CN103023536A - Device, system and method used for detecting and transmitting low-frequency magnetic field signal and judging distance - Google Patents
Device, system and method used for detecting and transmitting low-frequency magnetic field signal and judging distance Download PDFInfo
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- CN103023536A CN103023536A CN2010101664321A CN201010166432A CN103023536A CN 103023536 A CN103023536 A CN 103023536A CN 2010101664321 A CN2010101664321 A CN 2010101664321A CN 201010166432 A CN201010166432 A CN 201010166432A CN 103023536 A CN103023536 A CN 103023536A
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- G01—MEASURING; TESTING
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- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/023—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring distance between sensor and object
Abstract
The invention relates to a device and a method used for detecting and transmitting close-range low-frequency magnetic field signals and judging distance. The device comprises at least one low-frequency sensor module used for sensing low-frequency signals, at least one amplifier used for amplifying the low-frequency signals, at least one analog-digital converter connected with the output end of the amplifier, and a digital processing module connected with the analog-digital converter, wherein the digital processing module is used for judging the intensity of original signals and accomplishing the signal detection and output. The invention further provides a system combining the close range detection and the radio-frequency high-frequency communication of the low-frequency alternating magnetic field, which comprises a radio frequency communication terminal and a close range radio frequency communication device, wherein the radio frequency communication terminal comprises the device used for detecting and transmitting the close-range low-frequency magnetic field signals and judging the distance and a radio frequency transceiver circuit. The device, the method and the system can accomplish the pre-amplification of the low-frequency weak signals, the analog-digital conversion, the field intensity detection and the data communication by a simple circuit structure, so that the reliable bidirectional distance communication can be realized without modifying a mobile terminal.
Description
Technical field
The present invention relates to the communications field, relate in particular between a kind of terminal and the terminal, the detection of low frequency magnetic field signal and the apparatus and method of transmission when carrying out the controlled close-distance safety data communication of distance, the radio communication terminal (such as mobile phone, PDA etc.) that particularly contains radio-frequency unit (such as radio-frequency card) or have a close distance radio frequency communication function and close distance radio frequency communication equipment are (such as POS machine or card reader; POS, i.e. Pointof sales) distance control, magnetic field low frequency signal detect and the apparatus and method of transmission.
Background technology
Scientific and technological progress is today fast, people's life is also more and more convenient, wherein mobile payment industry is also arisen at the historic moment under such sight, nowadays, as long as being changed a SIM card, mobile phone can realize the mobile phone short-range communication, the appearance of this method so that mobile phone become one can supplement with money, consume, the super intelligent terminal of transaction and authentication, greatly satisfied the active demand in market.
This kind SIM card, the technology such as employing radio frequency UHF (U1tra High Frequency, hyperfrequency) embed it in mobile phone draw-in groove, need not to revise other structures and just can finish short-range communication and transaction.
But, because the transmission otherness of UHF in the different structure mobile phone, cause the mobile communication distance of different shielding propertiess to differ larger, far then several meters, closely then several centimetres, in the transaction of swiping the card such as public transport POS machine or subway gate, often the distance of can concluding the business there is stricter restriction, to guarantee to avoid misoperation.That therefore, adjusts the distance effectively has been controlled to extremely urgent demand.
Prior art has existed a kind of low frequency alternating magnetic field closely to detect system and method in conjunction with the communication of RF high frequency, has solved the problem of above-mentioned distance control.This system utilizes low frequency alternating magnetic field, realizes card reader to the one-way communication of card, finishes distance control and authentication, and recycling RF passage is realized the high speed communication between card reader and card.The characteristics of this system are for need not to transform portable terminal, and only the SIM card of need replacing terminal inner/TF/SD card can be realized reliable two-way range communication.
Card reader emission low frequency alternating magnetic field signal, card only need to receive this field signal, owing to be one-way communication, and need not card reader and provide energy by magnetic field, therefore can with receiving coil or other receiving circuit miniaturizations, be enough to put into SIM card/TF/SD card.Since receive signal a little less than, need to increase amplifying circuit in the card.
Place simultaneously the RF transmission circuit in the card in addition, realize the bidirectional high speed communication with the RF transmission circuit in the card reader, as previously described, the antenna of RF circuit is very little, can be integrated into easily in SIM card/TF/SD card.
Utilize low channel to realize that distance detects and control, card reader sends the unique ID r of self to card by the low frequency half-duplex channel, unique ID c together with card self after clamping is received sends card reader to by the RF passage, thereby realize unique binding of card reader and card, i.e. the process of so-called portable terminal access card reader.
