.56MHz/128=106Kb/s, the shared time cycle of a data is 9.4us.Modulation system adopts 100% ASK(amplitude keying modulation), in RF field, create one " gap (pause) " and transmit binary data.The Pause waveform of ISO/IEC14443Type A agreement regulation as shown in Figure 1.100%ASK modulation signal is after demodulator circuit as shown in Figure 2, output waveform as shown in Figure 3, VA is that envelope detector is at the RF envelope signal of the output of A point output, its direct current is fixed on 600mV by voltage follow-up amplifier, and DIN is that VA and threshold voltage Vref obtain demodulating data after in comparer.
International norm has been stipulated three kinds of typical antenna waveforms as shown in Figure 4: a kind of normal condition (t
1=3 μ s, t
2=1.4 μ s) and two kinds of extreme case (extreme case 1:t
1=3 μ s, t
2=0.5 μ s; Extreme case 2:t
1=2 μ s, t
2=0.7 μ s).Every kind of situation antenna waveform under different field intensity all can have different variations, and Fig. 5 has provided the roughly variation tendency that extreme case 1 lower envelope waveform increases with field intensity.
The paper " analysis and solutions of blind zone problem in Double interface intelligent card chip " being published in April, 2012 in < < Chinese Integrated Circuit > > is studied blind zone problem: because field intensity variation range is large, under the field intensity of 3A/m～6A/m, antenna waveform decline rate is slow, and decline process has a zone of transition, the demodulating data pause narrower in width that envelope waveform and fixed threshold relatively obtain, only have 0.5 μ s, differ greatly with 3 μ s width of standard.Even if improved afterwards mimic channel, the pause width finally obtaining still only has 1.8 μ s.
This shows, the variation of contact type intelligent card antenna waveform is very large, and it is also very greatly that the envelope waveform being obtained by mimic channel changes.If the compare threshold of comparer is fixed value, the wide variety of the Pause obtaining under different situations can be very large.The threshold value of take is selected in the full width constant-voltage of 300mV(at 600mV) be example, in the time of minimum, width can arrive 0.5 μ s, and the pause width of standard is 3 μ s.
Summary of the invention
For contact type intelligent card demodulating system comparer fixed threshold, can not adapt to well different field intensity and the large problem of antenna wave form varies, the invention provides a kind of method that in demodulating system, comparator threshold self-adaptation regulates, threshold value is along with the variation of envelope waveform regulates automatically.
To achieve these goals, the present invention by the following technical solutions.
Contact type intelligent card demodulating system is improved, increased adaptive threshold regulating circuit.Structured flowchart after improvement as shown in Figure 6, comprises AFE (analog front end) and digital circuit two parts, and digital circuit comprises again digital demodulating circuit and adaptive threshold regulating circuit (the dotted line mark part in Fig. 6).
AFE (analog front end) is carried out envelope detection by RF signal, and the DC voltage of the envelope signal of A point output is fixed on Vbuf by follower amplifier, and envelope signal compares and obtains demodulating data with threshold value in comparer.The threshold value of comparer has fixing multiple choices, and threshold value selects the Vref_config signal being returned by digital circuit to control.
Adaptive threshold regulating circuit completes the automatic adjusting of threshold value, mainly by threshold value, regulates control module, sampling module, sampling number counter, zero counter, judge module, adjustment module and time delay module etc. to form.
Threshold value regulates control module, is responsible for configuration adjustment parameter output adjusting enable signal tune_en.Smart card power-up initializing configuration finish and each send out number finish after and wait for a period of time, tune_en is effective; After receiving the adjusting end signal tune_over of judge module output, tune_en is invalid, and this regulates end.High threshold Vmax, lowest threshold Vmin, threshold steps, sampling Δ V, number of times higher limit CNT_TIMES, zero that the parameter of configuration mainly contains that threshold value regulates are counted higher limit NUM0, initialization time delay stand-by period PRE_TIME and handoff delay stand-by period WAIT_TIME.
The function of sampling module is with the clock of 13.56MHZ, the output signal of AFE (analog front end) comparer to be sampled.
Sampling number counting is for recording the number of times that sampling process is sampled.
Zero counting number is for recording the number of the zero level collecting.Number according to zero can judgment threshold height, zero number and the relation of threshold value are as shown in Figure 7.Threshold value adjustment process (before being Pause) before efficient communication data arrive is carried out, the signal that ideally sample circuit collects should be high level, but due to the countless ripplet that superposeed in actual envelope detector output waveform, when threshold voltage is Vref1, because Vref1 is too high, the ripplet of stack repeatedly passes through Vref1 level back and forth, makes to have occurred many " burr " in the output waveform of comparer.The appearance of " burr ", makes sample circuit collect zero level, if zero number is too much, illustrates that " burr " is too many, and threshold voltage is too high.If threshold voltage is lowered to Vref2, because the trough of ripplet is all positioned on Vref1 level, in the output waveform of comparer, no longer includes " burr " and occur, zero number is 0 or is reduced to below the upper limit of setting, illustrates that threshold value is normal.