Because card reader and unique binding of card, the communication after the access procedure adopts the RF passage to carry out, and still can guarantee the reliability of distance control and the reliability of communication.
In sum, no matter low frequency or the size of RF antenna all can be integrated in the card adopts the mode of low frequency and RF combination to realize both-way communication simultaneously, therefore need not to transform portable terminal, only the SIM card of need replacing terminal inner/TF/SD card can be realized reliable two-way range communication.
Therefore, how effectively to reduce circuit noise and ambient noise to the interference of low frequency signal, from low frequency signal, recover exactly data flow, realize that the one-way communication of card reader and card, the distance that the extraction range information is effectively controlled its transaction become present problem demanding prompt solution.
Summary of the invention
Technical problem to be solved by this invention provides a kind of for the method and apparatus of low frequency magnetic field input and transmission and Distance Judgment closely, be used for the induction low frequency signal, to low-frequency weak signal amplify in advance, analog-to-digital conversion, field intensity detects and the apparatus and method of data communication.
The technical scheme that the present invention solves the problems of the technologies described above is as follows: a kind of device for low frequency magnetic field input and transmission and Distance Judgment comprises that at least one is used to respond to the low frequency induction module of low frequency magnetic field signal, at least one be used for to amplify amplifier of low frequency induction signal, at least one analog to digital converter that is connected with amplifier out, and the digital signal processing module that is connected with analog to digital converter and exports for intensity and the settling signal detection of judgement primary signal.
The invention has the beneficial effects as follows: utilize the structure of apparatus of the present invention, need not to transform portable terminal, only the SIM card of need replacing terminal inner/TF/SD card can be realized reliable two-way range communication.
On the basis of technique scheme, the present invention can also do following improvement.
Further, described low frequency induction module is induction coil, Hall element, perhaps giant magnetoresistance.
Further, described amplifier adopts the mode of casacade multi-amplifier cascade.
Further, described amplifier is single-ended amplifier, also can be differential amplifier.
Further, every grade of input connects high-pass filtering circuit, every grade of output connection low-pass filter circuit in the casacade multi-amplifier of described cascade, and amplifier is low imbalance and the long-pending amplifier of high gain-bandwidth.
The beneficial effect that adopts above-mentioned further scheme is that every grade of input and output side is introduced high pass and low-pass filtering, improves signal to noise ratio.
Further, described analog to digital converter adopts parallel A/D converter.
Adopt the beneficial effect of above-mentioned further scheme to be: to improve rear end digital module treatment effeciency.
Further, described analog to digital converter speed is greater than 1KSPS, and input range is that 0V is to the analog to digital converter reference voltage.
Further, described analog to digital converter input front end is provided with the voltage follower that is connected with amplifier.
Adopt the beneficial effect of above-mentioned further scheme to be: the simulation amplifying signal of stabilizing amplifier output, the voltage drift of avoiding A/D front end high resistant to cause causes the analog-to-digital conversion distortion.
Further, be provided with between described analog to digital converter and the digital signal processing module for the digital spur filter that digital signal is carried out the burr filtering.
The present invention also provides a kind of low frequency alternating magnetic field closely to detect system in conjunction with the communication of radio frequency high frequency, comprise radio communication terminal and close distance radio frequency communication equipment, wherein, described radio communication terminal comprises such as claim 1 to 8 arbitrary described for the device of low frequency magnetic field input and transmission and Distance Judgment closely, and is connected the radio-frequency (RF) transmit-receive circuit that is used for close distance radio frequency communication equipment both-way communication with described for the device of low frequency magnetic field input and transmission and Distance Judgment closely.
It is a kind of for the method for low frequency magnetic field input and transmission and Distance Judgment closely that the present invention also provides, and method comprises:
Step a: measure magnetic induction module and induced voltage the voltage amplitude value through amplifier amplification after of the card reader that sends magnetic field at different distance point, determine the corresponding relation of voltage amplitude value and distance, and set up the corresponding table of range value and distance;
Step b: according to the swipe the card needs of distance of decoded low frequency signal transmitted data and control, in conjunction with the signal to noise ratio requirement, form sluggish judgement voltage threshold by comparison threshold the analog to digital converter output signal is adjudicated, obtain the code stream information of low-frequency magnetic place transmission; Form non-sluggish judgement voltage threshold by comparison threshold the analog to digital converter output signal is adjudicated, obtain the distance feature information that transmit in the low-frequency magnetic place;
Step c: signal after the non-sluggish judgment condition judgement sampled obtains 0,1 code stream sequence, 1 signal proportion thresholding is set, in the time window length of setting, this code stream sequence is added up, when the shared code stream sequence of 1 signal ratio reaches the preset ratio thresholding, then think to enter set distance range, otherwise think and do not enter this distance range; Burst after the sluggish judgment condition judgement is decoded, extract the code stream information of low frequency magnetic field, finish low frequency magnetic field signal one-way communication.
Further, among the described step b, according to the corresponding table of range value described in the step a with distance, in conjunction with the requirement of separating code distance, distance control, ratio thresholding that 1 signal is set comparison threshold in the digital signal processing module is set.
Further, among the described step b, use single, a plurality of single, a pair of, many to relatively magnetic field range information and code stream information are extracted in thresholding or its combination.
Further, a pair of comparison threshold is non-sluggish judgment condition in the described digital signal processing module, its method to set up is: the distance of establishing desired control is D1, search the corresponding table of range value and distance, obtain signal intensity amplitude corresponding to D1 for+A1 to-A1, the ratio thresholding that 1 signal is set is R1, according to A1 and R1, the level L1 of comparator is exported in setting, L2, satisfy in one-period, the fore device amplitude output signal equals R1 greater than L1 or less than the percentage of time of L2, namely then enters in distance B 1 scope of described requirement control greater than R1, otherwise does not enter in the described scope that requires command range D1.
Further, a pair of comparison threshold is sluggish judgment condition in the described digital signal processing module, its method to set up is: if the distance that expectation is decoded is D2, search the corresponding table of range value and distance, the amplitude of variation that obtains the D2 respective signal for+A2 to-A2, recording the amplitude that most of noises produce is A3, and the level L3, the L4 that export to comparator are set, so that L3 should be greater than+A3, and less than+A2; L4 is less than-A3, and greater than-A2, namely then allow decoding less than D2 when distance, otherwise not allow decoding.
Further, among the described step b, carry out the logic OR processing to using two output signals after a pair of non-sluggish judgment condition is judged, obtain after the processing for the digital signal of extracting range information.
Further, among the described step b, two output signals after using a pair of sluggish judgment condition to judge are carried out sluggishness process, obtain for the digital signal of extracting the magnetic field code stream information after sluggish the processing.
Further, when using single comparison threshold to extract the magnetic field code stream information, comparison threshold is set to amplifier input reference level; When using single comparison threshold output comparative level to extract the magnetic field range information, the comparison threshold method to set up is consistent with a pair of comparison threshold method to set up.
Further, the digital signal that described method uses single comparison threshold to export is more afterwards carried out the judgement of single distance and code stream, or the digital signal of using a pair of comparison threshold to export is more afterwards carried out the judgement of single distance and code stream; The digital signal that described method uses a plurality of single comparison thresholds to export is more afterwards carried out the judgement of a plurality of distances and code stream, or uses many digital signals that the comparison thresholding is exported more afterwards to carry out between a plurality of distances, a plurality of distance regions and the judgement of code stream.
Further, described method is mixed digital signal and the many digital signals that the comparison thresholding is exported more afterwards of using a plurality of single comparison thresholds export more afterwards and is carried out between a plurality of distances, a plurality of distance regions and the judgement of code stream.
Further, among the described step c, comprise the step that the digital signal of input is carried out the burr filtering, then from the signal of filtering burr, decode the low frequency magnetic field data flow.
Description of drawings
Fig. 1 is that the present invention is used for closely a kind of example structure figure of the device of low frequency magnetic field input and transmission and Distance Judgment;
Fig. 2 is the structural representation of induction coil induction low frequency mode of the present invention and single-ended input amplifier;
Fig. 3 is the structural representation of Hall element induction low frequency mode of the present invention and single-ended input amplifier;
Fig. 4 is the structural representation of giant magnetoresistance induction low frequency mode of the present invention and single-ended input amplifier;
Fig. 5 is the application example of induced signal difference input amplifier of the present invention;
Fig. 6 is the flow chart of embodiment of the invention medium and low frequency signal detecting method.
Fig. 7 be record by experiment in the embodiment of the invention induction module is inserted the different mobile communication terminal, the corresponding relation schematic diagram of distance and low frequency induction signal amplitude value.
Fig. 8 is the inside basic block diagram of embodiment of the invention analog to digital converter;
Fig. 9 is the schematic diagram that uses a pair of comparison threshold to adopt the low frequency magnetic field signal detecting method to decode and process in the embodiment of the invention;
Figure 10 uses a pair of comparison threshold to adopt the low frequency signal detection method to carry out the schematic diagram that distance control is processed in the embodiment of the invention;
Figure 11 is the schematic diagram that uses single comparison threshold to adopt magnetic field data low frequency signal detection method to decode and process in the embodiment of the invention;
Figure 12 uses single comparison threshold to adopt the low frequency signal detection method to carry out the schematic diagram that distance control is processed in the embodiment of the invention;
Figure 13 is that a kind of low frequency alternating magnetic field of the present invention closely detects the system architecture diagram in conjunction with the communication of radio frequency high frequency.