The function of judge module is that sampling number and zero number and the higher limit of each self-configuring are compared, and more present threshold value and minimum threshold.
The function of time delay module is to march into the arena and carry out that power-up initializing finishes and send out at every turn after number finishes, starting to carry out threshold value while regulating at smart card, and the PRE_TIME that waits for a period of time makes analog front circuit stable; Analog front circuit carries out threshold value switching after receiving the vref_config of renewal at every turn, and the WAIT_TIME that need wait for a period of time guarantees that AFE (analog front end) completes and switches and stable.
Adjustment module is used for exporting threshold value and regulates control signal Vref_config to AFE (analog front end), completes threshold value and switches.
An adaptive threshold control method in contact type intelligent card demodulating system, in non-contact IC card, realize according to the following steps successively:
Step 2, smart card is marched into the arena and is carried out power-up initializing configuration;
Step 3, after the confirmation analog front circuit that waits for a period of time is stable, by the output of time clock sampled analog front end comparer, records the zero number that sampling number and sampling obtain;
Step 4, judges according to sampled result, if sampling number does not reach the higher limit that zero number has reached setting in limited time, illustrates that existing threshold value is too high, deducts fixing threshold voltage step-length from current threshold value, obtains new threshold value; If sampling number reaches the upper limit, zero number does not reach higher limit, illustrates that current threshold value is suitable, does not carry out threshold value adjusting;
Step 6, if threshold value reaches minimum threshold, or has obtained suitable threshold value, stops regulating, and this regulates ends, the transmission of smart card wait card reader data carry out data demodulates;
Described threshold value adjustment process completed before efficient communication data arrive.
The march into the arena power-up initializing configuration of described smart card is initialized as mxm. by threshold value, and threshold value regulates carries out from high to low.
The invention has the beneficial effects as follows, in the field strength range of 1.5A/m～7.5A/m, for the multiple antenna waveform of ISO/IEC14443Type A agreement regulation, can automatically select comparator threshold, output pause width approaches the demodulating data of 3 μ s.
Accompanying drawing explanation
Fig. 1 is the pause oscillogram of ISO/IEC14443Type A agreement 100%ASK modulation;
Fig. 2 is for being contact type intelligent card AFE (analog front end) demodulator circuit;
Fig. 3 is that the voltage waveform of AFE (analog front end) demodulator circuit main node: RF is radiofrequency signal, and VA is A point voltage, and Vref is threshold voltage, and DIN is demodulating data;
Fig. 4 is the envelope of three kinds of antenna waveforms of international norm regulation;
Fig. 5 is that the envelope of 1 time antenna waveform of Fig. 4 extreme case is with the situation of change of field intensity;
Fig. 6 is contact type intelligent card demodulating system structured flowchart;
Fig. 7 produces the principle schematic of burr in comparer output waveform;
Fig. 8 is adaptive threshold control method process flow diagram involved in the present invention.
Embodiment
Below in conjunction with drawings and Examples, the present invention will be further described.
As shown in Figure 6, adaptive threshold control method process flow diagram involved in the present invention as shown in Figure 8 for contact type intelligent card demodulating system structured flowchart of the present invention.Threshold value automatically regulates and comprises the following steps:
Step 2, smart card is marched into the arena and is carried out power-up initializing configuration: setting judgement counts upper limit CNT_TIMES is 100 times, and it is 3 that the zero that permission occurs is counted upper limit NUM0.The high threshold Vmax=550mV that threshold value regulates, lowest threshold Vmin=300mV, threshold value regulates step delta V=25mV, from high threshold to lowest threshold totally 11 threshold value shelves, corresponding Vref_config4 Bit data A～0.Initialization time delay stand-by period PRE_TIME is 50* (1/f
c), it is 10* (1/f that threshold value is switched stand-by period WAIT_TIME
c), f wherein
c=13.56MHZ.Having configured the effective tune_en of rear adjusting enable signal is 1, and threshold value is initialized as high threshold;
Step 3, by the time of time delay module time delay PRE_TIME, after confirming that analog front circuit is stable, the output of the time clock sampled analog front end comparer of 13.56MHZ for sampling module, sampling number counter records sampling number, the number of the zero level that zero counter record collects;
Step 4, judge module compares judgement according to the value of two counters and higher limit separately.If do not reach at sampling number the higher limit that zero number has reached setting in limited time, illustrate that existing threshold value is too high, adjustment module deducts fixed threshold voltage step size by current threshold value and obtains new threshold value and regulate control signal Vref_config to export AFE (analog front end) to, completes threshold value switch by AFE (analog front end); If sampling number reaches the upper limit, zero number does not reach higher limit, illustrates that present threshold value is suitable;
Step 6, if threshold value reaches minimum threshold, or obtained suitable threshold value, stop regulating, by judge module output, tune_over is 1, regulate control module tune_over signal to be detected and make to regulate enable signal tune_en to revert to 0 after effectively, smart card wait for that card reader sends data carry out data demodulates;
The hardware circuit of the present embodiment designs under the 180nm of integrated circuit Manufacturing Co., Ltd of SMIC technique, final chip testing is known, for three kinds of antenna waveform situations of the field strength range of 1.2A/m～8A/m and international standard regulation, can select best threshold value relatively to obtain the demodulating data of the pause width that is near the mark.