In the accompanying drawing, the list of parts of each label representative is as follows:
01: the low frequency induction module
02: amplifier
03: analog/digital converter
04: digital logic module
05: comparator
06: the control module of analog to digital converter
07: analog to digital converter
08: data register
AIN: single-ended input signal
VINP: differential input signal anode
VINN: differential input signal negative terminal
VCM: common-mode voltage
Vref: reference voltage
VOUT: the outputting analog signal of amplifier afterbody
Ra1, Ra2, Ra3, Ra4, Ra5, R1, R2: resistance
R3, R4, R5, R6: Hall element internal components
C1, C2, C3, C4, C5, C6, C7, C8, C9, C10: electric capacity
L: induction coil
The D0-Dn-1:ADC digital output
A: voltage follower
B: analog to digital converter nucleus module.
Embodiment
Below in conjunction with accompanying drawing principle of the present invention and feature are described, institute gives an actual example and only is used for explaining the present invention, is not be used to limiting scope of the present invention.
Detection and the information communication of specific implementation low frequency magnetic field field intensity of the present invention have adopted a kind of structure by single-stage or cascade gain adjustable amplifier and analog to digital converter to finish collection and the response of information.The concrete amplifier that uses amplifies the front end small-signal, and the input of the signal connection mode number converter after the amplification is transferred to digital module and carried out digital algorithm after analog-to-digital conversion, thereby realizes distance control and communication.Describe below in conjunction with accompanying drawing:
Fig. 1 has described the structure chart that the present invention is used for the device of low frequency magnetic field input and transmission and Distance Judgment, the digital signal processing module 04 that it comprises low frequency induction module 01, the amplifier 02 that is used for amplifying the low frequency induction signal, the analog to digital converter 03 that is connected with amplifier out, is connected with analog to digital converter 03 and exports for intensity and the settling signal detection of judgement primary signal.The present invention is used for the device collection of low frequency magnetic field input and transmission and Distance Judgment and amplifies faint low frequency signal, through analog-to-digital conversion, digital algorithm, finishes at last distance control and transaction communication.
Figure 2 shows that a kind of structure example of a kind of cascade gain adjustable amplifier that uses for the device of low frequency magnetic field input and transmission and Distance Judgment closely of the present invention.Cascade gain adjustable amplifier in this example, adopt single-ended input, the variation voltage AIN that is coupled to by the low frequency magnetic field Strength Changes of induction coil L is input to the 1st grade of amplifier negative terminal as shown in Figure 2, next 4 grades of modes that all adopt anti-phase amplification are finished the pre-amplification of low-frequency weak signal altogether through 5 grades of inverting amplifiers.
High-pass filtering is introduced in every grade of input in this example, and low-pass filter circuit is put in feedback control loop.C1/Ra1 among Fig. 2, C3/Ra2, C5/Ra3, C7/Ra4, C9/Ra5 are the RC high-pass filterings of every grade of input, along with the increase of frequency, condensance constantly reduces, and causes circuit gain to rise, and forms high-pass filtering, and C2/Rb1, C4/Rb2, C6/Ra3, C8/Rb4, C10/Rb5 are the RC low-pass filtering of every grade of feedback control loop, along with the increase of frequency, the equivalence feedback impedance constantly reduces, and causes gain to descend, thereby forms low-pass filtering.In addition, the capacitor C 1 of the 1st grade of input plays simultaneously every straight effect, prevents that the DC differential pressure at induction coil two ends from causing signal to misplace large and error detection.The low-frequency cut-off frequency of every one-level is determined that by its RC high-pass filtering circuit the high-frequency cut-off frequency is determined by its RC low-pass filter circuit.
Every one-level multiplication factor is determined by corresponding Rb/Ra in this example, and the total magnification after 5 grades of amplifications is Rb1*Rb2*Rb3*Rb4*Rb5/Ra1*Ra2*Ra3*Ra4*Ra5, can according to circumstances increase and decrease progression in the practical application.This common-mode voltage is selected half of amplifier power supply voltage, and amplifier adopts single power supply, also can according to circumstances select the mode of positive-negative power supply in the application.Amplifier Rail toRail (rail-to-rail), and possess low imbalance and higher gain bandwidth product.
What Fig. 2 showed is the mode that induction module adopts induction coil, according to circumstances also can adopt other the low frequency induction mode such as Hall element or giant magnetoresistance, as shown in Figure 3 and Figure 4.
Fig. 2 to 4 example has been described the mode that the low frequency induction signal adopts single-ended input, according to applicable cases, also can select the mode of difference input, as shown in Figure 5, the 1st grade is adopted the difference input, Single-end output, the 1st grade of output introduced the passive low-pass filtering of RC, and rear level Four adopts the method for first order pole filtering, and input is introduced the RC high-pass filtering, feedback end is introduced the RC low-pass filtering, determines respectively lower-cut-off frequency and upper cut-off frequency.Common port is VCM (VDD/2), and the satisfaction induction signal is symmetrical up and down take VDD/2 as axis, to avoid the distortion of waveform.The advantage of introducing the method is to increase common-mode rejection ratio, the minimizing common-mode noise.What amplifier was selected in this example is the amplifier of Single-end output, according to actual conditions, also can select the difference input, the mode of difference output.
Fig. 6 is the flow chart of embodiment of the invention medium and low frequency signal detecting method.The detection of low frequency signal comprises the steps:
Step 601 is measured the range value that amplifies rear induced voltage in different distance;
Means are measured magnetic induction module and induced voltage the range value through amplifier amplify after of the card reader that sends magnetic field at different distance point at different mobile phone terminals, and are done corresponding record by experiment.
Step 602 is set up the corresponding table of range value and distance;
The measurement data of a plurality of terminals is processed, obtained the corresponding table of range value and distance.
Step 603 enters low frequency magnetic field data decode flow process;
The expectation distance of decoding is D2, searches the corresponding table of range value and distance, and the amplitude of variation that obtains the D2 respective signal arrives-A2 for+A2, the amplitude that records most of noises generations is A3, level L3, the L4 of comparator exported in setting, so that L3 should be greater than+A3, and less than+A2; L4 is less than-A3, and greater than-A2, namely then allow decoding less than D2 when distance, otherwise not allow decoding.
Step 609 is decoded to processing rear signal;
Decoder is decoded according to the signal of coded format after with logical process, obtains the low frequency magnetic field traffic flow information.Decoder arranges the digital spur filter can carry out the burr filtering to the digital signal of input.
Step 611 is finished the one-way communication of low frequency magnetic field signal;
With the application that data after the decoding are correlated with, finish the one-way communication function of low frequency magnetic field signal.
Step 604 enters apart from control flow;
Step 606 arranges 1 signal proportion thresholding and comparison threshold;
If the distance of desired control is D1, search the corresponding table of range value and distance, obtain signal intensity amplitude corresponding to D1 for+A1 to-A1, the ratio thresholding that 1 signal is set is R1, according to A1 and R1, the level L1, the L2 that export to comparator is set, satisfy in one-period, the fore device amplitude output signal equals R1 greater than L1 or less than the percentage of time of L2, namely then enters in distance B 1 scope of described requirement control greater than R1, otherwise does not enter in the described scope that requires command range D1.
When using a pair of comparison threshold to obtain when carrying out the digital signal of Distance Judgment between card reader and the card, then this a pair of digital signal is proceeded as follows: the output signal after will adjudicating by high comparison threshold with adjudicate by low comparison threshold after the output signal negate after carry out or operate, obtain the digital signal for Distance Judgment.
Step 612 uses the Preset Time window that 0,1 data are added up;
Preset Time window length, and 0,1 data in this time window are added up, calculate 1 proportion.
Step 614,616 compares statistics and set 1 signal proportion thresholding, finishes Distance Judgment, realizes distance control.
Fig. 7 be record by experiment in the embodiment of the invention induction module is inserted the different mobile communication terminal, the corresponding relation schematic diagram of distance and low frequency induction signal amplitude value.
Table 1 is the mapping table of embodiment of the invention medium and low frequency induced signal range value and distance.
| The distance of mobile communication terminal and card reader (cm) | Induced signal amplitude (dBmV) |
| 1cm | 52 |
| 2cm | 47 |
| |
40 |
| 4cm | 36 |
| 5cm | 30 |
| 6cm | 26 |
| 7cm | 21 |
| 8cm | 17 |
| 9cm | 11 |
| 10cm | 8 |
| 14cm | 5 |
Table 1
Figure 8 shows that the analog to digital conversion circuit basic framework of native system, the A/D of this example adopts the typical mode that compares one by one type, comprises voltage follower A and analog to digital converter nucleus module B.Wherein voltage follower A is mainly used to the simulation amplifying signal that stabilizing amplifier is exported, and the voltage drift of avoiding A/D front end high resistant to cause causes the analog-to-digital conversion distortion.Wherein the common mode input port adopts the same common-mode voltage VCM of front-end amplifier.C10 is sampling capacitance, and the appearance value is selected according to sampling rate.