Claims (3)
1. an adaptive threshold control method in contact type intelligent card demodulating system, is completed by improved contact type intelligent card demodulating system, it is characterized in that, automatically regulates the size of comparator threshold according to different field intensity and antenna waveform, comprises the following steps:
Step 1, described demodulating system AFE (analog front end) is obtained DC voltage and the clock of contact type intelligent card need of work by regulator rectifier circuit and clock recovery circuitry in the RF carrier signal of antenna reception;
Step 2, smart card is marched into the arena and is carried out power-up initializing configuration;
Step 3, after the confirmation analog front circuit that waits for a period of time is stable, by the output of time clock sampled analog front end comparer, records the zero number that sampling number and sampling obtain;
Step 4, judges according to sampled result, if sampling number does not reach the higher limit that zero number has reached setting in limited time, illustrates that existing threshold value is too high, deducts fixing threshold voltage step-length from current threshold value, obtains new threshold value; If sampling number reaches the upper limit, zero number does not reach higher limit, illustrates that current threshold value is suitable, does not carry out threshold value adjusting;
Step 5, waits for a period of time, and makes analog front circuit complete threshold value and switches, and then continues the result of output and the new threshold value comparison of sampled envelope detection; And carry out the judgement described in next round step 4;
Step 6, if threshold value reaches minimum threshold, or has obtained suitable threshold value, stops regulating, and this regulates ends, the transmission of smart card wait card reader data carry out data demodulates;
Step 7, after smart card is replied the data of card reader, initialization threshold value, restarts threshold value and regulates, and repeating step 3～6, until smart card and card reader sign off leave magnetic field.
2. adaptive threshold control method in a kind of contact type intelligent card demodulating system according to claim 1, is characterized in that, described threshold value adjustment process completed before efficient communication data arrive.
3. adaptive threshold control method in a kind of contact type intelligent card demodulating system according to claim 1, is characterized in that, the march into the arena power-up initializing configuration of described smart card is initialized as mxm. by threshold value, and threshold value regulates carries out from high to low.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106326800A (en) * | 2016-08-25 | 2017-01-11 | 江门市汇朗工业机器人有限公司 | RF card reader communication method |
| CN106611144A (en) * | 2015-10-23 | 2017-05-03 | 上海华虹集成电路有限责任公司 | Automatic adjusting system for sensitivity of demodulation circuit in radio frequency identification |
| CN107666753A (en) * | 2016-07-29 | 2018-02-06 | 松下知识产权经营株式会社 | Signal receives and dispensing device, lighting system, ligthing paraphernalia and illuminator |
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| CN101075296A (en) * | 2006-05-15 | 2007-11-21 | 上海华虹集成电路有限责任公司 | Self-adaptive threshold demodulation circuit for non-contacting IC card or radio-frequency recognition label |
| CN101937503A (en) * | 2009-06-29 | 2011-01-05 | 索尼公司 | Noncontact communication apparatus and noncontact communication method |
| JP2011097389A (en) * | 2009-10-30 | 2011-05-12 | Sony Corp | Communication equipment, and communication control method |
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| CN101075296A (en) * | 2006-05-15 | 2007-11-21 | 上海华虹集成电路有限责任公司 | Self-adaptive threshold demodulation circuit for non-contacting IC card or radio-frequency recognition label |
| CN101937503A (en) * | 2009-06-29 | 2011-01-05 | 索尼公司 | Noncontact communication apparatus and noncontact communication method |
| JP2011097389A (en) * | 2009-10-30 | 2011-05-12 | Sony Corp | Communication equipment, and communication control method |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106611144A (en) * | 2015-10-23 | 2017-05-03 | 上海华虹集成电路有限责任公司 | Automatic adjusting system for sensitivity of demodulation circuit in radio frequency identification |
| CN106611144B (en) * | 2015-10-23 | 2019-05-14 | 上海华虹集成电路有限责任公司 | Demodulator circuit sensitivity automatic adjustment system in radio frequency identification |
| CN107666753A (en) * | 2016-07-29 | 2018-02-06 | 松下知识产权经营株式会社 | Signal receives and dispensing device, lighting system, ligthing paraphernalia and illuminator |
| CN106326800A (en) * | 2016-08-25 | 2017-01-11 | 江门市汇朗工业机器人有限公司 | RF card reader communication method |
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