Select reference voltage Vref＞=amplifier simulation amplifying signal VOUT in this example, adopt the output of Parallel Digital amount, figure place is selected more than 8.
Fig. 9 is the schematic diagram that uses a pair of comparison threshold to adopt the low frequency magnetic field signal detecting method to decode and process in the embodiment of the invention;
DO shown in Fig. 9 is the output signal after digital to analog converter is changed amplifier input signal.High comparison threshold, low comparison threshold are according to separating code distance and arranging with the corresponding table of distance with reference to range value.DO2 is analog to digital converter output signal and the high comparison threshold output signal after relatively.DO3 is analog to digital converter output signal and the low comparison threshold output signal after relatively.DO4 is for carrying out the signal after sluggishness is processed to relatively rear signal DO2, DO3.This signal inputs to decoder and is used for decoded data.Decoder can arrange the digital spur filter can carry out the burr filtering to this input signal, and decoder is decoded according to the signal of coded format after with logical process, obtains the low frequency magnetic field traffic flow information.
Figure 10 uses a pair of comparison threshold to adopt the low frequency signal detection method to carry out the schematic diagram that distance control is processed in the embodiment of the invention;
DO shown in the figure is the output signal after digital to analog converter is changed amplifier input signal.Its rangeability is from-A1 to+A1, and the distance of its correspondence is L.The L that supposes to adjust the distance controls, and then at first searches the corresponding table of range value and distance, obtains the signal amplitude value on this distance.The ratio thresholding that 1 signal is set again is R1.According to R1, then high comparison threshold VG+, low arranging of comparison threshold VG-are satisfied in one-period, and the fore device amplitude output signal equals R1 greater than VG+ or less than the percentage of time of VG-.To output signal DO2, DO3 after the judgement of a pair of comparison threshold carry out or process after obtain signal DO4, this signal is sampled 0,1 data flow D5 after obtaining sampling.The default time window of dotted line frame representative on 0,1 data flow among the figure, setup times window length equals a signal period, in the time window 0,1 signal are added up, obtain 1 signal proportion, the ratio thresholding of this ratio and 1 signal is compared, if greater than the ratio thresholding, think that then induction module enters in the distance L; Otherwise think and do not enter this distance.
Figure 11 is the schematic diagram that uses single comparison threshold to adopt magnetic field data low frequency signal detection method to decode and process in the embodiment of the invention;
To be digital to analog converter carry out output signal after the analog-to-digital conversion to amplifier input signal to DO shown in the figure.Comparison threshold is set to amplifier input reference level.Signal directly inputs to decoder as the decoder supplied with digital signal relatively.Decoder arranges the digital spur filter can carry out the burr filtering to this input signal.Decoder is decoded according to the signal of coded format after with logical process, obtains the low frequency magnetic field traffic flow information.
Figure 12 uses single comparison threshold to adopt the low frequency signal detection method to carry out the schematic diagram that distance control is processed in the embodiment of the invention;
DO shown in Figure 12 is the output signal after digital to analog converter is changed amplifier input signal.Its rangeability is from-A1 to+A1, and the distance of its correspondence is L.The L that supposes to adjust the distance controls, and then at first searches the corresponding table of range value and distance, obtains the signal amplitude value on this distance.The ratio thresholding that 1 signal is set again is R1.According to R1, then arranging of comparison threshold VG satisfied in one-period, and the fore device amplitude output signal equals R1 greater than the percentage of time of VG.Output signal DO1 after relatively adjudicating is sampled 0,1 data flow DO2 after obtaining sampling.The default time window of dotted line frame representative on 0,1 data flow among the figure, setup times window length equals a signal period, in the time window 0,1 signal are added up, obtain 1 signal proportion, the ratio thresholding of this ratio and 1 signal is compared, if greater than the ratio thresholding, think that then induction module enters in the distance L; Otherwise think and do not enter this distance.
It is evident that, the digital signal that also can use a plurality of single comparison thresholds to export is more afterwards carried out the judgement of a plurality of distances and code stream, or uses many digital signals that the comparison thresholding is exported more afterwards to carry out between a plurality of distances, a plurality of distance regions and the judgement of code stream; Also can mix digital signal and the many digital signals that the comparison thresholding is exported more afterwards of using a plurality of single comparison thresholds to export more afterwards carries out between a plurality of distances, a plurality of distance regions and the judgement of code stream.
Figure 13 is that a kind of low frequency alternating magnetic field of the present invention closely detects the system architecture diagram in conjunction with the communication of radio frequency high frequency, as shown in the figure: system comprises radio communication terminal and close distance radio frequency communication equipment, the radio communication terminal comprises the low frequency alternating magnetic field signal receiving circuit, what be connected with the low frequency alternating magnetic field signal receiving circuit is used for the closely device of low frequency magnetic field input and transmission and Distance Judgment, and is connected with the device that is used for low frequency magnetic field input and transmission and Distance Judgment for the radio-frequency (RF) transmit-receive circuit of close distance radio frequency communication equipment both-way communication.
During work, close distance radio frequency communication equipment emission low frequency alternating magnetic field signal, the radio communication terminal receives this field signal by the low frequency alternating magnetic field signal receiving circuit, and be transferred to device for low frequency magnetic field input and transmission and Distance Judgment, utilize at last radio-frequency (RF) transmit-receive circuit and close distance radio frequency communication equipment to realize the two-way range communication.
According to above description, the present invention can finish low-frequency weak signal and amplify in advance, analog-to-digital conversion, and field intensity detects and data communication.
The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (21)
1. one kind is used for the closely device of low frequency magnetic field input and transmission and Distance Judgment, it is characterized in that, comprise that at least one is used to respond to the low frequency induction module of low frequency magnetic field signal, at least one be used for to amplify amplifier of low frequency induction signal, at least one analog to digital converter that is connected with amplifier out, and the digital signal processing module that is connected with analog to digital converter and exports for intensity and the settling signal detection of judgement primary signal.
2. device according to claim 1 is characterized in that, described low frequency induction module is induction coil, Hall element, perhaps giant magnetoresistance.
3. device according to claim 1 is characterized in that, described amplifier adopts the mode of casacade multi-amplifier cascade.
4. according to claim 1 or 3 described devices, it is characterized in that described amplifier is single-ended amplifier or differential amplifier.
5. device according to claim 3 it is characterized in that in the casacade multi-amplifier of described cascade that every grade of input connects high-pass filtering circuit, every grade of output connects low-pass filter circuit, and amplifier is low imbalance and the long-pending amplifier of high gain-bandwidth.
6. device according to claim 1 is characterized in that, described analog to digital converter adopts parallel A/D converter.
7. according to claim 1,3,5 or 6 arbitrary described devices, it is characterized in that described analog to digital converter speed is greater than 1KSPS, input range be 0 volt to the analog to digital converter reference voltage.
8. according to claim 1,3,5 or 6 arbitrary described devices, it is characterized in that described analog to digital converter input front end is provided with the voltage follower that is connected with described amplifier.
9. device according to claim 1 is characterized in that, is provided with between described analog to digital converter and the digital signal processing module for the digital spur filter that digital signal is carried out the burr filtering.
10. a low frequency alternating magnetic field closely detects the system in conjunction with the communication of radio frequency high frequency, comprise radio communication terminal and close distance radio frequency communication equipment, it is characterized in that, described radio communication terminal comprises such as claim 1 to 8 arbitrary described for the device of low frequency magnetic field input and transmission and Distance Judgment closely, and is connected the radio-frequency (RF) transmit-receive circuit that is used for close distance radio frequency communication equipment both-way communication with described for the device of low frequency magnetic field input and transmission and Distance Judgment closely.
11. one kind is used for the closely method of low frequency magnetic field input and transmission and Distance Judgment, method comprises:
Step a: measure magnetic induction module and induced voltage the voltage amplitude value through amplifier amplification after of the card reader that sends magnetic field at different distance point, determine the corresponding relation of voltage amplitude value and distance, and set up the corresponding table of range value and distance;
Step b: according to the swipe the card needs of distance of decoded low frequency signal transmitted data and control, in conjunction with the signal to noise ratio requirement, form sluggish judgement voltage threshold by comparison threshold the analog to digital converter output signal is adjudicated, obtain the code stream information of low-frequency magnetic place transmission; Form non-sluggish judgement voltage threshold by comparison threshold the analog to digital converter output signal is adjudicated, obtain the distance feature information that transmit in the low-frequency magnetic place;
Step c: signal after the non-sluggish judgment condition judgement sampled obtains 0,1 code stream sequence, 1 signal proportion thresholding is set, in the time window length of setting, this code stream sequence is added up, when the shared code stream sequence of 1 signal ratio reaches the preset ratio thresholding, then think to enter set distance range, otherwise think and do not enter this distance range; Burst after the sluggish judgment condition judgement is decoded, extract the code stream information of low frequency magnetic field, finish low frequency magnetic field signal one-way communication.
12. describedly according to claim 11 detect and the method for transmission system for low frequency signal closely, it is characterized in that, among the described step b, according to the corresponding table of range value described in the step a with distance, in conjunction with the requirement of separating code distance, distance control, ratio thresholding that 1 signal is set comparison threshold in the digital signal processing module is set.
13. described method for low frequency signal detection and transmission system is characterized in that according to claim 11, among the described step b, uses single, a plurality of single, a pair of, many to relatively magnetic field range information and code stream information are extracted in thresholding or its combination.
14. describedly according to claim 13 detect and the method for transmission system for low frequency signal closely, it is characterized in that, a pair of comparison threshold is non-sluggish judgment condition in the described digital signal processing module, its method to set up is: the distance of establishing desired control is D1, search the corresponding table of range value and distance, obtain signal intensity amplitude corresponding to D1 for+A1 to-A1, the ratio thresholding that 1 signal is set is R1, according to A1 and R1, the level L1 of comparator is exported in setting, L2, satisfy in one-period, the fore device amplitude output signal equals R1 greater than L1 or less than the percentage of time of L2, namely then enter in distance B 1 scope of described requirement control greater than R1, otherwise do not enter in the described scope that requires command range D1.
15. describedly according to claim 13 detect and the method for transmission system for low frequency signal closely, it is characterized in that, a pair of comparison threshold is sluggish judgment condition in the described digital signal processing module, its method to set up is: if the distance that expectation is decoded is D2, search the corresponding table of range value and distance, the amplitude of variation that obtains the D2 respective signal for+A2 to-A2, the amplitude that records most of noises generations is A3, level L3, the L4 of comparator exported in setting, so that L3 should be greater than+A3, and less than+A2; L4 is less than-A3, and greater than-A2, namely then allow decoding less than D2 when distance, otherwise not allow decoding.
16. describedly according to claim 14 detect and the method for transmission system for low frequency signal, it is characterized in that, among the described step b, carry out the logic OR processing to using two output signals after a pair of non-sluggish judgment condition is judged, obtain after the processing for the digital signal of extracting range information.
17. describedly according to claim 15 detect and the method for transmission system for low frequency signal, it is characterized in that, among the described step b, two output signals after using a pair of sluggish judgment condition to judge are carried out sluggishness process, obtain for the digital signal of extracting the magnetic field code stream information after sluggish the processing.
18. described method for low frequency signal detection and transmission system is characterized in that according to claim 13, when using single comparison threshold to extract the magnetic field code stream information, comparison threshold is set to amplifier input reference level; When using single comparison threshold output comparative level to extract the magnetic field range information, the comparison threshold method to set up is consistent with the described method of claim 16.
19. describedly according to claim 13 detect and the method for transmission system for low frequency signal, it is characterized in that, the digital signal that described method uses single comparison threshold to export is more afterwards carried out the judgement of single distance and code stream, or the digital signal of using a pair of comparison threshold to export is more afterwards carried out the judgement of single distance and code stream; The digital signal that described method uses a plurality of single comparison thresholds to export is more afterwards carried out the judgement of a plurality of distances and code stream, or uses many digital signals that the comparison thresholding is exported more afterwards to carry out between a plurality of distances, a plurality of distance regions and the judgement of code stream.
20. describedly according to claim 13 detect and the method for transmission system for low frequency signal, it is characterized in that described method is mixed digital signal and the many digital signals that the comparison thresholding is exported more afterwards of using a plurality of single comparison thresholds to export more afterwards and carried out between a plurality of distances, a plurality of distance regions and the judgement of code stream.
21. describedly according to claim 11 detect and the method for transmission system for low frequency signal, it is characterized in that, among the described step c, comprise the step that the digital signal of input is carried out the burr filtering, then from the signal of filtering burr, decode the low frequency magnetic field data flow.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN201010166432.1A CN103023536B (en) | 2010-05-10 | 2010-05-10 | Device, system and method used for detecting and transmitting low-frequency magnetic field signal and judging distance |
| PCT/CN2010/073764 WO2011140731A1 (en) | 2010-05-10 | 2010-06-10 | Device, system and method for low-frequency magnetic field signal detecting, transmission and distance estimating |
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| CN201010166432.1A CN103023536B (en) | 2010-05-10 | 2010-05-10 | Device, system and method used for detecting and transmitting low-frequency magnetic field signal and judging distance |
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| CN103023536B CN103023536B (en) | 2014-12-03 |
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| WO (1) | WO2011140731A1 (en) |
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Also Published As
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| CN103023536B (en) | 2014-12-03 |
| WO2011140731A1 (en) | 2011-11-17 |
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